exercise physiology 8

Principles of Exercise Training

Muscle Strength Maximal force that a muscle or muscle group can

generate.

Muscle Power Rate of the performing muscle, thus the product of the

force and velocity. Explosive aspect of strength, the product of strength

and speed of movement. Power = Force X Distance / Time Where (force = strength) and (distance/ Time = speed)

POWER = SPEED X STRENGTH

Power can be developed by:-

RESISTANCE RUNNING

HILL RUNNING

PLYOMETRICS

Muscular Endurance The capacity to sustain repeated muscular

contractions or a single static contraction.

Aerobic Power Rate of energy release by cellular metabolic processes

that depend upon the availability and involvement of oxygen.

Maximal aerobic power refers to the maximal capacity for aerobic resynthesis of ATP. Equivalent to aerobic capacity and maximal oxygen

uptake (VO2max). Best lab test is a graded exercise test to exhaustion.

Anaerobic Power Rate of energy release by cellular metabolic processes

that function without the involvement of oxygen. Maximum anaerobic power / anaerobic capacity –

maximal capacity for the anaerobic system to produce ATP

Tests: None universally accepted Critical Power Test Wingate anaerobic Test

General Principles of Training

Principle of Individuality No two individuals have exactly the same genetic

characteristics (except for identical twins).

Many factors contribute to variations in training responses among individuals: Heredity Relative Fitness Level Cellular Growth Rate Metabolism Cardiovascular and Respiratory regulation Neural and Endocrine regulation

Principle of Specificity Exercise response is specific to the mode and

intensity of exercise.

The training program must stress the physiological systems that are critical for optimal performance in the given sport to achieve specific training adaptations.

Specific exercise elicits specific adaptations, creating specific effects (Specific Adaptations to Imposed Demands principle).

Principle of Reversibility Detraining causes measurable reductions in

physiological functions and exercise capacity.

Reversal of improvements gained through training, decreasing to a level that meets the demands of ADLs.

Training program must include a maintenance plan.

Principle of Progressive Overload

Overload and progressive training form the foundation of all training.

Exercising @ intensities greater than normal induces a variety of highly specific adaptations that enables the body to function more efficiently.

Achieving the appropriate overload requires manipulating combinations of training: Frequency Intensity Duration Exercise Mode

Principle of Hard/Easy Training Hard

Training each day @ high intensities or for long durations or both.

Training Easy Provides a day active recovery so that the body is

prepared for future hard training.

Principle of Periodization Periodization is the gradual cycling of specificity,

intensity, and volume of training to achieve peak levels of fitness for competition. Macrocycle Mesocycle

Preparation Competition Transition

Microcycle

Resistance Training

Training Needs Analysis Should include the following assessment:

What major muscle groups need to be trained? What type of training should be used? What energy system should be stressed? What are the primary sites of concern for injury

prevention?

Prescriptions should entail: Exercises to be performed. Order in which they will be performed. Number of sets for each exercise. Rest period for between each set and between

exercises. Intensity or load. Number of repetitions. Velocity of movement to be used.

Selecting the Appropriate Resistance and Repetitions

The resistance to be used is generally expressed as a percentage of the maximal capacity.

Strength development is optimized by moderate to high resistance (60 – 80% of 1RM) with low to moderate repetitions (6- 12 reps).

Muscular endurance is optimized by low to moderate resistance (30 – 70% of the 1RM) and moderate to high repetitions (10 – 25 reps).

Power is optimized by alternating low to moderate resistance (30 – 60% of 1 RM) and low repetition (3 – 6 reps) at an explosive velocity with the traditional strength training recommendations.

To hypertrophy muscle – moderate to high resistance (70 – 100% 1RM) with low to moderate repetition (1 – 12 reps)

Selecting the Appropriate Number of Sets

Single set versus multiple sets.

Single set used for untrained persons or those needing to maintain a basic level of muscular fitness and not interested in further improvements.

Multiple sets used for additional gains in: Strength Endurance Power Hypertrophy

Periodization Refers to changes or variations in the resistance

program that are implemented over the course of a specific period of time (eg. a year).

It varies the exercise stimulus to keep the individual from overtraining or becoming stale.

Two forms of periodization: Classic Strength and Power Periodization Undulating Periodization

Classic Strength and Power Periodization Consists of 5 phases in each training cycle. Phase I

High volume with low intensity Phase II, III, and IV

Volume decreased with increasing intensity. Phase V (active recovery phase)

Either light resistance training or some unrelated activity is allowed to allow the person time to recover from the training cycle both physically and mentally.

Periodization for Resistance Training (1 year,5 phases)

Phase I Muscular hypertrophyHigh volume

Phase II Strengthintensity

Phase III Power

Phase IV Peak strength

Phase V Active recovery

Undulating Periodization Has more variations to accommodate the unique

demands of each sport.

Resistance Training Types of Resistance Training

Isometric Training Facilitate recovery and reduce muscle atrophy and

strength loss Free Weights Resistance used is limited by the weakest point in the

range of motion. More motor recruitment

Gain control of the free weight Stabilize the weight Maintain body balance

Variation in Strength Relative to the Angle of the Elbow During the Two-Arm Curl

Eccentric Training Maximize gains in strength and size

Variable Resistance Training Resistance reduced at weakest points and increased at

strongest points.

Isokinetic Training Motion speed is kept constant throughout. Contract at maximal force at all points in the range of

motion (if properly motivated).

A Variable-Resistance Training Device

© Human Kinetics

Plyometrics / Stretch Shortening Cycle Exercises Proposed to bridge the gap between speed and strength

training. Utilizes the stretch reflex to facilitate recruitment of

motor units. Stores energy in the elastic and contractile components

of muscle during the eccentric contraction (stretch) that can be recovered during the concentric contraction

Electrical Stimulation Training Reduce loss of strength and muscle size

Plyometric Box Jumping

Resistance Training Programs

Key Points

Low-repetition, high-resistance training enhances strength development

High-repetition, low-resistance training optimizes muscular endurance

Periodization is important to prevent overtraining and burnout

A typical periodization cycle has 4 active phases, each emphasizing a different muscular fitness component, plus an active recovery

(continued)

Resistance Training Programs (continued)

Key Points

Resistance training can use static or dynamic contractions

Eccentric training appears to be essential to maximizing hypertrophy

Electrical stimulation can be successfully used in rehabilitating athletes

Adaptations to Resistance Training

Increased motor unit recruitment

Coordination of motor unit recruitment (synchronous)

Rate Coding: firing frequency of the motor units

Decreased autogenic inhibition Decreased sensitivity of

the golgi tendon organs to tension

may lead to injury


Chronic Hypertrophy Relates to increase in muscle size that occurs with long

term resistance training. Fiber hypertrophy

Myofibrils Actin and Myosin filaments Sarcoplasm Connective tissue

Fiber hyperplasia


Transient Hypertrophy Due to increased blood flow to the muscles during

exercise. Fluid accumulation in the interstitial and extracellular

spaces that comes from the blood plasma. Lasts for a short time, as fluid returns to the blood within

hours after exercise.


Fiber Type Alterations muscle fibers begin to take

on certain characteristics of the opposite fiber type after opposing training occurs.

chronic stimulation of FT motor units with low frequency nerve stimulation transforms FT motor units into ST motor units within a matter of weeks!

extreme, prolonged training may produce skeletal muscle fiber type conversion.

Muscular Response to Resistance Training

Acute Muscle Soreness Pain felt immediately after exercise accumulation of H+ Lactate tissue edema Disappears minutesto hours after training.

Muscular Response to Resistance Training

Delayed Onset Muscle Soreness muscle and connective tissue damage inflammation (macrophages, white blood cells) increased chemical mediators (bradykinin) Edema

DOMS & Performance

Reduction in force generating capacity of the muscle.

Loss of strength due to: Physical disruption of the

muscle. Failure within the excitation –

contraction coupling process. Loss of contractile protein.

Muscle glycogen resynthesis is also impaired with muscle damage.

Adaptations to Aerobic and Anaerobic Training

Aerobic and Anaerobic Training

Aerobic (endurance) training

Improved central and peripheral blood flow

• Enhances the capacity of muscle fibers to generate ATP

Anaerobic training

• Increased short-term, high-intensity endurance capacity

• Increased anaerobic metabolic function

• Increased tolerance for acid–base imbalances during highly intense effort

EnduranceMuscular endurance: the ability of a single muscle or muscle group to sustain high-intensity repetitive or static exercise

Cardiorespiratory endurance: the entire body’s ability to sustain prolonged, dynamic exercise using large muscle groups

Evaluating Cardiorespiratory

EnduranceVO2max

• Highest rate of oxygen consumption attainable during maximal exercise

• VO2max can be increased by 10-15% with 20 weeks of endurance training

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Increases in VO2max

With Endurance Training

Fick equation:

VO2 = SV HR (a-v)O2 diff.

Changes in VO2max With 12 Monthsof Endurance Training

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Cardiovascular Adaptation to Training• Heart size

• Stroke volume

• Heart rate

• Cardiac output

• Blood flow

• Blood pressure

• Blood volume

Heart Size (Central) Adaptationto Endurance Training

Cardiac Hypertrophy / Athlete’s heart

• The left ventricle changes significantly in response to endurance training

• The internal dimensions of the left ventricle increase as an adaptation to an increase in ventricular filling secondary to an increase in plasma volume and diastolic filling time

• Left ventricular wall thickness and mass increase, allowing for greater contractility

Measuring Heart Size: Echocardiography

© Tom Roberts

Percentage Differences in Heart Size Among Three Groups of Athletes Compared With Untrained Group

Changes in Stroke Volume


Stroke Volume Adaptations

to Endurance TrainingKey Points

• Endurance training increases SV at rest and during submaximal and maximal exercise

• Increases in end-diastolic volume, caused by an increase in blood plasma and greater diastolic filling time (lower heart rate), contribute to increased SV

• Increased ventricular filling (preload) leads to greater contractility (Frank-Starling mechanism)

• Reduced systemic vascular resistance (afterload)

Heart Rate Adaptationsto Endurance TrainingResting

Decreases by ~1 beat/min with each week of training

Increased parasympathetic (vagal) tone

Submaximal

• Decreases heart rate for a given absolute exercise intensity

Maximal

• Unchanged or decreases slightly

Changes in Heart RateWith Endurance Training

Heart Rate Recovery• The time it takes the heart to return to its

resting rate after exercise

• Faster rate of recovery after training

• Indirect index of cardiorespiratory fitness

• Prolonged by certain environments (heat, altitude)

• Can be used as a tool to track the progress of endurance training

Changes in Heart Rate Recovery


Cardiac Output Adaptationsto Endurance Training

Q = HR x SV

Does not change at rest or during submaximal exercise (may decrease slightly)

Maximal cardiac output increases due largely to an increase in stroke volume

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Changes in Cardiac Output


Cardiac Output Adaptations

Key Points

• Q does not change at rest or during submaximal exercise after training (may decrease slightly)

• Q increases at maximal exercise and is largely responsible for the increase in VO2max

• Increased maximal Q results from the increase in maximal SV

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Blood Flow Adaptationsto Endurance Training

Blood flow to exercising muscle is increased with endurance training due to:

• Increased capillarization of trained muscles • Greater recruitment of existing capillaries in trained

muscles• More effective blood flow redistribution from inactive

regions• Increased blood volume• Increased Q

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Blood Pressure (BP) Adaptations

to Endurance Training Resting BP decreases in borderline and

hypertensive individuals (6-7 mmHg reduction)

Mean arterial pressure is reduced at a given submaximal exercise intensity (↓ SBP, ↓ DBP)

At maximal exercise (↑ SBP, ↓ DBP)

Blood Volume (BV) Adaptationsto Endurance Training

BV increases rapidly with endurance training

Plasma volume increases due to: Increased plasma proteins (albumin) Increased antidiuretic hormone and aldosterone

Red blood cell volume increases

Increases in Total Blood Volume and Plasma Volume With Endurance Training

Blood Flow, Pressure, and Volume Adaptations to

Endurance Training

Key Points

• Blood flow to active muscles is increased due to:– ↑ Capillarization– ↑ Capillary recruitment– More effective redistribution– ↑ Blood volume

• Blood pressure at rest as well as during submaximal exercise is reduced, but not at maximal exercise

(continued)

Blood Flow, Pressure, and Volume Adaptations to Endurance Training

(continued)

Key Points

• Blood volume increases

• Plasma volume increases through increased protein content and by fluid conservation hormones

• Red blood cell volume and hemoglobin increase

• Blood viscosity decreases due to the increase in plasma volume

Respiratory Adaptationsto Endurance Training

Key Points

• Little effect on lung structure and function at rest

• Increase in pulmonary ventilation during maximal exercise • ↑ Tidal volume • ↑ Respiratory rate

• Pulmonary diffusion increases at maximal exercise due to increased ventilation and lung perfusion

• (a-v)O2 difference increases with training, reflecting increased extraction of oxygen at the tissues

Adaptations in Muscleto Endurance Training

• Increased size (cross-sectional area) of type I fibers

• Transition of type IIx → type IIa fiber characteristics

• Transition of type II → type I fiber characteristics

• Increased number of capillaries per muscle fiber and for a given cross-sectional area of muscle

• Increased myoglobin content of muscle by 75% to 80%

• Increased number, size, and oxidative enzyme activity of mitochondria

Change in Maximal Oxygen Uptake and SDH Activity With Endurance

Training

Gastrocnemius Oxidative Enzyme Activities of Untrained (UT) Subjects,

Moderately Trained (MT) Joggers,and Highly Trained (HT) Runners

Adapted, by permission, from D.L. Costill et al., 1979, "Lipid metabolism in skeletal muscle of endurance-trained males and females," Journal of Applied Physiology 28: 251-255 and from D.L. Costill et al., 1979, "Adaptations in skeletal muscle following strength training," Journal of Applied Physiology 46: 96-99.

Adaptations in Muscle With Training

Key Points

Type I fibers tend to enlarge

Increase in type I fibers and a transition from type IIx to type IIa fibers

Increased number of capillaries supplying each muscle fiber

Increase in the number and size of muscle fiber mitochondria

Oxidative enzyme activity increases

Increased capacity of oxidative metabolism

Metabolic Adaptations to Training

Lactate threshold increases due to: – Increased clearance and/or decreased production of

lactate

– Reduced reliance on glycolytic systems

Respiratory exchange ratio decreases due to:– Increased utilization of free fatty acids

Oxygen consumption (VO2)– Unchanged (or slightly reduced) at submaximal

intensities– VO2max increases

– Limited by the ability of the cardiovascular system to deliver oxygen to active muscles

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Changes in Lactate ThresholdWith Training

Changes in Race Pace With Continued Training After VO2max Stops Increasing

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Increased PerformanceAfter VO2max Has Peaked

Once an athlete has achieved their genetically determined peak VO2max, they can still increase their endurance performance due to the body’s ability to perform at increasingly higher percentages of that VO2max for extended periods. The increase in performance without an increase in VO2max is a result of an increase in lactate threshold.

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Factors Affecting VO2max

Level of conditioning: Initial state of conditioning will determine how much VO2max will increase (i.e., the higher the initial value, the smaller the expected increase)

Heredity: Accounts for 25-50% of the variation in VO2max

Sex: Women have lower VO2max compared to men

Individual responsiveness: There are high responders and low responders to endurance training, which is a genetic phenomenon

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Cardiorespiratory Endurance

and Performance• It is the major defense against fatigue

• Should be the primary emphasis of training for health and fitness

• All athletes can benefit from maximizing their endurance

Adaptations to Aerobic TrainingKey Points

• Although VO2max has an upper limit, endurance performance can continue to improve

• An individual’s genetic makeup predetermines a range for his or her VO2max and accounts for 25-50% of the variance in VO2max

• Heredity largely explains an individual’s response to training

• Highly conditioned female endurance athletes have VO2max values about 10% lower than their male counterparts

• All athletes can benefit from maximizing their cardiorespiratory endurance

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Summary of Cardiovascular Adaptationto Chronic Endurance Training

Muscle Adaptationsto Anaerobic Training

• Increased muscle fiber recruitment

• Increased cross-sectional area of type IIa and type IIx muscle fibers

Energy System Adaptations

to Anaerobic Training Increased ATP-PCr system enzyme activity

Increased activity of several key glycolytic enzymes

No effect on oxidative enzyme activity

Anaerobic TrainingKey Points

Anaerobic training bouts improve both anaerobic power and anaerobic capacity

Increased performance with anaerobic training is attributed to strength gains

Increases ATP-PCr and glycolytic enzymes