Teach-in 2001 : Push-off & The Effect of Speed on Gait
by Chris Kirtley, The Catholic University of America, Washington DC


One of the most profound (and still somewhat controversial) findings of early gait analysis studies was the outstanding contribution of ankle push-off, which amounts to around 60-70% of forward propulsive power in natural, normal gait (Winter, 1983 - 15 normal subjects, using a 2D model & inverse dynamics).

This work transformed our understanding of gait, since previously (before computerized video analysis) the ankle was thought to be relatively unimportant for propulsion (Perry, 1992).

Winter's reports of the joint powers slow, natural and fast cadences (see graphs below from page 48 of his 1991 book) seem to indicate an increase in all power bursts at higher speeds - in particular, the A2 burst appears to be almost directly proportional to speed.


In 1997, Chen published the results of his 3D study of ten healthy children, in which he calculated the energy contribution of each joint to propulsion, as the area under the positive, concentric part, of the power curve at three speeds. It can be seen that, although the ankle energy is predominant at low speeds, the contributions of the hip and knee become progressively more important at higher speeds. In fact, ankle push-off seems to remain roughly constant.
Walking Speed
Ankle
(A2)
Knee
(K2)
Hip
(H1+H3)
Total
Slow (J/kg)
0.22
0.04
0.08
0.35
% Total
63
11
23
 
Natural (J/kg)
0.21
0.06
0.12
0.39
% Total
54
15
31
 
Fast (J/kg)
0.19
0.10
0.15
0.45
% Total
42
22
33
 



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Bibliography

Chen IH, Kuo KN & Andriacchi TP (1997) The influence of walking speed on mechanical joint power during gait Gait & Posture Volume 6, Issue 3: 171-176

Kirtley C & Whittle MW (1985) Influence of Walking Speed on Gait Parameters. Journal of Biomedical Engineering, 7: 282-288.

Perry J. (1992). Gait Analysis Normal and Pathological Function. Slack, Inc, Thorofare, NJ.

Winter DA (1983) Energy generation and absorption at the ankle and knee during fast, natural, and slow cadences. Clin Orthop. May;(175):147-54.


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