When you expose your body to heat, your muscles relax better, which first and foremost relieves tension and soreness. It also increases your blood circulation, in fact blood flow nearly doubles in a sauna (31), meaning your muscles will be exposed to more oxygen-rich blood and remove more ‘waste’ back to the kidneys. This improved ‘waste leads to faster recovery, less soreness, and overall improved tissue health, which is exactly why taking a sauna after a workout speeds up your recovery (32).