muscle. most abundant tissue (40-45% of bw) muscle composition endomysium – loose ct surrounding...
TRANSCRIPT
Muscle
Muscle Most abundant tissue (40-45% of
BW)
Muscle
Composition endomysium – loose CT surrounding
each fiber perimysium – dense CT that
bundles multiple fibers into fascicles
epimysium – fibrous CT that surrounds entire muscle (fascia)
Muscle
Muscle Collagen in perimysium /
epimysium tendons
Contraction forces transported thru CT tendons (inert) bones.
Musculotendinous Unit Tendon - spring-like elastic (very
stiff-tight)
In series with muscle (SEC)
Musculotendinous Unit Epimysium, perimysium,
endomysium, and sarcolemma PEC
parallel w/ contractile component
Musculotendinous Unit
CC
PEC
SEC
Functions of Elastic Components Ensure readiness for contraction Ensure contractile elements return
to resting position May prevent overstretching of
passive elements
Functions of Elastic Components
SEC and PEC are viscoelastic:
absorb energy to rate of force application
dissipate energy in time dependent manner
Storage of Elastic Energy SEC can store elastic energy
Return it to system
Plyometrics
Plyometrics Quick stretch/prestretch loads SEC
counter-movement
Elastic energy is returned to system and movement is carried out
Types of Contraction
Eccentric > Isometric > Concentric
Eccentric/Isometric supplemental tension thru SEC longer contraction times greater
cross-bridge formation
Types of Contraction
Isokinetic – constant velocity accommodating resistance
Isotonic – constant tension on muscle throughout ROM
Types of Contraction
Isoinertial constant resistance
int. torque resistance isometric
int. torque > resistance concentric
Types of Contraction
Isoinertial simulate ADL
inertia is overcome
muscle contracts concentrically and torque is submaximal
Force Production
Length–tension relationship
Tension/force is greatest when @ resting position
Length-Tension Relationship
Length-Tension Relationship
Length
Ten
sion
Res
ting
L
engt
h
Total Tension
Passive Tension
Active Tension
Length-Tension Relationship
CC --> Active Tension
SEC and PEC --> Passive Tension
> length --> greater contribution of elastic component to total tension
Length-Tension Relationship
Single joint vs. 2 joint muscles
Length-Tension Relationship
Constant muscular tension Lower metabolic cost for eccentric
contractions Mechanical energy is stored in
elastic components
Length-Tension Relationship
Length
Ten
sion
Short-fiber muscle of large cross-section
Long-fiber muscle of small cross-section
Force-Velocity Curve
Velocity
Load
Isometric
0
Eccentric Concentric
Force
Architecture Pennation
Fiber Length
PCSA
Pennation
FT = FMcos
Fiber Length
40 - 100 mm sartorius (450 mm) semitendinosus (160 mm) soleus (20 mm)
Fiber Length
longer fibers # of sarcomeres range of excursion producer velocityshorter fibers greater ability to produce force
PCSA Linearly related to max force
output
Relationship between PCSA and Fiber Length
PCSA and Fiber Length
Effect of Temperature in conduction velocity
in frequency of stimulation in force production
Effect of Temperature in metabolism efficiency of
muscle contraction
in elasticity of collagen in SEC and PEC extensibility in musculotendinous unit
Mechanisms of temperature in blood flow thru warming
up/exercise
in metabolism, release of energy from contractions, friction (contractile components
Muscle Injury & Mobilization Early motion may reduce atrophy
Generation of // fiber orientation
More rapid vascularization
Tensile strength returned more quickly
Muscle Disuse• Selective atrophy of Type I fibers
• electrical stimulation may help minimize atrophy
Resistance Training• Hypertrophy vs. hyperplasia
• Alteration of fiber type
Resistance Training
Basic Concepts:
• Apply resistance
• Progressive overload
• PRE
Stretching• muscle flexibility
• maintains/increases joint ROM
elasticity and length of musculotendinous unit
• permits musculotendinous unit to store energy (time and amplitude dependent) in SEC and contractile components
GTO• in series with contractile proteins
(extrafusal) – respond to increase in tension inhibit contract and enhance relaxation
Intrafusal muscle spindles
Primary• respond to changes in rate of
lengthening
• dynamic response
• strong
Intrafusal muscle spindles
Secondary• respond to the actual length
change
• static response
• weak
Conflicts
rate of stretch slow may bypass the dynamic response
• negating the spindles
Main Goal
inhibit muscle spindle effect and promote Golgi effect enhance stretch