Article

An understanding of age-related changes in motor behaviour is important when considering the design of training programs for fall-prevention in the elderly. Gait initiation is a phase of walking during which falls are often provoked and this study compares strategies employed by healthy older and young adults during gait initiation. Twenty-nine older, physically active subjects (65-79 years) and 28 younger individuals (23-40 years) were instructed to cross a staged road, when a traffic light changed from red to green, leading with a freely chosen or predetermined leg. Electromyography of tibialis anterior (TA) and lateral gastrocnemius (LG) muscles, ground reaction forces exerted and step lengths were recorded. The elderly displayed several striking differences compared to the young individuals. Weight bearing during initial standing was considerably more unequal and reaction time was 46% longer, with identical duration of gait initiation. Swing leg peak posterior force (% BW) tended to be smaller, but the increase of vertical force was larger. Eight elderly and one young subject lacked anticipatory TA onset; however TA anticipation increased with trial number in the elderly group. When the starting leg was predetermined, the deficiency in TA anticipation was no longer apparent. In the stance leg all forces were smaller and LG was recruited later, and unlike the young subjects generally after the swing leg had left the ground. The results revealed that ageing leads to significant alterations in weight bearing and ankle muscle activation in relation to gait initiation. Gait initiation changed significantly when the starting leg was predetermined and, in the elderly, with repetition.

Langue : ANGLAIS