Swing phase mechanics of healthy young and elderly men.

This study examined the effect of ageing on the swing phase mechanics of young and elderly gait. Sagittal plane marker trajectories and force plate data were collected while 10 young (24.9+/-0.9 years) and eight elderly (68.9+/-0.4 years) subjects walked at their preferred walking speeds. Comparison between young and elderly gait was made for a range of spatial-temporal, kinematic and kinetic variables with emphasis given to identifying possible differences at toe-off, minimum metatarsal-phalangeal joint clearance and heel contact. In order to control for the confounding effect of gait velocity on the dependent variables, a multivariate analysis of covariance was used to identify differences between the young and elderly subjects due to age. In contrast to studies that have reported lower preferred walking speeds in the elderly compared to the young [J.O. Judge, R.B. Davis III, S. Ounpuu, Step length reductions in advanced age: the role of ankle and hip kinetics, Journal of Gerontology: Medical Sciences 51 (1996) M303-312; D.C. Kerrigan, M.K. Todd, U. Della Croce, L.A. Lipsitz, J.J. Collins, Biomechanical gait alterations independent of speed in the healthy elderly: evidence for specific limiting impairments, Archives of Physical and Medical Rehabilitation 79 (1998) 317-322], no differences in walking speed nor in the spatial-temporal variables that determine walking speed were detected. The elderly were however, found to have a greater hip extension moment at the time of minimum metatarsal-phalangeal joint clearance, and a significantly higher anterior-posterior velocity heel contact velocity that was linked to a significantly higher shank and foot angular velocity at heel contact. Since many gait variables are highly correlated with walking speed [C. Kirtley, M.W. Whittle, R.J. Jefferson, Influence of walking speed on gait parameters, Journal of Biomechanical Engineering 7 (1985) 282-288; D.A. Winter, Biomechanical motor patterns in normal walking, Journal of Motor Behaviour 15 (1983) 302-330], differences between young and elderly gait found in the present study may therefore be attributed to ageing, rather than a secondary effect of differences in gait velocity.