Heat can help to decrease pain, relieve muscle spasm, increase the ability of muscles and other tissues to stretch, and improve circulation to the underlying tissue or joint.
Heat works by vasodilating (expanding) the blood vessels. This increases the circulation to the area where heat is applied. Heat also helps to decrease pain by stimulating sensory receptors that help to block the transmission of pain signals along the nerves.
When Heat Therapy is Effective
Heat therapy can offer benefit in the following scenarios:
- For pain relief not associated with acute (new) trauma or acute inflammation (swelling)
- To relieve muscle spasms and muscle tightness
- To enhance muscular flexibility or range of motion of your joints
For acute (new) trauma or acute inflammation (swelling) you might be interested in our article Cold Therapy for Arthritis.
If you are unsure of whether or not to use heat, ask your doctor or physiotherapist.
When to be Careful with Heat Therapy
Cold therapy should be used with caution or possibly avoided in the following scenarios:
- Over an area with compromised circulation or sensation
- Over an acutely inflamed or swollen joint
- Over an open wound or infected area
- In the presence of a confirmed malignancy/cancer
- Medical conditions such as hemophilia
If one or more of these apply to you, or you are concerned about how to safely use heat therapy, check with your doctor or physiotherapist.
Key Points for Safe and Effective Treatment
Its important to remember a few key points to maximize the benefits of heat therapy and avoid causing problems by overdoing it:
Heat should be comfortably warm: Effective heat feels comfortable and not feel like it is burning the skin. If heat is too hot, add one or two towels between the heat source and body part, or remove heat.
Continuously inspect the heated area: The heated area will appear red and possibly sweaty. If heat causes pain in the affected area, remove it and do not continue heat therapy until you consult with a physical therapist.
Use equal periods of heat and rest: Heat can be re-applied after leaving it off for the same period of time that it was applied. Make sure that all redness should be gone before re-applying heat.
Take care with hot packs and electric blankets: Do not lie on a hot pack or electric blanket! Do not fall asleep with a hot pack or electric blanket on your body!
Use safe temperatures: Heat sources should not exceed 45 degrees Celsius/120 degrees Fahrenheit; greater temperatures will cause tissue damage depending on the duration of heat exposure.
How to Apply Heat Therapy
There are a number of methods and techniques that can be used to apply heat therapy treatments at home:
Hot Water Bottle
The hot water bottle technique can be used for most body parts. It involves using a soft rubber container that can be purchased from most pharmacies.
- Fill the Hot Water Bottle with hot water
- Apply a damp towel to the skin to improve heat conduction.
- Apply 10 – 15 minutes
The Hot Pack technique can be used for most body parts. Packs made of silicate gel, beans, or corn (i.e. magic bags) can be purchased in stores.
Alternatively, you can make a pack by wetting a towel and placing it in a plastic bag and putting it in the microwave for 2 minutes. Be careful removing the hot towel!
- Prepare your hot pack
- Apply a damp towel to skin to improve comfort and conduction.
- Apply 10 – 15 minutes
Hot Water (Whirlpool) Baths
Hot Water (Whirlpool) Baths are usually used for the hands, arms, ankles, and feet, depending on the size of the bath. Water is mixed with air into a jet stream that stimulates receptors in the body to reduce pain, improve circulation, and increase range of motion.
- Ensure a good water temperature, usually between 36 – 41 degrees Celsius.
- Apply 15 – 20 minutes
Contrast baths involve alternating the use of cold and warm water.
- Fill one bowl with warm water and one with cold water.
- Soak in cold water for 30 seconds and warm water for 30 seconds.
- Repeat the process: apply for a total of 5 – 10 minutes
Wax Baths are used primarily in hospital settings. However smaller units can be purchased for home use. This technique is usually used to treat hands and wrists. The baths use a mixture of paraffin wax and mineral oil so that the wax’s melting point can be lowered (i.e. to keep the bath at a cooler temperature than if pure wax was heated on its own).
- Ensure a good temperature. Most baths are kept at a temperature of 42 – 52 degrees Celsius.
- Immerse the affected limb in the wax bath about 6 times.
- Wrap the affected limb in plastic and a towel to keep the heat in.
- Apply for 10 – 15 minutes.
Electric Blankets or Pads
Electric Blankets or Pads are most commonly used for the neck or back to help decrease muscle spasms and promote relaxation, although can be used on any body part. Pads are made with an electric resistance wire (heating element) contained in a suitable fabric that gets warm and provides conductive heating to the skin.
- Ensure the electric blanket or pad is at a safe and effective temperature.
- Continuously check skin for signs of over heating.
- Don’t forget to take rests from the heat.
- Do not fall asleep with an Electric Blanket or Pad turned on.