muscle mechanics Flashcards
purpose of muscles
3 of them
- enable boens to move at joints
- provide strength and protection to skeleton
- absorb shock and distribut loads
muscles properties
- extensibility
- elasticity
- contractility
connective tissue surrounding muscle fiber
- epimysium: covers muscles
- perimysium: covers fasicles
- endomysium: covers fibers
structures within muscle fiber
- sarcolemma: muscles cell membrane
- myofibril
- sarcomere
structures within a sarcomere
- actin
- myosin myofilaments
6 things affecting muscles funtion
- muscles actions
- joint structure
- muscles structure
- contraction type
- muscles mechanics
- neuromuscular
factors affecting muscle force production
- cross sectional area
- fiber type
- type of contraction
ratio of actin to myosin
6:1
what happens to cross sectional view of myofibril during muscle damage
- increases
- more actin and myosin added by proteins
mechanical properties that determine fiber type
- contraction force
- contraction time
- time to 1/2 relaxtion
- fatigue rate
what is an isoform and how does it affect muscle fiber types
- deviation from set protein
- changes mechanical properties
how many total isoforms are there
- 86 myosin
- 6 action
- 516 total
what is the size principle
fibers recruited slow to fast
what is selective recruitment
-send out signals for high amp/high freq fibers and bypasss slow twitch
what is rate coding
amplitude + frequency
-every muscles fibers of same MU has same rate coding
what is the mechanical model of the musculotendinous unit?
- contractile component: active
- series eleastic component: passive (eligned end to end)
- parallel elastic component: passive (elignd on top of eachother)
anatomical structures represented in mechanical model of MTU
- CE: muscles fibers
- SEC: tendons
- PEC: epi-, peri-, and endomysiums
contribution of CE/SEC/PEC in concentric contractions of a constant load (ex405lbs)
- CE= 100%
- PEC and SEC = 0%
contribution of CE/PEC/SEC in ecentric contraction of a contant load (ex405lbs)
-what does this tell you about the diff btwn 2 conctractions
- CE= 80%
- SEC= 15%
- PEC= 5%
- require less energy to eccentrically contract a constant load
contribution of CE/SEDC/PEC in concentric contractions of a constant intensity (1RM)
- CE= 100%
- SEC and SEC= 0%
contribution of CE/SEDC/PEC in ecentric contractions of a constant intensity (ex 1RM)
-what does this tell you about the diff btwn the 2 contractions
- CE= 100%
- SEC= 15%
- PEC= 5%
- can manage more load during eccentric contraction during constant intensity
why does the force potential production decrease as muscle length shortens?
-why does it eventually reach 0?
- # cross bridges formed decrease
- b/c actin overlap on eachother and bottom one will block top one from binding to myosin
- 0 b/c: myosin acts as barrier to Z discs
why does the force potential production decrease as muscle length lengthens?
-why does it eventually reach 0?
- # of cross bridges formed decreases
- b/c actin doesnt have any overlap with myosin
- 0 b/c: no overlap at all
what happens to the tension and speed of contraction as the load increases in a concentric and eccentric contraction
con: -tension increases
- speed drecreases
ecc: -tension increasees
- speed increases
when can the max force be produced in a muscle in relation to veolcity
- isometric contraction
- velocity = 0
what happens to force produced by an eccentric contraction as velocity increases
-force increases
what happens to force produced by a concentric contraction as velocity increases
-force decreases
why does force decrease w/ concentric contractions as velocity increases
- greater load so need mroe cross bridges
- more time needed to form more crossbridges
- if you go too fast the actin and myosin do not have time to make cross bridges as they slide past eachother
- increased latency period to transmit tension
equation of power
if decreased force what will power be?
P = F x V
-deceased power
factors affecting force production of the MTU
6 of them
- CSA
- fiber type
- type of contraction
- muscle fiber architecture
- force length relationship
- force velocity relationship
factors affecting velocity of contraction
4 of them
- muscle length
- shortening rate per sarcomere or muscles fiber (dependent on muscle fiber type)
- fiber arrangement
- the load needed to be moved
factors affecting muscles torque production
- all factors affecting force prodcution by MTU
- moment arm length
what happens to the force length curve as velocity increases
- curve gets smaller
- aka max point goes lower
what happends to force as velocity increases and length increases/decreases from rest length
-decrease
what happends to muscle length and moment arm length as jnt angle decreases
- muscle length decreases
- moment arm length increases, peaks, then decreases
factors affecting strength curve
- muscle length
- moment arm length
- velocity of contraction
what happens to strength curve as:
- concentric contractions get faster
- eccentric contractions get faster
- con:decreases
- will have less torque at a set jnt angle
- ecc: increases
- will have more totque at set jnt angle
