The lasting effects of spike insoles on postural control in the elderly
The purpose of the present study was to explore the lasting effects of a tactile sensitivity enhancement induced by spike insoles on the control of stance in the elderly. Healthy elderly subjects (n = 19, mean age = 68.8) and young adults (n = 17, mean age = 24.3) were instructed to stand or to walk for 5 minutes with sandals equipped with spike insoles. Postural control was evaluated four times during unperturbed stance: (1) before putting on the sandals equipped with spike insoles, (2) 5 minutes after standing or walking with them, (3) immediately after placing thin, smooth, and flexible insoles (no spike insoles) into the sandals to avoid the cutaneous contact with the spikes, and (4) after a sitting rest of 5 minutes with the no spike insoles. Sway parameters such as surface area, mean speed and root mean square were recorded. The present results suggest that (1) whatever the session (i.e. standing or walking) and the population, the artificial sensory message elicited by the spikes improved postural sway and, (2) the elderly were particularly perturbed when the tactile sensitivity enhancement device was removed. Whatever the age, the enriched sensory context provided by this tactile sensitivity enhancement device led to a better postural control; its suppression entailed a reweighting of the plantar cutaneous information. The difficulty that the elderly had to adjust the relative contribution of the different inputs probably reflected their poorer central integrative mechanisms for the reconfiguration of the postural set. A reduced peripheral sensitivity may also explain these postural deficits.