Phasic Muscle Activity

Question 1

what are the 3 phases of stance phase of gait

Answer 1

1. contact
2. midstance
3. propulsive

Question 2

what are the functions of muscle mechanics

Answer 2

• develop force and power
• dissipate mechanical energy
• stabilize movement until reflexes become active
• redistribute mechanical energy amont body segments

Question 3

factors affecting muscle strength

Answer 3

fiber type
age
gender
anthropometry (size, length, intersection point from a joint)
physiological cross sectional area
pennation angle
length tension ratio
psychological factors fatigue

Question 4

type 1 slow twitch

Answer 4

aerobic (oxidative metabolism)
fatigue resistant
red (myoglobin)
can work for hrs

Question 5

type II fast twitch

Answer 5

anaerobic (glycolytic metabolism)

less fatigue resistant

Question 6

types of type II fast twitch

Answer 6

IIa fast twitch (glycolytic & oxidative, < 30 min)

IIx (glycolytic, < 5 min)

Question 7

muscle biopsy will show

Answer 7

varying degrees of both types of fibers

Question 8

how can the proportion of fiber types change

Answer 8

training

pathology: post SCII –> IIx

Question 9

define psyhiological cross sectional area (PCA)

Answer 9

measure of the number of sacromers that are parallel w/ the angle of pull of the muscle

Question 10

formula for PCA

Answer 10

PCA = (mass of fibers)/(density of the muscle x physiological length of the muscle)

Question 11

most muscles have a density of

Answer 11

1.056g/cm3

Question 12

muscle strength is affected by

Answer 12

orientation of the fibers

Question 13

orientation of pennation fibers

Answer 13

are at an angle from the long axis of the muscle (tendon axis)
angle = pennation angle

Question 14

pennation angle affects the muscles ability to

Answer 14

produce power by change the PCA of the muscle

Question 15

an increase in pennation angle — as the muscle shortens

Answer 15

increases

Question 16

type 1 slow twitch

Answer 16

aerobic (oxidative metabolism)
fatigue resistant
red (myoglobin)
can work for hrs

Question 17

type II fast twitch

Answer 17

anaerobic (glycolytic metabolism)

less fatigue resistant

Question 18

myofiber is composed of

Answer 18

many myofilaments

Question 19

muscle biopsy will show

Answer 19

varying degrees of both types of fibers

Question 20

how can the proportion of fiber types change

Answer 20

training

pathology: post SCII –> IIx

Question 21

define psyhiological cross sectional area (PCA)

Answer 21

measure of the number of sacromers that are parallel w/ the angle of pull of the muscle

Question 22

formula for PCA

Answer 22

PCA = (mass of fibers)/(density of the muscle x physiological length of the muscle)

Question 23

most muscles have a density of

Answer 23

1.056g/cm3

Question 24

define eccentric muscle contraction

Answer 24

the muscle length increases while contracting
produces deceleration
associated with shock absorption
ex. soleus at midstance (decelerates the forward momentum of the tibia)

Question 25

orientation of pennation fibers

Answer 25

are at an angle from the long axis of the muscle (tendon axis)
angle = pennation angle

Question 26

pennation angle affects the muscles ability to

Answer 26

produce power by changing the PCA of the muscle

Question 27

an increase in pennation angle — as the muscle shortens

Answer 27

increases

Question 28

muscles are STRONGEST at what muscle length tension ratio?

Answer 28

at their physiological length

Question 29

does passive force build up when the muscle is at its resting length or less

Answer 29

no

Question 30

myofiber is composed of

Answer 30

many myofilaments

Question 31

each myofibril contains — myosin filaments and — actin filaments

Answer 31

1500

3000

Question 32

the distance between the two Z discs is

Answer 32

one sacromere

Question 33

during muscle contraction what happens to the thin (actin) and thick (myosin) filaments?

Answer 33

thin (actin) filaments slide inward past the thick (myosin) filaments pulling the two Z discs closer together, thus shortening the sacromere

Question 34

what are the 3 types of muscle contraction

Answer 34

1. concentric
2. eccentric
3. isometric

Question 35

define concentric muscle contraction

Answer 35

the muscle shortens while contracting; produces acceleration

ex. gastronemius at terminal stance

Question 36

define eccentric muscle contraction

Answer 36

the muscle length increases while contracting
produces deceleration
associated with shock absorption
ex. soleus at midstance (decelerates the forward momentum of the tibia)

Question 37

define isometric muscle contraction

Answer 37

the muscle length remains the same while contracting
produces stability
primary in postural muscles
ex. hip abductors in midstance

Question 38

the overall force of a muscle is the sum of

Answer 38

the active force, Fa and the passes force, Fp

Question 39

the active force results from

Answer 39

voluntary contraction of the contractile elements of the muscle

Question 40

the passive force results from

Answer 40

elongation of the connective muscle tissue beyond its resting length

Question 41

does passive force build up when the muscle is at its resting length or less

Answer 41

no

Question 42

the muscle force — with increasing shortening velocity

Answer 42

decreases

Question 43

what is EMG

Answer 43

is the summation of many asynchronous motor unit action potentials

Question 44

EMG amplitude is dependent on

Answer 44

number of recruited motor units

firing rates and synchonization

Question 45

MAKE CARDS ON

Answer 45

UNDERSTAND THE ROLE OF MUSCLE IN JOINT MOTION AND ONWARD