A warm shower or bath, hot water bottle, or warm cloth can help relax muscles and ease muscle spasms. A heating pad with an automatic off switch is better than a regular heating pad, which can burn skin if left on too long.
Be careful with microwavable heating pads, as these can have hot spots that burn. Apply heat to the sore area for 20 to 30 minutes every 2 hours. Don’t use heat on open wounds.