Source: The Conversation (Au and NZ)
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 doona, 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.
Exercise and the immune system
When you exercise, your muscles contract and release signalling proteins called myokines.
These natural chemical messengers help mobilise beneficial immune cells – particularly natural killer cells and T-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.
The evidence backs this up, if imperfectly. A 2022 review of the evidence concludes that physically active people consistently report fewer respiratory infections than those who do very little physical activity.
Prevention, not the cure
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.
There’s also a caveat, sometimes called the immune “J-curve”: very prolonged, high-intensity exercise can lead to a temporary dip in immune function in the hours afterwards.
This mostly affects endurance athletes doing significant amounts of training – think marathon training, not a lunchtime walk.
However, more recent research questions how large that risk really is. For most of us average folks, going beyond the healthy amount of weekly physical activity is not a concern.
How much exercise and physical activity do you actually need?
You don’t need to train like an athlete. Guidelines recommend adults do 150–300 minutes of moderate physical activity a week, or 75–150 minutes of vigorous intensity activity. Or you can do an equivalent combination of moderate and vigorous activity.
Moderate intensity means anything that noticeably lifts your heart rate and breathing: a brisk walk, cycling, swimming, raking leaves, even dancing in the kitchen. It doesn’t need to be a structured “workout”.
Vigorous intensity means any activity of any duration that gets us huffing and puffing.
A way to test exercise intensity is with the “talk and sing” test. At moderate intensity, you’ll be able to talk but not sing. At vigorous intensity, you won’t be able to talk without pausing to catch your breath.
Finding motivation when its cold and dark
Winter motivation is a genuine hurdle. But a few things can help:
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treat exercise as a fixed appointment, not something you’ll “find time” for
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move it indoors on bad weather days
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break it into smaller chunks, such as three five-to-ten minute walks – these work as well as a single 30-minute session
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exercise with a friend, if accountability helps you
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get outside when you can – especially when the sun is out.
To exercise or to rest? The million dollar question
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) 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) 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, a gentle walk is unlikely to do harm and may even help. But it’s also a good moment to prioritise sleep and lower the intensity rather than push through a hard session.
None of this makes exercise a substitute for a flu shot, hand-washing or staying home when you’re contagious.
But as one of the few winter habits genuinely within our control, regular exercise and physical activity is a reasonable, low-cost way to tilt the odds in your favour.
The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
Original source: https://analysis1.mil-osi.com/2026/07/27/does-regular-exercise-stop-you-getting-sick-in-winter/