Why Apply Heat to Sore Muscles?

Applying heat to sore muscles may or may not be the right thing to do, but when it is right it brings blood cells to the area, which bring nutrients, carry away debris and remove infection.

Why Apply Heat to Sore Muscles?

• When someone suffers from sore muscles, he might get contradictory advice. Some say apply cold compresses, some say apply heat. Which is right? Both, but at different times and for different reasons. Let's look closely at what's going on.

A Basic Principle

• The study of physics offers us a very simple principle: Heat increases kinetic energy; cold decreases it. Put simply, the warmer something is, the faster the elements are moving around. In terms of injury, we're talking about cell movement. Sometimes we want more cell action to address damage, and sometimes we want less.

  Heat, then, does two things. It will cause the cell activity to increase in the area and dilate the blood vessels (make them larger), which will bring more blood to the area.

Send in the Troops

• If part of the body is injured, the body sends all the troops to the site. In the case of the body, the troops are blood cells. Cells clean up the area. For instance, white blood cells eat bacteria and the debris of damaged cells. Cells also bring nutrients. After an injury, the body is working hard to repair the area, and it requires more energy to do that. Blood brings the nutrition to the hard-working cells.

  The cells also act as transports, taking infected material to the lymph nodes for destruction. If the infection is manageable, then increasing blood flow will increase this transport.

Continued Support

• After the initial injury, the body calls off the troops; there are many other fronts for the immune system to fight on. But we may want to keep the action concentrated on the area to speed recovery. That's one reason we apply heat--to draw more blood cells to the area and keep the (metabolic) rate high.

Another Way

• Under certain conditions, ice can reduce the amount of infection as well. If there is less movement, then fewer new infected cells will be produced. The transport of the cells will be limited, so the infection stays more localized.

  One of the body's goals is to swell the local tissues by filling them with liquid and immobilize the area, reducing further damage. Unfortunately, swelling can be, well, immobilizing, and thus uncomfortable and inconvenient. So doctors often recommend that when an injury is suffered, put ice on it. The ice will reduce the amount of swelling.

Overuse

• Overused muscles can hurt for two reasons. First, there can be micro tears, and second, a particular chemical concentrates in the muscles. For micro tears, apply ice initially and then heat. For soreness that starts a day or so after the exercise, the cause is likely lactic acid, which is a byproduct created when glycogen (an energy source to the muscle) is broken down. There's just one thing to do about lactic acid: Get it out. Massage might help, but definitely heat and not ice.

  So overall, if there is an injury, first apply ice, and after 20 minutes to an hour, apply heat. If it is just muscle soreness, give the area all the blood it can use. Attract the blood by applying heat to the area.

  This information assumes muscle strain or other simple injuries. For other conditions, consult your physician.