Acute effects of combined sauna bathing and cold-water immersion on cardiovascular regulation during physical stress: Preliminary findings from the REACT study

Combining thermal stressors, such as sauna bathing (SB) and cold-water immersion (CWI), is becoming increasingly popular. While SB and CWI individually have been associated with improved cardiovascular function and stress regulation, respectively, their combined impact has not been investigated. Thus, the aim of this study was to explore the acute effects of combined SB and CWI on cardiovascular regulation during physical stressors, including exercise and cold exposure. In addition, we explored the impact on the metaboreflex, an important blood pressure regulation mechanism during exercise. Eleven healthy normotensive participants (age: 37 ± 8 years, BMI: 23 ± 2 kg/m 2 , VO2max: 43 ± 10 mL/kg/min) were studied before and 30 minutes after completing a single session of combined intermittent SB (3x10-min; temperature: ~90ºC, humidity: <10%) and CWI (2x1-min; temperature: 4-6ºC). Manual systolic (SBP), diastolic (DBP), and heart rate (HR) were recorded every 2 minutes during a 10-minute rest period. Continuous beat-to-beat BP [(SBP, DBP, and mean arterial pressure (MAP)] and HR were recorded at rest and during 2 minutes of isometric handgrip exercise (HG; 30% of maximal voluntary contraction), post-exercise ischemia (PEI; metaboreflex isolation) and cold-pressor test (CPT). Data are reported as mean ± SD, unless otherwise stated. Resting DBP (before: 65 ± 2, after: 63 ± 2 mmHg, p=0.006) and MAP (before: 80 ± 8, after: 79 ± 8 mmHg, p=0.049), but not SBP and HR, were significantly attenuated after compared to before SB+CWI. In response to HG, DBP (median before: Δ 12, IQR: 11 – 26, after: 14, IQR: 8 – 18 mmHg, p=0.044) was significantly augmented while SBP (before: Δ 16 ± 9, after: Δ 21 ± 13 mmHg, p=0.051) and MAP (before: Δ17 ± 7, after: Δ 21 ± 11 mmHg, p=0.060) tended to be augmented after compared to before SB+CWI. No difference was observed for HR. The metaboreflex appeared to be unaffected by SB+CWI. Likewise, the BP and HR response to CPT was not different. These preliminary findings are the first to demonstrate that a single session of SB+CWI amplifies the BP response to exercise but not to cold exposure. Considering its increased popularity, these findings may warrant further consideration. However, additional research is needed. GC Rieber Foundations This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.