It is a common belief that exercising can help people feel better if they are sick because it promotes better sleep. Other benefits of exercising while sick (and in general) include good cholesterol levels and energy boosts. Recently, however, studies have shown that it might be better to stay home and rest instead of working out.
Rigorous exercises such as running, swimming, or cycling are not advised while you have a cold or flu. These exercises, also known as dynamic exercises, suppress the immune system and can make you feel much worse. If you have the flu, (with symptoms including a fever and congestion in the lungs), it is best to not work out. Exercising with these symptoms can lead to dehydration and can also put you at risk of having heart issues in the future.
Reducing exercise while you are sick is not only limited to having a cold or the flu. Other symptoms to look out for include paleness (or having a “flushed” appearance), dry mouth, back pain, and dizziness. Paleness is a sign of poor blood circulation, which can lead to pain if you exercise. Paleness can also be a sign of anemia. Dry mouth can be the result of a cold and could mean that you are too dehydrated to work out. Exercising while you have back pain is not only painful, but can also result in weakened muscles. Exercising while you feel dizzy can weaken the body as well.
Of course, exercising while sick is not completely off limits. If you have a mild cold, the American Council on Exercise suggests working out for no more than thirty minutes. It is important to get enough rest so that your body can rebuild its strength.