How to Apply Heat Therapy

Effective heat therapy products typically maintain a relatively warm – not piping hot – temperature. A few products utilize high temperatures, and are only safe when there is enough insulation between the heat source and the skin.

Sufficient time is required for the warmth to penetrate deep into the muscles. Usually, the longer the heat is applied, the more relaxed the muscles feel. The exact duration for heat application depends on the type and/or magnitude of the injury. Short durations, about 15 to 20 minutes, will suffice for minor back tension, while longer durations for up to 30 minutes, may be recommended for chronic conditions or severe, excruciating pain. It is never recommended to sleep with a heating pad.

Types of Heat Therapy

There are 2 broad categories of heat therapy.

• Dry heat therapy products and services are usually preferred for their consistent temperatures, ease of use, portability, and convenience.
• Moist heat products and services are usually preferred for penetrating deeper into the muscle tissues and achieving a higher increase in blood flow than dry heat.

Choice of heat therapy is mostly a matter of personal preference. For instance, moist heat tends to be more effective when body fat is above 25% of the body weight.¹Petrofsky JS, Laymon M. Heat transfer to deep tissue: the effect of body fat and heating modality. J Med Eng Technol. 2009;33(5):337-348. doi:10.1080/03091900802069547^,2Petrofsky J, Bains G, Prowse M, et al. Dry heat, moist heat and body fat: are heating modalities really effective in people who are overweight?. J Med Eng Technol. 2009;33(5):361-369. doi:10.1080/03091900802355508 Experimentation with the large variety of available options and a process of trial and error may help reveal which product or service is most effective.

14 Effective Heat Therapy Products

The most common options for heat therapy are available at a drug store, spa, gym, or physical therapy office. Heat therapy products and services vary in cost, usability, and accessibility. A majority of heat products and services fall into the following 14 categories:

1. Chemical heat packs

Chemical heat packs rely on exothermic reactions, or reactions that release heat. Instant heat packs are commercially available in a couple varieties:

• A reusable pack containing a salt solution. The solution usually consists of sodium acetate, magnesium sulfate, or calcium chloride. Reusable packs of sodium acetate typically contain a metal clicker, which is pressed or snapped to activate the chemical reaction that produces heat for about 30 to 45 minutes. Before reuse, the pack first needs to be immersed into boiling water and then cooled down to room temperature.
• A single-use pack containing sodium thiosulfate solution. Disposable instant hot packs are activated by squeezing the bag until the inner bubble pops, then massaging or shaking the bag to start the chemical reaction. These packs stay warm for about 20 to 25 minutes.

The flexible, sealed pouches come in small or large sizes, and can readily be applied on the lower back for fast pain relief. The small packs are easy to store, fitting easily into medium-sized handbags or briefcases, and are readily available as a part of emergency kits for home or for work. The temperature of the non-toxic solution can reach up to 130 degrees Fahrenheit, so it is important to avoid direct contact between the heat pack and the skin. A wrap or towel can provide insulation.

2. Heat wraps

Single-use heat wraps rely on iron oxidation, the reaction between iron powder within the product and oxygen from the air, which forms rust and releases heat.

Wraps tend to stay warm, at a temperature of about 104 degrees Fahrenheit, for about 6 to 8 hours. The cloth-like, thin material allows the wrap to be worn discreetly, under clothing and directly on the back. Long-lasting, consistent, and low-level heat makes the wraps ideal for all-day use, such as while working, driving, running errands, traveling, or sleeping.

3. Heated gel packs

Reusable pouches containing a water-based gel or gel beads often serve a dual purpose, as the pouches are often used for both ice therapy and heat therapy.

Just 30 to 60 seconds on a paper towel in the microwave is sufficient to heat the gel pack, and the heat lasts for up to 30 minutes. Temperature can vary, depending on the power of the microwave and on the duration heated. It is important to keep the gel pack wrapped in a clean towel before applying it to the back.

Watch Video: How to Make a Gel Ice Pack

Gel packs are flexible, soft, and durable. The easy reheating method makes gel packs usable anywhere there is access to a microwave, such as the home or the office.

4. Electric heating pads, blankets, or pillows

Electric heat pads, blankets, and pillows are available in many sizes and varieties. Heating products that use electricity typically rely on insulated wires and require an electrical outlet. The fabric is often polyester or acrylic or a blend of both, and such fabrics are less flammable than cotton. Heating elements in the product usually have adjustable temperature settings. While some products include automatic timers in case the user falls asleep or forgets to turn the heat off, it is best to unplug the product before going to sleep.

Electric heating pads and blankets are ideal for night-time use at low heat settings, unlike most other heating products. Stiff back muscles can be loosened up by lying on a heat pad for a couple of hours at night, for a fresh start to the morning with less pain. While all electric appliances generate an electromagnetic field, research suggests that electric blankets are not known to increase the risk of cancer.³Kabat GC, O'Leary ES, Schoenfeld ER, et al. Electric blanket use and breast cancer on Long Island. Epidemiology. 2003;14(5):514-520. doi:10.1097/01.ede.0000082047.13618.6b^,4Caplan LS, Schoenfeld ER, O'Leary ES, Leske MC. Breast cancer and electromagnetic fields--a review. Ann Epidemiol. 2000;10(1):31-44. doi:10.1016/s1047-2797(99)00043-5^,5Verreault R, Weiss NS, Hollenbach KA, Strader CH, Daling JR. Use of electric blankets and risk of testicular cancer. Am J Epidemiol. 1990;131(5):759-762. doi:10.1093/oxfordjournals.aje.a115565^,6Kato I, Young A, Liu J, Abrams J, Bock C, Simon M. Electric Blanket Use and Risk of Thyroid Cancer in the Women's Health Initiative Observational Cohort. Women Health. 2015;55(7):829-841. doi:10.1080/03630242.2015.1050545

Electric heating methods are not necessarily suitable for individuals with pacemakers or metal implants. As another note of caution, dry heat tends to draw out moisture from the body, and may leave the skin dehydrated.

5. Far infrared heating mat, belts, or wraps

Far infrared radiation is a novel approach to heat therapy. Crystals and stones within the products are heated through electrical means and then emit far infrared heat deep into the muscles. Far infrared products typically have adjustable temperature settings and automatic timers, similar to traditional electrical heating products.

The use of crystals and stones allows for a more controlled transfer of heat, such that the heating mat is not hot to the touch or likely to burn the skin. The stones typically take 10 to 15 minutes to heat to the desired temperature, and remains at the temperature until the product is unplugged. These products can be quite expensive, and tend to last for several years. Far infrared heating mats are slow to raise the body temperature, and may be suitable for people who are sensitive to heat.

6. Heating pillows

Often used at spas and sold commercially, small heating pillows can also be made at home using thick, sealable fabric, such as a cotton or flannel pillow cover or a sock, and filled with uncooked rice, flaxseed, buckwheat, or oatmeal. Commercial heating pillows are sometimes infused with essential oils, which are used to add a soothing effect.

Once sealed, these pillows or pouches can be heated in the microwave for 1 to 3 minutes and stay warm for up to 45 minutes. This heat therapy product is easy to reheat, granted there is access to a microwave. The size of the pillow is ideal to target specific muscles in small areas of the back for short periods of time, and ideal for use while sitting on a chair or commuting from home to work.

7. Dry saunas

The body is enticed to sweat in a dry sauna, which is a room that generates dry heat by heating rocks with far infrared radiation or by burning wood. A dry sauna is essentially the opposite of a steam bath, which provides a fully humid environment.

At a dry sauna, temperatures tend to be at or above 150 degrees Fahrenheit. It is recommended to limit dry sauna temperature to a maximum of 195 degrees Fahrenheit, and limit dry sauna use to 10 to 20 minutes at a time. Drinking adequate amounts of water and eating well before and after sessions will help prevent dehydration.

Many spas provide a free sauna that can be used before or after a spa service. For frequent spa customers, a dry sauna alongside a back massage is a convenient way to add heat therapy.

8. Hot stones

Small, smooth stones can be cleaned and heated in warm water, at about 120 degrees Fahrenheit for about 5 minutes. Once removed and dried on a towel, the hot stones are ready to use and can be kept on the skin for up to 5 minutes, as long as the stones do not feel too hot.

The safest way to use hot stones is by visiting a spa for a hot stone massage or by purchasing a massage stone heater for more affordable use at home. Stones are used while lying in a face-down position, so this heat therapy requires a partner to place the stones along the back.

9. Increased room temperature

Global heat, heat that is felt by the whole body, simply involves raising the temperature of a room using a thermostat. The chosen temperature and duration of heat can be easily controlled at comfortable levels, without aggravating existing health conditions such as diabetes. This heat therapy is the perfect option for individuals who cannot leave the home or do not wish to spend on spa visits or disposable heat packs.

10. Hydrocollator Packs

A fabric hydrocollator pack contains a hydrocolloid filling called bentonite clay, which is often used in wound dressings. By absorbing hot water, the filling forms a gel or paste that delivers moist heat to the back.

The reusable hydrocollator packs are heated in hot water or in a hydrocollator heating unit, at 150 to 160 degrees for about 30 minutes. The packs can be kept in place on the back for about 15 to 30 minutes at a time. Because of the high temperature, the pack may require several layers of hand towels or a single thick towel to protect the skin.

While the packs are bulky and take time to prepare, the products are well-suited for use in the bed or while resting at home. Compared to dry heat from electrical blankets, the moist heat from hydrocollator packs reaches deeper muscles and is considered more effective. Physical therapists may use hydrocollator heat packs to ease joint or muscle pain, before a set of exercises.

11. Hot water bottles

One affordable option is a thick rubber bottle, which can be filled with hot water at about 104 to 108 degrees Fahrenheit and stays warm for about 6 hours. This product is commercially available at most drug stores and can be insulated using a towel or a custom sleeve made of knitted fabric or fleece.

The bottles can be used between the back and an office chair, on a long drive, or in bed while sleeping. The rubber material of the bottle is wear-resistant and affordable, making this heat therapy indispensable for anyone with backaches and tense muscles.

12. Hot or steamed towel

To prepare a hot towel, it is best to immerse the hand towel in water, by running the towel under hot water in a faucet or by placing the towel in a pot of warm water around 105 degrees Fahrenheit, for 2 to 3 minutes. Squeezing the towel will remove excess water before applying to the back. Hot towels typically stay warm for 5 to 10 minutes, and will then need to be reheated.

This form of heat therapy is short-lived, making it suitable for quick relief of muscle tension or pain, such as before physical activity or during work breaks.

13. Hot baths

Steam baths, mud baths, wet saunas, whirlpools, balneotherapy (which uses mineral water), and hot springs are all forms of hot baths. Jet streams of water in a jacuzzi can even be directed at the lower back, for the feeling of a light massage. A hot bath quickly heats the body above its core temperature and can be used for about 30 minutes, or 10 minutes if the temperature of the water exceeds 100 degrees Fahrenheit.

The benefits of frequent sauna use, such as decreasing the risk of developing cardiovascular diseases,⁷Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med. 2015;175(4):542-548. doi:10.1001/jamainternmed.2014.8187 have been studied extensively in the Finnish population where saunas are customary. In other countries, saunas and other hot bath options may be expensive, and so are more cost-effective when used occasionally for intense muscle spasms or severe pain.

14. Sweat lodges

Ceremonies at a traditional sweat lodge can last for hours, providing heat in multiple sessions of 30 minutes each, at temperatures consistently above 100 degrees Fahrenheit. Such sessions elevate the body temperature to imitate heavy exercise, and work well for individuals who enjoy meditation or seek a spiritual experience associated with Native American culture, alongside back pain relief.

This heat therapy has the potential to lead to significant discomfort and prolonged heat exposure. It is advisable to leave the sessions when uncomfortable, weak, or dizzy.

Both moist and dry heat options work well alongside other treatments for low back pain, and are also useful for pain relief and recovery following back surgery. It is important to apply heat therapy according to package instructions or facility recommendations.