[Influence of a specific cognitive task on spatial-temporal walking parameters in elderly frail individuals]

Walking is a complex voluntary rhythmic motor behaviour. Its implicit nature suggests that reduced attention resources are required for its execution. The aim of this study was to demonstrate that, to perform a mental calculation while walking, might modify the spatial-temporal parameters of walking in fragile elderly patients.

We compared the walking, in a straight line over a distance of 10 meters, of 30 fragile elderly subjects (mean age 82.6 +/- 7.1 years) with that of 30 healthy controls (mean age 37.5 +/- 11.5 years). Two walking conditions were studied: with and without a counting task. The time, number of steps, lateral deviations and stops were recorded on a video camera.

The condition of a double-task provoked three types of effects on walking: an increase in time and the number of steps in both groups, but significantly greater in the elderly patients than in the control group of patients (6.4 s and 4.6 steps in the elderly versus 0.5 s and 0.4 steps in the controls); a reduction in the cadence and length of the step, only significant in the elderly patients, and a significant increase in the number of lateral deviations and stops in the double-task condition in the elderly patients.

Globally, these results indicate that walking requires more attention resources in the elderly than in the middle-aged. The loss of the implicit character of walking to the benefit of cognitive attention resources may partly explain the high risk of falling in fragile elderly subjects.