Biomarkers of Cold Strain and Physical Performance Decrements during Submaximal Exercise in Cold Environments with Brief Rewarming.

BACKGROUND Cold exposure impairs physical performance, with the severity of degradation depending on the degree of cold strain. Thresholds for impairment and non-invasive biomarkers to identify changes have yet to be identified. Therefore, this study examines the effects of cold exposure on physical performance, thermoregulation, salivary biomarkers, and the effects of a short-period of rewarming. METHODS 14 recreationally active participants (3F, 11 M), aged 18-44 years, completed a randomized, crossover study involving three experimental conditions: 20, 10, and 0 °C. For each condition, participants completed four 20-minute treadmill walks with physical performance tests, and a 10-minute rewarming period followed by another physical performance test in the respective condition. Physical performance was assessed via the Complete Minnesota Dexterity Test (CMDT), dominant and non-dominant handgrip strength (HGS) between the walks and after rewarming. Thermal discomfort, thermal sensation, body core temperature (Tc), skin temperature (Tsk), and salivary biomarkers (alpha-amylase, cortisol) were measured throughout the study. RESULTS Exposure to 0 °C caused reductions in skin temperatures, with peak reductions in the forearm (-10.51 ± 0.57 °C, p < 0.001) and fourth-finger skin temperatures (-11.60 ± 0.80 °C, p < 0.001). Declines were also found at 10 °C, with peak reductions in forearm (-6.69 ± 0.56 °C, p < 0.001) and fourth-finger skin temperatures (-8.56 ± 0.81 °C, p < 0.001), while no changes occurred at 20 °C. Thermal discomfort and thermal sensation were lowest at 0 °C. Dexterity and HGS significantly declined during 0 °C and 10 °C exposures, with reductions most severe at 0 °C, and no declines at 20 °C. Salivary alpha-amylase and cortisol were not different across environmental conditions or time. Rewarming for 10-minutes at 22 °C improved HGS, CMDT, and thermal discomfort by 30-50%. CONCLUSIONS Cold exposure at 0 °C and 10 °C impairs performance and a 10-minute period of rewarming at 23 °C partially restored performance. Potential salivary biomarkers were not strong predictors of impaired performance.