Neuromuscular responses of elderly women to tasks of increasing complexity imposed during walking.

The purpose of this electromyographic study was to examine the effects of age on lower limb muscle response characteristics during reaction tasks of varying complexity when standing and walking. Ten young (mean age 22 years) and ten elderly (mean age 68 years) women participated in the investigation. No differences between groups were recorded in muscle activation times (MAT) in response to a visual light directional stimulus (LDS) during all standing reaction tasks. All the women required a longer period of time to respond to LDS when walking than standing. Completion of complex walking reaction tasks produced significantly longer (P < 0.001) MAT in all subjects than the more simple walking reaction tasks. Delays in neuromuscular response were significantly greater (P < 0.05) in the older women as the complexity of the walking reaction task increased. Movement behaviour of subjects during the walking reaction trials suggested that relatively greater demands were placed on the neuromuscular systems of the elderly during those tasks of greatest complexity. It was postulated that these movements were directed more at compensating for a reduced neuromuscular ability to control efficiently balance homeostasis. The results of this study provide further support for the hypothesis that delays in the central processing of information during reaction tasks may occur with ageing.