Heat Therapy – What is it and its benefits

Heat therapy, also known as thermotherapy, involves the application of heat to a part or the whole body for therapeutic reasons. The superficial heat achieved during thermotherapy contributes to increasing soft tissue extensibility, reducing pain, improving circulation, and accelerating healing1. Heat therapy brings tremendous relief to people suffering from certain medical conditions, such as arthritis, and is also very beneficial for musculoskeletal injuries, to relieve pain and muscle stiffness. 

Why use heat?

Heat treatment is excellent for non-inflammatory body ailments, especially musculoskeletal injuries. Heat helps relieve pain and soreness and is highly relaxant, acting on both muscle and nerve level. Besides that, it usually alleviates cramps, spasms, overall sensitivity and stiffness, contributing to increased flexibility of both muscles and ligaments, joints and tendons, and bringing a sense of wellbeing, comfort and assurance2

Some examples of heat treatments include heat packs, heat rubs, warm baths and hot tubs, saunas and ultrasound therapy.

What happens during heat therapy?

Heat therapy is believed to accomplish its goals by1:

  • increasing blood flow (vasodilation)
  • reducing alpha motor neuron firing rate
  • increasing pain threshold (gating effect; reduced ischemia)
  • increasing metabolic activity (increasing the availability of oxygen to tissue)

Heat promotes the dilation of the blood vessels and therefore an increase in blood circulation. Blood transports oxygen, essential nutrients and hormones and an improved blood circulation will facilitate the delivery of these crucial constituents to all body tissues, accelerating the process of healing and recovery. Simultaneously, heat and increased blood circulation help to eliminate carbon dioxide and metabolic waste.

Using ultrasound as an example, this therapy relies, among other factors, on “the transference of thermal energy through supersonic waves. The energy of these waves causes vibration and heating of the tissues under the probe. The thermal energy absorbed, in turn, can induce dilation of blood vessels, which can increase cellular metabolism through oxygen and nutrient delivery3.”

More intense heat therapies, such as infrared sauna, cause a sudden elevation in the body core temperature, triggering the production of heat shock proteins, HSPs. These proteins are produced in response to environmental, physical and chemical stresses, such as heat shock, hypothermia, free radicals, ischemia, hypoxia, ultraviolet radiation, and viral infection4,5,6. In this case, HSPs are synthesized in response to thermal stress in the form of heat (they can also be produced when the body is exposed to lower temperatures than usual, hence also a benefit of cold therapy), and help limit consequences of damage and facilitate cellular recovery. These proteins are involved in the folding of newly synthesized proteins, prevention of misfolding and aggregation, and refolding of damaged or misfolded proteins. Besides that, HSPs also protect against apoptotic exchanges and participate in suppressing proinflammatory cytokines, in intracellular transport, and in the modulation of protein expression and cell function4,5,6In other words, HSPs help the body recover and benefit from conditions that could, in higher doses, cause death. Its benefits include repair of damaged or misfolded proteins, prevention of mutations, antioxidant activity, immune system support, sustain cell survival after damage, among others.

Similarly to cold therapy, heat therapy also induces a hormetic stress response that builds physiological resilience and confers tolerance to subsequent stress7.

What is considered Heat Therapy?

Heat therapy includes a variety of heating procedures, like heating pads, heated cloths, ultrasound, and hyperthermia, among others. One possible categorization of heat therapies differentiates between moist heat therapy (e.g., hot bath, damp towel) and dry heat therapy (e.g., heated pad, heated cloth). In terms of efficiency, there seems to be no clear difference between dry and moist heat2. Another way of differentiating heating therapies is based on the method of heat delivery, which can be8:

  • Direct Contact Heat Therapy

Usually, the easiest one to use at home, this method tends to be localized in a specific area of the body. Moist or dry heat can be applied to the surface of the affected area heating not just the superficial layers of the body, i.e., the skin, but also the muscles deeper underneath the skin, helping to reduce pain and induce a sense of relaxation. Good examples of direct contact heat therapy are:

  • warm damp towel on a tense muscle to reduce pain (moist heat therapy)
  • heated pad on the belly to alleviate menstrual cramps (dry heat therapy)
  • Systemic Heat Therapy

Systemic heat means raising the whole-body temperature, comparable to the effects of a fever. These can be done using hot baths and showers, steam baths, saunas, hot tubs, among others. Systemic heat therapy can be especially beneficial when there is whole body pain or musculoskeletal issues in more than one area. It is also great for overall relaxation, reduction of stress and tension, both physical and mental.

  • Infrared Heat Therapy

A type of systemic heat therapy, infrared heat therapy penetrates deeper into the body than direct contact therapy. Different areas of the body can be reached depending on the wavelengths of infrared light8

  • Near infrared reaches below the surface of the skin
  • Mid infrared reaches the soft tissues
  • Far infrared reaches fat cells

The most known example of infrared therapy is infrared saunas. Temperatures inside infrared saunas are adjustable, varying between 100°F (≈37.8°C) to 130 °F (54.4°C), allowing for longer times of exposure, increasing therapeutic benefits, and also making it tolerable for most people8.

At An Oasis of Healing, we use infrared saunas because they assist bodily processes, especially in terms of eliminating chemical toxins and heavy metals, increasing oxygenation and enhancing the immune system.

  • Therapeutic hyperthermia

Another type of systemic heat therapy, hyperthermia refers to either an abnormally high fever or the treatment of a disease by the induction of fever9. In oncology, “hyperthermia is a type of treatment in which body tissue is heated to as high as 113 °F to help damage and kill cancer cells with little or no harm to normal tissue10.”Hyperthermia alone can damage or kill cancer cells, and might potentiate the effectiveness of chemotherapy and radiation by softening the tumor tissue, however the effects of this therapy are highly dependent on the temperature and exposure time, and the complex dosing evaluation9,11.

Hyperthermia is another therapeutic intervention used at An Oasis of Healing and, as we explain in “Immunotherapy Series – What are the Objectives of Hyperthermia?”, the broad objectives of hyperthermia include12:

  • Increase cyclic AMP
  • Regenerate and recover mitochondria
  • Eliminate immunosuppressive agents produced by cancer
  • Stimulate and activate the immune system
  • Heal the body

Click here for more information on hyperthermia. 13

Benefits of Heat therapy

Heat therapy has been proven to have many health benefits, of which we will list only some.

  • Improved cardiovascular health (improved endothelium-dependent dilatation, arterial stiffness, intima media thickness and blood pressure) 14,15
  • Treatment of muscle tension, by increasing tissue extensibility and inducing muscle relaxation8 
  • Oncology treatment16
  • Facilitate healing and speeding up recovery (increased blood flow to affected areas, helps with acute injury, overall pain and discomfort) 8 
  • Increase physiological resilience and tolerance to stress7
  • Anti-inflammatory, analgesic, antioxidant, chondroprotective (protects joints), and anabolic effects7
  • Support immune system function (both innate and adaptive) and prevent and treat respiratory infections17,18 
  • Release of heat shock proteins, whose benefits include repair damaged or misfolded proteins, prevention of mutations, antioxidant activity, immune system support, sustain cell survival after damage, etc.4,5,6
  • Reduce pain, joint stiffness, muscle spasm and cramping2
  • Psychological benefits and enhanced mental wellness17
  • Reduce stress, enhance relaxation and sleep17
  • Relieve myalgia, contracture, tendinitis and bursitis19 
  • Purification or cleansing for environmentally induced illness20
  • Relieve menstrual pain
  • Among others

Side Effects of Heat Therapy

In general, heat therapy can be applied safely for extended periods of time for improved healing and relief, which is not possible with most cold therapies.

However, certain health conditions may not benefit or can even be worsened by heat therapy. Always consult with your physician before starting any type of therapy, including heat. For example, for hypertension and cardiac concerns, heat might be recommended or not, so take your doctor’s advice. Here are a few examples of conditions in which heat might be detrimental2:

  • Diabetes
  • Acute cognitive impairment
  • Acute injury, heat injury (burn, hyperthermia, etc.) or open wound
  • Sensory changes
  • Hyper or hypo-sensitive to heat
  • Circulatory problems
  • Bleeding disorders
  • Infection
  • Dermatitis
  • Peripheral vascular disease
  • Others (consult with your physician before any therapy)

How to safely use heat therapy

When applying heat therapy, here are some safety protocols1,2,21:

  • Avoid direct contact between the heat device and the skin, using a cloth or towel to protect the skin. Do not apply heat if the skin is injured with allergic reactions, wounds, or stitches.
  • Do not apply heat for more than 20 minutes, unless especially directed by a specialist. Do not fall asleep.
  • Because thermotherapy produces heat, the tissue needs to be capable of dissipating the heat via adequate blood circulation, hence avoid heat therapy if suffering from poor blood circulation.
  • Do not use heat therapy if suffering from diabetes, and other contraindicated medical conditions.
  • Patients must be capable of informing the clinician/specialist or be able to escape if the modality gets too hot or feeling unwell.
  • Do not use heat for swelling, use cold therapy instead. 

REFERENCES

  1. Batavia M. Contraindications in Physical Rehabilitation, Chapter 47 – Thermotherapy. W.B. Saunders. 2006. p. 678-698. https://doi.org/10.1016/B978-141603364-6.50050-1.
  2. Massage Guide. Heat Therapy: Benefits, Do’s, and Don’ts. Updated February 24, 2018. https://bestmassagechairguide.com/heat-therapy-benefits-and-when-to-use/. Accessed February 20, 2022.
  3. Matthews MJ, Stretanski MF. Ultrasound Therapy. 2021 Dec 15. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan–. PMID: 31613497.
  4. Szyller J, Bil-Lula I. Heat Shock Proteins in Oxidative Stress and Ischemia/Reperfusion Injury and Benefits from Physical Exercises: A Review to the Current Knowledge. Oxid Med Cell Longev. 2021 Jan 31;2021:6678457. doi: 10.1155/2021/6678457. PMID: 33603951; PMCID: PMC7868165.
  5. Verghese J, Abrams J, Wang Y, Morano KA. Biology of the heat shock response and protein chaperones: budding yeast (Saccharomyces cerevisiae) as a model system. Microbiol Mol Biol Rev. 2012 Jun;76(2):115-58. doi: 10.1128/MMBR.05018-11. PMID: 22688810; PMCID: PMC3372250.
  6. Beere HM. “The stress of dying”: the role of heat shock proteins in the regulation of apoptosis. J Cell Sci. 2004 Jun 1;117(Pt 13):2641-51. doi: 10.1242/jcs.01284. PMID: 15169835.
  7. Gálvez I, Torres-Piles S, Ortega-Rincón E. Balneotherapy, Immune System, and Stress Response: A Hormetic Strategy? Int J Mol Sci. 2018 Jun 6;19(6):1687. doi: 10.3390/ijms19061687. PMID: 29882782; PMCID: PMC6032246.
  8. Clearlight Infrared Saunas. What is Heat Therapy? Heat Therapy Benefits and Types. August 06, 2020.

https://infraredsauna.com/blog/what-is-heat-therapy/. Accessed February 21, 2022.

  1. Habash RWY. Therapeutic hyperthermia. Handb Clin Neurol. 2018;157:853-868. doi: 10.1016/B978-0-444-64074-1.00053-7. PMID: 30459045.
  2. National Cancer Institute. Hyperthermia to Treat Cancer. Updated June 17, 2021. http://www.cancer.gov/about-cancer/treatment/types/surgery/hyperthermia-fact-sheet. Accessed February 21, 2022.
  3. Lee SY, Szigeti GP, Szasz AM. Oncological hyperthermia: The correct dosing in clinical applications. Int J Oncol. 2019 Feb;54(2):627-643. doi: 10.3892/ijo.2018.4645. Epub 2018 Nov 23. PMID: 30483754; PMCID: PMC6317680.
  4. Goodyear N. An Oasis of Healing. Immunotherapy Series – What are the Objectives of Hyperthermia? April 13, 2021.  https://www.anoasisofhealing.com/immunotherapy-series-what-are-the-objectives-of-hyperthermia/. Accessed February 22, 2022.
  5. Goodyear N. An Oasis of Healing. Immunotherapy Series – The Power of Hyperthermia with Surgery. May 24, 2021. https://www.anoasisofhealing.com/?s=hyperthermia. Accessed February 22, 2022.
  6. Brunt VE, Wiedenfeld-Needham K, Comrada LN, Minson CT. Passive heat therapy protects against endothelial cell hypoxia-reoxygenation via effects of elevations in temperature and circulating factors. J Physiol. 2018 Oct;596(20):4831-4845. doi: 10.1113/JP276559. Epub 2018 Sep 12. PMID: 30118148; PMCID: PMC6187037.
  7. Brunt VE, Howard MJ, Francisco MA, Ely BR, Minson CT. Passive heat therapy improves endothelial function, arterial stiffness and blood pressure in sedentary humans. J Physiol. 2016 Sep 15;594(18):5329-42. doi: 10.1113/JP272453. Epub 2016 Jun 30. PMID: 27270841; PMCID: PMC5023696.
  8. Goodyear N. An Oasis of Healing. Immunotherapy Series – Anti-Cancer Benefits of Hyperthermia April 27, 2021.  https://www.anoasisofhealing.com/immunotherapy-series-anti-cancer-benefits-of-hyperthermia/. Accessed February 22, 2022.
  9. Cohen M. Turning up the heat on COVID-19: heat as a therapeutic intervention. F1000Res. 2020 Apr 24;9:292. doi: 10.12688/f1000research.23299.2. PMID: 32742639; PMCID: PMC7372531.
  10. Evans SS, Repasky EA, Fisher DT. Fever and the thermal regulation of immunity: the immune system feels the heat. Nat Rev Immunol. 2015 Jun;15(6):335-49. doi: 10.1038/nri3843. Epub 2015 May 15. PMID: 25976513; PMCID: PMC4786079.
  11. Miller DL, Smith NB, Bailey MR, Czarnota GJ, Hynynen K, Makin IR; Bioeffects Committee of the American Institute of Ultrasound in Medicine. Overview of therapeutic ultrasound applications and safety considerations. J Ultrasound Med. 2012 Apr;31(4):623-34. doi: 10.7863/jum.2012.31.4.623. PMID: 22441920; PMCID: PMC3810427.
  12. Crinnion WJ. Sauna as a valuable clinical tool for cardiovascular, autoimmune, toxicant- induced and other chronic health problems. Altern Med Rev. 2011 Sep;16(3):215-25. PMID: 21951023.
  13. https://www.sportsinjuryclinic.net/treatments-therapies/cryotherapy-cold-therapy/heat-therapy
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