Responsiveness of thermal sensors to nonuniform thermal environments and exercise

Background: We investigated the utility of finger temperature, hand heat flux, and mean skin temperature as indices of overall thermal balance during nonuniform thermal manipulations combined with exercise, with a view to identifying useful feedback sites for input into personal thermal control systems. Methods: There were 16 subjects who performed 4 X 30 s of 120% VO(2)peak cycling with a 4-min recovery. During recovery, subjects either received no cooling (CON), upper-body cooling (UC), or upper-body cooling combined with leg heating (UCLH) using a multi-zone liquid conditioning garment. Heat loss during recovery was approximately equal to heat production during exercise. Skin temperature was measured on the mid-medial phalanx of the fourth finger. Heat flux was measured on the dorsum of the hand. Results: Neither hand heat flux or finger temperature distinguished between the two cooling conditions during any of the recovery periods, though hand heat flux was very sensitive to the onset and cessation of exercise. Mean skin temperature was significantly different (p < 0.05) during CON (34.0 +/- 0.1degreesC), UC (32.5 +/- 0.2degreesC), and UCLH (33.0 +/- 0.2degreesC). Conclusion: Mean skin temperature may serve as a good indicator of overall heat exchange in the body, even when exposed to nonuniform thermal environments. As hand heat flux was very sensitive to the onset and cessation of exercise, it may be useful as a supplemental thermal feedback to modulate heat exchange in microclimate thermal control systems.