Short-term repeated cold air exposure does not impact cold thermoregulatory responses or manual performance in healthy humans.

Abstract

Habituation, a pattern of cold acclimatization, is characterized by a reduction in peripheral vasoconstriction and a subsequent increase in skin temperature (T_sk) during cold exposure. Habituation is achieved through repeated reductions in T_sk and is likely mediated by attenuated sympathetic activation. However, the effectiveness of habituation in alleviating the deleterious effects of cold on peripheral temperatures, thermal comfort, and hand function is unclear. Furthermore, the mechanisms by which habituation may improve extremity (hand and forearm) responses to cold are unclear. Ten healthy humans (8 male/1 female/1 female to male) underwent 8 days of repeated cold air exposure (8°C, 2 h/day). At baseline (1-2 wk prior) and on days 1 and 8, mean and extremity T_sk and skin blood flow (SkBF; laser-Doppler flowmetry) were recorded continuously. Thermal comfort was recorded at regular intervals, and manual dexterity was measured before and at the end of each exposure. At baseline, the day before, and the day following repeated exposure, reflex cutaneous vasoconstriction was elicited using a water-perfused suit (mean T_sk ∼33.5 to 30.5°C), whereas SkBF was recorded at a thermoneutral (uncovered) forearm skin site. In cold air, T_sk and SkBF decreased over time on each day (P < 0.05) but did not differ across days (P > 0.05). Thermal comfort and dexterity decreased in the cold (P < 0.05) but were largely unaltered across days (P > 0.05). Reflex vasoconstriction was unaffected by repeated exposure (baseline: 69.3 ± 26.0, pre: 65.2 ± 32.4, and post: 50.8 ± 31.0%CVC·°C AUC; P = 0.07). We therefore conclude that eight consecutive days of cold air exposure do not augment T_sk, thermal comfort, or manual dexterity in the cold.NEW & NOTEWORTHY In this study, we showed that 8 days of consecutive cold air exposure does not alter skin temperature, reflex vasoconstrictor responsiveness, thermal perception, or hand dexterity. These novel findings indicate that short-term repeated cold air exposure is unlikely to result in physiological adaptations that effectively increase extremity perfusion, temperature, or function.