You have been doing so well! Sticking to your fitness routine, making the time and working hard to get healthy. And then, when you least expect it, despite your best efforts … ACHOOOO! All of a sudden you are waylaid by a cold or flu.

What should you do? Should you skip the treadmill or forsake that cycling class for a late afternoon nap? Will you lose your momentum if you skip a day or two? The answer depends on what ails you. For example, exercising with a mild cold may be OK, but if you’ve got a fever, hitting the gym is a definite no-no. Are you infectious? Please think of others. Your cold may be quite serious to an immune-compromised individual.

Fever is the limiting factor. The danger is exercising and raising your body temperature internally if you already have a fever, because that can make you even sicker. If you have a fever greater than 101 degrees Fahrenheit, sit this one out.

A good rule of thumb for exercising when sick:

Do what you can do, and if you can’t do it, then don’t. Most people who are fit tend to feel worse if they stop their exercise, but if you have got a bad case of the flu and can’t lift your head off the pillow, then chances are you won’t want to go run on the treadmill. The general rule is that if it is just a little sniffle and you take some medications and don’t feel so sick, it’s OK to work out. But if you have any bronchial tightness, it’s not advisable to be working out.

Know your limits. If you are feeling kind of bad, you may want to consider a walk instead of a run. Take the intensity down or do a regenerative activity like yoga, because if you don’t feel great, it may not be the best day to do your sprints.

A neck check is a way to determine your level of activity during a respiratory illness. If your symptoms are above the neck, including a sore throat, nasal congestion, sneezing, and tearing eyes, then it’s OK to exercise. If your symptoms are below the neck, such as coughing, body aches, fever, and fatigue, then it’s time to hang up the running shoes until these symptoms subside. An uncomplicated cold in an adult should be totally gone in about seven days.

A flu that develops complications such as bronchitis or sinusitis can last two weeks. The symptoms of cough and congestion can linger for weeks if not treated. In general, the flu, even if uncomplicated, can make you feel pretty rotten for 10 days to two weeks. Sharing is a good thing, but not when it comes to illness. For heaven’s sake, wipe down what you touch with disinfectant when you are done. Please, if you feel the need to continue even light workouts, do it outdoors, away from others.

The best way to avoid the problem is not to get sick in the first place. Get a flu shot. They really do help and no, you will not get the flu from a flu shot. Exercise in general can help boost your body’s natural defenses against illness and infection. Thirty minutes of regular exercise three to four times a week has been shown to raise immunity by raising levels of T cells, which are one of the body’s first defenses against infection. However, intense 90-minute training sessions like those done by elite athletes can actually lower immunity.

Use common sense, take care of yourself, and be mindful of others. When feeling ill, rest, get proper nutrition, drink plenty of liquids, and soon you will be back into your regular fitness routine. Stay healthy, my friends.