The Science behind the Infrared Sauna

What is it?


We’re all familiar with the concept of a sauna: generally it is a small room or cabin that gets very hot. There are different types of saunas: traditional saunas work by having a source of heat in the room (so the room itself is hot); whereas infrared saunas, like the awesome one that we have at The Fit Partnership, work by emitting infrared that penetrates more deeply and heats up your body from the inside.





Benefits

Sauna use has been well-researched and the benefits are extensive. Studies have noted that sauna use is well-tolerated by most healthy adults and children, and that it may help lower blood pressure; improve cardiovascular function; provide relief to patients with asthma and chronic bronchitis; alleviate pain; improve joint mobility; and benefit patients with psoriasis.


Sauna use has even been shown to be associated with a reduction in all-cause mortality!


Anti-aging


Repeated sauna use in healthy volunteers was found to lead to increases in growth hormone and decreases in cortisol. A general decline in growth hormone with increasing age is well-documented. By increasing growth hormone levels, sauna use may help in mitigating this effect of ageing. At the same time, cortisol levels have been shown to be positively correlated with chronic inflammation, which in turn has been identified as the key driver of ageing. The decrease in cortisol levels caused by sauna use may then reduce inflammation levels, and so mitigate the ageing process.

Heat shock proteins (“HSPs”) are critical for cellular survival under stress. They decrease the levels of pro-inflammatory cytokines (immune messengers) and help to protect DNA from damage. The accumulation of damaged DNA is also implicated in ageing. Sauna use has been shown to trigger the release of heat shock proteins in a randomised controlled trial. It has been suggested that this is the mechanism by which sauna use leads to a decrease in all cause mortality.


Athletic Performance


A study on distance runners found that regular sauna use post-training increased their run time to exhaustion by 32%. The researchers also noted that the participants’ red cell and plasma volumes increased. The improvement in endurance was attributed to the increased blood volume. This increase in blood volume could also lead to an increased oxygen-carrying capacity (bigger blood cells could carry more oxygen) and the ability to perform at greater intensity as well as the demonstrated increase in endurance.


Detoxification


We are all exposed to innumerable chemicals: from pesticides in foods, to detergents on clothes and air pollution. A study compared the levels of different chemicals (organochlorinated pesticides) and how they were most efficiently excreted and found that sweating led to the greatest amount being removed from the body.


A review article has confirmed that arsenic, cadmium, lead, and mercury can all be removed from the body via sweat. They even noted that mercury levels normalised with repeated saunas, and that cadmium was more concentrated in sweat than in blood plasma.


A further study compared the levels of toxins present in the blood, sweat, and urine. They noted that many toxic elements were preferentially excreted through sweat and that some toxic elements found in sweat were not present in blood samples. They concluded that, “induced sweating seems to be a potential method for elimination of many toxic elements from the human body”.


When our modern world is so inundated with toxins, it is necessary to do what we can to remove them as efficiently as possible given that complete avoidance of them is probably not possible. Regular infrared sauna use is effective at helping to remove these toxins, thus reducing the burden on the body.


Cardiovascular Health


In general, sauna bathing has been noted to be associated with a decreased risk of cardiovascular mortality.

A study on patients with cardiovascular risk factors demonstrated that a single sauna session induced an increase in heart rate, but that during the “cool down” period following the session heart rate variability increased, indicating the “dominant role of parasympathetic activity and decreased sympathetic activity of the cardiac autonomic nervous system”. The authors speculated that this beneficial effect on heart rate and heart rate variability could be behind the long term beneficial cardiovascular effects of sauna use.


We’re all familiar with heart rate (usually the number of heartbeats per minute). Heart rate variability is a measure of the variation in the gap between heart beats: the higher your heart rate variability, the greater your body’s capacity to adapt to stress. The parasympathetic nervous system is responsible for your body’s relaxed “rest and digest” response, whereas the sympathetic nervous system is activated in response to stressors. So this study demonstrated that while the sauna was a stressor in the short term (heart rate increased), in the aftermath it led to a reduced stress load on the body (as shown by the increased heart rate variability).


A review of the evidence on sauna use and sudden cardiac death noted that regular sauna use is associated with a substantial risk reduction; and that the combination of regular physical exercise and sauna use conferred a greater risk reduction. They speculated that sauna use may be protective via the impact on cardiovascular function due to:

  • reduced arterial stiffness, inflammation and oxidative stress;

  • stabilisation of the autonomic nervous system;

  • beneficial changes in lipid profiles and other cardiovascular risk markers; and

  • the lowering of systemic blood pressure.


Another study looked at the ability of far infrared sauna use to improve endothelial function in patients with coronary risk factors: e.g. hypercholesterolemia, hypertension, diabetes mellitus and smoking. They concluded that the far infrared sauna treatment did improve the initially impaired endothelial function, which suggested that there could be a therapeutic role for sauna use in patients with risk factors for atherosclerosis.


There is an abundance of evidence that sauna use in general, and infrared sauna use in particular, is beneficial for cardiovascular health, both in preventing and improving risk factors for cardiovascular disease.


Immunity

Sauna use has been shown to acutely enhance immunity by increasing the number of circulating white blood cells.


A study was designed to assess whether regular sauna use could decrease susceptibility to colds. Participants were divided into a sauna group and a control group, who abstained from sauna use or any equivalent practices. They found that there were, “significantly fewer” colds in the sauna group. Moreover, after the first three months of regular sauna use, those in the sauna group had half the colds of those in the control group.


A study found that lymphocytes (white blood cells) withdrawn from hyperthermic (with a higher than normal body temperature) individuals produced ten times more interferon gamma than cells drawn at baseline from the same individuals. Interferon gamma is a chemical messenger used by the immune system: it activates other immune cells (macrophages, natural killer cells and neutrophils).


A study on healthy volunteers found that repeated hyperthermia (increased body temperature) modulated immune markers, indicating that, “repetitive mild hyperthermia treatment might suppress excessive sympathetic dominance and modify immunity”. When your sympathetic (fight or flight) nervous system is activated, your immune activity is down-regulated: if your body is focused on running from a stress, it is not worried about fighting off a cold. This study suggests that sauna use shifted the body from a sympathetic (stressed) state to a parasympathetic (relaxed) state, leading to enhanced immunity.


Taken together, this evidence suggests that sauna use acutely enhances immune activity, leading to better long-term health.


Joint Health


A study compared improvements in flexibility from stretching in a sauna with stretching under normal training conditions. Stretching sessions were shown to improve flexibility in both circumstances, but the sauna stretching session led to greater changes in acute flexibility. The benefits of the increased range of motion included: “less friction in joints, enabling joint function to diminish stiffness and joint relaxation”.


Mental Health


A comprehensive six week, randomised, double-blind study compared increased body temperature with a sham to assess the efficacy in treating major depressive disorder. After a single session, the group that underwent whole-body hyperthermia showed significantly reduced depression rating scores across the six week post-intervention study period. The authors concluded that: “whole-body hyperthermia holds promise as a safe, rapid-acting, antidepressant modality with a prolonged therapeutic benefit”.

Mimicking Exercise


A study in healthy volunteers found that the changes in blood pressure and heart rate induced by a 25 minute sauna session were equivalent to those during “submaximal dynamic exercise”.


The improvements in cardiovascular health, immunity, athletic performance, the release of heat shock proteins, weight loss and improved blood glucose control are all further indications that sauna use can function as an exercise mimetic. So you can get (at least some of) the benefits of exercise while relaxing in the heat!


Neurological Health


A large study of over 13,000 men and women in Finland showed that sauna use was related to a reduced risk of dementia.


Another study found that sauna use was inversely correlated with the rates of Alzheimer’s and dementia: the more frequently participants used the sauna, the lower their chance of being diagnosed with Alzheimer’s or dementia.


Skin Health


Near-infrared light therapy from LEDs (as we have in our sauna) has been shown to increase cell growth, decrease wound size, decrease wound healing time, decrease pain and improve musculoskeletal training injuries.


Another study showed that infrared radiation led to increases in the production of collagen and elastin in skin cells in proportion to the duration of the exposure. All patients in the trial reported good improvements in skin texture and roughness, and fair improvements in colour tone. The authors concluded that, “infrared radiation may have beneficial effects on skin texture and wrinkles by increasing collagen and elastin”.


A randomised controlled blinded trial revealed a “significant difference” in the reduction of acne lesions when comparing those treated with infrared radiation against those treated with conventional treatments alone. In addition, the clinical assessment of the severity of the acne lesions was “significantly lower” on the infrared treated side than the control side.


Sleep

In rats, exposure to FAR infrared radiation led to increased activity in the daytime and less activity at night, suggesting that it helpfully modulated their circadian rhythms. In humans, infrared exposure led to subjective improvements in sleep quality: participants felt they slept more deeply and woke less frequently during the night.


Weight loss


A review article looked at the effects of sauna use on obesity and diabetes. They found that heat therapy reduces fasting blood glucose levels, reduces glycated haemoglobin, body weight and adiposity. They suggested that these benefits may be due to the increases in heat shock proteins and nitric oxide that sauna use induces.


Haemoglobin is the protein in your red blood cells that carries oxygen. When it binds to glucose it is “glycated”. Doctors measure your levels of glycated haemoglobin to estimate your blood glucose levels over the past 8-12 weeks: the higher it is, the high your blood sugar levels are likely to have been in the preceding weeks.


It is acknowledged that far-infrared saunas are beneficial for treating high blood pressure, obesity, and congestive heart failure. A study in type 2 diabetics found that thrice weekly sauna sessions for three months led to decreases in both blood pressure and waist circumference.





Differences


Infrared saunas are typically not as hot as traditional saunas. But the infrared heat penetrates deeper into your body than the heat in a traditional sauna.


A study comparing a far infrared sauna with a control sauna (that emitted heat, but not via infrared radiation) found that thrice weekly far infrared sauna sessions over six weeks resulted in reductions in both systolic and diastolic blood pressures of the participants .


One study compared the effects of a far-infrared sauna with a traditional Finnish sauna on recovery from strength and endurance training sessions. The authors concluded that the deeper penetration of the infrared heat into fat tissue and the neuromuscular system was better for improving neuromuscular recovery.


For whom?


Infrared sauna use has a wonderful range of benefits from anti-aging to weight loss, to enhancing athletic recovery and performance. The immune-booting benefits are particularly impressive. It is sufficiently well-tolerated that most people would benefit from adding some time in the infrared sauna to their wellness routine.


Do get in touch with any questions, and we look forward to hopefully welcoming you to our relaxing sauna soon!


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