Cold or Fever: Should You Exercise?

Exercise may actually be beneficial when you have a cold. However, it's probably better to stop exercising altogether if you have a fever with aching muscles. When you exercise, your heart has to pump blood to your muscles to supply them with oxygen. It also must pump blood from your muscles to your skin where the heat is dissipated. When you have a fever, your heart has to work harder to get rid of extra heat.

You risk injury if you exercise when your muscles hurt at rest. When muscles are damaged, they release enzymes from their cells into the bloodstream and they fill with blood from broken blood vessels. One study reported markedly increased muscle damage during relatively minor exercise during an infection, with blood tests showing increases in muscle enzymes and ultrasound tests demonstrating hemorrhage into the muscles. You will not lose much conditioning if you take off a few days.