How Does Heat Therapy Work?

Dr. Rich Joseph, MD MBA
Dr. Rich Joseph, MD MBA
10 minute read
May 4, 2023
Image of a person using heat therapy in the form of infrared sauna at Restore Hyper Wellness.
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Heat therapy has been an integral part of many cultures since the dawn of human civilization. It seems reasonable to conclude that given its wide acceptance and staying power amongst various peoples, it must be doing something beneficial for our bodies.  A growing body of research is now substantiating this ancient intuition with new modalities for heat therapy—such as infrared saunas—and places to purposefully sweat are popping up everywhere from gyms to spas. Its staying power is an anecdotal testament to its perceived effectiveness as a performance enhancing modality. 

What Does Heat Therapy Do To The Body?

  • Heat stress increases core body temperature, promotes blood vessel dilation (vasodilation) and blood redistribution to the skin and extremities to facilitate cooling. Increase in core temperature also prompts increased sweat production.  Active vasodilation and sweating are initiated once core body temperature reaches a temperature threshold, usually ∼0.4°C above resting core temperature.
  • Cardiac output (the amount of blood pumped from the heart per minute) is increased and driven primarily by an elevation in heart rate. This is comparable to the increase seen with moderate intensity exercise.
  • During the cool down period, HRV (heart rate variability) increases as parasympathetic tone is enhanced and sympathetic output dampens.
  • Heat positively affects blood vessels by increasing shear stress, mitigating protein damage and aggregation, activating endogenous antioxidant and anti-inflammatory pathways, and increasing nitric oxide.
  • Acute heat stress also activates and upregulates heat shock proteins , which protect cells from the damaging effects of heat and other stressors and facilitate normal cell function.
  • Heat exposure can also change hormone levels. Preliminary data demonstrate increases in growth hormone, testosterone, prolactin and decreases in cortisol during sauna bathing. Changes in hormones appear to be short lived and data on longitudinal alterations is lacking.
  • In the brain, heat stress promotes a robust increase in beta-endorphins and BDNF which suppress pain, modulate reward circuitry and regulate functions that are critical to cognition and memory.

How Does Heat Therapy Benefit The Body?

  • Heat therapy provides similar benefits as cardiovascular exercise including vascular health, blood pressure, and overall reduced disease risk.
  • Heat has implications for musculoskeletal pain due to its reassuring, and hence analgesic effects.
  • With regard to inflammatory musculoskeletal conditions decreased pain and stiffness in have been noted for patients with rheumatoid arthritis, fibromyalgia, and other rheumatological disorders (i.e., systemic lupus erythematosus, systemic sclerosis, rheumatoid arthritis, Sjogren's syndrome, Behcet's disease, or aortitis syndrome).
  • There are limited studies that indicate indirectly that heat therapy may benefit several other clinical outcomes including dysmenorrhea, chronic pain and chronic fatigue syndromes, COPD, respiratory illnesses and overall longevity and healthy aging.
  • Sweating due to heat exposure may be a way to excrete physiologically unnecessary, and potentially harmful chemicals. 
Data on deliberate heat therapy demonstrates robust and widespread beneficial effects on cardiovascular health.

Does Heat Therapy Affect Physical Performance?

  • Heat therapy has been called an “exercise mimetic” due to its ability to enhance cardiorespiratory fitness and endurance and preserve muscle mass.
  • Heat therapy may also have a direct effect on muscle physiology. Heat stress can provide protection against atrophy in skeletal muscle, likely via increased heat shock protein expression and improved mitochondrial function.
  • There is correlative evidence that increased sauna use is associated with reduced circulating inflammatory markers, namely CRP, in humans.
  • Heat therapy may directly impact both performance and recovery by improvements in sleep.

What Type of Heat Therapy Does Restore Use?

Infrared saunas are a modern technology that utilize light at a particular wavelength to make heat. The infrared waves generated by these saunas are able to penetrate the skin, effectively heating the body from the inside out. There are three levels of infrared light - near, mid, and far. Near-infrared light measures 700-5,000 nanometers (nm), mid-infrared is between 5,000- 40,000nm, and far-infrared is 25,000-350,000nm.

Everything You Need to Know About Sauna/Heat Therapy 

  • The health benefits of heat therapy appear to be dose dependent. So barring safety concerns and taking care of hydration needs, the more time you spend in the heat, the better. With increasing duration and amplitude of heat exposure, the greater “heat fitness” you will develop.
  • Combine the stimulus of exercise with the stimulus of heat for an additive, synergistic effect. In a recent randomized controlled trial that looked at the combined effect of an exercise program followed by sauna use over 8 weeks, the researchers found that when combined with exercise, sauna bathing demonstrated a substantial synergistic effect on cardiorespiratory fitness, systolic blood pressure, and total cholesterol levels.
  • If for some reason an individual is unable to exercise or has physical impairments, consider employing heat therapy as an “exercise mimetic” that provides cardiovascular benefits and preserves lean muscle mass. To be clear, this is not a suggestion to replace exercise with heat therapy, but instead to use heat therapy if the ability to exercise is impaired.
  • Heat therapy is probably less useful as a recovery tool for physical performance. But to the extent that it provides a soothing sensation for tired muscles and painful joints, stress relief, and a space to pause, use it to reboot and recharge.
  • In general, if someone is physically able to walk into a sauna, then they are healthy enough to be in the sauna.
  • Another rule of thumb: if you are contemplating trying any new health intervention and you have pre existing medical conditions, it is always prudent to check with your healthcare provider before starting a regular thermotherapy routine.

Curious about Infrared Sauna at Restore Hyper Wellness? We can help.

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