sis30315 certificate iii in fitness learner guide

SIS30315 Certificate III in Fitness

Learner Guide

2

Contents Structural Levels of Organisation ....................................................................................................................... 4

The Skeletal System ........................................................................................................................................... 8

Anatomical Terminology .................................................................................................................................. 38

The Muscular System ....................................................................................................................................... 42

Movement Analysis .......................................................................................................................................... 52

Posture ............................................................................................................................................................. 56

The Nervous System ......................................................................................................................................... 59

The Cardiovascular System .............................................................................................................................. 66

Blood ................................................................................................................................................................ 72

Cardiovascular Terminology ............................................................................................................................... 73

The Respiratory System ................................................................................................................................... 75

The Lymphatic System ..................................................................................................................................... 80

Energy Systems ................................................................................................................................................ 82

The Endocrine System ...................................................................................................................................... 84

Digestive System .............................................................................................................................................. 86

Thermoregulation ............................................................................................................................................ 88

Exercise and Thermoregulation ....................................................................................................................... 90

References ....................................................................................................................................................... 95

This document is the property of FIAFitnation and contains confidential information of FIAFitnation.

Copyright in the whole and every part of this document belongs to FIAFitnation and may not be used, sold, transferred, adapted or modified or reproduced in

whole or in part in any manner or form or in any media, to any persons other than in agreement with FIAFitnation.

Original concept developed by Ewan Birnie First Edition, 2015 for FIAFitnation

This document remains the confidential information of FIAFitnation and should not be used for any other purpose other than that expressly approved by

FIAFitnation at the time the document was provided by FIAFitnation.

3

APF310 Anatomy and Physiology for Fitness

SISFFIT004 Incorporate anatomy and physiology

principles into fitness programming

4

Structural Levels of Organisation Cells All living things are comprised of a variety of different cells. Each of these cells is made up of a combination

of different atoms, serving a variety of purposes. Most cells have the same key features, as described and

shown below.

• Nucleus

The nucleus is the brain of the cell, the site of the genetic makeup of the cell and the body, containing the

genes. It is where DNA is stored and is the control centre of the cell.

• Mitochondria

The mitochondria are the part of the cell that is responsible for energy production through the building and

breakdown of ATP in relation to the aerobic energy system. The more mitochondria present within a cell,

the more energy it can produce in the presence of oxygen

• Cell Membrane

The cell membrane is the outer protective part of the cell. It encloses all contents of the cell. It is designed to

allow the transport of molecules in and out of the cell in specific amounts. This is known as being selectively

permeable.

• Cytoplasm

The cytoplasm is the gel-like substance within the cell membrane, holding all the cell’s internal sub-structures

(organelles), excluding the nucleus. It is within the cytoplasm that most of the cell’s activities are completed.

5

Tissues Different cells combine to form tissues. Some examples of tissues commonly found in the human body are

listed below. Each type of tissue has different features in relation to the function that they play within the

human body.

• Epithelial Tissue

This type of tissue has the function of lining various parts of the body. Epithelial tissue will often act as a

membrane around organs, providing a degree of protection. This type of tissue is found on the outer layer of

the skin, inside the mouth, inside the stomach and surrounding the main organs.

• Connective Tissue Connective tissue joins body parts together, providing structure and stability. They have fibrous properties,

increasing the strength of the tissue, essential for coping with the large forces that these tissues are exposed

to. Examples of connective tissue include tendons, ligaments, cartilage and bone.

• Muscle Tissue

Muscle tissue has a unique feature in the ability to contract and relax. This tissue contains a contractile

unit called a sarcomere, within which protein known as actin and myosin are present, allowing

muscles to shorten and lengthen.

• Nerve Tissue

The distinguishing feature of nerve tissue is its ability to generate and conduct electrical signals in the body,

controlling the actions of all tissues and organs.

Organs These tissues are then grouped together to form a specific function. When they are grouped together, they

are known as organs. The main organs in the human body are:

• Brain – Main component of the nervous system. Responsible for controlling most of the actions

within the body.

• Heart – Centre of the cardiovascular system. Responsible for distributing blood to the areas of the

body that require it.

• Liver – Produces and excretes bile, stores energy and releases hormones.

• Kidneys – Regulate fluid volumes in the body and contributes to the removal of waste and toxins.

• Bladder – Storage of waste in the form of urine prior to release from the body.

• Lungs – Key respiration structure in the body. Primary site of gas exchange, allowing oxygen to

enter and carbon dioxide to leave the body.

• Stomach – Primary site of digestion of food stuffs where food is mixed with a range of enzymes.

• Reproductive – Organs that produce sperm (male) and eggs (female) to facilitate procreation.

• Skin – Organ that protects other key systems from the external environment.

6

Systems Many of these organs are designed to interact. This interaction ensures that the body functions effectively at

rest and during exercise. The main systems are:

• Skeletal System

The skeletal system is comprised of over 200 bones (in an adult), as well as cartilage and other connective

tissues. It has 2 main sections - the axial and appendicular skeleton. Functions of the skeleton include

protection of vital organs, providing a shape & structure to the body and providing attachment points for

muscles to permit movement.

• Muscular System

Specialised tissue distributed across the body that, along with the skeletal and nervous system, produces

movement through the application of force on the skeleton. Muscles will cause movement at the joints they

cross. The muscular system also provides structure and support to the skeleton. There are different types of

muscle fibres that are distributed across the body. Each fibre type has different characteristics that match

the function that they are required to perform.

• Nervous System

This system has two main branches that control the activity of all the main organs and systems. These

branches are the central and peripheral nervous system. There are numerous neural structures within the

body that provide sensory information to the body, upon which it acts.

• Circulatory System

Consists of the heart, blood and a network of blood vessels. Its main responsibilities include the delivery of

oxygen and nutrients, and the removal of waste. This system works alongside the respiratory system. The

heart is the centre of the system, controlling the distribution of blood. The blood, along with the lymphatic

system fights infection and maintains pH of the body.

• Respiratory System

Working alongside the circulatory system, the lungs are responsible for the intake of oxygen and the removal

of carbon dioxide. These gases travel through the respiratory tree, with gas exchange occurring in small

structures in the lungs, known as alveoli, in muscles and in tissues.

• Endocrine System

The endocrine system is comprised of a series of glands throughout the human body. These glands release

hormones that impact on the function of numerous other systems. Examples of functions influenced by the

endocrine system include changes in heart rate and breathing rate.

7

• Digestive System

This system dismantles the food that consumed, breaking it down in to basic nutrients that our body can

utilize. Through interaction with the circulatory system, these nutrients are delivered via blood to areas of

demand. The digestive system also packages waste to be removed from the body.

• Lymphatic System

This system is largely responsible for fighting infection. A network of vessels collects fluid that has been

built up as a result fighting infection. This system works closely with the circulatory system to remove

waste.

• Urinary System

This system is also concerned with the removal of waste, in the form of urea. Two of the main organs that

are part of this system are the bladder and kidneys. There is a strong interaction with the endocrine system

in the production of urine, based on hydration levels.

• Reproductive System

This system is concerned with procreation through the production of sperm (male) and eggs (female).

APPLICATION TO THE TRAINER

Exercise responses and adaptations that we see and feel occur due to changes at a cellular level. Therefore,

understanding the structural levels of organization will allow the fitness trainer to correctly analyse the

body’s reaction and adaptation to a variety of exercises. It will also serve to give a more complete

understanding of the functioning of each of the following body systems. Understanding the interactions

between the systems of the body will give the trainer a greater insight into the impact that exercise can have.

8

The Skeletal System The skeletal system is comprised of over 200 bones, and connective tissue in the form of ligaments and

cartilage. The skeletal system has numerous functions. Within a fitness setting, the role of the skeleton

within movement is arguably of most importance. As a fitness instructor, an understanding of bones, joints

and possible movements is paramount if safe and effective exercise is to be prescribed.

The Functions of the Skeleton The skeletal system has 5 main functions:

• Support/Structure – Bones of different shapes and sizes give the body its shape. Through

interaction with the muscular system, the skeletal system allows the body to remain upright and

maintain its shape throughout all movements.

• Movement – Many bones have notches, grooves and ridges that provide attachment points for

muscles, via tendons. These muscles will pull on the bones to cause movement.

• Protection – A large proportion of skeletal mass is found around vital organs. This helps to protect

the organ from any potential impact injury. For example, the skull protects the brain and the

vertebral column protects the spinal cord.

• Storage – Bones are a storage site for minerals calcium & phosphorus.

• Blood Cell Production – At the centre of the bone in the bone marrow, red and white blood cells

are produced. Each of these cells have essential roles in both health and exercise performance.

Skeletal Anatomy The skeleton can be divided into 2 main sections.

• Axial

Supports the structures on the main axis of the body.

Comprised of the skull, vertebral column, sternum and rubs.

• Appendicular

Supports the limbs and attaches them to the body.

Comprised of the bones of the arms, legs, shoulder

and pelvic girdle.

9

Major Bones of the Human Body

Source: Essentials of Human Anatomy & Physiology (2017)

10

The Vertebral Column The vertebral column is responsible for the protection of the spinal cord. There are 33 vertebrae in total. It

has 5 main sections as shown and described below:

Section of Vertebral Column

Description Cervical This is the upper most part of the spine. There are 7 cervical vertebrae,

numbered C1-7. C1 is also known as the atlas and C2 known as the axis,

allowing the head to rotate and pivot. The cervical spine has a slight

lordotic curve.

Thoracic There are 12 thoracic vertebrae that sit inferior to the cervical spine.

These are numbered T1-12. The 10 pairs of true ribs attach to these

vertebrae. They are slightly larger than the cervical vertebrae. The

thoracic spine displays has slight kyphotic curve.

Lumbar Below the thoracic region, lie the lumbar vertebrae (L1-5). Again, an

increase in size is seen in the vertebrae to cope with the larger forces

that are applied to this region of the spine. It is in this region of the

spine that the majority of back pain is experienced. The lumbar spine

has a slight lordotic curve.

Sacrum The sacrum consists of 5 vertebrae, although these will be fused in a

mature adult. In a skeletally immature child, these bones will

appear separately.

Coccyx Below the sacrum lies the coccyx, comprising of 4 fused bones in a

mature adult. In a skeletally immature child, these bones will appear

separately.

Lumbar vertebrae

11

Bony Landmarks

In addition to identification of the major bones of the skeleton, trainers are also required to identify

key bony landmarks. This is particularly useful when conducting the screening process, where girth or

skinfold measurements may be taken. Some of the key bony landmarks are identified below:

Landmark

Position Picture

Acromion • Bony process of the

scapula

• It is a continuation of the

scapular spine that

articulates with the

clavicle

• It is the most lateral point

of the scapula

• Required for accurate

location of upper arm

girth

Inferior Angle of

Scapula

• The most inferior point

on the scapula where the

medial and lateral

borders of the scapula

meet

• Required for locating the

subscapular skinfold and

identifying postural

deviations (e.g protracted

scapula).

12

Landmark Position Picture

Proximal Patella • The most proximal point of

the patella


location of thigh girth

measurement

Radiale • The head of the radius

• The most proximal point of

the radius

• Can be located by feeling

for the space between the

humerus and radius


location of upper arm girth

Iliac Crest • Most superior border of the

ilium


location of measurement of

waist:hip ratio and

identifying postural

deviations (e.g hip hike).

13

Types of Bone The skeleton is made up of bones of all shapes and sizes. There are 4 general categories that bones can fall

into. They are long bones, short bones, flat bones and irregular bones.

Long Bones These bones are longer than they are wide. They function as levers and are the bones that move most

regularly during exercise. Examples of long bones include the femur, tibia, humerus, and fibula. They have

many important features, as shown below. The shaft of the long bone is known as the diaphysis. The

diaphysis sits between the epiphyses, which are the ends of the long bone. The epiphyses are comprised

out of cartilage in children, prior to developing into bone. The epiphyseal plate is located between the

diaphysis and epiphysis, and is essential for bone growth (see ossification below). The marrow in the centre

of the bone is responsible for blood cell production, specifically red and white blood cells. The periosteum is

the outer layer of the bone, which provides protection.

Short Bones Short bones are cube shaped. They are found in the wrist (carpal bones) and ankles (tarsal bones).

Flat Bones Bones shaped in this way generally have the function of either protection or muscle attachment. They have

broad surfaces. Examples include the ribs, sternum, cranium and the scapula.

Irregular Bones These bones have varied shapes, sizes and surface features. An example of this classification is vertebrae.

18

Long Bone Development – Ossification The process of bone formation is known as ossification. Development and changes in bone tissue occur at

all stages of the lifecycle, with new bone cells continuously produced and dead cells removed in the

remodelling process. This leads to changes in the size and shape of the bone. These changes are heavily

influenced by exercise habits and diet.

The primary stage at which bone development occurs is from birth to adolescence. As early as 6 weeks in

utero, the skeleton begins to form as membranes and cartilages. From here, bone cells begin to form,

replacing the membranes and cartilage. In infancy and youth, growth occurs at the epiphyseal plates,

located between the diaphysis (shaft), and the epiphysis (heads of the bone). This is known as interstitial

growth. These plates expand, forming new bone cells. As growth continues, the thickness of the epiphyseal

plate decreases, leading to plate closure. At this stage, bone development will cease. The point at which this

occurs varies from one individual to the next but is generally complete by the early to mid-twenties.

This process is responsible for bone elongation. It has long been debated as to what impact exercise can

have on the process of bone growth in children. For some time, the recommendations were for children to

avoid all forms of resistance training due to potential damage to growth plates. However, with a greater

understanding of the science of growth, these recommendations have relaxed to a certain extent, with a

carefully planned and supervised program deemed suitable and relatively low risk in relation to the impact

on growth.

19

Changes in thickness, strength and density of bone and general maintenance of bone health is controlled by

3 main bone cells:

• Osteoblasts – Cells that form bones through interaction with blood and mineral salts such as

calcium

• Osteoclasts – Cells that remove dead bone cells

• Osteocytes – Mature bone cells

The activity of these bones cells is responsible for appositional growth. During periods of growth,

osteoblast activity exceeds that of osteoclasts. This means that the number of developing bone cells is

increasing, leading to growth in thickness and strength, and therefore an increase in the density of bones.

This will generally occur at times of growth but can be influenced by regular participation in weight

bearing exercise, where the mechanical stress placed on the bone encourages bone mineralisation.

Components of the diet also have an impact on this process. Vitamin A, D, C, calcium and phosphorus are

all vital for normal bone development.

In the older population, the activity of osteoblasts decreases, meaning that new bone cells are formed at a

slower rate. However, the osteoclast activity remains the same, meaning that dead bone cells are

removed. This leads to a decrease in bone mineral density, which can often lead to a condition known as

osteoporosis. This condition is most common in elderly females, predisposing them to a greater likelihood

of fractures.


As a fitness trainer it is likely that you will work with clients of a variety of ages and skeletal health/maturity.

It is essential that you understand the development of the skeleton so that your programming is appropriate

for the client’s age, stage of skeletal development and bone health. For example, elderly clients should avoid

heavy impact activities, particularly if they are osteoporotic due to their increased susceptibility to

fractures.

20

Joints Joints (or articulations) exist when two or more bones meet. The function of that joint is influenced by the

anatomy and classification of the joint. There are 3 main classifications of joints within the human body, as

outlined below.

Joint Type Description Picture

Fibrous • Ends held together by

short, strong fibrous tissue

• Immovable

Between bones of the skull

Cartilaginous • Permit very little movement

• Bones will be joined by

cartilage or collagen fibres

• Bone ends can be

separated by a disc or plate

of tough fibrous tissue

Between vertebrae

Synovial • Permit maximum

movement

• Typically found at the end

of long bones

• Bones do not come into

direct contact

• Ligaments cross the joint

• Cartilage covers the bone

ends

Shoulder, hip, knee, elbow etc.

21

Synovial Joints The joint classification that is of most interest to fitness professionals is synovial joints as these are most

freely moveable and as a result will be involved in all exercises. Synovial joints have many key

distinguishing features as shown and described below.

• Ligaments

Primarily responsible for joint stability. Ligaments are fibrous bands that join bone to bone, outside of the

synovial membrane. They are relatively inelastic and can be prone to injury if large, excessive forces are

placed on them.

• Cartilage

Located on the surface of the articulating bones. Cartilage is responsible for reducing friction between

bones and cushioning any impact forces. If this deteriorates, it can cause severe pain and restrict movement

significantly. This wearing away is most common in weight bearing joints such as the hip and knee.

• Synovium/Synovial Membrane

The synovial membrane is composed of loose connective tissue. It lines the joint capsule internally and has

the responsibility of synovial fluid production.

• Synovial Fluid

The main function of synovial fluid is to decrease friction within the joint during movement.

• Articular Capsule

Covers the joint cavity. The articular capsule is tough and flexible, containing all of the synovial joint

structures within.

22

Types of Synovial Joints Synovial joints are not all identical in anatomy and therefore have different movement characteristics. An

understanding of these characteristics will contribute to exercise prescription and teaching.

Ball & Socket Joints

This is the most moveable of all synovial joints.

It is present at joints where the end of the bone

is ball-shaped and fits into a joint capsule. It is

found at the hip and shoulder joint.

Hinge Joint

These joints are much less moveable, primarily

allowing only flexion and extension movements.

Examples of this type of joint are the elbow, knee

and interphalangeal joints.

Pivot Joints

These joints occur when a bone rotates around a

bony prominence on another bone. An example

of this joint includes the joint between the radius

and ulna.

Gliding Joints

This type of joint is present when 2 flat surfaces slide

over each other. However, this form of joint

provides very little movement. Examples of these

types of joints are found between carpal bones and

also tarsal bones.

Saddle Joint

This is the least common type of synovial joint, being found only at the thumb. It occurs when the articulating surfaces are convex and concave.

23

Key Joints and their Movements The table below highlights the main joints in the body, the bones that they are comprised of, and the

movements that are possible at that particular joint.

Elbow Articulating Bones: Radius, Ulna, Humerus

Possible Movements: Flexion, Extension

Movement Starting Position Finishing Position

Flexion

Example

Exercise

Rows

Pull Ups

Biceps Curl

Extension

Example

Exercise

Bench

Press

Overhead

Press

Triceps

Extension

24

Shoulder

Articulating Bones: Scapula, Clavicle, Humerus

Possible Movements: Flexion, Extension, Abduction, Adduction, Horizontal Abduction, Horizontal

Adduction, Medial Rotation, Lateral Rotation


Flexion

Example Exercise

Narrow Grip Bench

Press

Narrow Grip

Overhead

Press

Front Raise

Extension

Example Exercise

Narrow Grip Row

Narrow Grip Pull Up

25

Abduction

Example Exercise

Wide Grip Overhead

Press

Lateral Raise

Adduction

Example Exercise

Lat Pulldown Pull Up

26

Horizontal Abduction

/Extension

Example Exercise

Wide Grip Row

Horizontal Adduction

/Flexion

Example Exercise

Bench Press Push Up

27

Medial/ Internal

Rotation

Lateral/ External

Rotation

28

Hip Articulating Bones: Pelvis, Femur

Possible Movements: Flexion, Extension, Abduction, Adduction, Medial Rotation, Lateral Rotation


Flexion

Example

Exercise

V-Sits Reverse

Crunches

Extension

Example

Exercise

Squat

Deadlift

Lunge

Leg Press

29

Abduction

Example

Exercise

Duck Walks

Adduction

Example

Exercise

Lateral Lunge

30

Medial/

Internal

Rotation

Lateral/

External

Rotation

31

Knee Articulating Bones: Femur, Tibia

Possible Movements: Flexion, Extension


Flexion

Example

Exercise

Hamstring Curl

Extension

Example

Exercise

Squat

Deadlift

Lunge

Leg Press

32

Ankle Articulating Bones: Tibia, Fibula, Tarsals

Possible Movements: Plantar Flexion, Dorsi Flexion, Inversion, Eversion


Plantar

Flexion

Example

Exercise

Squat

Deadlift

Lunge

Leg Press

Dorsi Flexion

Inversion

Eversion

33

Shoulder Girdle

Articulating Bones: Clavicle, Humerus, Scapula

Movements Possible: Protraction, Retraction, Upward Rotation, Downward Rotation, Elevation,

Depression


Protraction

Example

Exercise

Bench Press

Push Up

Retraction

Example

Exercise

Rows

34

Upward

Rotation

Example

Exercise

Overhead

press

Downward

Rotation

Example

Exercise

Lat Pulldown

Pull Up

35

Elevation

Example

Exercise

Shrugs

Olympic lifts

Depression

36

Spine Articulating bones: Between vertebrae

Possible Movements: Flexion, Extension, Lateral Flexion, Rotation


Flexion

Example

Exercise

Crunches

Extension

Example

Exercise

Back

Extensions

37

Lateral Flexion

Rotation

Example

Exercise

Woodchop


As a fitness instructor, knowledge of the features of the different joints and their actions is essential for

a variety of reasons. Firstly, injury to joints can be a common complaint of clients. Recognising the

features of the different joint classifications will allow the signs and symptoms of the injury to be better

understood, and therefore appropriate exercises can be selected. It is essential to note that the

presence of an injury should always trigger a referral to an allied health professional.

Knowledge of joint actions and the muscles causing the movements will allow the trainer to design a

program that is well balanced, targeting specific muscles of weakness. This can be further utilized to

provide coaching points and advice on exercise performance.

38

Anatomical Terminology

Anatomical Position When describing the anatomy of the body or movements, there is standardised terminology that is used

across a variety of professions. These terms are used to describe the anatomy of one part of the body in

relation to another. When using this terminology, the trainer should use the anatomical position as the

reference point. It is essential that the fitness professional has an understanding of this terminology. The

anatomical position is displayed below:

The key features of the anatomical position are feet together, arms straight by sides, palms facing forwards

and the head erect, facing forward.

Planes of Movement In addition to the anatomical position, there are a range of other terms that are used in relation to

movement of the body. The table below outlines different planes of the body. Movement is considered to

occur along one or more of these planes.

39

Sagittal Plane

Example Movements

Flexion or extension at the

shoulder, elbow, hip or knee.

Divides the body into right & left

sections.

Frontal/Coronal Plane

Example Movements

Abduction and adduction at the

shoulder or hip.

Divides the body into anterior

(front) and posterior (back) sections.

Transverse/Horizontal Plane

Example Movements

Pushing, pulling or rotation

actions.

Divides the body into superior

(upper) and inferior (lower)

sections.

41

Directional Terminology The terms below are used to describe the position of one area/part of the body in relation to another. The

terms will also often be utilised in the naming of bony landmarks and muscles in the body.

Term Definition Example

Superior Above The head is superior to the

shoulders

Inferior Below The knee is inferior to the hip

Anterior In front of The clavicle is anterior to the

scapula.

Posterior Behind The hamstring is posterior to the

femur

Medial Towards the middle/midline The sternum is medial to the ribs

Lateral Away from the midline The ribs are lateral to the

sternum.

Proximal Nearer to the attachment of a

limb

The shoulder is proximal to the

elbow

Distal Further from attachment of a

limb

The fingers are distal to the

elbow

Superficial Nearer the outside of the body The rectus abdominus is

superficial to the transverse

abdominus.

Deep Nearer the inside/core of the

body

The transverse abdominis is deep

to the rectus abdominis

Unilateral On one side of the body Performing a single arm row.

Bilateral On both sides of the body Performing a back squat.


When working in the fitness industry, it is common to work alongside allied health professionals (AHPs). The

terminology above is commonly used by a variety of AHPs to describe injuries, areas of weakness and range of

motion abilities. An understanding of these terms will give the trainer credibility when working alongside

other professional groups as they can communicate with clarity on a professional level.

Additionally, these terms increase understanding of movement and therefore exercise prescription. This will

allow well-balanced and appropriate exercise selections to be made and programs designed. In particular,

the use of planes of motion terminology is important when planning functional exercise.

42

Conditions of the Skeletal System A range of conditions can impact upon the skeletal system. These conditions result in different exercise

recommendations and limitations. In addition to osteoporosis as described above, another common skeletal

condition is arthritis. This comes in 2 main forms; osteoarthritis or rheumatoid arthritis. Osteoarthritis is a

condition where the articular cartilage at a joint has worn away, causing pain, discomfort and swelling.

Rheumatoid arthritis is an autoimmune condition that attacks the synovial features of a joint causing pain

and discomfort.

Postural abnormalities are also a common skeletal condition that occurs in conjunction with imbalances in

the muscular system. Tight muscles will pull on the skeleton, deviating it from its ideal position.

Another common skeletal condition is a ligament sprain. Incorrect loading through a joint can lead to

excessive stress being placed on ligament tissue, resulting in partial or complete tears. This will be painful

and cause joint instability.

If any of these conditions are present within a client a referral should be made to an allied health

professional. In the case of skeletal disorders, referral to a doctor or physiotherapist is likely to be of most

benefit.

The Muscular System There are over 620 muscles within the human body, each contracting to perform a variety of actions across

the skeleton. Movement is the primary function of the muscular system, with muscles causing movement at

the joints they cross. In addition to this, muscles can take on a range of other roles. For example, when

performing an exercise, muscles will be acting to stabalise joints, maintain posture and assist with

movements. They are also responsible for the production of heat. When muscles contract, they breakdown

ATP molecules for energy. One of the by-products of this reaction is the production of heat, hence why

taking part in exercise increases body temperature. This function is important whilst in extremely cold

climates where the automated response of shivering (tiny muscular contractions) is used to maintain core

body temperature.

Types of Muscle There are 3 main types of muscle, each with different features that allow effective performance of their

main functions. These are explained and shown in the diagram below.

• Cardiac Muscle

This is also known as the myocardium and is only found in one part of the body - the heart. The contraction

of this muscle is controlled involuntarily, through the action of the autonomic nervous system. The nervous

system controls the rate and strength of the contraction of the myocardium in response to the demands

being placed on the body.

• Smooth Muscle

This type of muscle lines organs and is also under involuntary control. Examples of its location include

arteries, the small intestine, bladder and uterus. This type of muscle contracts in a smooth and rhythmic

manner. For example, the smooth muscle of the small intestine contracts to move consumed food through

the digestive system to ensure that all digestive and absorption processes can be completed.

• Skeletal Muscle

43

This is the most common type of muscle found within the human body, responsible for the movement of the

skeleton. Generally, this type of muscle is under voluntary control through the central nervous system, except

for muscle twitches and cramps, which occur automatically. There are 4 key features to skeletal muscles.

These include contractibility (the ability to shorten and generate force), extensibility (the ability to stretch),

excitability (the ability to receive and respond to neural stimulation) and elasticity (returning back to

original position/shape).

The Main Skeletal Muscles The diagram below displays the main skeletal muscles from an anterior (A) and posterior (B) view. As a

fitness instructor it is essential that to demonstrate a thorough understanding of the anatomy of the

muscular system, to ensure effective exercise prescription and programming.

(Source: www.humanbodyanatomy.co)

http://www.humanbodyanatomy.co/

44

Skeletal Muscle Structure Each skeletal muscle consists of many thousands of muscle fibres that run along and across the length of a

muscle. Muscle fibres are grouped together in bundles known as a fasciculus. Each individual fibre within this

fasiculus is made up of up to 8000 myofibrils. Myofibrils are further broken down into sarcomeres. These are

considered to be the functional unit of the muscle fibre, with up to 4500 sarcomeres per fibre. It is within this

structure that the muscular contraction takes place. Sarcomeres are comprised of thick protein filaments

known as myosin, and thin protein filaments known as actin. These proteins interact to cause muscular

contraction.

45

Muscle Structure Description

Fascia Thin layer of connective tissue enclosing the

muscle belly.

Tendon

Attaches muscle to bone

Epimysium

Connective tissue that surrounds whole muscle

Muscle Belly

Whole muscle

Perimysium

Connective tissue that surrounds fascicle

Fascicle

Bundle of muscle fibres

Endomysium

Connective tissue that surrounds muscle fibre

Muscle Fibre Bundle of myofibrils

Myofibril Composed of actin and myosin

Arranged in parallel units called sarcomeres

Sarcomere Contractile unit of the muscle

Actin Thin filaments that attach to and form the walls of

the sarcomere

Myosin Thick filament with cross bridges that moves in

shortening and lengthening of a muscle

Muscular Contraction – The Sliding Filament Theory For a muscle to contract, it requires neural stimulation (see nervous system) and energy, in the form of

Adenosine Triphosphate (ATP). This triggers the process of muscular contraction through a range of

physiological processes, culminating in the sliding filament theory. These processes are amongst the most

complex within the field of physiology. It is during this process that the relationship between the muscular

system and nervous system is most apparent. On activation by the nervous system through sensory input,

various complex reactions occur, causing actin and myosin to join through the cross bridges that are present

on the myosin protein (see diagram below). The myosin pulls on the actin, sliding over each other. The

myosin then pulls back and moves on to the next actin molecule where the process is repeated. This process

continues until neural stimulation ceases. During this time, the muscle contracts and shortens, creating force

and pulling on the bone to move the skeleton.

The contraction of a muscle fibre occurs on an ‘all or none’ basis. This means that an individual fibre will

contract maximally, or not at all. If a large force is required, more fibres will be recruited to contract

maximally. If a smaller force is required fewer fibres will be recruited, but all will still contract maximally.

46

Muscle Fibre Types Not all fibres are equal. There are 3 different types of fibre, each with differing characteristics. Each person

has a different proportion of each of the fibre types, influenced primarily by genetics. The 3 fibre types are:

• Type I Fibre (Slow Twitch)

• Type IIa Fibre (Fast Twitch Oxidative)

• Type IIb Fibre (Fast Twitch Glycolytic)

The table below highlights the main characteristics of each fibre type.

47

Fibre Type Characteristics Example Activity

Type 1 • High aerobic capacity

• Low anaerobic capacity

• High fatigue resistance

• Red in appearance

• Large blood supply

• Smaller motor nerve

• Slow contraction speed

• Contraction strength is low

Endurance-based activities

(e.g. distance running,

swimming or cycling)

Type 2a • Medium aerobic capacity

• Medium anaerobic capacity

• Moderate fatigue resistance

• Pink/White in appearance

• Moderate blood supply

• Larger motor nerve

• Faster speed of contraction

• Larger strength of

contraction

Activities that combine aerobic

and anaerobic systems (e.g.

800m, soccer, netball)

Type 2b • Low aerobic capacity

• High anaerobic capacity

• Low fatigue resistance

• White in appearance

• Limited blood supply

• Largest motor unit

• Fastest contraction speed

• Strongest contraction

Power/strength-based activities

(e.g. powerlifting, 100m sprint)

48


As a trainer it is important that you have knowledge of the different muscle fibre types and their features for

a variety of reasons. Firstly, this will allow you to better understand a client’s performance and capabilities

within a given activity. For example, clients with type 2b fibres will adapt and excel in power-based activities

more effectively than they would in aerobic based activities. The opposite could be said for clients with a

high volume of slow twitch muscle fibres. Additionally, understanding the fibres recruited in a given activity

will allow the energy systems that are utilized to be identified. For example, power-based activities that utilize

type 2b fibres will make use of the ATP-PC system. This understanding can allow a trainer to design a

session that focusses on one energy system in particular.

Most muscles contain an even mixture of the three fibre types. The percentage of fibre types can limit the

trainability or sustainability a person may have toward a stimulus. An example of these splits in different

population groups is shown below.

Sport % Slow Twitch Fibres % Fast Twitch Fibres

Distance running 70 -80 % 23- 30 %

Track Sprinters 25-30 % 70-75 %

Weight Lifters 45-55 % 45-55 %

Non-athletes 47-53 % 47-53 %

Functions of Skeletal Muscle Skeletal muscle has 5 main functions:

1. Movement of the Skeleton - Muscle actions pull on tendons to move the bones of the skeleton.

2. Maintain Posture and Body Position - There is constant muscle action to maintain posture and body

position e.g. sitting, reading, standing

3. Support Soft Tissues - The abdominal wall and the floor of the pelvic cavity support the weight of

visceral organs and protect the organs from injury.

4. Guard Entrances and Exits - Specialised arrangements of muscle fibres surround entrances to

various internal organs involved in swallowing, defecation and urination.

5. Maintain Body Temperature - Muscles produce heat through lengthening and shortening which

assists in keeping the body temperature in the normal range for functioning.

49

Role of Skeletal Muscles Skeletal muscles do not function on their own; they function as part of a group, with each muscle in the

group taking on a different role. These roles include:

• Agonist

This is the muscle that is responsible for the movement (known as the prime mover). An example of a

prime mover would be the pectoralis major whilst performing a bench press.

• Synergists

This is the muscle that assists the prime mover, either helping with the movement or stabalising the

joint. Example of synergist muscles include the rotator cuff complex which works to stabalise the

shoulder joint when the humerus is moving.

• Antagonist

This is the muscle that opposes the prime mover (agonist). When the prime mover contracts, the

antagonist relaxes to allow free movement at the joint. This is due to a process known as reciprocal

inhibition. An example of an antagonist muscle would be the triceps during a biceps curl.

• Stabiliser

This is the muscle that stabilises a joint or body-part to allow the movement of the joint to occur. An

example of a stabiliser muscle is the erector spinae maintaining an upright position during a squat.

Stabiliser muscles usually work isometrically.

Understanding the role that a muscle is playing within a movement or exercise is essential so that correct

technique and coaching can be delivered, as well as assisting in exercise selection.

50

Types of Muscular Contraction Skeletal muscles can contract in different ways, depending on the movement at a joint. The contraction type

is categorised by changes in muscle length. The 3 main contraction types are:

• Concentric

This is when the muscle shortens under tension. This is seen during the up phase of an exercise. For example,

in a squat, when extending the hips and knees, there are concentric contractions in the gluteus maximus and

quadriceps.

• Eccentric

This is when the muscle lengthens under tension. This occurs in the down phase of an exercise or

when a resistance is lowered. In the example of the squat, there would be a lengthening of the

quadriceps and gluteus maximus when lowering the body towards the ground.

• Isometric

An isometric contraction occurs when a muscle maintains the same length under tension. This will occur in

exercises such a plank or wall sit where the exercise involves maintaining a static position throughout.

• Isokinetic

An isokinetic contraction occurs when the muscle is moving at a constant rate or speed. This requires an

isokinetic dynamometer instrument, whereby the resistance offered by the instrument is matched by the

force generated by the muscles. This is usually only used in rehabilitation or testing settings.


Knowledge of the different roles that muscles can play within a movement and exercise allows trainers

to accurately analyse the demands of that exercise, allowing informed exercise choices to be made.

An understanding of muscle contraction types can also be beneficial to the trainer as it can be used as a

tool within exercise programming. For example, a client wishing to build strength or power should focus

on the concentric part of the exercise, with those training for hypertrophy focusing on the eccentric

phase of the movement.

Muscle Fibre Arrangement There are 7 different types of muscle fibre arrangement. These different fibre arrangements will allow

the muscle to function optimally in the role that it is designed to perform. Each of the fibre

arrangements are listed and defined below, with specific example of each arrangement outlined in the

diagram.

• Circular – Muscle fibres are arranged in a circular fashion

• Convergent or Radiate – Several fibres radiate from the tendon at the origin and insert along

various borders

51

• Parallel – Long strap-like muscles with fibres running parallel

• Unipennate – Fibres travel along one side of the tendon

• Bipennate – Fibres travel along both sides of the tendon

• Fusiform– Similar to parallel muscles but with spindle shaped muscle bellies

• Multi-pennate – Many fibres and tendons converge into main tendon that is designed for strength

but limited mobility

52

Movement Analysis The prescription of fitness programs relies on an in-depth understanding of muscular activity during the

execution of an exercise. Breaking an exercise down into different joints, the actions at the joints, the

type of contraction occurring, and the active muscles allows the fitness instructor to gain insight into the

mechanics of the movement and understand the impact the selected exercise will have on the body.

Specific Muscle Activity The following tables identify the movement possible at a joint, and the muscles that are responsible for

causing this action.

Shoulder Joint

Muscle Group Muscles Responsible for Movement

Shoulder Joint Flexors Deltoid, Pectoralis Major, Biceps Brachii

Shoulder Joint Extensors Posterior Deltoid, Latissimus Dorsi, Teres Major,

Triceps Brachii, Subscapularis, Teres Minor

Shoulder Joint Abductors Supraspinatus, Deltoid

Shoulder Joint Adductors Pectoralis Major, Latissimus Dorsi, Teres Major,

Triceps Brachii, Subscapularis

Shoulder Joint Horizontal Abductors Deltoid, Infraspinatus, Teres Minor, Latissimus

Dorsi, Teres Major

Shoulder Joint Horizontal Adductors Pectoralis Major, Anterior Deltoid, Biceps Brachii

Shoulder Joint Medial Rotators Pectoralis Major, Latissimus Dorsi, Teres Major,

Subscapularis, Deltoid

Shoulder Joint Lateral Rotators Infraspinatus, Teres Minor, Deltoid

Shoulder Girdle


Shoulder Girdle Retractors Mid Trapezius, Rhomboids

Shoulder Girdle Protractors Pectoralis Minor, Serratus Anterior

Shoulder Girdle Upward Rotators Serratus Anterior, Upper Trapezius

Shoulder Girdle Downward Rotators Pectoralis Minor, Lower Trapezius

Shoulder Girdle Depressors Lower Trapezius

Shoulder Girdle Elevators Levator Scapula, Upper Trapezius, Rhomboids

53

Elbow Joint


Elbow Joint Flexors Biceps Brachii, Brachialis, Brachioradialis,

Pronator Teres

Elbow Joint Extensors Triceps

Hip Joint Muscle Group Muscles Responsible for Movement

Hip Joint Flexors Iliacus, Psoas, Rectus Femoris, Sartorius, Tensor

Fascia Latae, Adductor Longus

Hip Joint Extensors Gluteus Maximus, Biceps Femoris,

Semimembranosus, Semitendinosus

Hip Joint Abductors Gluteus Medius, Gluteus Minimus, Gluteus

Maximus, Tensor Fascia Latae

Hip Joint Adductors Adductors

Hip Joint Medial Rotators Gluteus Minimus, Semitendinosus,

Semimembranosus

Hip Joint Lateral Rotators Gluteus Maximus, Gluteus Medius, Iliacus, Psoas,

Sartorius, Biceps Femoris

Knee Joint


Knee Joint Flexors Semitendinosus, Semimembranosus, Biceps

Femoris, Gastrocnemius, Sartorius

Knee Joint Extensors Rectus Femoris, Vastus Medialis, Vastus

Intermedius, Vastus Lateralis

54

Ankle Joint


Ankle Joint Dorsi Flexors Tibialis Anterior

Ankle Joint Plantar Flexors Gastrocnemius, Soleus

Spine


Spinal Joint Flexors Sternomastoid, Rectus Abdominus, External

Oblique, Internal Oblique

Spinal Joint Extensors Erector Spinae

Spinal Joint Lateral Flexors Quadratus Lumborum, Rectus Abdominus,

Erector Spinae, External Oblique, Internal

Oblique

Spinal Joint Rotators External Oblique, Internal Oblique, Erector

Spinae, Multifidus

Exercise Classification In addition to analysing individual exercises and their joint actions, they can be classified according to

their movement patterns. This is particularly important for the prescription of functional exercise for

clients. The most productive and efficient training philosophy for the general population is one that trains

movements that are seen in everyday activities, not muscles. That said, the prescription of isolation

exercises is not without benefit for specific individuals.

The main movement patterns that functional exercises can be grouped into are push, pull and compound

leg movements. This will be expanded on further in the Exercise Instruction and Programming unit.

The table below summarises the muscle activity seen in these movement patterns.

Movement Pattern Muscles Recruited Example Exercise

Horizontal Push (wide grip) Shoulder Joint Horizontal Adductors

Elbow Joint Extensors

Wide Grip Bench Press

Wide Push Up

Horizontal Push (narrow grip) • Shoulder Joint Flexors

•

• Elbow Joint Extensors

Narrow Grip Bench Press

Narrow Push Up

55

•

Shoulder Girdle Protractors

Vertical Push (wide grip) • Shoulder Joint Abductors

•


•

• Shoulder Girdle Protractors

•

Shoulder Girdle Upward

Wide Grip Barbell Shoulder

Press

Vertical Push (narrow grip) • Shoulder Joint Flexors

•


•

• Shoulder Girdle Protractors

•

Shoulder Girdle Upward

Narrow Grip Shoulder Press

Horizontal Pull (wide grip) • Shoulder Joint Horizontal Abductors

•

Elbow Joint Flexors

Wide Grip Seated Row

Wide Grip Bent Over Barbell

Row

Horizontal Pull (narrow grip) • Shoulder Joint Extensors

•

• Elbow Joint Flexors

•

Shoulder Girdle Retractors

Narrow Grip Seated Row

Narrow Grip Bent Over Barbell

Row

Dumbbell One Arm Row

Vertical Pull (wide grip) • Shoulder Joint Adductors

•

• Elbow Joint Flexors

•

Shoulder Girdle Downward

Rotators

Wide Grip Lat Pulldown

Wide Grip Pull-Up

Vertical Pull (narrow grip) • Shoulder Joint Seated Row

56

Extensors

•

Elbow Joint Flexors

Shoulder Girdle Downward

Rotators

Narrow Grip Pull Up

Legs Hip Joint Extensors

Knee Joint Extensors

Ankle Joint Plantar Flexors

Squat

Deadlift

Lunge

Leg Press


Identifying the muscles that cause movement within an exercise is an essential skill for a trainer to

develop. This will allow the trainer to plan an exercise program that is well balanced, targeting the

movements of primary importance for that client.

It will also allow the trainer to provide accurate advice to the client on the muscles that are

recruited during their training session.

Posture The interaction between the skeletal and muscular system controls our posture. Posture refers to the

alignment of different parts of the body. The body has a natural shape and curves that may vary slightly,

depending on genetics and lifestyle habits. An understanding of ‘ideal’ posture, variances from this ideal

and how to correct postural variances is essential for a fitness instructor to ensure the prescription and

delivery of appropriate and safe exercises.

Ideal Posture In order to identify postural variances, the instructor first needs to establish a norm to which a comparison

can be made. Ideal posture is largely influenced by the position of the spine. A common term or reference

point that is used in the fitness industry when providing exercise instruction is ‘neutral spine’. This refers to

the ideal or natural alignment of the different sections of the spine. It is essential that this is maintained

throughout exercise performance as it is in this position that the spine is most effective at bearing weight.

Key observational points when determining posture should relate to the alignment of the ear, shoulder, hip,

knee and ankle from a lateral view. Ideally, a vertical line should dissect through each of these points. The

spine should display a natural curve of lordosis at the cervical spine and lumbar spine, with a kyphotic curve

in the thoracic spine. From an anterior and posterior view, the head should remain forwards, in a neutral

position without rotation or lateral flexion. Shoulders should be level, with arms hanging straight by the

sides. Similarly, the pelvis and knees should be level, in a neutral position, with the feet parallel to each

other. Maintaining this ideal posture as much as possible is essential to prevent the development of

injuries, particularly during exercise.

57

Postural Variances Many postural variances exist between individuals. The causes of these variances are determined by

genetics, lifestyle habits and muscular imbalances, with either tightness or weakness causing the skeleton

to drift from the ideal described above. These imbalances are often as a result of lifestyle habits such as

sitting slouched at a desk, or weight bearing through one leg for a prolonged period. Most common

postural deviations originate in the spine. These deviations are described below.

Scoliosis Scoliosis is an abnormal sideways curvature of the spine. This can occur due to genetics or commonly in

individuals that participate in activities that place an emphasis on one side of the body or regular rotation,

such as racket sports. These activities cause increase tightness and strength on one side of the body, with

weakness on the opposing side of the body.

58

Kyphosis This refers to an exaggerated kyphotic curve in the thoracic spine. This is commonly caused by tightness

through the pectorals and anterior deltoid, with weakness in the rhomboids, middle and lower trapezius

and posterior deltoids. This will give the shoulders a more rounded appearance, with a humped back. This

can be impacted upon positively by stretching the tight muscles and strengthening the weak ones.

Lordosis Lordosis refers to an exaggerated lordotic curve in the lumbar spine and cervical spine. It is caused by

tightness in the lower back and hip flexors, with weak and stretched abdominals and glutes. This can be

impacted upon positively by stretching the tight muscles and strengthening the weak ones.

59


The recognition of postural variances will allow the trainer to design a program that can correct the

deviations through strengthening of weak areas, and stretching of tight areas as identified in each of the

examples above. This will impact upon the client by potentially improving exercise technique and

functionality, whilst reducing the chance of injury.

Disorders of the Muscular System As a fitness instructor, it is essential to recognise that there are various disorders that can impact upon

the muscular system. These conditions result in different exercise recommendations and limitations.

The most common is known as Delayed Onset Muscle Soreness (DOMS). This is muscle pain, soreness or

muscle stiffness that occurs in the day or two after exercise. This is a normal response to unusual exertion

and is part of an adaptation process that leads to greater endurance and strength as the muscles recover

and build.

Another common muscular system disorder is a muscle strain. This occurs as a result of overstretching or

the placement of large loads beyond tissue capabilities can lead to partial or full muscle tears. This will

lead to decreased ROM, pain, swelling and bruising.

Another condition of the muscular system is Muscular Dystrophy. This is a genetic condition which causes

a decrease in muscle mass and strength with time.

Appropriate allied health professional referrals in the case of these conditions may be a doctor,

physiotherapist, occupational therapist or massage therapist.

The Nervous System The nervous system is considered the control centre of the body, with the ability to communicate with a

range of tissues and organs at incredible speeds. In order to communicate required responses, the

nervous system is involved in three main steps:

1. Receiving sensory information from internal and external sources. An example of an internal

source may be changes in the levels of gases in the blood, with an external source being

something that an individual as touched, seen or heard.

2. Interpreting and processing the sensory information. At this stage, the brain computes the

sensory information that it has received and decides on a course of action.

3. Delivering a motor output which will elicit a response in the appropriate area of the body. In the

case of exercise, this action relates to muscle recruitment.

Divisions of the Nervous System The central nervous system (CNS) is the focal point of all nervous system activity. It is comprised of the

brain and spinal cord, with all nerves branching out from these structures. These branches are known as

the peripheral nervous system (PNS), leading to all organs and tissues. The PNS is branches into sensory

60

and motor divisions. The sensory division is responsible for step 2 highlighted above, with the motor

division responsible for step 3.

The motor division of the peripheral nervous system has 2 further branches - the somatic nervous system

and the autonomic nervous system (ANS). The somatic branch is responsible for voluntary actions,

primarily skeletal muscle contraction, with the autonomic nervous system responsible for all automated

responses, such as heart rate, breathing rate and digestion. There are 2 further branches of the autonomic

nervous system; the sympathetic nervous system and the parasympathetic nervous system. The

sympathetic division is responsible for fight or flight responses such as an increased heart rate or breathing

rate. The parasympathetic nervous system is responsible for controlling rest and digest actions such as

slowing the heart rate or promoting digestion. These divisions are shown in the diagram below.

Nervous

System

CNS PNS

Brain Spinal Cord

Sensory

Division

Motor

Division

Somatic

Nervous

System

Autonomic

Nervous

System

Sympathetic

Para-

sympathetic

61

Nerve Cells Nerve cells are more commonly referred to as neurons. These are the functional units of the nervous

system. There are two main types of neurons - sensory (afferent) and motor (efferent). Sensory neurons

detect signals internal or external to the body, sending this information to the CNS for processing. The

motor neurons are then responsible for delivering and transmitting neural impulses to the appropriate

organs or tissues to trigger the required response, whether that is a muscular contraction, chemical release

or increased organ activity.

Neuron Structure Neurons have many key features that permit the fast delivery of neural impulses to the appropriate part of

the body. Each neuron has a cell body that houses the nucleus and associated organelles (mitochondria

etc.). Neurons also have a fibre leading from the cell that is known as an axon. This axon is surrounded by a

myelin sheath, which insulates the nerve giving faster neural transmission. The axon will eventually lead to

a synapse, which is where the neural impulse is transferred either to another neuron or an organ or tissue.

The transfer of this impulse is caused by a neurotransmitter, activating the receptor site, triggering the

appropriate actions within the cell.

Muscle Innervation For muscular contraction to occur, sensory input needs to be sent to the CNS. The CNS will compute this

sensory input, sending an electrical impulse to the required motor neurons, which then travels towards the

required muscle fibres. The innervated fibres plus the neuron are collectively known as a motor unit.

On arriving at the muscle fibre, the nerve impulse is transferred from the nervous system to the muscular

system at the neuromuscular junction. The nerve impulse causes the release of a neurotransmitter

(acetylcholine), which starts the process of muscular contraction through the sliding filament theory. Each

motor unit will contract fully, or not at all. If a larger contraction is needed, more neural impulses are sent,

activating more motor units. If smaller, more precise movements are required, less neural impulses are

fired, recruiting fewer motor units. The structures that comprise a motor unit are shown in the diagram

below:

62


The nervous system has a link with all other systems listed in this chapter. It is of importance to fully

understand the functioning of the muscular system. It will also allow trainers to explain adaptations to an

exercise program. For example, improvements in strength are due to the ability to recruit more muscle fibres

at a faster rate.

63

Sensory Receptors The nervous system has a variety of sensory receptors, each with a unique function. These functions are

wide ranging, with a focus on maintaining homeostasis within the body. Some common examples are

described below.

Muscle Spindle Organs These structures are a form of proprioceptors, responsible for causing a stretch reflex, with the intention of

preventing injury. These spindles are located within the belly of a muscle (see centre of diagram below).

When a stretch (see right hand side of diagram) is felt in these receptors that exceeds its comfortable level,

a message is sent to the CNS to cause this stretched muscle to contract. This prevents overstretching and

potential muscle damage. This reaction is a vital component of determining flexibility. In those that have

greater flexibility, this reflex will act at a later point in the stretch. In those with poorer flexibility, the stretch

reflex will become active much sooner.

(Source: http://www.bandhayoga.com/keys_fire.html)

http://www.bandhayoga.com/keys_%EF%AC%81re.html

64

Golgi Tendon Organs Another proprioceptive structure found between muscles and tendons are golgi tendon organs. These

structures also detect a stretch and change in muscle tension. This receptor is active when a muscle

stretches passively, causing the muscle to relax. This action is particularly important in flexibility training,

allowing a larger range of motion to be achieved.

Chemoreceptors Chemoreceptors detect changes in chemical levels within the blood. These chemicals may have an impact

on the pH of the body. The body works optimally at a neutral pH and therefore any shift from this can lead

to a decreased efficiency in a variety of processes. On detecting this shift in pH, chemoreceptors will

trigger a response to counteract this. For example, in exercise, hydrogen ions build up, lowering the pH of

the body. Chemoreceptors send a signal to the CNS to increase the rate and depth of breathing, allowing

the pH to increase and homeostasis to be achieved.

65

The Reflex Arc The reflex arc describes the process of the control of a reflex action. An example of this is the knee jerk

reaction. In this instance, the sensory input will not travel directly to the brain, but will instead be

processed in the spinal cord. This prevents the delay of the sensory input travelling all the way to the brain,

allowing a quicker and almost instant reaction. This is important in situations that may otherwise cause

injury, such as the example shown below. That said, the brain will still receive the sensory input whilst the

reflex action is occurring.


Knowledge of the structure and functions of the sensory receptors will allow the trainer to better explain the

response of the body to all forms of exercise. For example, during flexibility training, muscle spindle organs

will initially be active in the stretch until it is held for a prolonged period. This will then lead to activity of the

golgi tendon organ, relaxing the muscle and in turn allowing a greater stretch. This is an example of how the

application of this knowledge can result in safer and more effective exercise delivery.

Disorders of the Nervous System As a fitness instructor, it is essential to recognise that there are various disorders that can impact upon any

part of the nervous system. These conditions result in different exercise recommendations and limitations.

Epilepsy is a brain disorder which results in the production and transmission of abnormal electrical activity,

leading to seizures. This can have an obvious impact on exercise if not controlled through medication.

Although a stroke is considered a cardiovascular disorder, the impact that it has on the nervous system can

be significant due to brain tissue damage. The amount of damage depends on the area affected and the

duration for which blood supply is limited. In some cases, the signs and symptoms can result in significant

loss of movement function. Dementia is another condition of the nervous system caused by the

destruction of brain cells, making communication, learning and remembering more challenging. Trainers

should consider their coaching and exercise selection for these clients.

In the presence of any of the above conditions, referral to allied health professionals may include a doctor,

physiotherapist, massage therapist or occupational therapist.

66

The Cardiovascular System The cardiovascular system is one of the main transport systems within the body, allowing nutrients, chemicals

and gases to delivered and removed throughout the body. The cardiovascular system comprises of the heart,

blood and blood vessels.

The Heart This is the central point of the cardiovascular system. It is made up of cardiac muscle tissue, giving it the

essential feature of involuntary contraction. Its main function is to contract to pump blood effectively

around the body. In order to do this, the heart will contract on average 72 times per minute in males, and

approximately 80 times per minute in females, although this can vary significantly based on factors such as

lifestyle, training history and diet.

The heart is split into the right and left side through a muscular wall known as the septum, with 2 chambers

in each half. The chambers are known as atria and ventricles, with one of each located on each side of the

heart. There are valves between each of the chambers and on the exit from the ventricles to prevent back

flow of blood. In the right side of the heart, between the right atrium and right ventricle, there is the

tricuspid valve, with the pulmonary valve found on the exit from the right ventricle. In the left side,

between the atrium and ventricle there is the bicuspid or mitral valve, with the aortic valve found on exit

from the left ventricle. The heart collects blood through a series of veins, leading to larger veins known as

the inferior and superior vena cava. These deliver deoxygenated blood into the right side of the heart. This

deoxygenated blood will travel through the chambers of the right side of the heart, leaving through the

pulmonary artery towards the lungs. This blood will become oxygenated, returning to the left side of the

heart through the pulmonary vein. It will then leave the heart through the aorta, through contraction of the

left ventricle. This oxygenated blood will then travel to the tissues that have a demand for it. This process is

repeated every time the heart contracts.

The heart itself requires a large supply of oxygenated blood in order to contract repeatedly. This is supplied

through structures known as coronary arteries, which branch of from the aorta and feed into the cardiac

muscle.

67

Circulation through the Heart In addition to knowledge of the anatomy of the heart, it is also of benefit to understand the pathway that

blood takes through the heart and other cardiovascular structures. The table below summaries the

journey of blood around the body, starting with deoxygenated blood returning to the heart. This pathway

is also highlighted in the diagram below. Blue text represents deoxygenated blood, with red text

representing oxygenated blood.

1. Inferior and superior vena cava

2. Right atrium

3. Tricuspid valve

4. Right ventricle

5. Pulmonary valve

6. Pulmonary artery

7. Lungs (gas exchange occurs)

8. Pulmonary vein

9. Left atrium

10. Bicuspid valve

11. Left ventricle

12. Aortic valve

13. Aorta

14. Organs/Tissues/Cells (gas exchange occurs)

68

On leaving the heart, blood travels in a network of vessels that branch all over the body. Arteries are

responsible for transporting oxygen away from the heart, with veins returning blood to the heart. Arteries

have thicker, more muscular walls than veins, with greater elasticity. These are all important features to

ensure that arteries can cope with the higher blood pressure that they are exposed to. Blood will travel at a

much lower pressure in veins, and as a result veins contain valves, which prevent the back flow of blood.

All arteries branch from the aorta. These branches will decrease in size as the distance from the aorta

increases, eventually leading to tiny arterioles. These arterioles are found around tissues and organs, linking

with capillaries, where gas exchange takes place. These capillaries then join to venules (small veins), which

then join larger veins, feeding back in to the vena cava and the right side of the heart.

There are three main structures of blood vessels; arteries, veins and capillaries. The anatomical features and

physiological functions of each of these structures is highlighted below.

Artery Arteries are responsible for transporting blood away from the heart. This will generally be oxygenated blood,

with the exception of the pulmonary artery, in which deoxygenated blood is being transported to the lungs to

deposit carbon dioxide and gather oxygen. Arteries generally have thicker muscular walls than other vessels,

69

allowing them to cope with the higher blood pressures that are initiated by contraction of the heart. As the

distance increase from the heart, the arteries become smaller, eventually leading to arterioles.

Vein Veins are large vessels that transport blood back towards the heart. This will generally be deoxygenated

blood, except for the pulmonary vein, in which oxygenated blood is being transported to the heart to be

distributed around the body. Veins have thinner walls than arteries due to the lower pressure at which the

blood travels at within them. Due to this lower pressure, valves are present to prevent the backflow of

blood. As with arteries, the size of veins will decrease with greater distance from the heart. Eventually,

veins will branch off into smaller venules.

Capillary Capillaries are small, single cell walled vessels. These walls are very thin, allowing easier transportation of

gasses into and out of the cell. Capillaries will surround organs and tissues, facilitating the delivery of

nutrients and removal of waste.

The key structural features of each of the vessels are highlighted in the diagram below.

70

The diagram below demonstrates how capillaries are grouped together to form networks around organs and

tissues.

Blood will flow through the vascular system at different pressures, depending on the distance from the

heart, and the direction in which it is traveling (to or from the heart). On leaving the heart through the

aorta, the blood will be exerting a high pressure on the artery walls. The blood will then arrive at capillary

networks, where gas exchange will take place. Deoxygenated blood will then gather in venules and veins to

be returned to the heart. The blood will flow through veins at a much lower pressure than in arteries. This

low venous pressure is barely adequate to drive the blood back to the heart, particularly from the lower

body. As such, other mechanisms are required to assist with this process.

• Skeletal Muscle Pump

Veins will pass through and between skeletal muscles. On contraction, the muscle will squeeze the vein, and

in turn increasing the pressure in that part of the vein. This increase in pressure causes the valve closest to

the heart to open, and the valve furthest away to close. Repetitive contraction of skeletal muscle in the legs

during activities such as walking will prevent venous pooling. An example of this is shown in the diagram

below.

71

• Sympathetic Nervous System

Veins are innervated by sympathetic motor neurons. Input from these neurons causes the veins to

vasoconstrict and therefore increases the pressure at which blood is traveling. There will be heightened

activity of these neurons at times when there is a greater demand for waste removal such as during exercise.

• Respiratory Pump

The process of breathing help to drive venous blood out of the abdominal cavity, primarily through the action

of the diaphragm. As air is inspired, the diaphragm descends and increase abdominal pressure. This

increasing pressure squeezes the veins and moves the blood back towards the heart.

72

Blood Blood is considered a connective tissue that is found within the blood vessels and heart. It serves a multitude

of functions within the human body. These functions can be broadly divided into three main areas, as listed

below.

• Distributes nutrients, oxygen, and hormones to the body’s cells

• Carries metabolic waste to the kidneys and lungs for excretion

• Transports specialised cells that defend peripheral tissues from infection & disease

Blood is comprised of four main components; plasma, red blood cells (erythrocytes), white blood cells

(leukocytes) and platelets. Each of these components has a different role to play, as described below.

• Plasma

Plasma provides the liquid component of blood, contributing to roughly 55% of total blood volume. The fluid

itself has a yellow colour that is primarily made up of 90% water. It also contains nutrients, electrolytes,

organic waste, proteins, and hormones.

• Red Blood Cells (Erythrocytes)

These cells are a biconcave disc shape (as shown below), with the primary role of transporting gasses around

the body. These cells are manufactured within bone marrow. This production process is continuous, with

new red blood cells constantly created to replace worn out or dead cells. The average lifespan for a red blood

cell is around 120 days. Furthermore, certain forms of exercise can stimulate increased red blood cell

production. Importantly, red blood cells contain haemoglobin (as shown below), providing a ‘carrier’ for gases

that are to be delivered around the body.

• White Blood Cells (Leukocytes)

White blood cells are considered the mobile units of the body’s defence system. Whilst they are a component

of blood, they conduct their primary function of fighting infection outside of blood, within various tissues of

the body. There are five different types of white blood cells, each with a characteristic structure and common

function of helping to defend the body against foreign microbial infections. The production of white blood

cells occurs at varying rates depending on the changing defence needs of the body.

• Platelets

Platelets are small cell fragments that work with plasma to arrest bleeding from a broken vessel. They can also

assist in in tissue repair through blood constriction, platelet plugs and blood clotting.

73

Cardiovascular Terminology Blood Pressure Blood pressure refers to the pressure created by blood on the walls of blood vessels of the body. Each blood

vessel has its own blood pressure value, influenced by its position relative to the heart (as shown in the

figure below), physical activity level, diet and the prevalence of any cardiovascular disease. The pressure in

the systemic blood vessels falls continuously from the aorta until the blood re-enters the heart in the right

atrium. The systolic pressure represents the force with which the heart is ejecting blood from the ventricles

each time it contracts. The higher the pressure, the harder the heart is having to work. Diastolic pressure is

the pressure when the heart is in between contractions, at which time the ventricles fill. Even when the

heart is not contracting, there is still pressure in the vascular system since it is a closed system. Normal

blood pressure is 120/80mm Hg.

74

The terminology listed below is commonly used to describe the actions of the heart. An understanding of

these terms is essential to the fitness trainer to fully comprehend exercise responses and adaptations.

• Stroke Volume

This is the amount of blood that exits the heart in one contraction. This is estimated to be 1ml per kilogram

of bodyweight at rest. This can however vary significantly in the trained population.

• Heart Rate

This is the number of times that the heart contracts in one minute. Norm values are 60-80bpm, with gender

and fitness levels creating variance.

• Cardiac Output

This is calculated by multiplying stroke volume by heart rate, giving the total volume of blood that leaves the

heart in 1 minute. This is on average 5 litres at rest but can rise as high as 40 litres in elite athletes during

intense exercise to meet the increased oxygen demand that the contraction of skeletal muscle brings.


Heart rate and stroke volume can change in response to training, resulting in an altered cardiac output.

For example, aerobic-based training can lead to an increase in size of the left ventricle. This allows more

blood to collect in this chamber prior to contraction, giving a larger stroke volume. This larger stroke

volume means that the heart will need to contract less frequently at a given exercise intensity to meet the

demand for oxygen. This helps to explain why endurance athletes can have a much lower resting heart

rate. Exercise can also cause the heart muscle to increase in size (cardiac hypertrophy). A larger heart

muscle can provide a stronger contraction, which will give a higher stroke volume.

During exercise, blood pressure will increase to assist in meeting oxygen demands. This however it is not a

lasting effect and can in fact lower resting blood pressure in the long term. This occurs due to

vasodilation, the widening of the arteries. During exercise, this will occur to allow more blood to flow to

the working muscles. If this is repeated over a prolonged training program, vasodilation can be a chronic

adaptation, lowering the pressure placed on artery walls at rest.

Blood will be redirected to working muscles, away from areas where it is not required such as the kidneys

or digestive system. This occurs through widening the arteries where greater blood flow is required

(vasodilation) and a narrowing of arteries where less is required (vasoconstriction). Blood flow will also be

redirected to the skin to assist in thermoregulation.

75

Disorders of the Cardiovascular System As a fitness instructor, it is essential to recognise that there are various disorders that can impact upon the

cardiovascular system. These conditions result in different exercise recommendations and limitations.

Coronary heart disease is one of the most common conditions that a fitness trainer is likely to encounter.

This occurs when the coronary arteries that supply the cardiac muscle with blood become partially or fully

blocked, potentially resulting in a more serious cardiac event such as a stroke or heart attack.

Cardiomyopathy is a disease of the heart muscle where the function of cardiac muscle cells decreases,

increasing the potential of irregular heartbeats or serious cardiac events.

Atherosclerosis is a term is assigned to several diseases that impact on the health of the blood vessels. This

can manifest itself in high blood pressure or more severe cardiac events.

In the case of cardiovascular conditions, the most appropriate referral would be to a doctor, who could

prescribe medication and exercise recommendations for each client.

The Respiratory System The respiratory system works directly with the cardiovascular system to transport gases in and out of the

body. Oxygen is taken from the air through ventilation (breathing) and delivered to the blood through this

system. The interaction with the cardiovascular system allows a transfer of this gas to the blood so that it

can be delivered to the required tissues. In conjunction with this, carbon dioxide is removed from the

body.

Respiratory System Structures The structures of the respiratory system are regularly referred to as the respiratory tree (shown below) as

they branch off from each other. The system starts in the nose and mouth where air can enter the system.

From here, the air passes through a series of airways. This starts with the pharynx and larynx positioned in

the throat. From here, the air passes through the trachea which branches into bronchi for the right and

left lung. These branches continue to get smaller, until reaching air sacs within the lungs, known as alveoli.

It is within this structure that gas exchange occurs.

76

The table below provides further detail on each of the key structures and the role that they play within the

respiration process.

Structure Key Features and Role

Nasal

Cavity

Filters, humidifies and moistens the air before it enters the lungs.

Pharynx The nose, mouth & throat connect to each other by this chamber A common

passageway for both air and food - two tubes lead off from the pharynx (trachea

and oesophagus). When swallowing, the trachea is closed off by the glottis (see

figure below).

Larynx Also known as the voice box. Sits below the pharynx. Has vocal folds that produce many different sounds of speech. When swallowing, the larynx rises to bend the epiglottis over the glottis and the vocal

folds close of the entrance to the trachea.

Trachea Tough, flexible tube or “windpipe” Made up of cartilage rings that are “c” shaped.

Lungs Right and left with left being smaller due to positioning of heart (see figure below).

Contains bronchioles, alveoli, pulmonary blood vessels and large quantities of elastic connective tissue.

Shaped like a blunt cone with a tip pointing superiorly and base inferiorly. Enclosed in a double layered membrane called the pleural sac. Inside the cavity formed

by the double wall is pleural fluid which lubricates the membrane and allows lungs to

expand and contract.

Bronchi &

Bronchioles

The right and left bronchi are divisions of the trachea and enter the right and left lungs respectively. They continue to branch into narrower, shorter and more numerous airways called the

bronchioles - like the branches on a tree. Clustered at the ends of the bronchioles are the

alveoli - the tiny air sacs where gas exchange between air and blood takes place.

Alveoli Alveoli are small, thin-walled, inflatable air sacs encircled by a covering of pulmonary capillaries. Single cell thick to allow diffusion of gases - oxygen and carbon dioxide. Estimated to be over 600 million alveoli in average pair of lungs.

77

The Mechanics of Breathing Breathing has two phases, inspiration (breathing in) and expiration (breathing out). Gases will move from an

area of high pressure to an area of low pressure. This means that for air to enter the respiratory system, the

air pressure must be higher outside the body than inside, and vice versa for air to leave. These pressure

gradients are achieved by the lungs changing in shape and size, along with the assistance of respiratory

muscles such as the diaphragm (see diagrams below) and intercostal muscles between the ribs. During

inspiration, the diaphragm moves down, with the intercostal muscles contracting to lift the ribs up and out.

This increases the thoracic volume, lowering the internal pressure, causing air to rush into the respiratory

system.

For expiration, the stretch recoil of the lungs and return of the diaphragm to its original position provides

enough force to expel air from the lungs whilst at rest. During exercise however, more forceful expiration is

needed. In order to produce this force, the intercostal muscles contract, pulling the ribs downwards,

increasing the internal pressure, forcing air outwards.

78

Respiratory Volumes The volume of air that enters and exits the lungs varies for everyone depending on their lifestyle, exercise

habits, physical size and fitness levels. Tidal volume is the amount of air that enters or exits the lungs in one

breath. At rest, the average for an adult is 500ml. Total lung capacity is the term used to describe the

amount of air in the lungs after maximal inspiration, around 5 litres in the general adult population. On

breathing out, not all air is expired to prevent the lungs from collapsing. The air left in the lungs after

expiration is known as the residual volume. The amount of air that can be breathed in and out in one breath

is known as vital capacity. The amount of air that enters and exits the lungs in one minute is known as the

respiratory minute volume.

Gas Exchange Gas exchange occurs between the lungs and blood, as well as the blood and tissues. Gas exchange in the

lungs takes place in the alveoli, due to concentration differences. Oxygen will move from an area of high

concentration in the alveoli, to an area of low concentration in the blood. Carbon dioxide will move in the

opposite direction from an area of high concentration in the blood, to an area of low concentration in the

alveoli. From here, the now oxygenated blood will return to the heart to be distributed to the required

tissues.

A similar process will occur at respiring organs and tissues where oxygen from the blood will enter the

cells, with carbon dioxide moving in the opposite direction. The carbon dioxide rich blood will then return

to the heart to be pumped to the lungs to be expelled. This process is repeated with every breath.

In response to the increased demand for oxygen and waste removal during exercise, the following acute

changes will occur within the respiratory system. Firstly, whilst exercising, breathing with become both

deeper (increased tidal volume) and faster. These changes will in turn lead to an increase in minute

79

ventilation. Furthermore, the rate of gas exchange at both the alveoli and respiring tissues will increase,

due to the need for increased oxygen consumption.


As a trainer, it is important that you can recognize how the functioning of this system alters during

exercise performance. In response to the increased demand for oxygen and waste removal during

exercise, the following acute changes will occur within the respiratory system. Firstly, whilst exercising,

breathing with become both deeper (increased tidal volume) and faster. These changes will in turn lead

to an increase in minute ventilation. Furthermore, the rate of gas exchange at both the alveoli and

respiring tissues will increase, due to the need for increased oxygen consumption.

Disorders of the Respiratory System As a fitness instructor, it is essential to recognize that there are various disorders that can impact upon

any part of the respiratory system. These conditions result in different exercise recommendations and

limitations.

One of the most common respiratory conditions is Asthma. This is an inflammatory condition causing

airway obstruction and bronchospasm. This can make exercise extremely difficult in colder, drier climates.

Chronic Obstructive Pulmonary Disease is another condition of the respiratory system which can impact

on exercise performance. This disease causes the narrowing of the airways, resulting in shortness of

breath, particularly during exercise.

In the presence of a respiratory condition, it is recommended that a referral is made to a doctor to insure

adequate management of the condition.

80

The Lymphatic System The lymphatic system works closely with the cardiovascular system, forming the basis of the immune

system. The lymphatic system is a series of tubes including vessels and nodes that cleanse lymph fluid,

which collects all infections, bacteria and viruses that enter the body. The lymph fluid transports bacteria,

infections and any harmful substance to the nodes where it is cleansed. On completion of cleansing, the

fluid is secreted back into the cardiovascular system for removal. The main glands and lymphatic organs

are displayed in the diagram below.

(Source: https://www.lymphcareusa.com/professional/lymph-a-what/what-is-lymphedema/lymphatic-system.html)

The key features of the key lymphatic structures are described below.

• Lymph

Lymph is a clear fluid that flows in lymphatic vessels, containing millions of white blood cells. It may also

carry the dead bacteria from infections that have recently been fought. There will also be various protein

molecules that cannot be transported by the cardiovascular system, as well as fat molecules. In some ways

like blood, although it contains no red blood cells. The positioning of the lymphatic system relative to blood

vessels is shown in figure 40 below.

• Lymph vessels

Lymph vessels are thin-walled structures containing valves that carry lymph. They have a cross-section like

blood vessels but are much more permeable. Lymph vessels with gather waste and empty into the

lymphatic ducts that drain into the subclavian vein.

https://www.lymphcareusa.com/professional/lymph-a-what/what-is-lymphedema/lymphatic-system.html

https://www.lymphcareusa.com/professional/lymph-a-what/what-is-lymphedema/lymphatic-system.html

81

• Lymphocytes

There is a type of white blood cell responsible for fighting infections. They come in three main forms; T cells,

B cells and natural killer cells.

• Lymph nodes

Lymph nodes are small bean shaped nodules that appear along the course of the lymphatic vessels. They are

full of lymphocytes and macrophages, which are held in place by a matrix of connective tissue and function to

filter pathogens from the lymph, provide lymphocytes for the blood, and produce antibodies.

82

Energy Systems The consumption of food is essential to provide the body with energy not only for exercise, but also the

processes of daily living. This food can be processed through a variety of systems to build Adenosine

Triphosphate (ATP), the energy currency of the human body. This molecule is then broken down to release

energy. ATP is comprised of one adenosine molecule and three phosphate molecules.

The breaking of the bonds in an ATP molecule releases the energy that the body needs for all processes.

When this occurs, a phosphate molecule is released from the ATP structure, giving Adenosine Diphosphate

(ADP). There is enough ATP stored within a muscle to provide energy for only 3 seconds. After this supply is

exhausted, the resulting ADP molecule needs to be rebuilt into an ATP molecule. The processing of the

nutrients carbohydrates, fats and protein will facilitate this through one of three energy systems; the

phosphocreatine system/ATP-PC system, the lactic acid system/anaerobic glycolysis and the aerobic

system/aerobic respiration.

The ATP-PC System On depletion of stored ATP in the muscle, the ATP-PC system will be the first system utilised to resynthesise

ATP. This will make use of phosphocreatine (PC), also known as creatine phosphate (CP), stored within

skeletal muscle, to rebuild the ATP molecule. This molecule has a large amount of energy in the bonds

between the creatine and phosphate, which on breaking provide the energy for ATP to be rebuilt. This

system provides energy very quickly and is primarily used when there is insufficient time to break down

stored glycogen. However, supplies of phosphocreatine are very limited within the muscle and as such can

only provide enough energy for up to 10-15 seconds. A major positive of this system over others is that

there are no fatiguing by-products.

A common method used for enhancing this system is the supplementation of creatine. The theory behind

this is that resting level of creatine within muscle cells increases, which can maximize the time that this

system is used for.

The Lactic Acid System On depletion of stored phosphocreatine, the lactic acid system will take over energy production. This occurs

in the cytoplasm of the cell, where carbohydrate in the form of either glucose (in the bloodstream) or

glycogen (stored form in muscle and liver) is broken down without the presence of oxygen to resynthesise

ATP. If blood glucose cannot meet the demand for energy, then glycogen will be utilized. This process is

more complex than the ATP-PC system and as a result takes longer to produce energy. Furthermore, this

system produces fatiguing by-products in the form of lactic acid due to the lack of oxygen. This system is

primarily used in high intensity exercise lasting up to 120 seconds, although training status can impact on

this duration significantly. If exercise intensity is maintained at a high level, lactate will build up the muscle,

causing a burning sensation. This will eventually lead to the client needing to either stop exercising or adjust

the intensity, to allow lactate to be processed. Nutrition can also play an important role in this system, with

diet influencing blood glucose and stored glycogen levels, the energy sources for this system.

83

The Aerobic System The aerobic system utilises oxygen to produce energy within the mitochondria of the cell. This system can

produce the largest amount of ATP, but due to the complexity of the processes, it is the least efficient in

terms of time taken. At rest, fat is the preferred fuel source, with carbohydrates being preferred as

exercise intensity increases. Fats will also be utilized when carbohydrate stores have become depleted. In

general, the human body has enough carbohydrate stores in the muscle and liver to supply up to 90

minutes of aerobic exercise at an intensity of 50-75% maximum heart rate in activities such as endurance

running or cycling, after which a shift to fats as a fuel source will be seen. This shift will see a decrease in

performance level as the production of energy from fats is a more complex process. Carbon dioxide and

water are the waste products of this system, both of which are non-fatiguing and can be expelled from the

body through breathing, sweating and urination.

The 3 systems are summarised in the table below.

Energy

System

Aerobic or

Anaerobic

Fuel Source Time to

Exhaustion

Fatiguing By-

Products

Example

Activity

ATP-PC Anaerobic Phosphocreatine 10-15 secs None Powerlifting

100m

Lactic Acid Anaerobic Glucose or

Glycogen

120 secs Lactic Acid 800m sprint, 100m

Aerobic Aerobic Carbohydrates,

Fats or Protein

+120 secs None Long distance

run or cycle

The Energy System Continuum The above three energy systems work on a continuum. Whilst a training session may be targeted at

improving a specific system, any session or activity will see a client move in and out of the three systems.

For example, a client undertaking a body weight circuit targeting the lactic acid system with 10 stations

would initially utilize the ATP-PC system to fuel immediate changes in activity levels. This would be followed

by the use of the lactic acid system as they work through each station. During recovery between stations,

they are likely to shift into the aerobic system, processing the lactic acid.

84

The Endocrine System The endocrine system works closely with the nervous system to trigger responses in organs and tissues

within the body. The system is made up of a series of glands throughout the body that release hormones

and chemicals that impact on many processes within the body. These hormones can be carrying messages

around the body, much in the same way as the nervous system, albeit at a much slower pace. Whilst

nerve signals are carried electrically, the endocrine system delivers chemical messages.

The Glands of the Endocrine System

• Pituitary Gland

This gland is found inside the brain. Its role and responsibility is to oversee the activity of other glands to

ensure hormonal balance. It can stimulate the production of other hormones and has a direct link to the

nervous system in the hypothalamus. It impacts upon growth, blood pressure and kidney activity.

• Thyroid Gland

This gland is located inside the throat. It releases hormones that impact upon metabolic rate.

• Parathyroid Gland

The parathyroid gland is located next to the thyroid gland. Its primary responsibility is to control calcium

levels within the bloodstream.

• Adrenal Glands

These glands are slightly superior to each kidney. They are responsible for the release of stress hormones,

including adrenaline and cortisol. These hormones are released in response to a stressful situation, acting

upon blood pressure, immune function, pain sensitivity, increased energy production and blood glucose

levels.

• Pancreas

This gland is found in the abdomen, with the responsibility of releasing hormones insulin and glucagon,

which control blood glucose levels.

• Testes & Ovaries

These are considered the male and female sex organs, with the ovaries producing the female sex hormone

estrogen, with the testes producing and releasing the male sex hormone testosterone. These hormones

are responsible for the sexual characteristics of each gender.

85

Source: http://leavingbio.net/endocrine%20system/endocrine%20system.htm

http://leavingbio.net/endocrine%20system/endocrine%20system.htm

86

Digestive System The digestive system is comprised of a variety of different structures, which are highlighted in the diagram

below. The processes which the system is responsible for can be divided into transport, digestion and

absorption.

(Source: https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works)

The Mouth It is in the mouth that food is broken down mechanically by chewing. These smaller chunks of food are also

mixed with saliva, lubricating the food, making it easier to swallow. Additionally, this saliva contains the

enzyme amylase, which begins the chemical digestion of carbohydrates immediately. As the food is then

swallowed, a structure known as the epiglottis shuts, covering the trachea and in turn ensuring that the

food travels down the correct pathway of the esophagus.

The Esophagus No digestion occurs in this structure, it simply provides a vessel for the food to travel from the mouth to the

stomach in. The food is moved through the esophagus known as peristalsis, where there is a contraction of

muscular tissue behind the food, with relations in front. This occurs in a rhythmical manner, moving the

food relatively quickly to the stomach for further digestion.

https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works

87

The Stomach The stomach is an organ capable of expanding to hold up to 6 litres of food & liquids. The main mechanical

action that occurs here is a churning action creating an acidic semi-liquid mixture known as chyme.

This process will take around 2-3 hours although; this is influenced by how much food/liquid has been

consumed and the form in which the food has been consumed. There is also some chemical activity

occurring. Hydrochloric acid is released which activates pepsinogen into its active form, pepsin which

allows the digestion of protein to occur.

The Small Intestine The small intestine is where most of the action happens in digestion. The small intestine has 3 parts; the

duodenum which is the exit of the stomach/entrance of the small intestine; the jejunum which is the main

part of the structure & finally the ileum which is the exit of the small intestine, leading to the large

intestine. Mechanically, the process of peristalsis is occurring here also, allowing the chyme to be moved

through the small intestine. There is a large amount of chemical activity here, with numerous enzymes

present. Amylase is present to digest any complex carbs that are yet to be broken down. Also, maltase,

sucrose & lactase will breakdown any disaccharides, turning them into monosaccharides. Proteases such

as trypsinogen are present to break down proteins into their most basic amino acid structures. And finally,

lipase completes the digestion of fats, breaking them down into fatty acids.

In addition to the large amount of digestion occurring in the small intestine, absorption of the nutrients

from the digested food also occurs through the walls of the small intestine. There are various features of

the small intestine which allows this process to be as efficient as possible.

On the inside of the small intestine there are numerous folds known as villi. On top of these folds are

further smaller folds known as microvilli. These features help to increase the surface area of the small

intestine that is exposed to the nutrients that are to be absorbed, therefore increasing absorption rate.

These villi are shown on the diagram below.

88

The Large Intestine/Colon After absorption of all required nutrients has occurred, the remaining waste is transported into the

large intestine, also known as the colon. There are 3 main parts to the large intestine, the ascending

colon, the transverse colon and the descending colon. No digestion occurs here although water &

electrolytes are absorbed at this stage. The formation of faeces occurs here which moves to the rectum

until it is to be expelled.

The Pancreas There are many essential structures involved in the digestion process that food does not actually pass

through. The first of these is the pancreas. The pancreas is responsible for the release of many

digestive enzymes and hormones. The pancreas produces and secretes proteases, lipase and amylase

through the pancreatic duct which leads to the small intestine. Bicarbonate is also released which is

responsible for neutralizing the acidic environment created by the chyme. In addition to these

enzymes, insulin and glucagon are 2 essential hormones released by the pancreas which control blood

sugar levels.

The Liver The liver has a wide range of roles to play in the body. In relation to digestion, its primary role is the

production & secretion of bile, an essential chemical for fat digestion. On secretion from the liver, the

bile is transported to the gallbladder.

The Gallbladder The gallbladder acts as a storage site for bile when it is not required for fat digestion. When it is

required, it will be secreted and transported through the common bile duct into the small intestine.

Thermoregulation The human body regulates temperature by keeping a tight balance between heat gain and heat loss.

The temperature regulation system is more analogous to the operation of a home fireplace, as

opposed to the function of an air conditioner. Humans regulate heat generation and preservation to

maintain internal body temperature or core temperature. Normal core temperature at rest varies

between 36.5 and 37.5 °Celsius (°C).

Core temperature is regulated by the hypothalamus (in the brain), which is often called the body’s

thermostat. The hypothalamus responds to various temperature receptors located throughout the

body and makes physiological adjustments to maintain a constant core temperature. For example, on a

hot day, temperature receptors located in the skin send signals to the hypothalamus to cool the body

by increasing the sweat rate.

89

Heat Loss Mechanisms The body can lose heat in a range of ways. Heat loss is an important element of maintaining

homeostasis whilst exercising. The key mechanisms are shown below:

• Radiation – emission of electromagnetic heat waves

• Conduction – direct transfer of heat through a liquid, solid, or gas (direct contact)

• Convection – transfer of heat via air currents over surface of skin

• Evaporation – vaporization of water from respiratory passages or surface of skin (2-4 million

sweat glands)

90

Mechanisms of temperature regulation The body undergoes a range of physiological changes that can allow these mechanisms to be used.

When it is hot there is an increased need for heat loss from the body. The body achieves this by:

• Vasodilation of subcutaneous blood vessels which leads to more sweating and increased heat

loss. Blood is directed closer to the surface.

• There is decreased muscle activity which leads to decreased secretion of hormones (thyroxine

and epinephrine) resulting in a decrease in heat production.

When it is cold there is the need for heat retention within the body. The body achieves this by:

• Vasoconstriction of the skin blood vessels decreases heat loss in the body by directing blood

deeper and away from the skin.

• Shivering and increased voluntary muscle activity which increases secretion of hormones

(thyroxine and epinephrine) that increases heat production.

Exercise and Thermoregulation During all types of exercise, the body’s ability to thermoregulate is challenged. Heat is produced as a bi-

product of metabolism (metabolism is defined as all of the reactions that occur in the human body).

However, the human body is only 25% efficient, therefore approximately 75% of energy is lost as heat.

During exercise, heat is produced mainly from working muscle contractions, with it possible for core

temperature can go above 40 °C.

Water in the Body Water makes up approximately 60% of total body composition. In addition, 73% of lean body mass or

muscle is composed of water. It is the essential nutrient for survival and is required for all cell

functions. Water is also an important constituent in thermoregulation, because it is a major

component of blood volume. It is mainly lost through sweat, respiration, and waste. However, when

the body is dehydrated, most of the water lost is from the blood.

The average person has 2.6 million sweat glands. Sweat is made up of water and electrolytes such as

sodium, chloride, and potassium. When the hypothalamus senses an increase in core temperature it

will act by increasing blood flow to the skin, stimulating the sweat glands. The result is an increase in

the rate of water lost through sweating.

91

Water loss during exercise During low- to moderate-intensity exercise of less than one hour, there are minimal electrolyte losses

because the body reabsorbs most of the electrolytes from the sweat. However, during moderate- to

high-intensity exercise of greater than one hour, the electrolyte loss in sweat becomes significant and

the sweat rate is too fast for re-absorption of electrolytes.

During high-intensity exercise, a person can lose up to 2 litres of water per hour. However, 1 litre of

water per hour is more common. Sweat rate can vary depending on the environmental temperature,

humidity, type of clothing worn during exercise, intensity of exercise, fitness level of the individual and

acclimation of the individual to the environment. Replacing fluids during and after exercise is very

important for staying hydrated and preventing dehydration. Signs of dehydration include dark coloured

urine, muscle cramps, decreased sweat rate, and increased fatigue.

Factors affecting Heat Loss Heat loss can be influenced by a wide range of external factors. These include:

• Increased ambient temperature. This reduces the effectiveness of heat loss particularly by

radiation, conduction, and convection.

• Increased relative humidity. This reduces the effectiveness of heat loss

• by evaporation.

• Decreased wind velocity. This reduces both convective and evaporative effectiveness.

• Reduced surface exposed to environment. This reduces the effectiveness of all heat loss

mechanisms.

Cardiovascular Response to Exercise in the Heat The cardiovascular system is impacted upon by heat, particularly when exercising. Some of these key

responses include:

• Cardiac Output stays the same during submaximal effort

• Heart rate increases

• Stroke volume decreases at maximal exercise

• Heart rate increases but not enough to offset decrease in stroke volume

Cardiovascular Need Vs Temperature Regulation Need The changes described above often lead to a conflict of sorts in relation to blood demand. Blood is

obviously required for normal cardiovascular functioning, but also plays an important role in

controlling temperature.

• Maintenance of blood flow to muscle takes precedence over regulation of temperature in the

body and can lead to increase heat build-up in core. Hence the problem of heat illness during

exercise.

92

• Core temperature will increase as exercise intensity increases. The more trained and

acclimatized individual is the greater tolerance to increased body heat.

Consequences of Dehydration One of the main concerns about prolonged exercise in hot conditions is dehydration. Performance and

overall health can suffer significantly. Some of the key facts around dehydration include:

• Fluid loss equivalent to 1% of body mass increases core body temperature

• Fluid loss equivalent to 5% of body mass

• Increases core temperature and heart rate

• Decreases sweating rate, VO2 max, and aerobic capacity

Factors that Improve Heat Tolerance Becoming more tolerant to heat will allow an individual to improve their performance and recovery

when exposed to these conditions. Some of the factors that influence heat tolerance are discussed

below.

Acclimatization The human body will adapt to improve its tolerance to heat. Around 2 to 4 hours of daily exposure to a

hot environment allows the body to adjust and acclimatize to heat within 10 days. Adjustments

include:

• Improved blood flow to the Skin

• Improved blood distribution

• Sweating starts sooner when exercising

• Sweat rate increases

• Greater distribution of sweat over body surface

• Decreased loss of salt in sweat

The benefits of acclimatization can be lost within 2-3 weeks when no longer exposed to a hot

environment.

Exercise Training Simply being fitter will improve heat tolerance through the mechanisms listed below:

• Increases sweating response (sweat sooner)

• Greater plasma volume in the blood

• Also, other responses noted in acclimatized individual

Age Age is not a major issue with heat tolerance in most physically matured individuals. Issues can occur

with children due to:

• A lower sweat rate relative to adults

• Higher core temperature response to exercise

• Have large number of sweat glands

• Different sweat composition (Electrolytes) than adults

93

Some recommendations to consider for Children working in Hot Environments include:

• Exercise at a lower intensity

• Hydrate appropriately

• Allow greater acclimatisation time

Gender The sweating response does differ from between the sexes due to:

• Women having more heat-activated sweat glands

• Men sweating sooner and more than women

• Women have lessened chance of dehydration compared to men

• Women can cool faster due to larger surface area relative to Men.

Body Fat Level The greater the amount of body fat and individual carries, the greater potential for heat problems due

to insulating effect trapping heat within the body.

Exercise in Cold Environments The human body loses heat at different rates depending on the type of environment it is in. Heat is lost

2- 4 times faster in water compared to air due to the increased conduction rate of water.

The colder the air temperature, the greater the oxygen consumption used by the body and there is an

additional energy cost that occurs due to shivering to stay warm. Body fat is protective against the cold

and it has been found that swimmers generally have more subcutaneous fat than other athletes not

subjected to colder temperatures and environments.

Acclimatisation to the Cold It is more difficult for the body to adapt to a cold environment than hot environment. With

Acclimatization the body can increase heat production, but this also increases heat loss from the body.

Individuals can regulate at a slightly lower core temperature when acclimatised.

Cold Air and Exercise Some urban myths exist about freezing your lungs during exercise in cold air temperatures, but this is not likely, as

incoming cold air is warmed up by the time it gets to bronchi.

Significant water and heat loss can occur via the respiratory tract due to air being expired from the lungs so it is

important to remain hydrated during prolonged exercise in the cold air temperatures.

The body only loses about 20% of its heat through the head but is recommend keeping it covered in cold temperatures. It

is also recommended to wear light layers of clothes while exercising in these temperatures.

Exercise at Altitude With an increase in altitude, there is a decrease in partial pressure of Oxygen (PO2) which is the amount of oxygen

dissolved in the blood. The oxygen (O2) molecules are not as close together as they are at lower altitudes.

For example, at sea level the PO2 is 100 mmHg but at the top of Mt. Everest (8,848 m), it is 28 mmHg, so there is only

58% oxygen saturation of arterial blood. But there is still 20.9% O2in the air at altitude. It takes approximately 2 weeks to

adapt to an altitude of 2300 meters. For each additional 610 m in altitude, it takes an additional week (up to 4572

meters).

The body adapts in the short term by hyperventilating to increase the amount of air entering the lungs. Fluid loss is

increased due to increased respiratory rates and loss of fluid into the cold, dry air. The cardiac output is increased

primarily due to an increase in heart rate, but the stroke volume remains relatively stable.

With long-term exposure the body adapts by increasing resting ventilation rates and increasing both cardiac output and

heart rate. The oxygen carrying capacity of the blood is improved by increased plasma volume and red blood cells.

Cellular adaptations include an increase in the concentration of capillaries in muscle and the number of mitochondria

within the individual cells. The aerobic capacity of the body decreases with an increase in altitude with approximately 1.5

to 3.5% decrease in VO2 max per each 300 meters increase above 1500 altitude. Cardiovascular function decreases

maximal cardiac output primarily due to decreased stroke volume. Interesting this does not improve with stay at altitude.

References Australian Bureau of Statistics. 2011. Physical Activity in Australia: A Snapshot 2007-08. Accessed: 19 November 2013. Retrieved at: http://www.abs.gov.au/ausstats/[email protected]/cat/4835.0.55.001 Australian Diabetes Council Australia. (2003). What is diabetes? http://www.australiandiabetescouncil.com/diabetes-

education/about-diabetes

Australian Government – National Health and Medical Research Council (2013) Eat for Health - Australian Dietary Guidelines. Canberra: National Health and Medical Research Council. Benardort, D. 2012. Advanced Sports Nutrition. Lower Mitcham: Human Kinetics. Batman, P., Richardson, A., Richmond, W., Wilhelmi, D, 2002.The complete guide to fitness instruction, Fitness Institute

Australia, Sydney, Australia

C.H.E.K Institute (Paul Chek, Scientific Back Training 1993)

C.H.E.K Institute (Paul Chek, Advanced Swiss Ball Training For Rehabilitation, 2002)

Department of Health, 2010. Hygienic food preparation and handling food in business. Melbourne: Australian Government

Fitness Australia, 2012. Adult Pre-Exercise Screening Tool & User Guide, viewed 16 July 2012. Retrieved at:

http://www.fitness.org.au/page.php?id=33

Fitness Australia, 2004 Identifying and Managing Members with Eating Disorders and/or Problems with Excessive Exercise. Sydney: Fitness Australia

Food Standards Australia New Zealand (FSANZ). Retrieved at: http://www.foodstandards.gov.au/consumer/labelling/Pages/default.aspx

Food Standards, 2013. Labeling. Accessed 19 November 2013. Retrieved at: http://www.foodstandards.gov.au/industry/labelling/pages/default.aspx

Levangie, P., & Norkin, C. (2007) Joint Structure & Function , A Comprehensive Analysis, Fourth Addition

McArdle, W., Katch, F. & Katch, V. 2001. Exercise Physiology: Nutrition, Energy & Human Performance. Baltimore: Lippincott Williams & Wilkins.

Marchese, R., & Hill, A, 2011.The essential guide to fitness: For the fitness instructor. Pearson, Australia

National Health and Medical Research Council. Eat for health. Retrieved at: http://www.eatforhealth.gov.au/eating-well/how-understand-food-labels Powers, S. & Howley, E. (2011)Exercise Physiology, Theory and Application To Fitness and Performance Sixth Addition

The University of Sydney. 2013. About Glycemic Index. Accessed: 19 November 2013. Retrieved at: http://www.glycemicindex.com/about.php Top end sports, 1997-2012. Beep test ratings. Retrieved at: http://www.topendsports.com/testing/beep-norms.htm

http://www.abs.gov.au/ausstats/abs%40.nsf/cat/4835.0.55.001

http://www.australiandiabetescouncil.com/diabetes-education/about-diabetes

http://www.australiandiabetescouncil.com/diabetes-education/about-diabetes

http://www.fitness.org.au/page.php?id=33

http://www.foodstandards.gov.au/consumer/labelling/Pages/default.aspx

http://www.foodstandards.gov.au/industry/labelling/pages/default.aspx

http://www.eatforhealth.gov.au/eating-well/how-understand-food-labels

http://www.glycemicindex.com/about.php

http://www.topendsports.com/testing/beep-norms.htm

Top end sports, 1997-2012. Sit up test at home. Retrieved at: http://www.topendsports.com/testing/tests/home-

situp.htm

Top end sports, 1997-2012. Push up test at home. Retrieved at: http://www.topendsports.com/testing/tests/home-

pushup.htm

World Health Organisation. 2013. BMI Classification. Accessed: 19 November 2013, Retrieved at: http://apps.who.int/bmi/index.jsp?introPage=intro_3.html Smart Image Base (2013) – Endeavour Online Library

http://www.topendsports.com/testing/tests/home-situp.htm

http://www.topendsports.com/testing/tests/home-situp.htm

http://www.topendsports.com/testing/tests/home-pushup.htm

http://www.topendsports.com/testing/tests/home-pushup.htm

http://apps.who.int/bmi/index.jsp?introPage=intro_3.html

sis30315 certificate iii in fitness learner guide

Documents