I see the drug stores have a heat wrap for use with low back pain. These are kept on for up to eight hours. I thought too much heat isn't good? I've always been told to use heat for up to 30 minutes.

Disposable heat wraps can be worn for hours and even worn to bed. This differs from precautions given when using a heating pad or other heating device. The heat wrap gives gentle, controlled heat just slightly above body temperature (104 degrees F).

The patient can move around and remain active while wearing the heating wrap. These features make it safer than moist hot packs that start off hot and cool off or a heating pad that can get too hot when lying on it.

Movement will also help prevent fluid build-up from the heat. A gentle increase in the temperature of muscle tissue decreases pain and increases tissue stretch. A warm muscle contracts more smoothly. A warm muscle is more resistant to tearing or further injury. Wearing the wrap while exercising also gives a slight support to the lower back.

So far studies have shown favorable result with the low-level continuous heat wraps for painful conditions without swelling.

John M. Mayer, PhD, et al. Treating Acute Low Back Pain With Continuous Low-Level Heat Wrap Therapy and/or Exercise: A Randomized Controlled Trial. In The Spine Journal. July/August 2005. Vol. 5. No. 4. Pp. 395-403.