Finger dexterity, skin temperature, and blood flow during auxiliary heating in the cold

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Abstract
The primary purpose of the present study was to compare the effectiveness of two forms of hand heating and to discuss specific trends that relate finger dexterity performance to variables such as finger skin temperature (Tfing), finger blood flow (Q̇fing), forearm skin temperature (Tfsk), forearm muscle temperature (Tfmus), mean weighted body skin temperature (T̄sk), and change in body heat content (ΔHb). These variables along with rate of body heat storage, toe skin temperature, and change in rectal temperature were measured during direct and indirect hand heating. Direct hand heating involved the use of electrically heated gloves to keep the fingers warm (heated gloves condition), whereas indirect hand heating involved warming the fingers indirectly by actively heating the torso with an electrically heated vest (heated vest condition). Seven men (age 35.6 ± 5.6 yr) were subjected to each method of hand heating while they sat in a chair for 3 h during exposure to -25°C air. Q̇fing was significantly ( P < 0.05) higher during the heated vest condition compared with the heated gloves condition (234 ± 28 and 33 ± 4 perfusion units, respectively), despite a similar Tfing (which ranged between 28 and 35°C during the 3-h exposure). Despite the difference in Q̇fing, there was no significant difference in finger dexterity performance. Therefore, finger dexterity can be maintained with direct hand heating despite a low Q̇fing. ΔHb, T̄sk, and Tfmus reached a low of -472 ± 18 kJ, 28.5 ± 0.3°C, and 29.8 ± 0.5°C, respectively, during the heated gloves condition, but the values were not low enough to affect finger dexterity.