INTRODUCTION: Extreme cold conditions have a negative impact on endurance exercise performance such as in biathlon, where muscle as well as shooting performance, due to a decrease in manual dexterity, is affected. Hence, it is paramount that biathletes adopt clothing strategies preventing excessive cooling during downhill sections and on the shooting range, while avoiding excess heat production during the skiing bouts. The purpose of the present study was to measure the thermoregulatory response at different body parts during exercise in a cold environment in biathletes. METHODS: Thirteen Swiss elite biathletes (6 females, 7 males; age: 27 ± 4 years) performed two skiing exercise bouts (men: 4.12 km; women: 3.49 km) lasting approximately 15 min in the skating technique on two consecutive days at about 78 ± 4 % of maximal heart rate. They were wearing a race suit in accordance to skiing conditions (ambient temperature: -3.7 ± 2.3 °C; relative humidity: 92.9 ± 6.3%). Heat flux, core and skin temperature were measured with a synchronized sensor-system (CORE, greenTEG AG, Rümlang, Switzerland) placed on the thigh, back, anterior and lateral thorax throughout the entire bout. The subjective perceived rate of thermal comfort (SUBJ) was assessed for the torso, arms, hands, legs, feet, head, neck and whole-body via a visual analog 7-point Likert-scale [1] in winter clothing (REF), right before (PRE) and after exercise (POST). RESULTS: Heat flux measurements during the warm-up demonstrated differences (p < 0.001) between sensor locations, with the thigh showing the highest heat loss (344 ± 37 kJ/m2), followed by the back (269 ± 56 kJ/m2), the lateral thorax (220 ± 47 kJ/m2), and the anterior thorax (192 ± 37 kJ/m2). While core temperature slightly increased from 37.0 ± 0.2°C to 37.5 ± 0.2 °C (NS), skin temperature decreased for all measured body parts (p < 0.001). However, the thigh skin temperature decreased to a larger extent (-7.5 ± 1.2 °C) compared to the skin temperature on the back (-2.8 ± 1.0 °C), the anterior thorax (-4.4 ± 2.0 °C) and the lateral thorax (-2.5 ± 1.5 °C). From PRE to POST, SUBJ at the hands decreased from 0.51 ± 0.9 a.u. to -0.53 ± 1.8 a.u. (p < 0.01). Although SUBJ for other body parts did not change significantly from PRE to POST, a large inter-subject variability was measured, in particular for the hands, head, and whole-body. CONCLUSION: During moderate intensity cross-country skiing in cold environment, heat flux in the lower extremities appears to be higher compared to the upper body, resulting in a significant drop in skin temperature and potential negative impact on performance.
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