Cold Habituation Does Not Alter Thermal Responses or Manual Dexterity During Prolonged Cold Air Exposure

Abstract

Background: Habituation is a pattern of cold acclimatization characterized by attenuated cold defense responses, including a reduction in peripheral vasoconstriction and subsequent increase in skin temperature (TSk) as well as a decrease in shivering thermogenesis. Habituation is achieved through repeated reductions in TSk, rather than deep body core temperature (TC), via exposure to prolonged cold air or brief cold-water immersion. Due to improvements in TSk, enhanced manual dexterity and peripheral cold injury risk reduction are purported benefits of cold habituation. Warfighters frequently operate in cold climates and experience decrements in manual dexterity and strength. These functional losses can negatively impact mission critical tasks and training exercises; however, the effectiveness of cold habituation as a potential countermeasure to alleviate the deleterious effects of prolonged cold exposure on peripheral temperatures, thermal comfort, and hand function is unclear. Purpose: To evaluate the influence of eight consecutive cold air exposures on the thermal (TC and TSk), perceptual (thermal comfort and sensation), and functional (manual dexterity and strength) responses to cold air. We hypothesized that TSk would be higher and perceptual responses and manual dexterity improved, following repeated cold exposure. Methods: Eight young adults (6 M/1 F/1 FTM; 21 ± 2 years; %BF 24.5 ± 7.0) underwent a 2-h cold air exposure (8 °C, ~50% RH) on 8 consecutive days wearing minimal clothing. On Day 0 (baseline exposure ~1 week prior) and Days 1 and 8 of repeated exposure, TC was recorded continuously via a telemetry pill used as a rectal suppository. Extremity (Thand and Tfinger) and mean weighted TSk (MWTSk) from 8 skin sites were recorded continuously. Thermal comfort (TC) and thermal sensation (TS) were recorded at 20 min intervals. Expired gases were collected at 20 min intervals and used to calculate metabolic heat production (MHP). Manual dexterity was assessed using the Purdue Pegboard and Minnesota Manual Dexterity Test (MMDT), and hand strength were measured before and at the end of cold exposure. Results: TC changed across time ( p < 0.05) but did not differ between days ( p > 0.05). MWTSk, Thand, and Tfinger decreased across time ( p < 0.05) but also did not differ between days ( p > 0.05). Mean and minimum whole-body TS and TC were not different between days ( p > 0.05). MHP increased across time ( p < 0.05) but did not differ between days ( p > 0.05). Purdue Pegboard, MMDT task performance, and hand strength did not differ between days ( p > 0.05). Conclusion: Eight consecutive days of cold air exposure does not augment extremity skin temperature, thermal comfort, or manual performance during prolonged cold conditions. Supported by U.S. Army Medical Research and Development Command, Military Operational Medicine Research Program; author views not offcial US Army or DoD policy. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.