Heat as medicine.
Science as practice.

During a sauna session, core temperature rises and the cardiovascular system responds as it would to moderate to vigorous aerobic exercise. Heart rate rises, cardiac output increases and blood vessels dilate throughout the body. A 2025 review in Frontiers in Cardiovascular Medicine confirmed that the physiological responses to sauna bathing closely resemble those of moderate to vigorous aerobic exercise, activating heat shock proteins, endothelial nitric oxide synthase and vasodilation mechanisms (Sastriques-Dunlop et al., 2025). This cardiovascular conditioning without the mechanical load of exercise is one of the most significant findings in sauna research, particularly for populations who cannot train intensively. At the cellular level, heat triggers the production of heat shock proteins, molecular chaperones that repair damaged proteins, protect cells from subsequent stress and play a direct role in cellular resilience and longevity.

Infrared and steam sauna produce overlapping but distinct physiological effects. A 2025 study in the American Journal of Physiology compared the two directly and found that traditional steam sauna produces a stronger cardiovascular and thermoregulatory response, including greater core temperature rise and cardiac output increase (Akerman et al., 2025). Infrared operates at lower ambient temperatures but penetrates approximately 3 to 4 centimetres into fat tissue and the neuromuscular system, producing a deeper tissue heating effect at more tolerable temperatures, peer-reviewed evidence confirms this penetration depth specifically (Mero et al., 2015). This makes infrared particularly effective for muscle recovery, chronic pain and musculoskeletal conditions where tissue penetration matters. The long-term mortality and cardiovascular health data from Finnish cohort studies is based on traditional steam sauna. For recovery and deep tissue work, infrared has the edge. For cardiovascular conditioning and the full sauna experience, steam produces a stronger response.

Sweat contains water, electrolytes, urea, ammonia and trace amounts of various metabolic compounds. Sauna-induced sweating produces a significant increase in sweat volume and rate. The heat also opens pores, supporting skin surface clearance and renewal. Regular sauna use has been associated with improved skin hydration, reduced acne and improved skin texture through the combined effects of heat exposure and profuse sweating. It is worth being clear that the kidneys and liver remain the primary detoxification organs. Sauna supports rather than replaces these systems, and claims about heavy metal clearance through sweat are not as strongly supported by evidence as the skin health and sweat-volume benefits.

Heat stress triggers a significant release of growth hormone, with peer-reviewed studies confirming meaningful increases following sauna sessions. The magnitude varies depending on protocol, temperature and frequency. Growth hormone drives muscle repair, fat metabolism and cellular regeneration. Research on far-infrared sauna specifically confirmed significant growth hormone increases in both strength and endurance recovery contexts, alongside the deep tissue penetration effect of infrared wavelengths at 3 to 4 centimetres (Mero et al., 2015). For athletes and physically active clients, the growth hormone response from regular sauna use supports recovery between training sessions alongside the direct effects of heat on muscular tension release and connective tissue flexibility.

The humid heat of steam sauna opens airways and supports mucociliary clearance, the process by which the respiratory tract clears mucus and pathogens. Regular sauna use has been associated with reduced frequency of respiratory infections and improved respiratory function in people with conditions including asthma and chronic bronchitis. The anti-inflammatory effects of heat exposure, mediated through heat shock proteins and suppression of pro-inflammatory cytokines, also reduce systemic inflammation over repeated sessions, supporting autoimmune and chronic inflammatory conditions alongside the direct respiratory benefit.