Download - Neuromuscular Fundamentals
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Neuromuscular Fundamentals
Anatomy and Physiology of Human Movement
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Outline Introduction Structure and Function Fiber Arrangement Muscle Actions Role of Muscles Neural Control Factors that Affect Muscle Tension
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Introduction Responsible for movement of body and all of its
joints Muscles also provide
Protection Posture and support Produce a major portion of total body heat
Over 600 skeletal muscles comprise approximately 40 to 50% of body weight
215 pairs of skeletal muscles usually work in cooperation with each other to perform opposite actions at the joints which they cross
Aggregate muscle action - muscles work in groups rather than independently to achieve a given joint motion
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Muscle Tissue Properties
Irritability or Excitability - property of muscle being sensitive or responsive to chemical, electrical, or mechanical stimuli
Contractility - ability of muscle to contract & develop tension or internal force against resistance when stimulated
Extensibility - ability of muscle to be passively stretched beyond it normal resting length
Elasticity - ability of muscle to return to its original length following stretching
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Outline Introduction Structure and Function Fiber Arrangement Muscle Actions Role of Muscles Neural Control Factors that Affect Muscle Tension
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Structure and Function
Nervous system structure Muscular system structure Neuromuscular function
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Figure 14.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Nervous System Structure
Integration of information from millions of sensory neurons action via motor neurons
Figure 12.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Nervous System Structure Organization
Brain Spinal cord
Nerves Fascicles
Neurons
Figure 12.2, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Figure 12.7, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Nervous System Structure Both sensory and motor neurons in nerves
Figure 12.11, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Nervous System Structure
The neuron: Functional unit of nervous tissue (brain, spinal cord, nerves) Dendrites: Receptor sites Cell body: Integration Axon: Transmission
Myelin sheath: Protection and speed Nodes of Ranvier: Saltatory conduction Terminal branches: Increased innervation Axon terminals: Connection with muscular system Synaptic vescicles: Delivery mechanism of “message” Neurotransmitter: The message
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DendritesCell body
Axon
Myelin sheath
Node of Ranvier
Terminal branch
Terminal ending
Figure 12.4, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Figure 12.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
Terminal ending
Synaptic vescicle
Neurotransmitter: Acetylcholine (ACh)
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Figure 12.19, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Structure and Function
Nervous system structure Muscular system structure Neuromuscular function
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Classification of Muscle Tissue Three types:
1. Smooth muscle
2. Cardiac muscle
3. Skeletal muscle
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Skeletal Muscle: Properties
Extensibility: The ability to lengthen Contractility: The ability to shorten Elasticity: The ability to return to original
length Irritability: The ability to receive and respond
to stimulus
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Muscular System Structure Organization:
Muscle (epimyseum) Fascicle (perimyseum)
Muscle fiber (endomyseum) Myofibril Myofilament Actin and myosin
Other Significant Structures: Sarcolemma Transverse tubule Sarcoplasmic reticulum Tropomyosin Troponin
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Figure 10.1, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Figure 10.4, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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http://staff.fcps.net/cverdecc/Adv%20A&P/Notes/Muscle%20Unit/sliding%20filament%20theory/slidin16.jpg
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Figure 10.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Structure and Function
Nervous system structure Muscular system structure Neuromuscular function
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Neuromuscular Function
Basic Progression:
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments
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Nerve Impulse
What is a nerve impulse?
-Transmitted electrical charge
-Excites or inhibits an action
-An impulse that travels along an axon is an ACTION POTENTIAL
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Nerve Impulse
How does a neuron send an impulse?
-Adequate stimulus from dendrite
-Depolarization of the resting membrane potential
-Repolarization of the resting membrane potential
-Propagation
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Nerve Impulse
What is the resting membrane potential?-Difference in charge between inside/outside of the neuron
-70 mV
Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Nerve Impulse
What is depolarization?
-Reversal of the RMP from –70 mV to +30mV
Propagation of the action potential
Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Nerve Impulse
What is repolarization?
-Return of the RMP to –70 mV
Figure 12.9, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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-70 mV
+30 mV
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Neuromuscular Function
Basic Progression:
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments
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Release of the Neurotransmitter
Action potential axon terminals
1. Calcium uptake
2. Release of synaptic vescicles (ACh)
3. Vescicles release ACh
4. ACh binds sarcolemma
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Ca2+
ACh
Figure 12.8, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
34Figure 14.5, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Neuromuscular Function
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments
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Ach
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AP Along the Sarcolemma
Action potential Transverse tubules
1. T-tubules carry AP inside
2. AP activates sarcoplasmic reticulum
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Figure 14.5, Marieb & Mallett (2003). Human Anatomy. Benjamin Cummings.
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Neuromuscular Function
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding Filaments
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Calcium Release
AP T-tubules Sarcoplasmic reticulum
1. Activation of SR
2. Calcium released into sarcoplasm
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Sarcolemma
CALCIUM
RELEASE
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Neuromuscular Function
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments
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Coupling of Actin and Myosin
Tropomyosin Troponin
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Blocked Coupling of actin and myosin
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Neuromuscular Function
1. Nerve impulse
2. Neurotransmitter release
3. Action potential along sarcolemma
4. Calcium release
5. Coupling of actin and myosin
6. Sliding filaments
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Sliding Filament Theory
Basic Progression of Events
1. Cross-bridge
2. Power stroke
3. Dissociation
4. Reactivation of myosin
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Cross-Bridge
Activation of myosin via ATP
-ATP ADP + Pi + Energy
-Activation “cocked” position
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Power Stroke
ADP + Pi are released Configurational change Actin and myosin slide
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Dissociation
New ATP binds to myosin Dissociation occurs
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Reactivation of Myosin Head
ATP ADP + Pi + Energy Reactivates the myosin head
Process starts over Process continues until:
-Nerve impulse stops-AP stops-Calcium pumped back into SR-Tropomyosin/troponin back to original position
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Outline Introduction Structure and Function Fiber Arrangement Muscle Actions Role of Muscles Neural Control Factors that Affect Muscle Tension
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Shape of Muscles & Fiber Arrangement
Muscles have different shapes & fiber arrangements
Shape & fiber arrangement affects Muscle’s ability to exert force Range through which it can effectively exert force
onto the bones
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Shape of Muscles & Fiber Arrangement
Two major types of fiber arrangements Parallel & pennate Each is further subdivided according to shape
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Fiber Arrangement - Parallel
Parallel muscles fibers arranged parallel to length of
muscle produce a greater range of movement
than similar sized muscles with pennate arrangement
Categorized into following shapes: Flat Fusiform Strap Radiate Sphincter or circular
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Fiber Arrangement - Parallel
Flat muscles Usually thin & broad, originating from broad, fibrous,
sheet-like aponeuroses Allows them to spread their forces over a broad area Ex: Rectus abdominus & external oblique
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.
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Fiber Arrangement - Parallel
Fusiform muscles Spindle-shaped with a central belly
that tapers to tendons on each end Allows them to focus their power onto
small, bony targets Ex: Brachialis, biceps brachii
Figure 3.3. Hamilton, Weimar & Luttgens (2005). Kinesiology: Scientific basis for human motion. McGraw-Hill.
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Fiber Arrangement - Parallel
Strap muscles More uniform in diameter
with essentially all fibers arranged in a long parallel manner
Enables a focusing of power onto small, bony targets
Ex: Sartorius, sternocleidomastoid
Figure 8.7. Hamilton, Weimar & Luttgens (2005). Kinesiology: Scientific basis for human motion. McGraw-Hill.
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Fiber Arrangement - Parallel
Radiate muscles Also described sometimes as being triangular, fan-
shaped or convergent Have combined arrangement of flat & fusiform Originate on broad aponeuroses & converge onto a
tendon Ex: Pectoralis major, trapezius
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.
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Fiber Arrangement - Parallel
Sphincter or circular muscles Technically endless strap muscles Surround openings & function to close them upon
contraction Ex: Orbicularis oris surrounding the mouth
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.
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Fiber Arrangement - Pennate
Pennate muscles Have shorter fibers Arranged obliquely to their tendons in a manner
similar to a feather Reduces mechanical efficiency of each fiber Increases overall number of fibers “packed” into
muscle Overall effect = more crossbridges = more force!
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Fiber Arrangement - Pennate
Categorized based upon the exact arrangement between fibers & tendon Unipennate Bipennate Multipennate
Modified from Van De Graaff KM: Human anatomy, ed 6, Dubuque, IA, 2002, McGraw-Hill.
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Fiber Arrangement - Pennate
Unipennate musclesFibers run obliquely from a tendon on
one side onlyEx: Biceps femoris, extensor digitorum
longus, tibialis posterior
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Fiber Arrangement - Pennate
Bipennate muscleFibers run obliquely on both sides from
a central tendonEx: Rectus femoris, flexor hallucis
longus
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Fiber Arrangement - Pennate
Multipennate musclesHave several tendons with fibers running
diagonally between themEx: Deltoid
Bipennate & unipennate produce more force than multipennate
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Outline Introduction Structure and Function Fiber Arrangement Muscle Actions Role of Muscles Neural Control Factors that Affect Muscle Tension
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Muscle Actions: Terminology
Origin (Proximal Attachment): Structurally, the proximal attachment of a muscle
or the part that attaches closest to the midline or center of the body
Functionally & historically, the least movable part or attachment of the muscle
Note: The least movable may not necessarily be the proximal attachment
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Muscle Actions: Terminology
Insertion (Distal Attachment): Structurally, the distal attachment or the part that
attaches farthest from the midline or center of the body
Functionally & historically, the most movable part is generally considered the insertion
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Muscle Actions: Terminology
When a particular muscle is activated It tends to pull both ends toward the center Actual movement is towards more stable
attachment Examples:
Bicep curl vs. chin-up Hip extension vs. RDL
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Muscle Actions Action - when tension is developed in a
muscle as a result of a stimulus Muscle “contraction” term is exclusive in
nature As a result, it has become increasingly
common to refer to the various types of muscle contractions as muscle actions instead
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Muscle Actions Muscle actions can be used to cause,
control, or prevent joint movement or To initiate or accelerate movement of a body
segment To slow down or decelerate movement of a
body segment To prevent movement of a body segment by
external forces
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Types of Muscle Actions
Muscle action (under tension) Isometric Isotonic
Concentric Eccentric
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Types of Muscle Actions
Isometric action: Tension is developed within
muscle but joint angles remain constant
AKA – Static movement May be used to prevent a
body segment from being moved by external forces
Internal torque = external torque
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Types of Muscle Actions
Isotonic (same tension) contractions involve muscle developing tension to either cause or control joint movement AKA – Dynamic movement
Isotonic contractions are either concentric (shortening) or eccentric (lengthening)
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Types of Muscle Actions
Concentric contractions involve muscle developing tension as it shortens Internal torque > external torque Causes movement against gravity or other resistance Described as being a positive action
Eccentric contractions involve the muscle lengthening under tension External torque > internal torque Controls movement caused by gravity or other resistance Described as being a negative action
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Modified from Shier D, Butler J, Lewis R: Hole’s human anatomy & physiology, ed 9, Dubuque, IA, 2002, McGraw-Hill
What is the role of the elbow extensors in each phase?
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Types of Muscle Actions
Movement may occur at any given joint without any muscle contraction whatsoever referred to as passive solely due to external forces such as those
applied by another person, object, or resistance or the force of gravity in the presence of muscle relaxation
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Outline Introduction Structure and Function Fiber Arrangement Muscle Actions Role of Muscles Neural Control Factors that Affect Muscle Tension
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Role of Muscles
Agonist muscles The activated muscle group during concentric or
eccentric phases of movement Known as primary or prime movers, or muscles
most involved
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Role of Muscles
Antagonist muscles Located on opposite side of joint from agonist Have the opposite concentric action Also known as contralateral muscles Work in cooperation with agonist muscles by
relaxing & allowing movement Reciprocal Inhibition
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Role of Muscles
Stabilizers Surround joint or body part Contract to fixate or stabilize the area to enable
another limb or body segment to exert force & move
Also known as fixators
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Role of Muscles
Synergist Assist in action of agonists Not necessarily prime movers for the action Also known as guiding muscles Assist in refined movement & rule out undesired
motions
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Role of Muscles
Neutralizers Counteract or neutralize the action of another
muscle to prevent undesirable movements such as inappropriate muscle substitutions
Activation to resist specific actions of other muscles
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Outline Introduction Structure and Function Fiber Arrangement Muscle Actions Role of Muscles Neural Control Factors that Affect Muscle Tension
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Factors That Affect Muscle Tension
Number Coding and Rate Coding Length-Tension Relationship Force-Velocity Relationship Uniarticular vs. Biarticular Muscles Cross-sectional Diameter Muscle Fiber Type
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Number Coding & Rate Coding
Difference between lifting a minimal vs. maximal resistance is the number of muscle fibers recruited (crossbridges)
The number of muscle fibers recruited may be increased by Activating those motor units containing a greater
number of muscle fibers (Number Coding) Activating more motor units (Number Coding) Increasing the frequency of motor unit activation (Rate
Coding)
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Number Coding & Rate Coding
Number of muscle fibers per motor unit varies significantly From less than 10 in muscles requiring precise
and detailed such as muscles of the eye To as many as a few thousand in large
muscles that perform less complex activities such as the quadriceps and gastrocnemius
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Number Coding & Rate Coding
Greater contraction forces may also be achieved by increasing the frequency or motor unit activation (Rate Coding)
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All or None Principle Motor unit
Single motor neuron & all muscle fibers it innervates
Typical muscle contraction The number of motor units responding (and number of
muscle fibers contracting) within the muscle may vary significantly from relatively few to virtually all
All of the fibers within the motor unit will fire when stimulated by the CNS
All or None Principle - regardless of number, individual muscle fibers within a given motor unit will either fire & contract maximally or not at all
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Factors That Affect Muscle Tension
Number Coding and Rate Coding Length-Tension Relationship Force-Velocity Relationship Uniarticular vs. Biarticular Muscles Cross-sectional Diameter Muscle Fiber Type
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Length - Tension Relationship
Maximal ability of a muscle to develop tension & exert force varies depending upon the length of the muscle during contraction
Active Tension
Passive Tension
93Figure 20.2, Plowman and Smith (2002). Exercise Physiology, Benjamin Cummings.
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Factors That Affect Muscle Tension
Number Coding and Rate Coding Length-Tension Relationship Force-Velocity Relationship Uniarticular vs. Biarticular Muscles Cross-sectional Diameter Muscle Fiber Type
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Force – Velocity Relationship When muscle is contracting (concentrically or
eccentrically) the rate of length change is significantly related to the amount of force potential
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Force – Velocity Relationship
Maximum concentric velocity = minimum resistance
As load increases, concentric velocity decreases
Eventually velocity = 0 (isometric action)
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Force – Velocity Relationship As load increases beyond muscle’s ability
to maintain an isometric contraction, the muscle begins eccentric action
As load increases, eccentric velocity increases
Eventually velocity = maximum when muscle tension fails
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Muscle Force – Velocity Relationship
Indirect relationship between force (load) and concentric velocity
Direct relationship between force (load) and eccentric velocity
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Factors That Affect Muscle Tension
Number Coding and Rate Coding Length-Tension Relationship Force-Velocity Relationship Uniarticular vs. Biarticular Muscles Cross-sectional Diameter Muscle Fiber Type
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Uni Vs. Biarticular Muscles
Uniarticular muscles Cross & act directly only on the single joint that
they cross Ex: Brachialis
Can only pull humerus & ulna closer together
Ex: Gluteus Maximus Can only pull posterior femur and pelvis
closer together
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Uni Vs. Biarticular Muscles
Biarticular muscles Cross & act on two different joints
May contract & cause motion at either one or both of its joints
Advantages over uniarticular muscles
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Advantage #1
Can cause and/or control motion at more than one joint
Rectus femoris: Knee extension, hip flexion Hamstrings: Knee flexion, hip extension
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Advantage #2
Can maintain a relatively constant length due to "shortening" at one joint and "lengthening" at another joint (Quasi-isometric)
- Recall the Length-Tension Relationship
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Advantage #3
Prevention of Reciprocal Inhibition This effect is negated with biarticular
muscles when they move concurrently Concurrent movement:
Concurrent “lengthening” and “shortening” of muscle
Countercurrent movement: Both ends “lengthen” or “shorten”
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What if the muscles of the hip/knee were uniarticular?
Hip
Knee
Ankle
Muscles stretched/shortened to extreme lengths!
Implication?
106Figure 20.2, Plowman and Smith (2002). Exercise Physiology, Benjamin Cummings.
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Hip
Knee
Ankle
Quasi-isometric action? Implication?
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Active & Passive Insufficiency Countercurrent muscle actions can reduce the
effectiveness of the muscle As muscle shortens its ability to exert force
diminishes Active insufficiency: Diminished crossbridges
As muscle lengthens its ability to move through ROM or generate tension diminishes Passively insufficiency: Diminished crossbridges and
excessive passive tension
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Factors That Affect Muscle Tension
Number Coding and Rate Coding Length-Tension Relationship Force-Velocity Relationship Uniarticular vs. Biarticular Muscles Cross-sectional Diameter Muscle Fiber Type
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Cross-Sectional Area
Hypertrophy vs. hyperplasia Increased # of myofilaments
Increased size and # of myofibrils Increased size of muscle fibers
http://estb.msn.com/i/6B/917B20A6BE353420124115B1A511C7.jpg
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Factors That Affect Muscle Tension
Number Coding and Rate Coding Length-Tension Relationship Force-Velocity Relationship Uniarticular vs. Biarticular Muscles Cross-sectional Diameter Muscle Fiber Type
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Muscle Fiber Characteristics
Three basic types:
1. Type I:
-Slow twitch, oxidative, red
2. Type IIb:
-Fast twitch, glycolytic, white
3. Type IIa:
-FOG