Symptoms below the neck (chest cold, bronchial infection, body ache) require time off, while symptoms above the neck (runny nose, stuffiness, sneezing) don’t pose a risk to runners continuing workouts.
Because exercise may help to boost immune function, it’s usually safe to exercise with a cold as long as you listen to your body.
Still, if you exercise with a cold, it’s important to listen to your body.
If you have asthma and a cold, make sure you talk with your doctor before you exercise. If your asthma symptoms are worse with a cold, you’ll need to use caution. Exercising with a cold and asthma may cause increased respiratory symptoms such as coughing, wheezing, and shortness of breath. If you have a fever with a cold, exercise may stress your body even more. That’s why it’s important to wait a few days to get back to your regular exercise regimen. Working out too hard with a cold could stress your body, causing you to feel worse. This additional stress may hinder your recovery.
Not surprisingly, winter weather increases risk of sinusitis. In dry air, the nasal passages and mouth lose moisture, causing irritation. “The sinuses need time to recover,” says Dr. Dobken, “just like a knee or foot.” So Dr. Dobken recommends including treadmill running in your winter training regimen.
If you’re still in doubt about whether it’s safe to run or not, take your temperature. If it’s above 99 degrees, skip your run. “Some people think that they can ‘sweat out’ a fever by running,” says Nieman. “That’s wrong. Running won’t help your immune system fight the fever.”
“Running with a fever makes the fever and flu-like symptoms worse,” says Nieman, “and it can lead to other complications.” During exercise, your heart pumps a large amount of blood from your muscles to your skin, dissipating the heat your body generates. If you have a fever, your temperature will rise even higher, and your heart will be put under greater strain to keep your temperature from soaring. In some cases, this can produce an irregular heartbeat. Also, a virus can cause your muscles to feel sore and achy; exercising when your muscles are already compromised could lead to injury. Sometimes cold medications such as decongestants can increase your heart rate. In addition, your heart rate is increased with exercise. The combination of exercise and decongestants can cause your heart to pump very hard. You may become short of breath and have difficulty breathing.
Your immune system fights most effectively when it isn’t stressed. Research confirms that a moderate exercise program may increase immunity and your resistance to respiratory infections. But scientists also note that athletes who train rigorously without recovery are more susceptible to viral infections like colds or flu.