There are lots of reasons to exercise, but one that most people don’t think about is how exercise impacts their ability to fight off cold and flu viruses. Yes, a moderate amount of exercise is a good thing when it comes to keeping flu symptoms at bay. A number of studies have shown that physical activity can reduce the likelihood of getting a cold or flu virus. In fact, recent research published in the British Journal of Sports Medicine found that healthy adults who exercised five out of seven days at a light to moderate intensity were 43% less likely to develop an upper respiratory tract infection compared to couch potatoes.
If some exercise is good, more must be better, right? Not necessarily. In fact, overdoing it i.e. running for long distances and overtraining can have the opposite effect – suppress immunity and lower your ability to fight off infection. The key is moderation. Pushing yourself too hard and overtraining, especially during flu season, can hamper the ability of immune cells that fight infection to do their job. Most research shows that strenuous exercise temporarily suppresses immunity, for a few hours up to a day, but this corrects itself with rest.
Exercise and Immunity: Moderation Matters
On the other hand, if you follow one strenuous exercise session with another one too quickly, your immune system can’t completely recover, putting you at greater risk for infection. Combine this with inadequate sleep and nutrition, and the risk is even greater. Overtraining also increases cortisol levels, and cortisol suppresses immunity.
Exercise is a double-edged sword. It protects against cold and flu viruses in moderation but can suppress your immunity if you don’t allow time for rest and recover. This seems to apply mostly to cardiovascular exercise. Intense strength-training sessions don’t seem to have the same negative effects on immunity.
How to Use Exercise to Reduce the Risk of Colds and Flu
The key to getting the immune-enhancing benefits of exercise without the negative effects that come from overtraining is to give your body time to recover. If you do high-intensity workouts, train lighter the next day to let your body recover. It’s longer, high-intensity workouts that suppress immunity short-term, while low to moderate-intensity exercise seems to have the opposite effect. Here are some tips for reducing the number of sick days and protecting yourself against the flu when you exercise:
Eat a Nutritionally-Rich Diet and Don’t Overly Restrict Calories
Keep your immune system primed by eating a nutritionally-balanced diet of whole foods with adequate amounts of protein and calories. Vitamins and minerals that are especially important for immunity are vitamin A, vitamin C, vitamin D and zinc. Make sure you’re getting adequate amounts of these. Vitamin D levels are lowest in the winter when you’re not exposed to the sun.
Eat yogurt. Yogurt is a good source of probiotic bacteria that may help to keep bacteria and viruses that cause illness in check. Look for yogurt with live cultures. It should say so on the label. Some yogurt has been heat-treated. This can destroy the good bacteria that help prime your immune system.
Get at least 7 hours of sleep and eight is better. Sleep keeps cortisol, a hormone that suppresses immunity, in check. If you do high-intensity workouts, sleep is even more important.
Meditate. A study published in the Annals of Family Medicine found that light to moderate intensity exercise and meditation were both effective for reducing the risk of upper respiratory infections.
Exercise at home. What could be worse than exercising in a closed environment where you’re breathing deeply and people around you are coughing and sneezing? In a crowded gym, there’s a good chance that a few people are carrying the flu during flu season and spreading it to others. Even if you spray the equipment off, there’s still airborne “germs.” You can get a great workout at home using DVDs and minimal equipment.
Don’t work out if you’re running a fever. If you have mild cold symptoms and aren’t experiencing body aches or a fever, you can safely do a workout but lower the intensity until you’re feeling back to normal.
The Bottom Line?
Moderate exercise along with a healthy diet and adequate sleep may help you avoid the flu and other respiratory infections, but don’t overdo it. Give yourself recovery time between high-intensity workouts and spend a little time meditating too. The combination of all these things can help you stay healthy during flu season.
Ann Fam Med July/August 2012 vol. 10 no. 4 337-346.
Med Sci Sports Exerc 37:57-62, 2005.
Med Sci Sports Exerc 37:57-62, 2005.
Oxygen Magazine. January 2013. “Lift Weights and Save Your Sick Days”