1. DO a check of your symptoms first. If you have above the neck signs, such as a runny nose, sneezing, or a sore throat, moderate exercise is generally safe as long as you do not have a fever. You can resume intense workouts as soon as symptoms disappear. If you have below the neck signs, such as extreme tiredness, muscle aches, vomiting, diarrhea, chills, swollen lymph glands, or a hacking cough, allow at least two weeks before returning to intense training.

2. DON'T exercise with a fever. Fever (a body temperature above 98.6 degrees Fahrenheit) signifies you are doing battle with a virus. Exercising under these conditions increases risk of dehydration, heatstroke, and even heart failure.

3. DO modify your exercise intensity. If you have cold or flu symptoms, you cannot power away your ailment through more intense workouts. In fact, you may make your illness worse. A simple sore throat, for example, could indicate an infection, and your immunity to fight it will be reduced if you continue vigorous exercise. Moderate exercise, however, is fine for mild cold symptoms as long your heart rate and body temperature do not increase excessively.

William A. Primos Jr., MD, and James R. Wappes in The Physician and Sports Medicine (January 1996) suggest working out at half speed for about 10 minutes. If you feel fine, you can increase your intensity. Stop exercising if you feel dizzy, nauseous or experience any other exacerbated symptoms.

4.DON'T over train or stress out. Over training can lead to suppressed immune function and exposure to opportunistic infections, notes medial exercise specialist Michael Youssouf, MA. In addition, attempting new or harder activities can lead to failure. Such stress may influence your immune system. Choosing activities you enjoy and can do consistently may  improve your exercise adherence and immune function.

5. DO exercise to keep your immunity strong. Researchers have found a link between regular exercise and improved immune function response. Primos and Wappes note that during moderate exercise immune cells circulate more quickly through your body and are better at destroying viruses and bacteria.

6.DON'T infect or become infected. Be alert to air-quality conditions at your training facility. During cold and flu seasons, exercise during less-crowded hours to avoid catching or transmitting viruses. Consider outdoor activities if weather conditions permit.

7.DO use common sense. Ken Baldwin, president of Premier Fitness in Cambridge, Massachusetts, advises ill clients to stay home, rest, and drink plenty of fluids. It's difficult to exercise when you're coughing and sniffling.