What the research says
People have used heat and cold for centuries. Here is what published studies have measured, in plain language, with a link to every source and an honest note on its limits.
50%
Lower risk of fatal heart events
In a study that followed 2,315 Finnish men for about 20 years, those who used a sauna 4 to 7 times a week had about half the risk of fatal cardiovascular events of those who went once a week.
An observational study: it shows an association, not proof of cause.
150
Beats per minute your heart can reach in a sauna
A 2018 review of sauna research reported that heart rate can rise to 100 to 150 beats per minute during a session, a cardiovascular response comparable to low-to-moderate intensity exercise.
A review of mostly observational research; benefits depend on regular use.
Laukkanen JA, Laukkanen T, Kunutsor SK. Mayo Clinic Proceedings, 2018
250%
Rise in dopamine after a cold plunge
In a controlled study, immersion to the neck in 57°F water raised blood dopamine by about 250% and noradrenaline by about 530%, the chemistry behind the alert, clear feeling people describe after the cold.
A small study of healthy men; effects were measured during one hour of immersion.
Šrámek P, et al. European Journal of Applied Physiology, 2000
17
Trials reviewed on cold and muscle soreness
A Cochrane review of 17 small trials found that cold water immersion after exercise reduced delayed-onset muscle soreness compared with resting.
The reviewers rated the evidence as low quality and called for better trials.
Bleakley C, et al. Cochrane Database of Systematic Reviews, 2012
136
Adults in a controlled red light trial
In a controlled trial of 136 volunteers, red and broad-spectrum light improved skin complexion and skin feeling, and ultrasound measured higher collagen density, compared with a control group.
Results reflect regular sessions over several weeks.
Wunsch A, Matuschka K. Photomedicine and Laser Surgery, 2014
Research summaries for education, not medical advice. These products are not intended to diagnose, treat, cure or prevent any disease. Talk to your doctor before starting heat or cold exposure, especially if you are pregnant or have a heart condition.
