Cardiac output, a measure of the amount of work the heart performs in response to the body's need for oxygen, increases by 60 to 70 percent, while the heart rate (the number of beats per minute) increases and the stroke volume (the amount of blood pumped) remains unchanged.
Repeated sauna use acclimates the body to heat and optimizes the body's response to future exposures (known as hormesis). Hormesis triggers a vast array of protective mechanisms that not only repair cell damage but also provide protection from subsequent exposures to more devastating stressors.
Sauna use has been proposed as an alternative to exercise for people who are unable to engage in physical activity due to chronic disease or physical limitations.
Heat exposure induces protective responses against the deleterious biological processes that drive cardiovascular disease and related disability. Some of these responses recapitulate those experienced during exercise.
Like exercise, long-term sauna use generally improves blood pressure, endothelial function, and left ventricular function, and reduces inflammation.
Moderate sauna users (two to three times per week) are 27 percent less likely to die from cardiovascular-related causes, and frequent users (four to seven times per week) are 50 percent less likely to die from cardiovascular-related causes. In addition, the frequent sauna users were found to be 40 percent less likely to die from all causes of premature death, regardless of age, activity levels, and lifestyle factors.
Congestive heart failure
Two weeks of dry sauna use improves endurance, heart size, and disease status compared to those who received standard medical care and reduced the number of premature ventricular contractions experienced in a 24-hour period.
Ischemic heart disease, also known as coronary artery disease
A randomized controlled trial examined the effects of sauna use in 24 patients with ischemic heart disease with chronic total coronary artery occlusion (full blockage of one or more of the arteries that supply the heart) who had not responded to non-surgical procedures and were not candidates for surgical interventions. The findings demonstrated that 15 dry sauna sessions given over a three-week period improved the patients' vascular endothelial function.
Peripheral artery disease
A pilot trial involving 20 patients with PAD who received 50 sessions over a period of 10 weeks demonstrated improvements in pain levels, walking endurance, and lower extremity blood flow.
Regular sauna use modulates serum cholesterol and lipoproteins in healthy adults. Women who were exposed to seven 30-minute sauna baths over a period of two weeks exhibited reduced total cholesterol levels and reduced low-density lipoprotein levels. Similarly, men who were exposed to ten 45-minute sauna baths over a period of three weeks exhibited reduced total cholesterol levels and reduced LDL levels.
A common element among sauna users, however, is lower incidence of hypertension through improvements in arterial compliance. Men who used the sauna two to three sessions every week were found to have a 24 percent lower risk of developing hypertension, and men who used the sauna four to seven times per week had a 46 percent lower risk for hypertension, compared to men who used the sauna only once per week. Just a single sauna session has been shown to lower blood pressure and improve arterial compliance.
Sauna use may serve as a non-pharmacological means to address, or even prevent, hypertension.
Two weeks of sauna therapy improved endothelial and cardiac function in patients with CHF.
Left Ventricle Dysfunction
Both single-session and long-term (five days per week for four weeks) sauna use improved ventricular function in men with CHF and may have therapeutic value for treating late-stage cardiovascular disease.
Health Benefits Associated
with Sauna Use
Sauna use, reduces blood levels of CRP.
Cognitive and Mental Health
Heat stress and exercise increase the expression of brain-derived neurotrophic factor, or BDNF, a protein that acts on neurons in the central and peripheral nervous systems, to promote the growth of new neurons. BDNF modulates neuronal plasticity and ameliorates anxiety and depression from early-life stressful events. It is active in the hippo-campus, cortex, cerebellum, and basal fore-brain – areas involved in learning, long term memory, and executive function. BDNF is also produced in exercising muscle tissue, where it plays a role in muscle repair and the growth of new muscle cells.
Men who used the sauna four to seven times per week had a 65 percent reduced risk of developing Alzheimer's disease, compared to men who used the sauna only one time per week.
Sauna use has been shown to reduce symptoms of depression.
Four weeks of sauna sessions can reduce symptoms of depression – such as improving appetite and reducing body aches and anxiety.
Mental Focus and Attention Span
When young men stayed in a sauna that was heated to 80°C (176°F) until subjective exhaustion, their nor-epinephrine levels increased by 310 percent and their prolactin levels increased by 900 percent. Levels of cortisol, a hormone commonly associated with the stress response, were slightly decreased. Similarly, in a study involving women who participated in 20-minute sessions in a dry sauna twice a week experienced an 86 percent increase in nor-epinephrine and a 510 percent increase in prolactin after the session.
May also help with ADHD
Hormonal and Metabolic Function
Sauna use promotes growth hormone release, which varies according to time, temperature, and frequency.
Repeated exposure to whole-body heat treatment through sauna use has an even more profound effect on boosting growth hormone immediately afterward: Seventeen men and women who were exposed to two one-hour sauna sessions at 80°C (176°F) dry heat (typical Finnish-style sauna) per day for seven days exhibited a 16-fold increase in growth hormone levels by the third day. The growth hormone effects generally persisted for a few hours post-sauna.
Insulin and Glucose
Repeated treatment with a far-infrared sauna has been shown to significantly lower fasting blood glucose levels.
Physical Fitness and Athletic Performance
Heat stress from using the sauna may modulate improvements in physical fitness and athletic performance by increasing endurance and maintaining or promoting gains in muscle mass.
Repeat sauna use on athletic performance and other physiological effects in six male distance runners. The findings showed that one 30-minute sauna session twice a week for three weeks post-workout increased the time that it took for the study participants to run until exhaustion by 32 percent compared to their baseline.
In a small study involving nine female athletes who sat for 20 minutes a day for five days in a hot environment (50°C [122°F], in low humidity) wearing a sauna suit to replicate sauna conditions, the women experienced improvements in thermoregulatory, cardiovascular, and perceived strain compared to a control group.
Muscle Mass Maintenance
Sauna use may reduce the amount of protein degradation that occurs during disuse by increasing HSPs, reducing oxidative damage, promoting release of growth hormone, and improving insulin sensitivity.
Maintaining positive net synthesis has special relevance for recovery from injury since injury can tip the balance towards protein degradation and away from protein synthesis in the muscles, which can promote muscle atrophy.
Sweating facilitates the excretion of certain toxicants that bioaccumulate in the muscle, adipose tissues, and organs of humans.