There are times when either heat or ice can be helpful in reducing pain and encouraging healing during the body’s recovery from muscle pain or soreness. When it comes to applying heat via a heating pad, there are multiple health and safety issues to consider to ensure you don’t make the injury worse or introduce other injury risks. Below are answers to four commonly asked questions about the use of heating pads to treat muscle soreness.

When muscles spasm and tighten, especially after an injury or vigorous exercise or activity, blood vessels close or are constricted. With delayed onset muscle soreness (DOMS) brought on by strenuous activity, the lactic acid produced gets trapped by constricted vessels. The application of heat in these cases, whether from a heating pad or hot bath, jacuzzi or shower, dilates the blood vessels in the area being warmed and increases blood flow, bringing cells to help heal the affected area. These blood cells get more oxygen and nutrients to the site and aid in eliminating the bad stuff (such as lactic acid) from the affected area, which ultimately helps eliminate muscle pain and soreness. The application of heat can also facilitate the stretching and loosening of tight muscles, helping to alleviate stiffness around joints. One way to think of it: Imagine heating mozzarella sticks in the oven. They are much more pliable when warmed up.

There is also a role that heat is believed to play in what’s known as the gate theory of pain. Simply put, different nerves carry different messages (hot, cold, pressure, pain) to the brain. The brain puts all those messages together, and we then experience the sum of those messages as a sensation. If we are experiencing terrible muscle aches from a rigorous hike or HIIT workout, those muscles have their pain receptors activated and work full time to send constant pain signals back to the brain. When we apply heat to the area that is hurt, we activate different nerves to transmit this new, non-painful message to the brain.

Don’t get hurt! Heating pads can cause severe burns if they get too hot or stay on one body area too long. Electric heating pads use household current to produce heat. Consider a heating pad that escalates heat settings so you can start at a lower level and adjust as needed. Automatic shutoffs or preset timers are additional features to consider, especially if there is a chance of accidentally falling asleep with the heating pad on. Having a cover or some fabric between the device and your skin will also help to prevent burns. Beyond burn concerns, electric heating pads can create a fire hazard or electrocution risk. Avoid pads with multiple wires and always keep them away from water.

Moist heating pads use water to dampen the pad before placement on the skin. They can reach very high temperatures and are often used by physical therapists for heat therapy. However, it is best to avoid this type of heating pad for home use to prevent burns. One of the safest types of heating pads to consider is the disposable heating wrap or pad. These can be found in most drugstores and can be used for easy, convenient and safe heat therapy on almost any part of the body.

Generally, not. Heat or ice, for that matter, can cause severe and disfiguring burns. While you sleep, your body recovers naturally. Let nature do its job without a heating pad. However, if you are going to sleep in an extremely cold environment and feel that you need a heating pad, make sure it is covered by cloth or a towel to create a barrier between the pad and your skin to avoid burns. Some circulating hot water pads also can be used at night.

Although there are no precise rules, it should stay on for about 10-30 minutes to be effective. If a heating pad isn’t on long enough, the muscle or joint may not have an opportunity to warm up. But if it’s on for too long, it raises the risk of burns and extreme inflammation.

In short, while heating pads can absolutely play a role in relieving muscle pain and healing a muscle injury, they must be used with extreme caution. Make sure you don’t fall asleep while using one and that you don’t use the device for too long or allow it to get too hot in one area of the body.