A single 25-min sauna session was comparable to moderate physical exercise with respect to heart rate elevation/blood pressure effects.

Heart rate/blood pressure elevated during sauna or exercise but dropped below the participant’s baseline levels after.

This study compared the effect of either moderate exercise on an exercise bike or a 25-minute sauna session on heart rate and blood pressure in healthy participants. The participants' blood pressure and heart rate reached the same levels during the sauna session as they did with a load of about 100 watts during the exercise test. After either the exercise test or the sauna both heart rate and blood pressure dropped to levels below what the participants started with.

This study used a sauna that was 199.4 F (93 C) plus humidity which makes it even hotter!