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Kin 158 Biomechanics Lecture > Midterm #3 > Flashcards

Midterm #3 Flashcards

1
Q

sensory receptors in the muscle

A

muscle spindle

golgi tendon organs

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2
Q

charcteristics of muscle spindle

A

located parallel to muscle fibers
monitor muscle lenght
limits stretch in muscle

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3
Q

which muscle fibers/at what state do muscles need to be to be excited or inhibited by the muscle spindle

A

excitation of stretched muscle fibers and synergist muscle

inhibition of antagonist muscles

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4
Q

location of golgi tendon organ

A

muscolotendinous junction

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5
Q

charactersitics of golgi tendon organ

A

stimulated with stretch of tendon
inhibits muscle contraction
threshold can be changed with practive
protective mechanism

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6
Q

mechanism of stretch shortening cycle

A

storage of enery in PEC and SEC
stimulation of muscle spindle reflex
algnment of cross bridges in slack muscle fibers
eccentric activation give more time for slow twitch fibers to develop tension

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7
Q

what is a motor unit

A

a nerve and all the muscle fibers it innervates

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8
Q

two main strategies of motor nuron activation

A

recruitment

rate coding

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9
Q

what do the main strategies of motor neuron activation allow

A

large range of force

gradual change in force

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10
Q

recruitment

A

activation via action potential of specific motor neurons

cause excitation and activation of muscle fibers

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11
Q

result of recruitment

A

a muscle twitch - contraction

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12
Q

muscle fibers within a motor unit

A

share similar characteristics
distirbuted randomly across muscle
1 muscle fiber controls 5-2000 muscle fibers

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13
Q

lower innervation ratio

A

small # of motor units recruited

accurate movement

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14
Q

high innervation ratio

A

large # of motor units recruited

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15
Q

henneman size principle

A

small motor units recruited first then larger and large motor units
allows smooth and controlled increase in force

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16
Q

rate coding

A

the force produced by motor unit is strongly regulated by rate of production of action potentials

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17
Q

discharge rate of rate coding

A

from 10hz, 100ms intervals, up to 50hz

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18
Q

twitch related to rate coding

A

messgae send as an interval

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19
Q

unfused tetanus

A

no breaktime in incomeing APs

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20
Q

fused retnus

A

maximal contraction

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21
Q

how does a motor unit create greater overall force

A

when its activated at a higher rate

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22
Q

eccentric activation

A

less motor units recruited compared to concentric

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23
Q

what does it require to initiate a fast strong isometric contraction

A

use of rate coding

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24
Q

component of muscle force

A

rotary component

stabilizing component/destabilizing component

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25
Q

rotary component

A

causes rotation

perpendicular to the bone of insertion

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26
Q

stabilizing/destabilizing component

A

stabilizes or destabilizes joints
parallel to bone of insertion
causes compression or distraction

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27
Q

muscle adaptations to training

A

hypertrophy

hyperplasia

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28
Q

hypertrophy

A

muscle growth -> increase in muscle force
increase in size of each muscle fiber
no change in # of fibers

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29
Q

hyperplasia

A

increase in # of muscle fibers

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30
Q

neural adaptation to training

A 
increased strength without changes in cross sectional area
increased recruitment and rate coding
motor unit synchronization
increased coordination
inhibition of golgi tendon organ
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31
Q

increase in force production but no increase in EMG

A

strength gain due to neural factors

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32
Q

increase in EMG in direct correlation to the increase in force

A

strength gain due to hypertrophy

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33
Q

increase in force greater than increase in EMG, and increase in both

A

stregth gain due to neural factors and hypertrophy

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34
Q

what can strength training be largely attributed to

A

motor unit activation of the trained agonist muscle

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35
Q

when does chronic load lead to lengthened muscle adaptation

A

increase in sarcomere # by 20%

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36
Q

when does chronic load lead to shortened muscle adaptation

A

decreased sarcomere # by 40%

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37
Q

where are sarcomeres added

A

at the musculotendinous junction

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38
Q

which muscles are most adaptable

A

antigravity muscles

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39
Q

what will chronic use of high heels lead to

A

increased risk for lateral ankle sprain (increased plantarflexion)
increased risk for achilles tendon injury

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40
Q

categories of muscle architecture

A

longitudinal (fusiform)

pennate

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41
Q

longitudinal muscle arrangements

A

anatomical and physiological cross sectional areas are equal

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42
Q

subsection of longitudinal muscle arrangements

A

fusiform
strap
radiate

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43
Q

subsections of pennate muscle arrangements

A

unipennate
bipennate
multipennate

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44
Q

unipennate muscle arrangements

A

one group of muscle fibers parallel to each other but oblique to the tendon

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45
Q

bipennate muscle arrangements

A

two groups of muscle fibers
oblique to each other an to tendon
within the group fibers parallel to each other

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46
Q

multipennate muscle arrangements

A

more than 2 groups of fibers

fibers are parallel to each other within the group but oblique to other groups and tendon

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47
Q

physiological cross sectional area

A

perpendicular to muscle fibers

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48
Q

anatomical cross sectional area

A

perpendicular to midline of muscle

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49
Q

what does a greater pennation lead to

A

greater physiological cross sectional area -> larger force

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50
Q

different sarcomere arrangements within a muscle

A

parallel

in series

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51
Q

which sarcomere arrangement has larger physiologicalcross section area (greater force)

A

parallel sarcomere

52
Q

what advantage have sarcomeres in series

A

fast control of range of motion

53
Q

what does the length of a muscle influence

A

the speed and distance a muscle can shorten

54
Q

what is one gait cycle

A

step with left leg followed by step with right leg

same as 1 stride

55
Q

1 stride length (gait cycle length)

A

144 cm

56
Q

walking speed

A

step length x step rate

stride length x stride rate

57
Q

phases of a gait

A 
reference limb
stance phase
swing phase
single limb support
double limb support
58
Q

what are the 3 tasks performed during 1 stride

A

accept weight on foot once it is on the ground
support weight on single leg
advance swing limb in front of body

59
Q

critical elements for each phase of gait

A

weight acceptance
single limb support
swing limb advancement

60
Q

weight acceptance

A 
intial contact, loading response
contact floor with heel
stabilize hip
restrain knee flexion
restrain ankle, plantar flexion
61
Q

single limb support

A

midstance -> stabilize hip in frontal plane, extend knee, restrain ankle dorsiflexion
terminal stance -> forward free fall, raise heel

62
Q

swing limb advancement

A

preswing, initial swing, midswing -> flex knee and hip, dorsiflex ankle
terminal swing -> decelerate ankle and knee extension, neutral position of ankle

63
Q

external forces during gait cycle

A

Ground Reaction Force
weight of body
intersegmental torque

64
Q

internal forces acting during gait cycle

A

active - muscles

passive - connective tissue

65
Q

what dictates the type of external torque created at a joint at a specific time of the gait cycle

A

location of ground reaction force

66
Q

what torques are generated by ground reaction force at heel contact

A

plantar flexion torque

eversion torque

67
Q

where oes most of the torque for propelling the body forward come from

A

ankle plantar flexion 53%

hip flexion 30%

68
Q

peak ground reaction forces during gait cycle

A

certical -> 120% BW
anterior-posterior -> 20% BW
medial-lateral -> 5% BW

69
Q

running phases by Dr. Jackuelin Perry

A

stance
early float
middle swing
late float

70
Q

stance

A

right heel strike to right toe off
35% of gait cycle
single limb stance

71
Q

early float

A

right toe off to left heel strike
15% of gait cycle
both limbs are in the air

72
Q

middle swing

A

left heel strike to left toe
35% of gait cycle
contralateral limb is in single leg stance

73
Q

late float

A

left toe off to right heel strike
15% of gait cycle
both limbs in the air

74
Q

ratio of stance to float in running

A

35% stance

65% float

75
Q

phases within stance

A

loading response
mid stance
terminal stance

76
Q

hip knee and ankle at lowest point of stance

A

hip 25F
knee 40F
ankle 20DF

77
Q

ankle knee and hip motion during swing

A

ankle from 30 PF to 5 DF
knee from 10F to 100F
hip 10 Ext to 30F

78
Q

what does float in running replace from walking

A

double limb support

approxx. 2.1 m/sec

79
Q

stance in walking and running

A

drops from 60% to 35%

80
Q

angular displacement

A

is larger during running at the hip and the knee

81
Q

foot position during running and walking

A

running -> rearfoot striker/midfoot and frontfoot

walking -> rearfoot

82
Q

ankle position in running vs. walking

A

running -> neutral position at initial contact, followed by dorsiflexion
walking -> neutral to plantar flexion

83
Q

magnitude relation in walking vs. running

A

forces magnitude 2-4 times larger in running

84
Q

highest/lowest potential energy during walking

A

highest: midstance
lowest: double limb support

85
Q

highest lowest kinestic energy during walking

A

highest: double limb support
lowest: midstance

86
Q

energy during running

A

elastic energy
kinetic energy
potential energy

87
Q

kinetic energy during running

A

highest in float phase

88
Q

potential energy during running

A

highest during float phase

89
Q

major clinical problems faced by runners

A

muscle pveruse
pressure of floor contact
mechanics of eccentric contraction

90
Q

what bones are at greater risk for injury during running

A

the first 3 metatarsal heads and the big toe

91
Q

what may prolonged running lead to

A

stress fructure

92
Q

what can help muscles to reduce risk of injury during running

A

strength and flexibility training

93
Q

muscles that contract eccentrically

A 
RF
Vastii
BFSH
BFLH
semimembranosus
94
Q

when and where does strain occur

A

in tnedon and aponeuroses while muscles are contracting isometrically

95
Q

what does faster running require

A

rapid and severe lengthening of tendons and aponeuroses

96
Q

what can be done to prevent running injuries

A

increased strength and endurance of muscles
progressive tissue adaptation to eccentric load
cushioning

97
Q

what is classified as fluids

A

liquids and gases that flow and change shape

98
Q

fluid mechanics

A

study of forces tha fluids exert on objects

99
Q

two different forces

A

buoyant force

dynamic force

100
Q

characteristics of buoyant force

A

due to immersion in fluid
vertical force
always acts upwards

101
Q

what causes buoyant force

A

increase in depth -> linear increase in pressure

102
Q

equation of buoyant force

A

pressure = force / unit area

103
Q

2 findings of archimedes related to buoyant force

A

buoyant force is difference between the force acting upward and downward on an object
also equlas the weight of the volume of fluid displaced by the object

104
Q

what should the weight of an object be to float

A

needs to be equal to the weight of the fluid

105
Q

weight of an object to accelerate up/down in water

A

accelerate up -> object needs to be lighter than the weight of the fluid
accelerate down -> object needs to be lighter to accelerate down

106
Q

specific gravity

A

weight of an object / weight of an volume of water

107
Q

what is another way to determine if an object sinks or floats

A

density = mass/volume

108
Q

dynamic fluid force

A

force due to relative motion

109
Q

what is dynamic fluid force proportional to

A

fluid density x surface area of the object x relative velocity

110
Q

relative velocity

A

compares my velocity to the velocity of air

difference between both the velocity of fluid and an object

111
Q

in what is dynamic fluid force resolved into

A

drag force

lift force

112
Q

drag force

A

acts in opposite to relative motion of the object
will tend to slow down the relative velocity of the object
produced by surface drag and form drag

113
Q

calculation of drag force

A

1/2 coefficient of drag(roughness of surface) x density of fluid x area of object x relative velocity (squared)

114
Q

surface drag

A

sum of driction forces between fluid and suface of object

115
Q

what increases surface drag

A

higher viscocity

116
Q

form drag

A

sum of impact between object and fluid molecules

increases as the amount of turbulent flow increases

117
Q

turbulent flow

A

fluid molecules separate from the surface

118
Q

laminar flow

A

molecules of the fluid stay close to the object and press against it

119
Q

what reduces stream force

A 
smoother body surface
streamline the shape of the body
lower air density - warmer air
reduce surface area exposed to flow
use wind
drafting
120
Q

lift force

A

dynamic fluid component that acts perpendicular to relative motion of object

121
Q

direction of lift force

A

determined by direction of flow of fluid

perpendicular to the flow of fluid

122
Q

what causes lift force

A

lateral deflection of fluid molecules as they pass an object

123
Q

what kind of force is used at an airfoil

A

the net force generated is lift force

124
Q

Bernoulli´s Principle

A

faster moving fluids exert less pressure than slower moving fluid
fluids on a curved surface move faster than on a straight surface

125
Q

why did ski jumpers change the position to a V position

A

to increase the surface area -> increase the lift

126
Q

magnus effect

A

curving of a ball in the air
if backspin, motion of the air molecules at the top of the ball is slower
motion of air molecules at the bottom of the ball move faster
down motion of ball due to Bernoulli´s Priniple

Kin 158 Biomechanics Lecture (3 decks)

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