Thermal and cardiovascular responses to sauna are attenuated by adding cold water immersion to cooling breaks

The independent effects of different cooling practices, such as cold-water immersion (CWI), on thermal and cardiovascular responses to sauna remain unclear. This study tested the hypothesis that thermal and cardiovascular responses to sauna are attenuated when CWI was included in a cooling break compared to cooling in air only. In a counterbalanced, crossover design, 16 healthy adults (8 females; age 31 (7) years) participated, on separate visits, in two trials involving 2 × 15 min, 85°C sauna bouts, each followed by a 10-min cooling break in 23°C air (AIR), or AIR with a 90-s, 20°C whole-body CWI. At the end of the second sauna bout, core temperature and heart rate were lower in CWI than AIR (P ≤ 0.003, 37.55°C versus 38.03°C, -0.48°C [95% CI: -0.71, -0.25], d = 1.28, and 108 bpm versus 125 bpm, -17 bpm [95% CI: -26, -6.6], d = 1.05). Skin temperature was also lower in CWI than in AIR (P < 0.001). Systolic blood pressure and mean arterial pressure did not differ between conditions (P ≥ 0.090), whilst diastolic blood pressure was lower in AIR than CWI at the end of cooling breaks and 20 min into recovery (P ≤ 0.038). Participants reported feeling less hot and more able to tolerate the second sauna in CWI than in AIR (P ≤ 0.002, d = 1.27 and 0.97). In conclusion, CWI substantially attenuated thermal and cardiovascular strain and improved the perceptual responses to sauna compared with air cooling alone, making sauna more tolerable and reducing heat illness risks.