Heat vs. Cold

It can be confusing to determine when to apply cold or heat to relieve pain. Generally, follow these basic rules:

  • Use cold for acute pain or a new swollen/inflamed injury.
  • Use heat for chronic pain or an injury that is a day or more old.

Ultimately, you need to choose what works best for you. If icing feels unpleasant, then opting for a heat solution may provide more comfort. There are important factors to consider, however, based on what type of injury you are dealing with. A recent knee sprain or a persistent muscle spasm will require different treatments for proper healing.

Heat (Thermotherapy)

Heat is relaxing. That’s why overworked muscles respond best to heat, which stimulates blood flow, relaxes spasms, and soothes sore muscles. Generally, heat is the preferred treatment for pain.

How It Works

Overworked muscles are sore because of a chemical called lactate that accumulates when the muscles are put under stress in an oxygen-depleted environment. When there is decreased blood flow to a damaged area, chemicals don’t get flushed out of the muscle. This chemical build-up creates painful muscle ache, best soothed by heat therapy which restores blood flow.

When to Use Heat

Heat is best in treating chronic (persistent, ongoing) pain. Heat increases blood supply, stimulating the elimination of chemicals and relaxing soreness and stiffness to bring relief. If you suffer from an ongoing injury, apply heat before exercising. Because heat raises your temperature, applying heat after exercise can aggravate the existing pain.

Types of Heat

Local, applying heat to a specific area:

  • hot water bottle
  • heating pad
  • moist heat (hot, damp towel)
  • heat wraps

Systemic, raising your body temperature:

  • hot bath
  • saunas
  • steam bath
  • hot shower

Tips for Applying Heat

  • Protect yourself from direct contact with heating devices; wrap heat sources within a folded towel to prevent burns.
  • Stay hydrated during hot baths. While all that waste elimination from sweating is good, it’s important to replace the fluids so you don’t stress your system.

Cold (Cryotherapy)

Generally, ice helps fresh injuries. When your body is injured, the damaged tissue becomes inflamed which can manifest in pain, swelling, or redness. This is your body’s natural and immediate response to defend itself. Unfortunately, the pain may not be the most pleasant experience. 

How it Works

Ice numbs the injury. The cold narrows blood vessels and slows down blood flow that builds up in the affected area. This controls inflammation and swelling and relieves—but doesn’t treat— pain.

When to Use Cold

Cold is best for acute (recent tissue damage and sprains) pain. If the pain is recent, red, inflamed, or sensitive, you’ll want to apply ice. Cold therapy can also help relieve pain in some chronic injuries. But unlike heat, you want to apply ice after going for a run, for example. The cold treatment following a run will help reduce inflammation.

Types of Cold

  • ice pack
  • ice towel (dampened towel, sealed in plastic and placed in the freezer for about 15 minutes)
  • ice massage
  • cold gel packs
  • bag of frozen peas

Tip for Applying Cold

  • Apply immediately after injury or intense high-impact exercise
  • Apply directly on the affected area
  • Repeatedly icing painful or swollen tissues is fine—as long as you avoid over-icing. Be sure to remove ice once the area is numb.