Most individuals can continue to exercise if they have a cold with no fever. As a general rule, if symptoms are "above the neck" (e.g., runny or stuffy nose, sneezing, or sore throat) exercising should pose little or no risk. In fact, mild to moderate exercise has been shown to help boost immune system function. However, if symptoms are "below the neck" (e.g., chest congestion or tightness, hacking cough, upset stomach or diarrhea) exercise workouts should be postponed. Exercise workouts should also be avoided if a fever, fatigue, nausea or widespread muscle aches (i.e., flu-like symptoms) are present. You should use common sense when it comes to exercising when ill. For example, you should reduce the intensity and duration of your workouts and “listen” to your body. If your symptoms worsen following your workouts, you should curtail future workouts and rest until you are healthier. Keep in mind that skipping a few workouts is not the end of the world. In fact, a little extra rest and recovery is sometimes the best thing you can do for yourself. One final thought, be mindful of your fellow gym goers and consider not exposing them to your illness.
Source: www.acefitness.org/fitness-fact-artic...