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Biomechanics IV > Exam 1 lecture: gait cycle > Flashcards

Exam 1 lecture: gait cycle Flashcards

1
Q

what is the line of progression?

A

best fit straight line b/t 2 contacts

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2
Q

what is step, step length?

A

distance b/t 2 successive imprints (R –> L)

not a full gait cycle

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3
Q

what is stride, stride length?

A

distance b/t a common spot on both feet

may not be the same from R –> L and L –> R

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4
Q

what is a full gait cycle?

A

both limbs complete 1 “stride”

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5
Q

what is a stride?

A

what happens from one imprint to the next on the same limb

not technically a gait cycle; one limb has undergone one full cycle, other is out of phase

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6
Q

how much foot flare is considered acceptable in a normal walking gait?

A

5˚ - 7˚

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7
Q

what happens to foot flare as cadence (speed) increases?

A

it decreases

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8
Q

effects of too much toe out

A

increased stress on lower extremity –> injury

inefficient –> more muscle work, decreased stride length

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9
Q

which is more common: toe in or toe out?

A

toe out

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10
Q

what are the 2 phases of the gait cycle

A

swing and stance

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11
Q

in RUNNING, how much of the gait cycle is swing? how much is stance?

A

60% swing, 40% stance

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12
Q

in WALKING, how much of the gait cycle is swing? how much is stance?

A

40% swing, 60% stance

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13
Q

what is stance phase?

A

foot is in contact w/ground; closed kinetic chain

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14
Q

what is swing phase?

A

foot is not in contact w/ground: open kinetic chain

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15
Q

when the speed of the gait cycle increases, there is an increase in these forces: (6)

A 
compression
distraction
torsion
shear
bending
inertia
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16
Q

why does compression force increase as speed increases?

A

increased speed of hitting the ground

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17
Q

how does torsion increase as speed increases?

A

increased body twisting

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18
Q

how can torsion cause injury?

A

when torsion increases beyond normal limits, tissue begins to break down –> increased demand on muscles and bones –> failure

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19
Q

what are some problems that can cause increased torsion?

A

too much foot flare, too much pronation

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20
Q

which force is most damaging?

A

shear

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21
Q

how can bending help prevent injury?

A

changes the forces the body has to deal with, takes away initial compression forces as foot hits the ground

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22
Q

how does muscle control help to prevent injury?

A

muscles interacting w/ground to act as shock absorbers contract more to control increased inertia w/increased velocity; convert energy into managable motions

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23
Q

what increases injury risk?

A

increased ground reaction forces, increased muscle activity (esp. eccentrically)

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24
Q

what are the 3 divisions of stance phase?

A

contact/foot strike
midstance
takeoff

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25
Q

t or f: toe off is the same as take off

A

false. toe off is at the very end of take off.

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26
Q

what is a closed kinetic chain?

A

distal end of limb is connected to a fixed object (aka the ground)

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27
Q

what is it called when both feet are on the ground in different parts of stance phase?

A

double support

this only occurs during WALKING

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28
Q

what is it called when both feet are in the air in different parts of swing phase?

A

float

this only occurs during RUNNING

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29
Q

why is walking less injurious than running?

A

amount of muscle contraction running takes to control the action

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30
Q

t or f: during contact, the foot lands directly under the center of gravity.

A

false. the foot lands ahead of the center of gravity.

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31
Q

what are the important functions of contact (phase)?

A

absorb shock

adapt to ground forces

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32
Q

what is pronation?

A

medial rotation of the foot

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33
Q

t or f: the foot can be pronating in a supinated position or pronating in a pronated position.

A

true

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34
Q

what are the 2 important joints of pronation?

A

subtalar and midtarsal jts.

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35
Q

what is it called when the weight begins to transfer forward on the foot?

A

heel rocker

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36
Q

what is the calcaneus doing in pronation?

A

eversion, dorsiflexion relative to talus

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37
Q

t or f: talus dorsiflexes only after pronation has begun.

A

false. the talus dorsiflexes before pronation of foot occurs., then begins plantar flexion when pronation begins.

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38
Q

how does the foot land when walking at contact?

A

2˚ supinated

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39
Q

what initiates pronation of the foot?

A

plantar flexion of the talus

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40
Q

what is the ideal pronation ROM?

A

6˚ - 10˚

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41
Q

what is the clinical normal pronation ROM?

A

5˚ - 15˚

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42
Q

what happens to the tibia and femur during contact?

A

internal rotation

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43
Q

why is it important the the tibia and femur internally rotate?

A

reduces torque (moves in the same direction as foot; opposite directions would create torsion)

44
Q

which 2 types of stresses are most deleterious to connective tissue?

A

shear, torsion

45
Q

why is torsion so damaging?

A

wears down collagen fibers quickly

46
Q

how to calcaneus and talus motion differ?

A

talus moves w/leg, not at ankle

calcaneus moves w/foot

47
Q

when is rearfoot strike utilized?

A

walking, jogging/slow running

48
Q

when is forefoot strike utilized?

A

fast running

49
Q

what muscle eccentrically controls plantar flexion at the ankle joint and pronation of the foot?

A

tibialis anterior

50
Q

when does the foot/talus plantar flex during rearfoot strike?

A

after the heel initially strikes the ground

51
Q

what large thigh msl does the tibialis anterior assist?

A

quadriceps

52
Q

in forefoot strike, when does the foot dorsiflex?

A

after the metatarsal heads first strike the ground - heel moves toward ground

53
Q

initial foot strike is pronated or supinated?

A

2˚ - 4˚supinated

54
Q

t or f: pronation occurs much faster during forefoot strike than rearfoot strike

A

true.

55
Q

what muscles control dorsiflexion?

A

gastroc-soleus

56
Q

what muscles control pronation?

A

tibialis anterior and posterior

57
Q

during midstance, where is the center of gravity?

A

directly over the stance limb

58
Q

what position is the foot in during midstance?

A

pronated

59
Q

t or f: the foot is pronating during midstance

A

false. the foot is pronated, but pronation should be done by the time midstance begins

60
Q

what is the foot doing (i.e. what motion)?

A

supinating (a shift back toward neutral)

61
Q

when does most pronation occur?

A

contact

62
Q

how long does midstance last?

A

from foot flat to heel lift when walking

63
Q

what is the ankle rocker?

A

center of gravity/leg continues to move forward w/foot planted on the ground –> ankle undergoes rocking motion

64
Q

what are the leg and thigh doing during midstance? why?

A

externally rotating to reduce torque

65
Q

when should heel lift occur?

A

after the swing limb passes the stance limb;

when walking: heel lift same time as heel strike of opposite limb.

66
Q

why might the heel lift early?

A

tight stance limb gastrocsoleus/achilles tendon

67
Q

where is the center of gravity during take off?

A

anterior to stance foot

68
Q

what muscles lift the heel?

A

gastrocsoleus

69
Q

what does the calcaneus do during take off?

A

inverts to complete rearfoot supination

70
Q

what muscle inverts the calcaneus?

A

tibialis posterior

71
Q

when is the foot the most rigid?

A

during supination - at take off (except toes)

72
Q

why are the toes not rigid during take off?

A

to prevent injury

73
Q

what allows the foot to roll onto the ball of the foot?

A

passive toe extension

74
Q

what happens to the plantar fascia when toes extend? why?

A

plantar fascia tenses to help maintain arch

hallux is particularly important for this

75
Q

what is the metatarsal break?

A

oblique angle of metatarsal heads

76
Q

what is toe off?

A

the very end of take off

77
Q

t or f: supination occurs at end of take off.

A

false. slight pronation occurs at end of take off

78
Q

why does the foot pronate at the end of take off?

A

to increase load bearing on 1st & 2nd metatarsals - 4th and 5th are too weak to handle weight of take off

79
Q

which ray is most important to forefoot control just before take off?

A

1st ray

80
Q

what muscles are important to 1st ray stabilization & control of pronation just before toe off? (5)

A 
peroneus longus
flexor hallucis longus
flexor hallucis brevis
adductor hallucis
abductor hallucis
81
Q

what happens to the tibia and femur during take off?

A

externally rotate

82
Q

what happens if there is too much pronation late in take off?

A

late pronation –> foot tries to medially rotate, leg and body try to laterally rotate –> torsion –> stress fractures of tibia, pelvis, femur, etc., stress on jts, may affect spine

83
Q

t or f: all flat feet over pronate

A

false.

84
Q

what does peroneus longus do during take off?

A

lifts cuboid and lateral foot
depresses & plantar flexes 1st ray
maintains contact b/t ground and 1st metatarsal head

85
Q

what gives peroneus longus the most leverage? (pronated vs. supinated foot)

A

supinated foot

86
Q

what is a possible cause of posterior shin splints?

A

excessive pronation at end of stance phase –> inhibited peroneus longus –> tibialis ant. & post. fatigue

87
Q

what are the 3 divisions of swing phase?

A

initial swing
midswing
terminal swing

88
Q

what division of swing phase is most prominent in walking?

A

midswing

89
Q

what division(s) of swing phase is accentuated in running?

A

initial and terminal swing

90
Q

what does the tibia do during initial swing?

A

internally rotates

91
Q

what does the hip do during initial swing?

A

extends and externally rotates

92
Q

what muscles eccentrically decelerate @ the hip and knee?

A

hip flexors

93
Q

t or f: there is more initial swing in walking than there is in running.

A

false. initial swing is drastically increased during running.

94
Q

what is the problem with over-striding?

A

more stretch on hip flexors –> more potential for strain injuries

95
Q

when in initial swing, what is the opposite limb doing when running vs. when walking?

A

running: terminal swing
walking: end of foot strike

96
Q

what is the bowling ball effect?

A

momentum pulls body forward when leg swings forward

hip flexors very important for this

97
Q

when does midswing start?

A

when leg starts swinging forward

98
Q

at the end of midswing, what muscles eccentrically slow the forward swinging limb at the hip and knee?

A

gluteals and hamstrings

99
Q

what position is the foot in during midswing?

A

neutral/slightly dorsiflexed (prevent foot drag)

100
Q

does the hip internally or externally rotate during midswing?

A

internally rotate

101
Q

when does terminal swing begin?

A

when foot begins moving backward (toward ground to begin heel strike)

102
Q

what muscles are responsible for terminal swing?

A

hip extensors and knee flexors

103
Q

t or f: foot flare and amt of rearfoot inversion at next foot strike is determined during swing phase

A

true.

104
Q

when are hamstrings at greatest tension?

A

terminal swing

105
Q

what factors can increase risk of hamstring injury?

A

decreased flexibility and strength of hamstrings

106
Q

t or f: foot rotates in same direction as leg and thigh

A

true. this is to reduce torsion on ankle jts.

107
Q

what could change the direction of rotation in the foot?

A

over pronation

Biomechanics IV (5 decks)

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