The acute effects of continuous and intermittent whole-body passive heating on cardiovascular disease risk indicators in healthy and young males and females.

Purpose: Heat therapy is recognised to promote cardiovascular health, and whilst most recent heat therapy investigations have focussed on continuous heat exposure, traditional sauna use often includes recovery periods. This study compared the acute effects of continuous versus intermittent whole-body heating on cardiovascular function markers in males and females.

Methods: Twenty healthy participants (25 ± 3 years; 10 males, 10 females) were exposed to 2 passive heating regimens: continuous heating (CH) for 60 min and intermittent heating (IH) comprised of 3 × 20-min blocks interspersed by 15-min cooling breaks. Skin perfusion, blood pressure (BP), plasma nitrite, interleukins, body temperature, and thermal perceptual responses were assessed.

Results: Greater increases in rectal temperature (T_rec) (CH: 1.2 ± 0.1 °C; IH: 0.5 ± 0.1 °C), skin perfusion, systolic blood pressure (SBP), heart rate (HR), interleukin-6 (IL-6) and plasma nitrite were found in CH compared to IH (p ≤ 0.01), but the thermal perceptual response was more unfavourable during CH (p < 0.01). Females had higher skin perfusion and plasma nitrite concentrations (p ≤ 0.04), but lower brachial and central BP than males in both conditions (p ≤ 0.01). Furthermore, females reached a higher T_rec and more unfavourable thermal perception in CH (p ≤ 0.02).

Conclusion: More pronounced cardiovascular responses were associated with higher T_rec and discomfort. Females exhibited higher skin perfusion and plasma nitrite concentrations than males and reported less favourable thermal perception in CH, but not in IH.