How much exercise do I need to protect my immunity in winter?

The evidence-supported threshold is 150–300 minutes of moderate-intensity activity per week, or 75–150 minutes of vigorous activity — the same as the general adult exercise guidelines. The mechanism is cumulative: regular exercise builds a more responsive immune system over time, not from one session. A brisk 30-minute daily walk five days a week sits comfortably within this range.

Does exercise actually keep you well in winter? Here's the evidence

Q: Should I exercise when I already have a cold?

The 'neck check' is a practical clinical guide: symptoms above the neck — runny nose, mild sore throat, sneezing — are generally compatible with light-to-moderate exercise. Symptoms below the neck — fever, chest cough, body aches, fatigue — are a signal to rest. Exercise will not shorten an existing cold, and pushing through significant systemic symptoms can delay recovery and increase injury risk.

What just happened

Researchers from Monash University published a review in The Conversation this week addressing a question that lands in general practice waiting rooms every winter: does regular exercise actually reduce your risk of getting sick?

The short answer is yes — with caveats worth understanding, because the mechanism matters more than the headline.

The key biology is this: when you exercise, your muscles release signalling proteins called myokines. Myokines mobilise natural killer cells and T-cells — the immune cells that identify and destroy virally infected cells — temporarily flooding circulation with them. The burst is short-lived: cell counts return to baseline within hours of stopping. But the benefit is cumulative. Regular exercise trains the immune system to mount faster, more efficient responses over time — not from any single session, but from the pattern.

This is not new biology, but the Monash review revisits it at a time when winter illness prevention conversations are happening across the country, and when many patients are looking for things they can do without needing to see a specialist or wait for a PBS listing.

Both-and

The evidence for regular exercise is solid — within a specific range

The evidence-supported target is the same as the standard adult physical activity guideline: 150–300 minutes of moderate activity or 75–150 minutes of vigorous activity per week. For most people, that means roughly 30 minutes of brisk walking five days a week, or equivalent.

Within this range, the research supports a genuine reduction in upper respiratory tract infection risk during winter. This sits on relatively robust observational data, though the challenge with exercise research — as with all lifestyle interventions — is that people who exercise regularly also differ from sedentary people in multiple ways that are difficult to isolate. The signal is consistent, but the precise magnitude is harder to pin down.

The practical test for gauging intensity is useful here: moderate means you can hold a conversation but can’t sing. Vigorous means you need to pause between sentences. Most activities that feel like real effort without leaving you gasping sit in the moderate zone.

The J-curve debate — and why it matters less than it used to

The older model of exercise immunity had a J-curve: sedentary people had elevated infection risk, moderate exercisers had reduced risk, but elite-level athletes doing prolonged high-intensity training had elevated risk again — an “open window” of suppressed immunity immediately after intense exertion.

Newer research challenges how clinically significant this “open window” actually is. The risk appears more pronounced in people doing extreme ultramarathon-level efforts, back-to-back training blocks with insufficient recovery, or in athletes who are also under-fuelling. For someone exercising moderately or even regularly at higher intensity within a reasonable weekly load, the immune-suppression concern is largely theoretical.

What this means in practice: the old advice to “be careful not to over-exercise or you’ll get sick” was somewhat overstated for most people doing non-elite volumes. If you are running five days a week at moderate intensity, you are far more likely to be in the protective range than in the suppressive range.

Exercise does not shorten a cold you already have

This is where the evidence is unambiguous: there is no support for the idea that you can “sweat out” a viral illness. Exercise during an established illness does not accelerate recovery, and there is no identified mechanism by which it would.

The practical guide for when you already feel unwell is the neck check: symptoms above the neck — runny nose, mild sore throat, sneezing — are generally compatible with light-to-moderate movement if you feel up to it. Symptoms below the neck — fever, chest cough, body aches, significant fatigue — are a signal to rest. The body mounts a febrile immune response for a reason; adding exercise load to that is adding a stressor to an already-stressed system.

What this doesn’t address

Exercise is one input among many that influences immune function. Sleep, nutritional status (particularly vitamin D and zinc in winter), chronic stress load, social connection, and underlying conditions all interact. An exercise habit does not compensate for persistent sleep deprivation or severe nutritional deficiency — the immune benefit of exercise operates in context, not in isolation.

This matters for patients who are already exhausted, dealing with high sympathetic load, or navigating chronic illness. The recommendation to “just exercise more” lands very differently when the person in front of you is already carrying a chronic fatigue presentation or an unmanaged autoimmune condition. The conversation about exercise and immunity for that patient is more nuanced and individual than the population-level evidence suggests.

My two cents

Regular moderate exercise as an immune-support strategy passes the test that many lifestyle recommendations do not: the mechanism is understood, the evidence is consistent across populations, and the action is specific enough to be useful. 150–300 minutes per week is a target, not a mystery.

What I find worth noting is that this is one of the few domains where the evidence-based recommendation and the intuitive patient recommendation align completely. Most people already sense that being physically active makes them feel more resilient. The biology confirms it.

The nuance for general practice: exercise conversations work best when they meet the patient where they are. “Go to the gym” is not a useful prescription for someone who is exhausted, working two jobs, and managing three children. “A 20-minute walk after dinner” is a different conversation, and often a more actionable one. The threshold is not intimidating — it is achievable in chunks, in ways that fit real lives.

Verdict: yes — the evidence for regular moderate exercise as a winter illness risk reducer is consistent, the mechanism is understood, and the action is specific. Worth raising in any consultation where immune health or winter wellness is already on the table.

Sources cited

Ahmadi M, Caldwell Odgers J, Koemel N. Does regular exercise stop you getting sick in winter? The Conversation, 27 July 2026. https://theconversation.com/does-regular-exercise-stop-you-getting-sick-in-winter-287783