Moist Heat Physical Therapy Modality

Moist heat—also called superficial heat—is a physical therapy modality used to control pain, speed healing, relax muscles, and increase range of motion. In a moist heat treatment, a hot pack is placed on the tight or painful area and left there for about 10 or 15 minutes. Other physical therapy treatments include ultrasound, electrical stimulation, and iontophoresis.

Woman with heat pack on her neck
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Feels Good and Does Good

With the exception of certain types of massage, moist heat treatment is perhaps the most relaxing of all the physical therapy modalities. It's often used at the beginning of a physical therapy session to loosen your muscles and get them ready for exercise.

About Moist Heat Packs

Moist heat packs used in physical therapy clinics are made of bentonite covered in canvas. The packs are stored in very hot (158 to 167 degrees F) water. When the moist heat packs are prepared for use, they are placed in towels and/or special wraps. This not only helps to prevent burns, but it also slows down cooling, giving you more time to enjoy and benefit from the treatment. And of course, it's more sanitary.

How Moist Heat Controls Pain

Moist heat may help control your pain by blocking pain signals from being transmitted. Application of heat may also help reduce pain by relaxing muscle spasm and enhancing healing (see below for more about that).

Although opinions on this differ, many experts recommend that moist heat be used only for chronic or sub-acute back or neck pain. The thinking is if you put a hot pack on an acute injury, you risk increased swelling or bleeding which may aggravate the area and cause more pain.

How It Speeds Healing

Put a hot pack on an injured or tight area of your back, and you'll likely increase circulation. Increased circulation speeds the delivery of blood, and therefore oxygen and nutrients. It also accelerates the removal of waste products.

Another way moist heat helps the healing process is by increasing enzyme activity. This raises your metabolic rate and helps release oxygen from the hemoglobin molecule into your tissues, where it helps with repair.


Moist heat relaxes muscles and other soft tissue. In fact, your therapist may guide you in using stretching as an adjunct. Stretching during or after this treatment may result in longer-lasting improvements in flexibility and joint range of motion.

2 Sources
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  1. American Academy of Physical Medicine and Rehabilitation. Therapeutic modalities.

  2. Lohman III EB, Sackiriyas KSB, Bains GS, et al. A comparison of whole body vibration and moist heat on lower extremity skin temperature and skin blood flow in healthy older individuals. Med Sci Monit. 2012;18(7):CR415-CR424. doi:10.12659/MSM.883209

By Anne Asher, CPT
Anne Asher, ACE-certified personal trainer, health coach, and orthopedic exercise specialist, is a back and neck pain expert.