A hot bath instead of a sauna? Scientists have found out which is more effective for health

This is the conclusion reached by scientists from the Bowman Centre for Sports Science at the University of Oregon (USA). The study was published in the American Journal of Physiology.

Read more: Jessica K. Atencio et al, Comparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalities, American Journal of Physiology-Regulatory, Integrative, and Comparative Physiology (2025). DOI: 10.1152/ajpregu.00012.2025

Researchers compared the effects of three popular heat therapy methods: traditional dry sauna, infrared sauna and hot bath. The experiment involved 20 people aged between 20 and 28 years who regularly exercise. They all took turns undergoing sessions of each type of heat treatment, during which experts recorded body temperature, heart rate, blood pressure, cardiac output and levels of inflammatory markers in the blood.

"Hot water was found to be the most effective way to increase body temperature, which is what triggers physiological responses that are beneficial to health," explained lead study author Jessica Atencio, a graduate student in physiologist Christopher Minson's lab.

An increase in body temperature promotes better blood flow, which in turn has a positive effect on vascular health. The researchers emphasise that, unlike in a sauna, in water the body cannot be effectively cooled by sweating, which means that the heat lasts longer and has a deeper effect.

After each session, the scientists took blood from the participants for analysis. Interestingly, it was the hot bath, not the sauna, that triggered a marked immune response - specifically, increased levels of cytokines (molecules associated with the immune system) and changes in immune cell populations.

"The results didn't surprise us," Atencio says. - "Immersion in water causes more pronounced changes because the heat cannot dissipate as it does when exposed to hot air."

Christopher Minson, professor of physiology and director of the Bowman Centre, has been studying heat therapy for more than 20 years. He argues that regular use of heat treatments promotes good health, especially in those who can't exercise.

"If repeated in moderation, heat stress is quite comparable to the positive effects of exercise," Minson noted. However, he emphasised that heat therapy does not eliminate the need for motor activity, but can be a good complement to it.

"It can be a relaxing, even almost spiritual or cultural experience. The social component and the feeling of relaxation are also important and can enhance the wellness effect," the scientist added.

Atencio, who is a runner herself, emphasises: "We always say that physical activity is the foundation of a non-drug approach to promoting health. But if someone can't or doesn't want to exercise, heat treatments are a good help."

At the same time, the authors of the study recommend consulting a doctor beforehand:

"It is important to understand who is suitable for heat therapy. Sometimes light physical activity like walking or stretching is enough, and sometimes it's wise to start with moderate heat therapy," says Minson.