Many of us believe that it’s best not to exercise if we are sick. We probably think we need our energies to get better. Medical researchers have been studying the relationship between our immune system and exercise, and it turns out that to be more interesting and complex than was originally believed.
Australian and American immune experts just published their findings in the Journal of Applied Physiology. The principle author, Dr. Jonathan M. Peake, recently gave an interview where he explained the major findings, in lay terms. Here is a summary.
What happens to the immune system during exercise?
The body reacts to exercise like it is a stress, and certain hormones are released including cortisol, epinephrine, and growth hormone. When we are not stressed, most of our immune cells wait in our lymph glands, ready to release when they are needed. During exercise (a mild stress), these infection fighting cells are released into our blood.
What happens after exercise?
The number of infection-fighting cells falls. Researchers have known this for years, but only recently discovered is that the cells are not disappearing, but are moving from the bloodstream into our tissues (lungs, skin, mucous membranes in our mouth, and intestinal wall) where they might be needed to fight an infection.
Is this a problem?
If the exercise is very strenuous, it might be a problem if too many of the cells are diverted into the tissues. This makes us prone to an infection. But if the exercise is relatively mild, like walking or easy jogging, our immune system is not overworked or depressed.
Do people who repeatedly perform very stressful workouts have a higher risk of getting infections?
The research suggests that yes, people who exercise very heavy, and especially if they don’t rest their body between workouts, are more likely to get colds and other respiratory infections.
What about people that do regular moderate exercise?
These people get LESS upper respiratory infections than people who are sedentary, or people who exercise heavily.
Is there anything people who train hard can do to cut their risk of getting more upper respiratory infections?
Yes, if during high-intensity or long exercise sessions they take in enough carbohydrates, it seems to help support their immune system because their blood glucose levels are suuported. Dr. Peake recommends between 30 and 60 grams of carbohydrates should be consumed for every hour of heavy exercise. It helps even more if the person continues to take in adequate carbohydrates for a few hours after the exercise as well.
What other advice for people who exercise vigorously and want to avoid getting sick?
Dr. Peake recommends washing your hands frequently, and avoiding contact with people who are themselves sick.
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