Full Length ArticleThe effects of foot cooling on postural muscle responses to an unexpected loss of balance

- Cooled foot soles to reduce somatosensory information and examine effect on balance.
- Reduced foot sole sensitivity lead to delayed and larger postural muscle responses.
- Magnitude of EMG changes imply minimal functional consequences to balance recovery.

The purpose of this study was to examine the role of foot sole somatosensory information during reactive postural control. Twenty young adults (22.0 ± 1.4 y) participated in this study. Baseline skin sensitivity from the foot sole was assessed using Semmes-Weinstein monofilaments. Postural muscle responses, in the form of electromyographic (EMG) onset latencies and amplitudes, were then obtained while participants recovered their balance while standing on a moveable platform that could translate in either the forward or backward direction. Following these baseline measures, the participant's foot soles were immersed in a 0-2 °C ice-water bath for 12 min followed by a 3 min re-immersion period. At the completion of foot cooling, foot sole sensitivity and postural muscle responses to the balance perturbations were re-assessed. Results indicated that the foot cooling protocol reduced foot sole sensitivity and remained reduced throughout the duration of the experiment (p < 0.001). The reduction in foot sole somatosensation resulted in the soleus EMG onset latency being delayed by 3 ms (p = 0.041) and the soleus and medial gastrocnemius EMG amplitudes increasing by 14-23% (p = 0.002-0.036) during the balance perturbation trials. While the magnitude of these results may suggest that foot cooling has a minor functional consequence on reactive postural control, it is likely that the results also reflect the ability of the central nervous system to rapidly adapt to situations with altered somatosensory feedback.