The normal resting adult human heart rate ranges from 60–100 bpm. Subjected to the heat of a sauna, your body dissipates heat via your skin. To do so, the blood vessels just underneath your skin expand and more blood flows to the top layers of your skin. In a sauna, your cardiovascular performance increases by about 50% in order to maintain your blood pressure as your vessels expand. When you cool down after the sauna, your blood vessels contract again and your heart rate returns to normal. Exercising your blood vessels in this manner helps you react to heat and cold stimuli better and faster. This is why people who use the sauna regularly sweat faster in the heat.