muscle systems and movement Flashcards
type I muscle fibers:
diameter size
appearance
fatigue speed
metabolism
ex:
slow twitch/ oxidative fibers
- small diameter
- dark (myoglobin and mitochrondria)
- slow fatigue
- fibers depend on aerobic metabolism
ex: high % in postural muscles - erector spinae, soleus
type II muscle fibers:
diameter size
appearance
fatigue speed
metabolism
ex:
fast twitch/ fast oxidative - IIa and IIb
- large diameter
- white
- quick fatigue
- associated w anaerobic metabolism
ex: high % in phasic muscles (rapid force and power) ex: hamstrings, gastrocs, UE flexors
agonist muscle:
principle moving muscle that produces contraction (concentric, eccentric, isometric)
antagonist muscle:
produces opposite motion of agonist, typically passively elongates/ shorten during activity
do muscles pull w equal or unequal force on their origin and insertion?
equal
where are muscles the weakest?**
the musculotendinous junction
what conditions (4) make predicting muscle function possible and why do these conditions RARELY occur:
- proximal attachment is stabilized
- distal attachment moves towards proximal
- proximal attachments often move toward the fixed distal attachments (CKC)
- contractions can be con/ecce/isometric - distal segment moves against gravity
- movement can be assisted by gravity - muscle acts alone
- seldom occurs
isometric contraction:
action
no apparent change in joint angle
- stabilizing
concentric contraction:
action
work?
muscle shortening
- accelerating
- muscle is doing = positive work
eccentric contraction:
action
work?
muscle lengthening
- decelerating
- outside force responsible for motion being controlled by the muscle = negative work
isotonic activation:
contraction resulting in joint moving through ROM
*torque exerted by weight chnages as joint angle changes
isokinetic activation:
contraction occurs when rate of movement is constant
3 functions of a synergist (most common muscular function):
- identical activity as agonist
- stabilize proximal joints to support distal
- obstruct unwanted agonist action (ex: flexor carpi radialis and extensor carpi radialis longus)
viscosity:
resistance to external force that causes permanent deformation
ex: heat to stretch
extensibility:
ability to stretch
elasticity:
ability to elongate and return to normal length
viscoelasticity:
the more extensibility a tissue has, the less viscosity
stress strain:
amount of deformation a structure can tolerate before succumbing to stress
is getting in the plastic range always bad?
no - microscopic damage b/n collagen fibrils occurs, but if muscle is too tight we might want that change
toe region
up to 2% strain - intital slack uptake
necking range
just before 10% strain = macroscopic damage
further strain = failure
creep:
elongation of tissue from low level load over time
ex: long duration stretching
dynamic stretching:
used when?
actively moving thorugh full ROM
- pre-activity
4 stretching types for gaining tissue length:
- static stretching = muscle moved into lengthened position
- active assisted
- PNF = contract/ relax to retain communication n/n brain&body part
- ballistic = rapid bouncing to push elongation
C/I’s to stretching:
- disrupt healing/ result in injury
- myositis ossifications
- incomplete fracture healing
- joint subluxation/ dislocation
- bony block
- acute inflammation
- sharp pain
- hypermobile joints
- shortened tissues = beneficial
ex: high divers
ex: deficient ACL - keep hammies tight to increase joint stability by decreasing muscular flexibility
stretching precautions:
- post injury; tissue healing stage
- post immobilization or radiation
- age of osteoporosis
- muscle relaxants
- newly healed fractures
- ensure cooldown post exercise
- know typical ROM and respect it
does static stretching impair performance?
yes, if for 60+ seconds before strength tasks
factors that influence muscle strength(8):
- muscle size
- fiber architecture
- passive components of muscles
- length-tension relationship of the muscle
- moment arm of the muscle
- speed of muscular contraction
- active tension
- age and gender
2 parameters of muscle size:
- length = fibers in series
- width
what is length vs width of muscle associated with/ what does it provide?
length:
- associated w speed
- longer muscles = mobility
width:
- associated w greater ability to produce force
- shorter muscles = stability
how does CSA impact muscle?
larger CSA = greater force-generating capacity
2 types of fiber architecture:
- fusiform
- pennate
fusiform fibers:
“strap” = fasicles are long and parallel
- great distance, less form
ex: sartorious
pennate fibers:
types?
attach at oblique angles to a common tendon = more rows of fibers
- greater capability to produce force
1. unipennate
2. bipennate
3. multipennate
what is the total strength of pennate muscles?
sum of CSA of each pennate
more layers = more force
3 types of fascia:
- endomysium = fiber layer
- perimysium = groups of fasicles
- epimysium = entire muscle
passive components influencing muscle strength:
- parallel elastic component
- series elastic component
parallel elastic component:
fascia is parallel to muscle fibers
muscle elongates past slack = fascia is passively stretched as muscle keeps lengthening
series elastic component
tendon-muscle-tendon
muscle transfers forces along tendon to bone - motion
do parallel and series lengthen together?
yes - this results in muscular stiffness/ tension
when are the max crossbridges available?
at resting length
when is torque typically greatest?
at mid range (100% of muscle force rotates joint when insertion is perpendicular to bone segment)
how does angle of insertion influence torque?
changes line of pull and devotes force to compression or distraction
does rate of m contraction affect m force?
yes
consider force velocity curve
what is active tension?
affected by?
force produced by as muscle
affected by:
- #MU
- type of MU recruited
- rate/ frequency of MU firing
which type of muscle fiber is recruited first?
small before big (larger axon = less excitable)
slow before fast (type I before II)
how do age and sex impact muscle strength?
- peak strength 20-30yrs
- # MU decline w age
- males > females
- lean/whole body mass ratios
muscle excursion:
how far a muscle can shorten beyond its resting length
functional excursion:
the distance a muscle can shorten after being lengthened as far as its moveable joint allows
what muscles have the most excursion?
2 joint muscles
- generate power in many places at once
passive insufficiency
muscles elongated over 2+ joints simultaneously
- one muscle completely shortened, antagonist completely lengthened
ex: hamstring, hip flexor
tenodesis
passive tension of 2 joint muscles resulting in passive movements of these joints
active insufficiency
multijoint muscles
- cant create enough tension to concurrently move all joints through full ROM
ex: grip strength in wrist flexion
biceps at elbow - which position is optimal?
length of muscle optimal at 0 (full extension) BUT
internal moment arm optimal at 90
what contributes to crossbridge mechanisms and elastic forces?
mechanical contributions = PE returned as KE following rapid stretch of a muscle tendon unit
neural contributions = w quick stretch, facilitation of stretch reflex
do most muscles show greater force at longer or shortened legnths?
longer
ex: pronator teres
what muscles rely more on internal moment arms?
quadriceps femoris
delayed onset muscle soreness:
decrease in ROM due to pain/ discomfort and decrease in max muscle forces
- damage at sarcomere level throughout muscle = body adapting, not bad
muscle strain:
varying degrees of micro-macro strain
- typically at muscle-tendon junction
