Postural sway during single and repeated cold exposures.

INTRODUCTION: Tissue cooling changes sensory and neuromuscular functions that are also involved in postural control. The purpose of the study was to determine how acute and repeated exposures to cold affect whole body postural control.

METHODS: Postural sway was measured from 10 subjects during standing with eyes open (EO) and closed (EC) using an inclinometer-based method. Sway was assessed at at 10 degrees C on 10 consecutive days and at 25 degrees C on days 1, 5, and 10. Sway path length, area, velocity, side-to-side and forward-backward movement were assessed. At the same time, rectal and skin temperatures, muscle tonus/ shivering, thermal sensations, and comfort were recorded.

RESULTS: Acute exposure to 10 degrees C caused thermal discomfort, significantly lowered (26.1-26.5 degrees C) mean skin temperatures, slightly lowered rectal temperature (36.7 degrees C) and increased (140-260%) muscle tone, increased sway path length (67-87%, p < 0.05), velocity (63-71%, p < 0.05), total sway area (42-67%, p < 0.05), and forward-backward movement (35-57%, p < 0.05) compared with 25 degrees C. Side-to-side movements were not altered in the cold. Postural sway increased with EC, and further when exposed to cold, but the effect of cold was smaller compared with EO. Repeated exposures over the 10-d period decreased sway 10-40% both at 25 degrees C and at 10 degrees C (p < 0.05-0.01), suggesting motor learning. The difference in sway between 25 degrees C and 10 micro C remained the same throughout the 10-d period, suggesting that the observed cold habituation responses do not affect sway.

CONCLUSIONS: The results demonstrate that postural control is impaired in cold, which may affect physical performance in cold environmental conditions.