While saunas have dominated wellness conversations in recent years, promising exercise recovery and longevity benefits, new research suggests that a simple hot bath may actually deliver superior health outcomes—and it is far more accessible to the average person.
Researchers from the University of Oregon conducted the first comprehensive comparison of three different heat therapies, examining how hot water immersion stacks up against dry heat and far-infrared saunas. The findings, published in the American Journal of Physiology, offer encouraging news for individuals who lack access to sauna facilities.
"We compared the most commonly utilized modalities of passive heating as they're used in everyday life and studied in scientific research," said lead author Jessica Atencio, a doctoral student in the lab of Professor Christopher Minson.
The study monitored 20 participants—10 men and 10 women between the ages of 20 and 28 who exercised regularly. Researchers tracked body temperature, blood pressure, heart rate, cardiac output, immune cell populations, and blood biomarkers of inflammation before, during, and after each heating method. The objective was to isolate the physiological responses to each therapy in a young, healthy population.
The results demonstrated that hot water immersion proved most effective at increasing core body temperature, which serves as the primary stimulus for beneficial physiological responses. This temperature elevation triggers increased blood flow, and the mechanical force of blood moving through vessels contributes to improved vascular health.
"We saw that hot water immersion was the most impactful in increasing core body temperature, which is the main stimulus for these subsequent responses," Atencio explained. "Increasing body temperature causes an increase in blood flow, and just the force of blood moving across your vessels is beneficial for your vascular health."
Blood samples taken after each heat therapy session revealed that only hot water immersion produced a measurable inflammatory response, as indicated by levels of inflammatory cytokines and immune cell populations. The research team attributed this finding to the unique thermal properties of water immersion.
"Hot water immersion gives you the most robust changes in core temperature because you can't effectively dissipate heat as you can if you have contact with the air and you're sweating to cool the body," Atencio noted. "When you're submerged in water, the sweat mechanisms aren't efficient."
Professor Christopher Minson, who has studied heat therapies for more than two decades, emphasized the broader health implications of these findings. His research has examined how heat interacts with factors such as age, exercise, and illness in both men and women.
"There's no doubt in my mind that if people are willing to do some heat therapy, it's going to align with improved health, as long as it's done in moderation," Minson stated.
The research builds upon extensive sauna studies conducted by Dr. Jari Laukkanen, a Finnish cardiologist, clinician, and research scientist. His multi-year investigations have demonstrated that longer and more frequent sauna sessions yield the greatest benefits. However, the Oregon study suggests that hot tubs may achieve similar or superior results more quickly and efficiently.
Both saunas and hot tubs can replicate certain exercise benefits by elevating heart rate, but hot water immersion appears to produce this effect with greater speed and efficiency. This finding holds particular significance for individuals who face limitations with moderate exercise.
Minson suggested that heat therapy can serve as an effective substitute for aerobic exercise when traditional physical activity is not feasible, though he acknowledged that regular exercise still provides superior results in certain respects. He emphasized that numerous laboratories have documented improved health outcomes from heat therapy, but urged individuals to exercise caution and consult with their doctor before beginning any heat therapy regimen.
The accessibility factor distinguishes this research from previous studies focused primarily on saunas, which remain far more prevalent in Finland than in other countries. For individuals seeking the cardiovascular and inflammatory benefits associated with heat therapy, a hot bath may offer a practical and effective alternative to specialized sauna facilities.