force, velocity, and power Flashcards
what is the shape of the length tension curve
inverted U shape
why does the length tension curve have that shape
at contractile end of ROM
- muscle produces less force because there’s not much room to move
at tensile end of ROM
- muscle produces less force because there’s not enough overlap for cross bridge cycling
what affects the force velocity characteristics of muscle contraction
number of cross bridges forms
environmental conditions
what are the sarcomere properties during isometric hold
amount of filament overlap depends on the length at which the muscle is held prior to activation
what are the sarcomere properties during shortening (concentric)
- sliding movement allows myosin filaments to become overlapped by actin
- tension in muscle increases while the muscle is getting shorter
what are the sarcomere properties during lengthening (eccentric)
- cross bridges generate less tension than the external stretching force applied to the muscle (lengthen)
- opposing acting filaments in the sarcomeres are pulled away from each other
- tension in muscle increases when the muscle is stretched
what causes active vs passive tension
active = actin and myosin
passive = titin
- exponential increase in titin activity as muscle length increases
how does total tension change through movement
- increases (active)
- decreases (dip between active and passive tension)
- increases again (passive - titin)
what is the popping sarcomere hypothesis
uncontrolled extension of individual half sarcomeres in each myofibril
how do sarcomeres “pop”
sarcomeres are stretched until its passive tension is unable to support the force and the half sarcomere pops
- occurs one at a time from weakest to strongest
- actin and myosin aren’t overlapping but titin maintains structure
what causes DOMS
after eccentric contraction
- half sarcomeres popped
- sarcomere length increases (stretched)
- metabolites released into muscle and accumulate
- activates free nerve endings
what do group III/IV (mostly III) afferents respond to
mechanical deformation and intramuscular substances that cause pain
- project to the CNS and promote sensation of pain
what is the shape of the force-velocity curve
non linear inverse relationship
- less force = higher velocity
- more force = lower velocity
(zero velocity = highest force)
what is the shape of the power curve
inverted U
- with optimal F and V values below 50% of their max values
what are the values of P and V at F max
P and V = 0
what are the values of P and V at F <50% max
P = max
V <50% max
what are the values of P and V at F = 0
P = 0
V = max
when are there more sarcomeres in series
when the muscle is less pennated
when are there more sarcomeres in parallel
when the muscle is more pennated
what is the function of sarcomeres in series
more energy efficient in terms of displacement
- high speed
ex: hamstrings and dorsiflexors (longer muscles with less force but higher speed)
what is the function of sarcomeres in parallel
more efficient in force production
ex: plantar flexors, and quads (short muscles with large force and slow velocity)
what causes more sarcomeres in parallel
hypertrophy
what values are equal and unequal between the two types (series and parallel)
equal = work and power potential
unequal = force, displacement, velocity
what is ACSA
largest CSA along the length of the muscle (girth only)
what is PCSA
total CSA of all fibres within the muscle (perpendicular to fibres)
- depends on muscle pennation
what is the effect of pennation on muscle force production
more pennated = stronger muscle
- can become more pennated with high resistance training - more sarcomeres in parallel
less pennated = faster muscle - lower force production
