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Biomechanics V5 > 16/17: Gait Cycle - Vardaxis > Flashcards

16/17: Gait Cycle - Vardaxis Flashcards

1
Q

define gait

A

complex set of movements, moments, powers, forces, coordination and balance all working together to form what is commonly called walking

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2
Q

define gait cycle

A

duration that occurs from the time when the heel of one leg strikes the ground to the time at which the same leg contacts the ground again

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3
Q

** 5 major motor functions during gait

A
  • support of upper body (prevent collapse of the lower limb during stance)
  • dynamic balance (maintenance of upright posture and balance of the total body)
  • foot trajectory control (achieve safe ground clearance and gentle heel or toe landing)
  • generation of mechanical energy (maintain or increase forward velocity)
  • absorb mechanical energy (for shock absorption and stability or to decrease the forward velocity of the body)
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4
Q

loading response period correlates with what task …

A

weight acceptance

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5
Q

mid stance and terminal stance periods correlate with what task …

A

single-limb support

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6
Q

what periods correlate with limb advancement task?

A

pre-swing; initial swing; midswing; terminal swing

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7
Q

0%

A

initial contact

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8
Q

10%

A

opposite toe off

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9
Q

30%

A

heel rise

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10
Q

50%

A

opposite initial contact

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11
Q

60%

A

toe off

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12
Q

73%

A

feet adjacent

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13
Q

87%

A

tibia vertical

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14
Q

100%

A

next initial contact

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15
Q

what percent of the gait cycle is stance phase?

A

60%

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16
Q

what percent of the gait cycle is swing phase?

A

40%

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17
Q

initial contact –> opposite toe off

A

loading response period; weight acceptance task

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18
Q

opposite toe off –> heel rise

A

midstance period; part of single-limb support

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19
Q

heel rise –> opposite initial contact

A

terminal stance period; part of single-limb support

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20
Q

opposite initial contact –> toe off

A

preswing period; part of the limb advancement

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21
Q

toe off –> feet adjacent

A

initial swing period; part of limb advancement

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22
Q

feet adjacent –> tibia vertical

A

mid swing period; part of limb advancement

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23
Q

tibia vertical –> next initial contact

A

terminal swing period; part of limb advancement

24
Q

how much of the gait cycle is double support time?

A

22%

  • decreases with speed
  • increases in elderly or patients with balance disorders
25
Q

what increases stride length? decreases?

A
  • increases with speed

- decreases in elderly

26
Q

what is a normal cadence?

A
  • 80-110 steps/min
slow = less than 70 steps/min
fast = greater than 120 steps/min
27
Q

what increases walking speed?

A
  • increases with increased cadence and/or stride length

- higher walking speed results in decrease in duration of all the component phases

28
Q

when in gait are you at center of motion highest vertical point? lowest?

A

highest = single support
lowest = double support
vertical displacement is usually 5 cm

29
Q

what is normal medial-lateral displacement of center of motion?

A

4 cm

- stays close to the weight baring foot

30
Q

1 gait cycle = how many steps

A

2

31
Q

how are potential and kinetic energy related?

A

kinetic and potential are inversely related

KE=1/2mvsq.
PE=mgh

32
Q

what factors help reduce COM displacement?

A
  • horizontal plan pelvic rotation
  • adding sagittal plane ankle rotation
  • adding stance phase knee flexion
  • adding frontal plane pelvic rotation
33
Q

where is body is displacement vertical least?

A

near the head

decreases as you move cephally

34
Q

head and pelvis acceleration in older individuals compared to younger

A
  • there is reduction in head acceleration in comparison to pelivs is all groups except the elderly
  • head and pelvis ML acceleration amplitude may be related to incidence of falls
35
Q

what is an average toe clearance?

A

only 1.3 cm

36
Q

is the toe or thigh moving faster in gait?

A

toe (4.6 m/s versus 1.4 m/s)

37
Q

calculate hip zero based angle

A

= 180 - hip natural

knee zero based angle = 180 - knee natural
ankle zero based gait = 90 - ankle natural

38
Q

how many arcs of motion in sagittal plane hip?

A

two
extension (5-50%) gait
flexion (50-85%) gait

39
Q

how may arcs of sagittal plane motion in knee?

A
  • full extension to flexion (95-15%)
  • extension (15-40%)
  • flexion (40-70%)
  • extension (70-95%)
40
Q

the knee is always in what POSITION during gait?

A

flexed

- position is not the same as motion

41
Q

what are the four arcs of motion in sagittal plane ankle?

A
  • plantarflexion (0-5%)
  • dorsiflexion(5-50%)
  • plantarflexion (50-60%)
  • dorsiflexion (60-100%)
42
Q

kinetic variables during gait

A
  • ground reaction forces
  • joint moment
  • joint power
43
Q

describe a force/time graph for foot kinematics

A

spike

then “m-shaped” bump

44
Q

forces that control gait

A
  • gravity
  • ground reaction forces (natural = vertical, shear= medial lateral or ant/post)
  • internal muscle forces
  • air resistance
45
Q

120% BW

A

peak value for vertical GRF

46
Q

double peaks of vertical GRF =

A
  • 1st peak at heel strike: the action of body momentum

- 2nd peak at push -off: contraction of calf m.

47
Q

why is vertical GRF lower than BW during midstance?

A

knee flexion

48
Q

what does the antero-posterior GRF component look like during dif phases of gait?

A
  • in posterior direction at heel strike for slowing the progression of body
  • in anterior direction at toe off for propelling body forward
  • propulsive force of one limb is applied simultaneously to the braking force of the other limb when the weight is transferred from one limb to the other
49
Q

larger step length = ______ shear forces

A

greater

50
Q

peak value of antero-posterior GRF component

A

20% BW

51
Q

what is the peak value of the medio-lateral GRF component?

A

5% BW

52
Q

the magnitude of the medial-lateral shear force depend on the position of the COM relative to the foot

A
  • in lateral direction at heel strike

- in medial direction at rest of stance phase

53
Q

larger step width = ___________ shear forces

A

greater

- b/c greater angle of between the lower extremity and floor

54
Q

define joint power

A
  • rate of work performed by controlling muscles
  • product of net joint moment and the joint angular velocity
  • indicates the net rate of generating or absorbing energy by all muscles and other connective tissues crossing the joint
  • positive = power generation = concentric
  • negative = power absorption = eccentric contraction
55
Q

where are the sources of energy at joints?

A

ankle and hip are sources of energy during gait

knee is more a controlling area

56
Q 
when are the following muscles active during gait?
gluteus maximus
iliopsoas
hamstrings
quadriceps
triceps surae
tibialis anterior
A
  • beginning stance phase
  • beginning swing phase
  • ending swing phase
  • beginning and ending stance phase
  • middle/end stance phase
  • low through swing phase, high at beginning stance phase

Biomechanics V5 (3 decks)

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