The effect of cooling below the knees on dynamic standing postural control

The purpose of this study was to examine the effect of afferent signals from mechanoreceptors related to the feet and ankle joints, and from proprioceptors of the crural muscles on postural control. Eighteen healthy young adults were the subjects of this study. Cooling below the knees was carried out, then the balance ability of the subjects was assessed using the Equitest apparatus. Under eyes closed, sway-referenced vision and sway-referenced support surface conditions, sway of center of gravity tended to increase and strategy tended to a hip strategy as the complexity of tasks increased from single tasks to combined tasks. With regard to latency, postural sway backwards after the support surface was perturbed forwards was significantly delayed compared to postural sway forwards after the support surface was perturbed backwards. Therefore, we consider that time is required to restore standing posture from a displacement inducing postural backward sway. In both forward and backward translations of the support surface, ankle joint plantar and dorsiflexion strengths, which are required for restoring standing posture, were significantly decreased after the cooling. Thus, we consider that factors of muscle strength around the ankle are important in postural equilibrium.