167 Cards in this Set
| Front | Back |
|---|---|
|
3 types of muscle:
|
Smooth muscle *involuntary control
Cardiac muscle *involuntary control
Skeletal muscle *voluntary control
|
|
Skeletal Muscle:
|
Over 600 responsible for movement of body & all joints
|
|
Role of skeletal muscle:
|
Movement
*215 pairs work in cooperation w/ each other to perform opposite joint actions @ joints they cross
Provide protection
Contribute to posture & support
Produce major portion of total body heat
Striated muscle tissue
Under voluntary control (controlled by the somat…
|
|
Skeletal Muscle: structure & function:
|
In order for a muscle to attach to a bone (at origination & insertion points), must have tendons
Tendons don’t have a lot of blood; muscles & bones have a rich amount of blood
|
|
Tendons:
|
Flexible but inelastic cord of strong fibrous collagen tissue; they will tear
Attaches muscle to bone
Come from all 3 mysium which from skeletal muscle fusing together
|
|
Skeletal muscle composed of 3 types of mysium:
|
Epimysium *outside
Perimysium *middle
Endomysium *inside
|
|
Epimysism:
|
Surrounds entire muscle & holds it together
Outermost layer
|
|
Perimysium:
|
Surrounds group of muscle fibers (aka: fasciculi)
“Middle layer”
|
|
Endomysium:
|
Surrounds individual muscle fibers
Inner most layer
|
|
Endomysium surrounds:
|
Sarcolemma
*Cell or plasma membrane
Sarcoplasm
*Fluid inside cell or cytoplasm
Muscle cell
*In scarcoplasm are muscle fibers, called myofibers
|
|
Myofibers made up
|
of myofibrils; Myofibrils composed of chain of scaromeres
|
|
Scaromere:
|
The smallest functional unit of a muscle
The basic functional unit of a myofibril
|
|
Within each myofibril there are 2 types of small protein filaments that are responsible for muscle action:
|
Myosin filament and actin filament
|
|
Myosin and actin are the two proteins,
|
within the sarcomere, that actually cause the muscle action
|
|
Myosin:
|
One of the proteins that forms filaments that produce muscle action
|
|
Actin:
|
A thin protein filament that acts w/ myosin filaments to produce muscle action
|
|
Myosin & Actin are:
|
Contractile proteins that make up muscle fiber, called myofibril
|
|
Myofibril:
|
The contractile element of skeletal muscle
Cause muscle contraction
|
|
Within myofibril, muscle contraction happens btwn: Two muscle fibers:
|
actin & myosin
|
|
Myosin filament:
|
Thick filament
Contains myosin heads which protrude from the myosin filament
Myosin heads form cross-bridges
*cross-bridges: interact during muscle actin w/ specialized active sites on actin filaments
|
|
Actin filament is
|
a thin filament
|
|
Actin filament Made up of the following:
|
Actin mol.
Troponin
Tropomysin
|
|
together, troponin and tropomysin prevent binding of actin
|
with myosin during resting stage of sliding filament theory
|
|
Muscle contraction:
|
The use of actin and myosin during muscle contractions is best described by the sliding filament theory
|
|
Sliding filament theory:
|
Cycle of repetitive events that cause the thin, actin filament to slide over the thick, myosin filament to generate tension in the muscle
Initiated by an action potential
5 distinct stages
The complex series of events in muscle contraction are set in motion by an electrical motor-nerve…
|
|
5 stages of sliding filament theory:
|
Rest
Excitation-coupling
Contraction
Recharging
Relaxation
|
|
Sliding filament theory: Rest:
|
Myosin cross bridge has ATP @ tip
*ATP bids to myosin & is hydrolyzed by ATPase into ADP & phosphate
*Energy released by this process activates myosin head & cocks it into high-energy, extended position
Myosin cross bridge is not attached
*Tropomyosin & troponin are blocking a…
|
|
Sliding filament theory: Excitation-coupling:
|
Action potential
Calcium ions flood in & attaches to troponin actin mol.
*Unlocks binding site on actin
*Results in excitation
-The thin actin filament shifts & changes shape in anticipation of myosin attachment
Myosin heads bind to newly exposed active site on thin, …
|
|
Sliding filament theory: Contraction:
|
Myosin releases the ADP & phosphate & returns to low energy position
As release ATP, myosin pulls thin, actin filament dragged to new location = results in Power Stroke
*Myosin cross-bridge changes shape
|
|
Sliding filament theory: Recharging:
|
A new ATP mol. Is put back on the tip of the myosin cross-bridge
*If this does not happen, the myosin will not let go of the actin (possible cause of muscle cramping)
Myosin detaches from actin
*If actin binding sites are still available, myosin can bind again with actin
|
|
Sliding filament theory: Relaxation:
|
When action potentials stop arriving
Calcium release stops & calcium floods away
*Due to motor nerve impulse
Binding sites on actin closed; myosin can no longer achieve strong binding state with actin
Crossbridge is prevented
Relaxation of muscle is achieved passively
|
|
Action potential:
|
Stimulates the opening of calcium channels
This opening allows for inflow/ outflow of calcium which play a hugely important role in muscle contraction
|
|
Factors affecting muscle tension development: Action potential:
|
An electrical signal from brain & spinal cord which travels to muscle by way of efferent (motor) nerves signaling the particular motor unit(s) to contract
Initiates the excitation-coupling of myosin & actin during sliding filament theory
*Stimulating the voltage-gated calcium channe…
|
|
Varying levels of strength of action potential:
|
Subthreshold Stimulus: not strong enough to produce action potential in one motor unit
Threshold stimulus: strong enough to produce action potential in one motor unit
Submaximal stimulus: strong enough to produce action potentials in additional motor units
Maximal stimulus: stron…
|
|
Factors affecting muscle tension development:
|
Arrival of single action potential produces a weak, very brief action of fiber, called a twitch
One twitch is not very useful for most activities, because contraction is weak
|
|
Producing strong contraction can be accomplished two ways:
|
Increase the number of fibers contracting
Increasing frequency of motor unit activation within a single fiber
Sending multiple action potentials to muscle fiber
Greater contraction forces can be generated by increasing frequency of motor unit activation
|
|
Frequency of motor unit activation of single fiber follows these steps:
|
Latent period
No change in muscle fiber length
Contraction phase
Muscle fiber begins to shorten
Relaxation phase
Muscle fiber begins to lengthen back
Summation
Occurs when successive stimuli are provided before the relaxation phase of the first twitch is complete
S…
|
|
Tetanus:
|
Occurs if the stimuli are provided at a frequency high enough that no relaxation of the muscle fiber can occur between contractions
|
|
Treppe:
|
Occurs when multiple maximal stimuli are provided at a low enough frequency to allow complete relaxation between contractions to rested muscle
*Slightly greater tension is produced by the 2nd stimulus than with the 1st
*3rd stimulus produces even greater tension than the 2nd
|
|
Nervous signals 2 Types:
|
Afferent (away from the muscle to the brain)
Efferent (away from the brain to the muscle)
|
|
Afferent (sensory) nerves:
|
From muscle to brain
Sends information from muscles to CNS
|
|
Efferent (motor) nerves:
|
From brain/ spinal cord to muscle
Tell muscles to contract 8
|
|
Somatic Motor Neuron:
|
Nerve cell that processes and transmits information from CNS to muscle
Composed of:
Dendrite
Cell body
Axon – w/ myelin sheath
|
|
Myelin:
|
Fatty substance wrapped around axon
Speeds up rate of conduction of neurons
Prevents signal decay
|
|
Motor Neuron:
|
Nerve cells that processes and transmits information to directly or indirectly control muscle, including skeletal muscle
Signaled motor neuron may innervate (communicate with) one or many muscle fibers
The motor neuron and all of the muscle fibers which it innervates are collectivel…
|
|
Neuromuscular Synapse/ Junction:
|
Connects the nervous system to the muscular system
Located at the end of the motor neuron
Allows for the motor nerves to communicate with or innervate muscle fibers
|
|
Action Potential/ Efferent Nervous Signal:
|
The signal that travels down the motor nerve fiber, reaching the terminal button (the end of the motor neuron) at the neuromuscular junction
Signals the voltage gated calcium channels to open
Calcium is allowed to move from the sarcoplasmic reticulum (where the calcium is stored) in…
|
|
Motor unit:
|
A motor nerve & all that it innervates or communicates with
Signals the contraction of muscle fibers if stimulus is adequate for each of the fibers
*Action potential
To produce more force, the main method I to recruit more fibers to contract; ie recruitment
|
|
Motor unit: Recruitment:
|
increase the number of fibers innervated
The main muscular response used to produce greater muscle tension
|
|
Recruitment Depends on:
|
The number of muscle fibers within each activated motor unit
The number of motor units activated
|
|
All or none principle:
|
Regardless of number, individual muscle fibers within a given motor unit will either fire and contract maximally or not at all
|
|
All muscle fibers w/ in one
|
motor unit are the same type of muscle fiber
|
|
The motor nerve dictates what type of
|
fiber (SO, FG, FOG) the particular motor unit is
|
|
The recruitment of fiber toes usually occurs in a preferential manner according to the size of the motor nerve supplying the fibers:
|
The smallest fibers are recruited first; have more endurance; slow twitch
The largest fibers are recruited last; have less endurance; fast twitch
|
|
Fiber composition of motor units:
|
Can have motor units w/ a lot or a few fibers
|
|
Fiber composition of motor units: Very precise:
|
small motor unit
a small # of fibers controlled by one motor unit
ex. Motor units that control eye movement
|
|
Fiber composition of motor units: Less precise:
|
Large motor unit
A large # of fibers controlled by one motor unit
|
|
All muscle contractions/ actions are
|
caused by muscle fibers
|
|
Two types of muscle fibers have been identified:
|
Slow twitch
Fast twitch
|
|
Slow twitch:
|
Build & decrease tension slowly
|
|
Only one type of slow twitch:
|
Slow oxidative (SO)
|
|
Fast twitch:
|
Build & decrease tension quickly
|
|
Two types of fast twitch:
|
Fast glycolytic (FG)
Fast oxidative & glycolytic (FOG)
|
|
Slow oxidative (SO): Fuel source:
|
oxidative phosphorylation
*Oxidative phosphorylation creates ATP through the electron transport chain; Requires oxygen to create energy
|
|
Slow oxidative (SO): Characteristics:
|
Low strength of contraction
Low anaerobic capacity
Small in size
High capillary density
Highly resistant to fatigue
Their red because of the capillaries
|
|
Slow oxidative (SO): When Used:
|
Activities that are done over a longer period of time but that don’t require a great deal strength
Exs: running a marathon, hiking, walking, swimming long distances
|
|
Fast Oxidative & Glycolytic (FOG): Energy source:
|
Hybrid
C/ use energy made fast w/o oxygen (anaerobic pathway)
C/ use energy made slowly w/ oxygen (aerobic pathway)
|
|
Fast Oxidative & Glycolytic (FOG): Characteristics:
|
High speed & strength of contraction
C/ use energy made aerobically & anaerobically
Intermediate sized fibers
High capillary fibers
Fatigability varies
*More fatigable than SO
*Not as fatigable as FG
|
|
Fast Oxidative & Glycolytic (FOG): When Used:
|
Depends on energy source
|
|
Fast Glycolytic (FG): Fuel source:
|
Glycolysis
*Glycolysis energy pathway w/ 12 steps that gives off a lot of ATP quickly but also runs out quickly; No oxygen required to create energy
|
|
Fast Glycolytic (FG): Characteristics:
|
High speed & strength of contraction
High anaerobic capacity
Largest of the three types of muscle fibers
Low capillary density
Low aerobic capacity
Most easily fatigable
|
|
Fast Glycolytic (FG): when used:
|
Activities that are forceful & quick
Exs: sprints, grabbing kid from in front of bus
|
|
Cannot change fiber composition of:
|
Fast twitch fibers to slow twitch fibers
Slow twitch fibers to fast twitch fibers
|
|
Can change fiber composition of:
|
Fast glycolytic fibers into fast oxidative & glycolytic fibers
Fast oxidative fibers & glycolytic fibers into glycolytic fibers
*Possible b/c all w/ in the fast twitch category
*The aerobic capacity & glycogen content of the muscle c/ b improved w/ training
*Done through speci…
|
|
Neurons tend to recruit smaller fiber
|
types then larger fiber types
*smallest to largest, because they can with stand the duration of the activity a lot better than the fast ones
|
|
Producing strong contraction can be accomplished two ways:
|
Increase the number of fibers contracting
Increasing frequency of motor unit activation within single fiber
|
|
If summation/ tetanus is reached, the force of muscle contraction of fiber will increase accordingly, because
|
of increased calcium available and a muscle contraction will occur
|
|
Contraction-
|
when tension is developed in a muscle as a result of a stimulus
|
|
Two types of muscle contractions:
|
Isometric- still contraction
Isotonic- moving contraction
|
|
Isometric contraction/ action:
|
Active tension is developed within muscle but joint angles remain constant
Static contractions that prevent motion
Significant amount of tension may be developed in muscle to maintain joint angle in relatively static or stable position
May be used to prevent a body segment from b…
|
|
Isotonic contraction/ action:
|
Involve muscle developing active tension to either cause or control joint movement
Dynamic contractions
The varying degrees of tension in muscles results in joint angles changing
Isotonic contractions are either concentric or eccentric on basis of whether shortening or lengthenin…
|
|
Concentric contractions involve muscle developing active tension
|
as it shortens; Causing motion; when you stretch your arm out
|
|
Eccentric contractions involve the muscle
|
lengthening under active tension; Controlling motion; when you bend your arm
|
|
Concentric contraction (muscle action):
|
Muscle develops active tension as it shortens
Occurs when muscle develops enough force to overcome applied resistance
Causes movement against gravity or resistance
Described as being a positive contraction
Accelerates movement
|
|
Eccentric contraction (muscle action):
|
Muscle lengthens under active tension
Force developed by the muscle is less than that of the resistance
Occurs when muscle gradually lessens in tension to control the descent of resistance with gravity or resistance
Described as a negative contraction
Decelerates movement
|
|
Players during muscle action/ contraction:
|
Musculotendinous proprioceptors
Fiber length
Length-tension relationship
Elastic components
Insufficiencies
Force-velocity relationship
|
|
Proprioceptors:
|
Are mechanism by which the body is able to regulate body position & movement by responding to stimuli subconsciously & sending that information back to brain
Respond to changes in position & acceleration of body segments
|
|
These internal receptors are located:
|
In the skin
In the inner ear
In & around the joint, muscles, & tendons
|
|
Proprioceptors: Provide feedback relative to the:
|
The position of the body & limb
Movements of the joint
|
|
Multiple types of proprioceptors: Two stimulated during muscle actions/ contraction called:
|
Musculotendinous receptors
|
|
Two types of Musculotendinous receptors:
|
Golgi tendon organs
Muscle spindal
|
|
Musculotendinous receptors-
|
Used in muscular control & coordination
|
|
Provide feedback relative to the movements of the joint, specifically:
|
Tension within muscles
Length of muscles
Rate-of-change in length of muscles
Contraction state of muscles
|
|
Golgi tendon organs:
|
Located in the tendons
Sensitive to tension development in tendons
|
|
Golgi tendon organs: Due primarily to:
|
Muscle contraction
Passive stretch of tendon
|
|
Golgi tendon keeps muscle
|
from excessively contracting by inhibiting the motor nerve (protective effect)
|
|
Tension in tendons & GTO increases as muscle contracts, activating GTO:
|
GTO stretch threshold is reached
Impulse sent to CNS
CNS sends signal to muscle to relax
Facilitates activation of antagonist as a protective mechanism
|
|
Golgi tendon organs: Signals:
|
Afferent signal sent up spinal cord in response to excessive contraction or passive stretch of tendons
|
|
Responding efferent signal has two proposes:
|
Inhibition (relaxation) of the contraction of the associate muscle (agonist)
Excitation (contraction) of the opposing muscle, the associated muscles’ antagonist
|
|
When Golgi tendon signals fire, the result is
|
Inhibition/ relation of the agonist (working muscle)
Excitation/ contraction of the antagonist (associated muscle)
|
|
Musculotendinous receptors: Muscle Spindal:
|
Located in muscles between the fibers
|
|
Musculotendinous receptors: Muscle Spindal: Sensitive to:
|
Degree of muscle stretch
Rate of muscle tension
|
|
Musculotendinous receptors: Muscle Spindal: As you stretch a muscle:
|
Stretch of muscle spindals
Causes excites sensory nerves to sends signal up spinal cord
CNS sends motor signal to cause a reflexive contraction of the associated muscle (agonist contracts) occurs
*Called: Myotatic or stretch reflex
|
|
Musculotendinous receptors: Muscle Spindal: Signals:
|
Afferent signal sent up spinal cord in response to excessive stretch or rapid stretch
Efferent sent in response to “stretch” has two purposes
*Excitation & contraction of the associated muscle (agonist)
*Inhibition & relaxation of the associated muscles’ antagonist; Antagonist pr…
|
|
When muscle spindal signals fire, the result is
|
Contraction of the agonist (working muscle)
Inhibition/ relaxation of the antagonist (opposing muscle)
|
|
Musculotendinous receptors: Reciprocal Inhibition:
Two things can happen when muscle contracts:
|
Sensory nerve excites agonist & inhibits antagonist
Caused by: muscle spindal
Sensory nerve excite antagonist & inhibit agonist
Caused by: Golgi tendon organs
Either one occurring is called: Reciprocal Inhibition
|
|
Another factors that affects the contraction of the muscle is the
|
length of the muscle fiber before it is stimulated
|
|
This length before stimulation & subsequent tetanic tension development is called
|
the length-tension relationship
|
|
For each muscle, an optimal length exists for
|
developing tetanic tension (maximal tension development during the contraction)
This optimal length corresponds with maximum overlap of thick myosin filament & thin actin filament
|
|
Development of tension optimized when maximal
|
number of active actin sites are available for attachment of myosin crossbridges
|
|
If a sarcomere is stretched beyond its optimal length, force
|
output steadily declines
Decline occurs because thin filaments pulled away from thick filaments, preventing myosin heads from binding to active actin sites
|
|
If a sarcomere is not stretched to its optimal length,
|
force output is virtually zero
Lack of force production is due to actin sites being blocked by previously attached myosin heads physically preventing new myosin cross-bridges from binding
|
|
the theoretical optimal length of an
|
intact muscle corresponds to muscles resting length
|
|
The elastic force contributed by elastic components
|
changes this optimal length for optimal force production
|
|
The relationship between muscle length & muscle tension, at time muscle is stimulated to contract is as follows:
|
Shorter muscle= less tension
Longer muscle= more tension
But if muscle is too long= less tension
|
|
If don’t stretch beyond 70-80% of resting length =
|
ability to develop contractile tension and exert force is essentially reduced to zero
|
|
If stretched beyond 120-130% of resting length =
|
significant decrease in the amount of tension a muscle can develop & amount of force a muscle can exert
|
|
Generate greatest amount of tension can be developed
|
when a muscle is stretched between 120-130% of its resting level
|
|
Muscle articulation-biarticulate disadvantage: Active & passive insufficiencies:
|
Cannot contract (active) the same amount of muscle tension or stretch (passive) with the same amount of flexibility across two joints at the same time
No insufficiencies w/ one joint muscle
|
|
Muscle articulation-biarticulate disadvantage: Two types:
|
Active insufficiency
Passive insufficiency
|
|
Active insufficiency:
|
Point reached when muscle becomes shortened to point it can no longer generate/ maintain active tension
Ex: Hamstring Muscle
If shorten/ contract across on joint, ex: Hip
Cannot keep shortening (contracting) across other joint: Knee
Ie. Muscle can only shorten/ contract so much
…
|
|
Passive insufficiency
|
State reached with a muscle becomes stretched to point where it can no longer lengthen & allow movement
Ex: Hamstring muscle
If lengthen across on joint, ex: Hip
Cannot keep lengthening (stretching) across other joint: Knee
Ie. Muscle can only lengthen/ stretch so far
|
|
Final Player affecting force production during muscle action is: velocity of the contraction Called the Force-Velocity Relationship:
|
the greater the load against which a muscle must contract, the lower the velocity of that contraction will be
|
|
Force-Velocity Relationship: Angle of Pull:
|
@ 90 degress = 100% of muscle force contributes to movement of the bones
Muscle is strongest at 90 degrees
Muscle is weaker @ either end of 90 degrees
|
|
One of two situations occurs when tension is produced in a muscle:
|
A segment moves
A segment does not move
|
|
Two types of tension:
|
Dynamic tension (isotonic contraction)
Static tension (isometric contraction)
|
|
Dynamic tension (isotonic contraction)
|
When the segment moves in the direction or opposite to the direction of applied muscular tension
|
|
Dynamic tension (isotonic contraction) Two types:
|
Concentric tension:
Contraction of a muscle during which the muscle shortens & causes movement towards the midline of the body
Ex: up movement of push-up for triceps & down movement of push-up for biceps
Eccentric tension:
Contraction of a muscle during which the muscle length…
|
|
Static tension (isometric contraction)
|
When a muscle produces tension or force against an opposing force or resistance & the segment of muscle does not move
|
|
Only one type of static tension: Isometric tension:
|
Muscular contraction during which no discernible segmental movement is taking place
Ie. Muscles develop tension with no visible change in muscle length
Ex: plank; wall squats
Ex: arm wrestling someone with exactly equal strength
|
|
Force-Velocity Relationship:
|
A muscle c/ adjust the force of its contraction to match the resistance that it experiences during a contraction, at the cost of the speed of the contraction
The greater the load against which a muscle must contract, the lower the velocity of that contraction (fig. 11.20 p. 323 in hard…
|
|
Concentric (isotonic) contractions:
|
Slower speed (velocity) of concentric contraction – more force
Faster speed (velocity) of concentric contraction – least force
Probably due to:
High metabolic cost
Faster the contraction …
|
|
Static (isometric) contraction:
|
B/c static contraction occurs w/ out muscle movement- velocity is not an issue
Static contraction = more force than ANY concentric contraction
Ie. Static contraction c/ develop more force than even the slowest concentric contraction
Probably due to:
Maximal cross bridge intera…
|
|
Eccentric (isotonic) contraction:
|
Slower eccentric contraction- not as much force…
Faster eccentric contraction- more force (*up to a certain point where maximal force production reached)
Eccentric contractions, no matter the velocity, c/ develop more force than ANY velocity concentric contractions & even more than …
|
|
Amount of force generated listed from least to greatest:
|
Faster concentric contraction
Slower concentric contraction
Static/ isometric contraction
Slower eccentric contraction
Faster eccentric contraction
|
|
Force-Velocity Relationship: Muscle Power:
|
Due to force-velocity relationship, get maximum amount of force generation @ approx.ly 30% of maximal contraction velocity
Beyond = 30% of maximal velocity, force production decrease with increasing velocity
= slow down amount of the time spent on contraction (velocity of shortening…
|
|
Skeletal muscle tissue has four main neuromuscular properties related to its ability to produce force & movement about joints:
|
Irritability/ excitably
Contractility
Extensibility
Elasticity
|
|
Irritability/ excitably:
|
The sensitivity or responsiveness of a muscle to a stimulus-either chemical, electrical or mechanical
Ie. Muscles are considered irritable b/c can receive and respond to a signal
Without irritability/ excitability, muscles wouldn’t fire = no movement
This function allows for ALL …
|
|
Contractility:
|
The ability of muscle to change shape, contract (become shorter & thicker), and develop tension or internal force against resistance, if & only if, appropriate stimulus (action potential) is provided
Ie. Muscles can develop tension
Ex: some people can lift enormous amount of weight
…
|
|
Extensibility:
|
Ability of a muscle to be passively stretched & extended beyond its normal resting length
Ie. Can stretch a muscle & all that runs through it
Allows for contractility & flexibility
|
|
Elasticity
|
Ability of muscle to return to its original or normal resting length following a stretch
Given the chance, once stretched, a muscle will spring back into original position
Ex: bubble gum vs. rubber band
Allows for flexibility
|
|
With these properties, skeletal muscles can exhibit:
|
Flexibility
Strength
Endurance
Power
|
|
Flexibility:
|
Muscle can stretch through a small or large range of motion
Dependent on the joint:
Ie. Just b/c flexible are hip does not mean flexible at hamstring
|
|
Strength:
|
The component of muscle force that produces torque at the joint
Measured as a function of the collective force-generating capability of a given functional muscle group
Ie. Maximal force can produce at one period of time with one muscle or muscle group
Measured w/ 1 rep max = one …
|
|
Factors that affect strength (4):
|
Training state of muscle
With both concentric & eccentric strength gain in strength over approx.ly first 12 weeks appears to be related to neuromuscular adaptation, and not increase in cross-sectional area
Muscle cross-sectional
Relates to tension-generating…
|
|
Neuromuscular adaptation: the improved innervation of the trained muscle; includes:
|
Increased neuronal firing rates
Increased excitability
Increased levels of motor output from the CNS
|
|
Endurance:
|
The ability of the muscle to exert tension over time
The longer the tension is exerted, the greater the endurance
Ie. Repeated submaximal force development
Measured over time or by the number of reps can do at certain submaximal amount of force
Importan…
|
|
Factors that affected power:
|
Muscular strength (force production at muscle)
Movement speed (velocity)
*Important for anaerobic activities that require explosive movements, such as Olympic weight lifting, throwing, jumping, sprinting
Therefore, FT muscle fibers are an asset for individuals trainin…
|
|
Power:
|
The rate at which work is performed
The product of muscular FORCE & the VELOCITY of muscle shortening
|
|
The rate of force or torque production at a joint:
|
Muscle Power
= work or force * velocity
= work * velocity
|
|
Muscle Power:
|
force production per unit time
How quickly c/ you generate a lot of time
Two important factors:
Force of contraction
Velocity of movement (time)
|
|
Peak powers occur at:
|
Intermediate level of velocity
Beyond 30% of maximal velocity, power production decreases
&
Intermediate level of muscle shortening & tension generation
If not stretched beyond 70-80% of resting length, ability to develop contractile tension and exert f…
|
|
When training for flexibility, strength, endurance, & power, skeletal muscles can exhibit:
|
Fatigue
Strains
Contusions
Cramps
DOMS *delayed
Compartment Syndrome *very uncommon
|
|
Fatigue:
|
An exercise-induced reduction in the maximal force capacity over time of muscle
The opposite of endurance
The more rapidly a muscle fatigues, the less endurance it has
|
|
Fatigue may occur in:
|
The muscle fiber
The motor unit itself (inhibiting ability to generate an action potential = no muscle twitch or contraction)
|
|
Variety of factors affect rate of fatigue of muscle:
|
Type & intensity of exercise
Specific muscle groups involved in exercise
Physical environment in which the activity occurs
Muscle fiber type & pattern of motor unit activation
|
|
Cause of fatigue:
|
Inconclusive, but postulations include:
Reduction in rate of intracellular calcium release & uptake by sarcoplasmic reticulum
This is major theory thought to be best explanation
Increases in muscle acidity & intracellular potassium levels
|
|
Characteristics of fatigue:
|
Reduction of muscle force production capabilities
Reduction of shortening velocity
Prolonged relaxation of motor units between recruitment
Prolonged twitch duration
Prolonged sarcolemma action potential of reduced amplitude
|
|
Stains:
|
Overstretching of muscle tissue
Magnitude of injury related to size of overload & rate of overloading
|
|
Severity & symptoms of strain can be:
|
Mild
Minimal structural damage
Feelings of tightness or tension in muscle
Moderate
Partial tear in muscle tissue
Symptoms include pain, weakness, loss of function
Severe
Severe tearing of muscle
…
|
|
Most frequently strained muscle in human body:
|
hamstrings cause their not flexible because they are 2 joint
|
|
Contusions
|
Muscle bruises
Caused by: compression forces sustained during impacts
Symptoms; hematomas within muscle tissue
If it is severe enough it can lead to development of much more serious condition called myositis ossificans, or calcification within the muscle
|
|
Cramps
|
Include moderate to severe muscle spasms with proportional levels of accompanying pain
Causes:
Etiology is not well understood
Possibly factors include:
Electrolyte imbalances
Deficiencies in calcium & magnesium
Dehydration
|
|
Delayed onset muscle soreness (DOMS)
|
Occurs after some period of time following unaccustomed exercise
Arises 24-72 hours after participating in long or strenuous bout of exercise (hints name Delayed, as it is not immediate)
Caused by: Microtearing of muscle tissue
Symptoms include:
Same kind of histological chang…
|
|
Compartment Syndrome:
|
Hemorrhage or edema within a muscle compartment
|
|
Compartment Syndrome: Caused by:
|
injury or excessive muscular exertion
Pressures increase within the compartment causing sever damage to neural & vascular structures within compartments following the absence of pressure release
|
|
Compartment Syndrome: Characterized by progressive:
|
Swelling
Discoloration
Diminished distal pulse
Loss of sensation
Loss of motor function
|
KIN 365: EXAM 1