Balance problems are often related to a loss of plantar-sensitivity in elderly people. The purpose of this study was to explore the contribution of plantar cutaneous inputs induced by a spike support surface to the control of stance. Nineteen elderly (mean age 69.0 years, range 62-80) and 19 young adults (mean age 25.9 years, range 21-32) were instructed to stand (standing session) or to walk (walking session) for 5 min with sandals equipped with spike insoles (spike condition). Both sessions also involved a no spike condition in which participants stood or walked for 5 min without these insoles (no spike condition). In all conditions, postural responses were assessed during unperturbed stance and were performed (1) immediately after putting the spike or the no spike insoles, and (2) 5 min after standing or walking with them. Sway parameters, such as centre of foot pressure mean location, surface area, mean speed, root mean square and median frequency on the antero-posterior and medio-lateral axes, were calculated. As postural performances are often related to plantar-surface sensitivity, cutaneous sensitivity threshold was also evaluated with Semmes-Weinstein monofilaments.Although no immediate effect of the spike insoles was found, results indicated that standing or walking for 5 min with sandals equipped with spike insoles led to a significant improvement of quiet standing in the elderly. Balance improvement was also observed in young adults. The results provided evidence that wearing sandals with spike insoles can contribute, at least temporarily, to the improvement of unperturbed stance in elderly people with relatively intact plantar cutaneous sensation. Further research is needed to assess the effects of longer and discontinuous stimulations with spike insoles on postural control.

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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.

BackgroundThis study investigated the effects of obesity on attentional resources allocated to postural control in seating and unipedal standing.MethodsTen non obese adults (BMI = 22.4±1.3, age = 42.4±15.1) and 10 obese adult patients (BMI = 35.2±2.8, age = 46.2±19.6) maintained postural stability on a force platform in two postural tasks (seated and unipedal). The two postural tasks were performed (1) alone and (2) in a dual-task paradigm in combination with an auditory reaction time task (RT). Performing the RT task together with the postural one was supposed to require some attentional resources that allowed estimating the attentional cost of postural control. 4 trials were performed in each condition for a total of 16 trials.Findings(1) Whereas seated non obese and obese patients exhibited similar centre of foot pressure oscillations (CoP), in the unipedal stance only obese patients strongly increased their CoP sway in comparison to controls. (2) Whatever the postural task, the additional RT task did not affect postural stability. (3) Seated, RT did not differ between the two groups. (4) RT strongly increased between the two postural conditions in the obese patients only, suggesting that body schema and the use of internal models was altered with obesity.InterpretationObese patients needed more attentional resources to control postural stability during unipedal stance than non obese participants. This was not the case in a more simple posture such as seating. To reduce the risk of fall as indicated by the critical values of CoP displacement, obese patients must dedicate a strong large part of their attentional resources to postural control, to the detriment of non-postural events. Obese patients were not able to easily perform multitasking as healthy adults do, reflecting weakened psycho-motor abilities.