Cold and Flu season are rapidly approaching, and one of the most powerful tools you have for prevention is regular, reasonable exercise. The average American gets 2-4 colds per year, and each one sticks around for 7-10 days, which is 14 to 40 days per year spent feeling miserable. At the low end this means you’d lose 336 hours per year, whereas working out 3 days per week only takes 156 hours per year. So, since regular exercise definitely helps to reduce the frequency, duration and severity of colds, exercise is definitely worth the investment.

While we don’t know for sure how exercise supports your immune system, but there are several theories:

  1. The deep and full breathing might help to flush out your lungs, and make you more resistant to respiratory infections.
  2. Exercise helps to balance your stress hormones like cortisol. When cortisol is too high, it will suppress your immune function. (This is why workouts that are too intense or too long undermine your immune system.)
  3. Regular exercise seems shift your T cells to the ones that are better at fighting disease.

Don’t Push Too Hard or Too Long

There is a fad in fitness of working out until you collapse, or are exhausted and can’t keep going. Besides being dangerous and ineffective over time, this kind of exercise actually suppresses your immune system because they stimulate the secretion of too much cortisol.

This kind of exercise makes it worse than no exercise because it makes it more likely that you will get sick, and makes the symptoms worse. Long exercise sessions – anything at moderate intensity or higher that lasts longer than 90 minutes – also seem to suppress your immune system because these long sessions stimulate high cortisol levels. So, if you are preparing for a marathon, then take extra care after your long runs by washing your hands more.

Should You Exercise When You’re Sick?

Yes! (Probably.) If it is above the neck, then yes! The exercise (if not excessive) will probably boost immune function, help suppress bacterial growth and get you better faster. Listen to your body, and tone down your efforts to match your energy levels.

However, if you have a fever, diarrhea, vomiting, and/or other below-the-neck issues, then wait until all of those symptoms have gone away. After you feel better, wait a few days, and take it easy when you come back.

Anything else?

Regular, reasonable exercise is very important to keeping your immune system in tip-top shape, but it’s not the only important factor. The other important factors are: getting enough quality sleep, getting enough vitamin D, stress management (laughing helps a lot), and avoiding sugar and other highly processed carbs.