16/17: Gait Cycle - Vardaxis Flashcards
define gait
complex set of movements, moments, powers, forces, coordination and balance all working together to form what is commonly called walking
define gait cycle
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
** 5 major motor functions during gait
- 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)
loading response period correlates with what task …
weight acceptance
mid stance and terminal stance periods correlate with what task …
single-limb support
what periods correlate with limb advancement task?
pre-swing; initial swing; midswing; terminal swing
0%
initial contact
10%
opposite toe off
30%
heel rise
50%
opposite initial contact
60%
toe off
73%
feet adjacent
87%
tibia vertical
100%
next initial contact
what percent of the gait cycle is stance phase?
60%
what percent of the gait cycle is swing phase?
40%
initial contact –> opposite toe off
loading response period; weight acceptance task
opposite toe off –> heel rise
midstance period; part of single-limb support
heel rise –> opposite initial contact
terminal stance period; part of single-limb support
opposite initial contact –> toe off
preswing period; part of the limb advancement
toe off –> feet adjacent
initial swing period; part of limb advancement
feet adjacent –> tibia vertical
mid swing period; part of limb advancement
tibia vertical –> next initial contact
terminal swing period; part of limb advancement
how much of the gait cycle is double support time?
22%
- decreases with speed
- increases in elderly or patients with balance disorders
what increases stride length? decreases?
- increases with speed
- decreases in elderly
what is a normal cadence?
- 80-110 steps/min
slow = less than 70 steps/min fast = greater than 120 steps/min
what increases walking speed?
- increases with increased cadence and/or stride length
- higher walking speed results in decrease in duration of all the component phases
when in gait are you at center of motion highest vertical point? lowest?
highest = single support
lowest = double support
vertical displacement is usually 5 cm
what is normal medial-lateral displacement of center of motion?
4 cm
- stays close to the weight baring foot
1 gait cycle = how many steps
2
how are potential and kinetic energy related?
kinetic and potential are inversely related
KE=1/2mvsq.
PE=mgh
what factors help reduce COM displacement?
- horizontal plan pelvic rotation
- adding sagittal plane ankle rotation
- adding stance phase knee flexion
- adding frontal plane pelvic rotation
where is body is displacement vertical least?
near the head
decreases as you move cephally
head and pelvis acceleration in older individuals compared to younger
- 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
what is an average toe clearance?
only 1.3 cm
is the toe or thigh moving faster in gait?
toe (4.6 m/s versus 1.4 m/s)
calculate hip zero based angle
= 180 - hip natural
knee zero based angle = 180 - knee natural
ankle zero based gait = 90 - ankle natural
how many arcs of motion in sagittal plane hip?
two
extension (5-50%) gait
flexion (50-85%) gait
how may arcs of sagittal plane motion in knee?
- full extension to flexion (95-15%)
- extension (15-40%)
- flexion (40-70%)
- extension (70-95%)
the knee is always in what POSITION during gait?
flexed
- position is not the same as motion
what are the four arcs of motion in sagittal plane ankle?
- plantarflexion (0-5%)
- dorsiflexion(5-50%)
- plantarflexion (50-60%)
- dorsiflexion (60-100%)
kinetic variables during gait
- ground reaction forces
- joint moment
- joint power
describe a force/time graph for foot kinematics
spike
then “m-shaped” bump
forces that control gait
- gravity
- ground reaction forces (natural = vertical, shear= medial lateral or ant/post)
- internal muscle forces
- air resistance
120% BW
peak value for vertical GRF
double peaks of vertical GRF =
- 1st peak at heel strike: the action of body momentum
- 2nd peak at push -off: contraction of calf m.
why is vertical GRF lower than BW during midstance?
knee flexion
what does the antero-posterior GRF component look like during dif phases of gait?
- 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
larger step length = ______ shear forces
greater
peak value of antero-posterior GRF component
20% BW
what is the peak value of the medio-lateral GRF component?
5% BW
the magnitude of the medial-lateral shear force depend on the position of the COM relative to the foot
- in lateral direction at heel strike
- in medial direction at rest of stance phase
larger step width = ___________ shear forces
greater
- b/c greater angle of between the lower extremity and floor
define joint power
- 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
where are the sources of energy at joints?
ankle and hip are sources of energy during gait
knee is more a controlling area
when are the following muscles active during gait? gluteus maximus iliopsoas hamstrings quadriceps triceps surae tibialis anterior
- 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
