Sauna and cold water immersion shift blood pressure and heart rate in healthy young women

A single-session study tracked cardiovascular responses in 28 normotensive women as they cycled three times through a Finnish sauna followed by cold water immersion. Systolic blood pressure, diastolic blood pressure, and heart rate all changed significantly across the heating and cooling phases, though the patterns differed by measure.

What the study found

The study found that all three cardiovascular measures — systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) — responded significantly to the alternating heat and cold exposures, but not in the same direction or with the same consistency.

During the sauna phases, SBP rose above baseline in the first heating round, while DBP moved in the opposite direction, falling below baseline. Heart rate climbed above baseline in all three heating sessions. This divergence between systolic and diastolic pressure during heat exposure is a notable feature of the data.

Across the three heating rounds, SBP showed a declining trend — meaning the initial spike appeared to moderate with each successive sauna session. No comparable trend was detected during the cold immersion intervals. DBP and heart rate held relatively steady across repeated cycles of both heating and cooling.

The authors interpret the pattern in SBP as potentially reflecting an acute cardiovascular adaptation to repeated thermal stress, but they are careful to frame this as a preliminary observation. They note that a single-session design cannot establish whether such responses persist, accumulate, or translate into longer-term cardiovascular effects.

Limits worth knowing

The study enrolled only 28 participants, all young, healthy, normotensive women, which sharply limits how far the findings can be generalized — to men, older adults, or people with any cardiovascular condition. Only acute, within-session responses were measured; there was no follow-up to assess whether any changes persisted. The protocol was conducted at a single site and in a single session, ruling out any assessment of adaptation over time. Funding sources are not disclosed in the abstract. The authors themselves call for future longitudinal work across different age groups, sexes, and health profiles before broader conclusions can be drawn.

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