Running while Catholic

A sauna is not a passive activity. Your heart works about as hard as it does during light cardio, and that changes how you should read the survival data. Sauna gets treated as relaxation, which makes the longevity findings look like magic, but the mechanism is simple. When you sit in heat that intense, your body's main job is to get rid of heat before your core temperature rises. It does this by opening the blood vessels in your skin and sending a large share of your blood to the surface, where the heat can escape. With so many vessels open, your blood pressure would fall, so your heart has to pump faster and harder to hold it steady. Your heart rate climbs and stays up for the whole session. One study tracked heart rate and blood pressure through a 25-minute sauna session and compared it with an exercise bike test in the same people. The strain on the heart matched light to moderate exercise, roughly the effort of an easy to steady bike ride. Sitting still in the heat was doing real cardiovascular work. In another study, 102 adults who each had at least one heart disease risk factor did a single 30-minute session. Afterward their arteries were measurably less stiff, and the top number of their blood pressure dropped from 137 to 130. One session moved both in a healthy direction. The survival data lines up with that. In a study of 2,315 Finnish men followed for about 20 years, the more often someone used the sauna, the less likely he was to die during the study. Death rates dropped step by step. They were highest in men who went once a week, lower in those who went two to three times, and lowest in those who went four to seven times a week. Deaths from heart disease followed the same pattern, so the benefit grew with how often the men went, not just whether they went at all. This study observed one group of middle-aged Finnish men rather than running a controlled experiment, so it cannot prove that sauna caused the benefit, and the frequent users may have been healthier to begin with. No trial has tested sauna directly against lifespan. What the evidence does show is that heat gives your heart and blood vessels a real workout, and the dose that matters appears to be how often you do it. References: Laukkanen et al., JAMA Internal Medicine, 2015. Laukkanen et al., Journal of Human Hypertension, 2018. Ketelhut and Ketelhut, Complementary Therapies in Medicine, 2019.