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Influence of body heat content on hand function during prolonged cold exposures

¹School of Health and Human Performance, Dalhousie University, Halifax; and ²School of Recreation Management and Kinesiology, Acadia University, Wolfville, Nova Scotia, Canada

Submitted 16 February 2006 ; accepted in final form 3 May 2006

We examined the influence of 1) prior increase [preheating (PHT)], 2) increase throughout [heating (HT)], and 3) no increase [control (Con)] of body heat content (H_b) on neuromuscular function and manual dexterity of the hands during a 130-min exposure to –20°C (coldEx). Ten volunteers randomly underwent three passive coldEx, incorporating a 10-min moderate-exercise period at the 65th min while wearing a liquid conditioning garment (LCG) and military arctic clothing. In PHT, 50°C water was circulated in the LCG before coldEx until core temperature was increased by 0.5°C. In HT, participants regulated the inlet LCG water temperature throughout coldEx to subjective comfort, while the LCG was not operating in Con. Thermal comfort, rectal temperature, mean skin temperature, mean finger temperature (_fing), change in H_b (H_b), rate of body heat storage, Purdue pegboard test, finger tapping, handgrip, maximum voluntary contraction, and evoked twitch force of the first dorsal interosseus muscle were recorded. Results demonstrated that, unlike in HT and PHT, thermal comfort, rectal temperature, mean skin temperature, twitch force, maximum voluntary contraction, and finger tapping declined significantly in Con. In contrast, _fing and Purdue pegboard test remained constant only in HT. Generalized estimating equations demonstrated that H_b and _fing were associated over time with hand function, whereas no significant association was detected for rate of body heat storage. It is concluded that increasing H_b not only throughout but also before a coldEx is effective in maintaining hand function. In addition, we found that the best indicator of hand function is H_b followed by _fing.

neuromuscular function; manual dexterity; finger temperature; preheating; heat storage