>Winter has a way of making the office, train and school pick-up line feel like a giant petri dish of germs and potential infection. It’s also when many of us quietly let our exercise routine slide.

With late sunrises and a warm bed, a run in the rain or snow has lost its appeal. But could skipping that workout actually make you more likely to catch the flu or seasonal bug?

The short answer: regular, moderate exercise probably does lower your risk of catching a cold or flu. But it won’t cure you once you’ve got it, and more exercise isn’t always better.

When you exercise, your muscles contract and release signalling proteins called myokines. These natural chemical messengers help mobilise beneficial immune cells and redistribute them throughout the bloodstream and bodily tissues. This improves the immune system response to threats, making your body better at fighting infection.

However, the effect isn’t permanent. Within hours after exercise, your cell counts (a measure of how your immune system is responding) return to normal.

But researchers think repeated bouts of these immune “boosts” do add up over time, building an immune system that detects and responds to viruses more efficiently.

Regular moderate exercise also appears to lower chronic inflammation, which otherwise prevents your immune system working as well as it should.

Exercise won’t shorten a cold you already have, and there’s no evidence an intense gym session “sweats out” a virus.

What the research supports is exercise as a preventative tool. Think of exercise as a way to reduce your chances of getting sick rather than preventing it altogether. Even very fit people catch colds and flu.

The trickiest calls come when you’re not quite sick but feel run down.

Many clinicians use a simple “neck check”. This means if symptoms are above the neck (for example, a runny nose, sneezing, a mild sore throat) then light-to-moderate exercise is generally fine, though it’s sensible to ease off the intensity and duration.

If you have symptoms below the neck (such as a chest cough or upset stomach) or symptoms affecting your whole body (such as fever, body aches or serious fatigue) then rest is the better call.

Exercising with a fever raises your core temperature further, can worsen dehydration, and adds strain on your heart.

If you’re simply feeling flat or short on sleep (rather than unwell), then a gentle walk is unlikely to do harm and may even help.

Adapted from The Conversation: 28 July 2026.