skeletal muscles mechanics

Question 1

strength depends on?

Answer 1

muscle force x moment arm

Question 2

what are the mechanical factors of strength?

Answer 2

rotary component of muscle force and length of moment arm

Question 3

what are the physiological factors of strength?

Answer 3

length of the muscle, velocity of contraction, fiber orientation, cross sectional area, and fiber type

Question 4

what are the 3 types of muscle fibers?

Answer 4

type 1 type 2a type 2b

Question 5

what are type 1 muscle fibers?

Answer 5

slow twitch oxidative

Question 6

what are some characteristics of type 1 muscle fibers?

Answer 6

small diameter, red in color, dense in capillaries, seed of contraction is slow, rate of fatigue is slow

Question 7

what are muscles predominantly type 1 called?

Answer 7

stability or postural tonic muscles

Question 8

what are type 2a muscle fibers?

Answer 8

fast twitch oxidative glycolytic

Question 9

what are some characteristics of type 2a muscle fibers?

Answer 9

intermediate diameter, fast speed of contraction, and intermediate rate of fatigue

Question 10

what are type 2b muscle fibers?

Answer 10

fast twitch glycolytic

Question 11

what are some characteristics of type 2b muscle fibers?

Answer 11

large diameter, white in color, sparse capillarity, fast speed of contraction and fast rate of fatigue

Question 12

what are muscles predominantly type 2 called?

Answer 12

mobility, non postural, phasic muscles

Question 13

________ surrounds the whole muscle

Answer 13

epimysium

Question 14

________ surrounds the fascicules

Answer 14

perimysium

Question 15

________ surrounds the individual muscle cells

Answer 15

endomysium

Question 16

What are contractile elements?

Answer 16

contractile proteins (actin and myosin)

Question 17

what are parallel elastic elements (PEC)?

Answer 17

peri, ei, and endomysium (fascia)

Question 18

what are series elastic elements (SEC)?

Answer 18

tendons

Question 19

T/F with an isometric contraction the contractile element shortens and the series elastic element lengthens

Answer 19

true

Question 20

by passively pulling on a muscle beyond rest length will ______ the PEC and they will also contribute to the _________

Answer 20

stretch, tension

Question 21

what else will muscle force also vary with in accordance with the length tension curve?

Answer 21

muscle length

Question 22

muscle force varies with cross sectional area of the muscle. what is key issue in determining the total cross sectional area?

Answer 22

fiber arrangement

Question 23

cross sectional area increases what years? meaning?

Answer 23

0-20s max strength is at 20-30 years old

Question 24

what percent of muscle strength do we have at age 65 compared to 20

Answer 24

85%

Question 25

key notes with changes with aging

Answer 25

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

Question 26

_________ of muscle contraction is a function of the load being lifted

Answer 26

velocity

Question 27

speed of shortening of the myofilaments os the rate at which?

Answer 27

the myofilaments are able to slide past one another and form/reform cross bridges

Question 28

speed is related to _______ ________ and ________

Answer 28

fiber type and length

Question 29

T/F force generated is a function of the velocity of muscle contraction

Answer 29

true

Question 30

when does max shortening speed occur?

Answer 30

when there is no resistance to shortening, however, no tension is developed in the muscle bc there is no resistance

Question 31

describe concentrics muscle force generation

Answer 31

as shortening speed dec tension inc (slower = more force)

Question 32

describe isometrics muscle force generation

Answer 32

speed is zero, therefore greater tension generated compared to concentrics

Question 33

describe eccentrics muscle force generation

Answer 33

as speed of lengthening inc tension ince (faster= greater force)

Question 34

muscle force with isometric

Answer 34

great strengthening but only at that joint angle +/- 10º

Question 35

muscle force with concentric

Answer 35

dynamic, but velocity tension relationship often limits strengthening at higher velocities

Question 36

muscle force with eccentric

Answer 36

great strengthening, possible tissue damage due to potential for large muscle force production

Question 37

muscle force with isotonic

Answer 37

dynamic contractions, but intensity limited by capability in weakest part of ROM (typically end range)

Question 38

muscle force with isokinetic

Answer 38

good strengthening throughout the range of motion but not functional