skeletal muscles mechanics Flashcards
strength depends on?
muscle force x moment arm
what are the mechanical factors of strength?
rotary component of muscle force and length of moment arm
what are the physiological factors of strength?
length of the muscle, velocity of contraction, fiber orientation, cross sectional area, and fiber type
what are the 3 types of muscle fibers?
type 1 type 2a type 2b
what are type 1 muscle fibers?
slow twitch oxidative
what are some characteristics of type 1 muscle fibers?
small diameter, red in color, dense in capillaries, seed of contraction is slow, rate of fatigue is slow
what are muscles predominantly type 1 called?
stability or postural tonic muscles
what are type 2a muscle fibers?
fast twitch oxidative glycolytic
what are some characteristics of type 2a muscle fibers?
intermediate diameter, fast speed of contraction, and intermediate rate of fatigue
what are type 2b muscle fibers?
fast twitch glycolytic
what are some characteristics of type 2b muscle fibers?
large diameter, white in color, sparse capillarity, fast speed of contraction and fast rate of fatigue
what are muscles predominantly type 2 called?
mobility, non postural, phasic muscles
________ surrounds the whole muscle
epimysium
________ surrounds the fascicules
perimysium
________ surrounds the individual muscle cells
endomysium
What are contractile elements?
contractile proteins (actin and myosin)
what are parallel elastic elements (PEC)?
peri, ei, and endomysium (fascia)
what are series elastic elements (SEC)?
tendons
T/F with an isometric contraction the contractile element shortens and the series elastic element lengthens
true
by passively pulling on a muscle beyond rest length will ______ the PEC and they will also contribute to the _________
stretch, tension
what else will muscle force also vary with in accordance with the length tension curve?
muscle length
muscle force varies with cross sectional area of the muscle. what is key issue in determining the total cross sectional area?
fiber arrangement
cross sectional area increases what years? meaning?
0-20s max strength is at 20-30 years old
what percent of muscle strength do we have at age 65 compared to 20
85%
key notes with changes with aging
loss is reversible or can be minimized
loss of strength is more in legs than arms bc of sitting
males tend to be stronger than females
_________ of muscle contraction is a function of the load being lifted
velocity
speed of shortening of the myofilaments os the rate at which?
the myofilaments are able to slide past one another and form/reform cross bridges
speed is related to _______ ________ and ________
fiber type and length
T/F force generated is a function of the velocity of muscle contraction
true
when does max shortening speed occur?
when there is no resistance to shortening, however, no tension is developed in the muscle bc there is no resistance
describe concentrics muscle force generation
as shortening speed dec tension inc (slower = more force)
describe isometrics muscle force generation
speed is zero, therefore greater tension generated compared to concentrics
describe eccentrics muscle force generation
as speed of lengthening inc tension ince (faster= greater force)
muscle force with isometric
great strengthening but only at that joint angle +/- 10º
muscle force with concentric
dynamic, but velocity tension relationship often limits strengthening at higher velocities
muscle force with eccentric
great strengthening, possible tissue damage due to potential for large muscle force production
muscle force with isotonic
dynamic contractions, but intensity limited by capability in weakest part of ROM (typically end range)
muscle force with isokinetic
good strengthening throughout the range of motion but not functional
