Phasic Muscle Activity Flashcards

1
Q

what are the 3 phases of stance phase of gait

A
  1. contact
  2. midstance
  3. propulsive
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2
Q

what are the functions of muscle mechanics

A
  • develop force and power
  • dissipate mechanical energy
  • stabilize movement until reflexes become active
  • redistribute mechanical energy amont body segments
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3
Q

factors affecting muscle strength

A
fiber type
age
gender
anthropometry (size, length, intersection point from a joint)
physiological cross sectional area
pennation angle
length tension ratio
psychological factors fatigue
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4
Q

type 1 slow twitch

A

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

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5
Q

type II fast twitch

A

anaerobic (glycolytic metabolism)

less fatigue resistant

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6
Q

types of type II fast twitch

A

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

IIx (glycolytic, < 5 min)

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7
Q

muscle biopsy will show

A

varying degrees of both types of fibers

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8
Q

how can the proportion of fiber types change

A

training

pathology: post SCII –> IIx

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9
Q

define psyhiological cross sectional area (PCA)

A

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

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10
Q

formula for PCA

A

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

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11
Q

most muscles have a density of

A

1.056g/cm3

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12
Q

muscle strength is affected by

A

orientation of the fibers

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13
Q

orientation of pennation fibers

A

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

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14
Q

pennation angle affects the muscles ability to

A

produce power by change the PCA of the muscle

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15
Q

an increase in pennation angle — as the muscle shortens

A

increases

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16
Q

type 1 slow twitch

A

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

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17
Q

type II fast twitch

A

anaerobic (glycolytic metabolism)

less fatigue resistant

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18
Q

myofiber is composed of

A

many myofilaments

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19
Q

muscle biopsy will show

A

varying degrees of both types of fibers

20
Q

how can the proportion of fiber types change

A

training

pathology: post SCII –> IIx

21
Q

define psyhiological cross sectional area (PCA)

A

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

22
Q

formula for PCA

A

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

23
Q

most muscles have a density of

A

1.056g/cm3

24
Q

define eccentric muscle contraction

A

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

25
orientation of pennation fibers
are at an angle from the long axis of the muscle (tendon axis) angle = pennation angle
26
pennation angle affects the muscles ability to
produce power by changing the PCA of the muscle
27
an increase in pennation angle --- as the muscle shortens
increases
28
muscles are STRONGEST at what muscle length tension ratio?
at their physiological length
29
does passive force build up when the muscle is at its resting length or less
no
30
myofiber is composed of
many myofilaments
31
each myofibril contains --- myosin filaments and --- actin filaments
1500 | 3000
32
the distance between the two Z discs is
one sacromere
33
during muscle contraction what happens to the thin (actin) and thick (myosin) filaments?
thin (actin) filaments slide inward past the thick (myosin) filaments pulling the two Z discs closer together, thus shortening the sacromere
34
what are the 3 types of muscle contraction
1. concentric 2. eccentric 3. isometric
35
define concentric muscle contraction
the muscle shortens while contracting; produces acceleration | ex. gastronemius at terminal stance
36
define eccentric muscle contraction
the muscle length increases while contracting produces deceleration associated with shock absorption ex. soleus at midstance (decelerates the forward momentum of the tibia)
37
define isometric muscle contraction
the muscle length remains the same while contracting produces stability primary in postural muscles ex. hip abductors in midstance
38
the overall force of a muscle is the sum of
the active force, Fa and the passes force, Fp
39
the active force results from
voluntary contraction of the contractile elements of the muscle
40
the passive force results from
elongation of the connective muscle tissue beyond its resting length
41
does passive force build up when the muscle is at its resting length or less
no
42
the muscle force --- with increasing shortening velocity
decreases
43
what is EMG
is the summation of many asynchronous motor unit action potentials
44
EMG amplitude is dependent on
number of recruited motor units | firing rates and synchonization
45
MAKE CARDS ON
UNDERSTAND THE ROLE OF MUSCLE IN JOINT MOTION AND ONWARD