We know regular exercise can prevent type 2 diabetes, heart disease and some cancers. It can also add years to your life. But what about that pesky cold or flu? Can exercise prevent the sniffles and other infections? Is there a relationship between exercise and the immune system?

Historically, exercise has been blamed for both increasing and reducing sickness in people. Early studies suggested that vigorous exercise may lead to more illness. This was believed to be due to suppression of the immune system as ultra-marathoners reported more infections in the weeks following these races.

However, these studies relied on self-reported symptoms to indicate an infection and have been debunked. This is because self-report isn’t reliable and not all symptoms indicate an infection. When 37 athletes reporting infection were tested, less than one-third were actually confirmed infections. And in a study of 11 elite endurance athletes, the number of training hours was associated with fewer sick days.

For good or bad, however, sick days don’t always translate into sickness. Many of us will go to work with a cold or work from home rather than take a sick day. A more robust study followed 1000 people for three months over the fall and winter seasons. Each person was assessed for the presence of respiratory infections. Those people who exercised more than five days per week had nearly half the number of infections compared to people who exercised less than 1 day per week.

What Happens to the Immune System When You Exercise?

When immune system markers are measured in the blood, a single bout of exercise appears to enhance the immune system. This is because exercise increases the number of cells in the blood that fight off infections. Even walking for 30 minutes can have an effect. And while the effects seem to diminish with age, older adults still derive some benefit.

It’s believed the benefits from one exercise session are only temporary but regular exercise can make the effect last longer. People who completed an eight-week exercise program had less respiratory infections than a non-exercising control group. And this benefit persisted for four months after the sessions stopped. In the long term, regular exercise may also lower the chances of flu-related deaths.

Even though these studies were carried out following strict scientific methods, there is a limit to what we can do and learn in humans. Therefore, some research looks at the effects of exercise on the immune system in mice. Mice purposely infected after exercising had a lower chance of infection compared to mice infected without exercising. Even after an infection was present, mice assigned to exercise had a lower chance dying from it.

Beyond Exercise and the Immune System

But exercise won’t help much if you aren’t mindful of other considerations. If you exercise in the cold weather, make sure you dress appropriately. Using layers is great because you can remove them as your body warms up. Once your workout is finished, get out of those sweaty clothes. In cooler weather wet clothes soak the heat right out of you and lower your core temperature. While being cold itself doesn’t lead to catching the flu or a cold (you still have to be exposed to the virus), some viruses spread more readily in cold weather. There is also some research to suggest being cold may lower your immune response.

If you exercise in a gym or community centre, use the sanitizer before and after using the equipment. This will help to keep the bacteria at bay as it’s not uncommon for bacteria to be present in gyms.

And if you’re sick, listen to your body. If you’ve got the sniffles and symptoms above the neck, exercise is probably not a problem. It may even help loosen up your airway passages and doesn’t seem to affect recovery time or lung function. But if your symptoms are below the neck such as chest congestion or you have a fever, do yourself a favour and get some rest.

Lastly, don’t forget the basics either. One of the best ways to prevent getting sick and spreading infection is by washing your hands.

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