Thermal stress, hydration, and salivary and respiratory stress markers in curling players performing a match in the cold.

Curling is a target-based team sport played in a cold environment. The type of stress curling players face during a curling match remains to be determined. In the present study, 16 Japanese curling players performed a practice curling match (6 ends lasting 90 min), wherein the following parameters were documented: core and skin temperatures, heart rate, thermal sensation and comfort, urine specific gravity, body fluid loss, salivary cortisol, α-amylase activity, salivary secretory immunoglobulin A (SIgA) levels, and fractionated exhaled nitric oxide (FeNO, a respiratory stress marker) levels. Pre-match resting core temperature was 37.24 ± 0.31 °C, which increased up to 37.73 ± 0.41 °C during the match (P<0.001). Facial skin temperatures decreased after the match (all P≤0.015), whereas finger skin temperatures remained unchanged (P≥0.375). Thermal discomfort increased following the match but thermal sensation remained unchanged. Following the match, players lost 0.29 ± 0.15 L body fluid (sweat, respiratory evaporation, and urine), which was nearly compensated by fluid ingestion of 0.22 ± 0.13 L (P=0.119). Nevertheless, urine specific gravity increased from 1.021 ± 0.010 to 1.024 ± 0.008 after the match (P=0.012), with 31% and 50% players being dehydrated at pre- and post-match, respectively. Salivary cortisol decreased (P<0.001) after the match without changes in salivary SIgA, α-amylase activity, and FeNO (all P≥0.113). Therefore, during a curling match, the core temperature and thermal discomfort increase, whereas the face skin temperature decreases. Additionally, players may undergo dehydration before the match, which could be exacerbated after the match.