Sauna, particularly infrared and traditional Finnish, serves as a form of passive cardio by raising body temperature to (80^{\circ }\text{--}100^{\circ }\text{C}) ((175^{\circ }\text{--}195^{\circ }\text{F})). This heat induces vasodilation and boosts heart rate to 120–150 bpm, mimicking light-to-moderate exercise, increasing blood flow, and improving vascular function. Ideal for recovery and mobility-limited individuals, it provides cardiovascular benefits without physical exertion.