Why is exercise during cancer treatment helpful?
Somewhere between the diagnosis and the first cycle of treatment, someone may have mentioned that exercise would be beneficial.
It could have been a leaflet in a waiting room, or a nurse said it in passing while setting up a cannula, but suggesting exercise is helpful and actually knowing what or how to do it is another thing.
In this article, I will try to answer those questions; however, this is not what to do; that has to be built around you, your diagnosis, and your treatment.
Why you've probably been told to rest For a long time, that was the advice. Rest was standard guidance for unwell patients, and there are health conditions where exercise genuinely isn't recommended. In cancer care specifically, there were good-faith clinical reasons for caution too. The 2019 international consensus statement on exercise for people with cancer notes that there is "a history of clinical recommendations to refrain from aerobic or resistance training" after breast cancer surgery, out of concern about triggering or worsening lymphoedema.
That caution didn't come from nowhere, but it also outlasted the evidence that justified it. Trials through the 2000s and 2010s progressively showed that supervised, gradually progressed resistance training doesn't increase lymphoedema risk, and by 2019 the international consensus had shifted to recommend it rather than avoid it. Guidance took time to catch up. If you were told to rest, that reflected the caution of its time; it wasn't a mistake, and it wasn't misinformation; it was advice that hadn't yet been updated to match newer evidence.
That's a separate question from whether anyone has raised exercise with you at all. If they haven't, it's less likely to be about outdated caution and more likely to be about capacity: oncology appointments run to fifteen or twenty minutes and are already full of decisions that can't wait, and in most parts of the UK there's no clear, obvious place to refer you to even when a clinician wants to. That's not a claim about any individual clinician's judgement; it's a description of a system with a missing piece. But it's also worth asking your team directly. The absence of a conversation isn't proof there's nothing to say.
Cancer-related fatigue isn't ordinary tiredness Cancer-related fatigue has a clinical definition. The National Comprehensive Cancer Network describes it as a distressing, persistent sense of physical, emotional or cognitive exhaustion related to cancer or its treatment that is 'not proportional to recent activity' and interferes with normal functioning. Unlike ordinary tiredness, it is widely recognised in the clinical literature as not being relieved by rest.
Ordinary tiredness is earned: you did something, you feel it, you rest, it lifts. Cancer-related fatigue arrives without having been earned, and the usual repair mechanism doesn't work on it. Macmillan puts the same point in plainer terms: people with cancer may get tired more quickly after less activity, and feel exhausted "even if they are getting enough rest and sleep."
Which explains something that a lot of people quietly experience. You rest more, do less, and you feel no better, and often somewhat worse, because doing less makes you deconditioned, and being deconditioned makes ordinary tasks harder, which makes you rest more. That is the reason exercise is in the conversation at all. Not as willpower, and not as a lifestyle suggestion, but because for this particular symptom, the usual treatment doesn't work and something else does.
What exercise actually does during treatment The evidence base here is substantial, and it is specific. The 2019 international roundtable reviewed the research outcome by outcome and only issued recommendations where the evidence was strong enough to justify one. In 2022, the American Society of Clinical Oncology reviewed the trials again, this time only in people receiving active treatment, and recommended that oncology providers advise both aerobic and resistance exercise during treatment given with curative intent, to reduce the side effects of therapy.
Energy and fatigue: This is the best-evidenced benefit. Moderate-intensity aerobic exercise, done consistently over a period of weeks, significantly reduces cancer-related fatigue both during and after treatment. And in the largest comparison of the available options, a meta-analysis of 113 trials and more than 11,500 people, exercise and psychological support both improved fatigue, while drug treatments did not. The authors' conclusion was that clinicians should be prescribing exercise or psychological support as first-line treatment for it.
Holding onto strength and physical function: Muscle is lost during cancer treatment; that is well documented across chemotherapy studies. It matters because strength is what stairs, shopping bags and getting out of a low chair are made of. Aerobic training, resistance training, or the two combined, done around three times a week over 8 to 12 weeks, significantly improved people's physical function in the trials reviewed.
Mood and anxiety: Both anxiety and depressive symptoms improved with regular moderate-intensity aerobic exercise, or with aerobic and resistance training combined, during and after treatment. Notably, the improvements were greater in supervised programmes than in ones people did entirely alone.
Sleep: Some trials suggest regular moderate aerobic activity, walking included, improves overall sleep quality. But this is one of the outcomes the 2019 roundtable couldn't yet issue a formal exercise prescription for; the evidence points in a positive direction without being strong enough to state as settled.
Quality of life: Combined aerobic and resistance exercise improved health-related quality of life during and after treatment, and the combination worked better than either on its own. This is the closest the research comes to measuring the thing people actually want back: feeling like a functioning version of themselves while treatment goes on around them.
What it doesn't do Exercise is not a cancer treatment. It doesn't directly shrink tumours; it isn't an alternative to anything your oncology team has recommended, and nothing here should displace a single element of your treatment plan.
It has also not been proven to help you tolerate or complete your chemotherapy — but this is the one area where the picture is shifting. When the 2019 roundtable assessed it, the evidence was judged insufficient to issue a formal recommendation, and that's still the official position. Since then, individual trials have been more encouraging than the earlier evidence base: a 2024 randomized trial found meaningfully better treatment response in women who did structured exercise and nutrition support alongside neoadjuvant chemotherapy, and an earlier landmark trial found less nausea and vomiting, and better-maintained fitness, in the exercise groups. Promising isn't the same as proven, and no guideline body has yet updated its recommendation on the strength of this newer evidence — so we're not claiming it. But it's the outcome most likely to move from "insufficient evidence" to "recommended" as more trials report.
The picture is thinner for chemotherapy-induced nerve pain and numbness, and for the memory and concentration problems people call chemo brain. Even after several hundred new trials published since 2019, both remain in the "insufficient evidence" category, without the same encouraging individual results that tolerance and completion now have. Insufficient evidence, in every case, means exactly that — not disproved, but not yet demonstrated.
And most of the research so far, across all of these outcomes, has been done in early-stage breast and prostate cancer. If you are living with advanced or metastatic disease, the honest position is that far less is known, and your programme should be built with that uncertainty respected rather than glossed over.
But I feel awful — how could I possibly exercise? This is the point at which most people stop reading, so let's be straight about it. Nothing in the evidence-based literature has been undertaken with patients who feel at their best. These trials were run in people going through chemotherapy and radiotherapy, people having bad weeks, low blood counts, and days where getting dressed is the achievement.
What that requires is a programme that moves with you. The 2019 guidance is explicit that a clinician should watch for early signs that training isn't being tolerated and adjust the dose accordingly, "even if this means dropping below recommended training volumes." In other words: the guideline itself expects the plan to bend around the person. Macmillan's guidance is a good practical test of intensity. At the end of an activity, you should feel energised, not exhausted. Little and often is more manageable than one big effort. And "doing something like stretching or a short walk is better than doing nothing at all." Some days that will be a long-based session and some days it will be five minutes and a cup of tea; both count and are helpful.
Is it safe during chemotherapy, radiotherapy or after surgery? Broadly, yes — and that is the position of the international guidelines, which conclude that exercise training is generally safe for people with cancer, and that everyone should "avoid inactivity." Cancer Research UK states it just as plainly: international guidelines say it is safe to be active during cancer treatment and afterwards.
Safety comes from screening, not avoidance. The international guidance sets out a straightforward triage: If you have no other significant health problems, no special assessment is needed before starting gentle activity. If you have peripheral neuropathy, joint or musculoskeletal problems, reduced bone density or lymphoedema, a medical assessment first is recommended, and the programme should be modified around it. If you have had lung or abdominal surgery, have a stoma, heart or lung disease, balance problems, severe fatigue, significant nutritional problems or bone metastases, you should be assessed and cleared by a doctor first, and your programme should be delivered by someone appropriately trained, for example a Clinical Exercise Physiologist.
Guidance across Macmillan, Cancer Research UK and NHS cancer services agrees on one thing: talk to your healthcare team before you start. There may be specific things to avoid at particular points in your treatment, after surgery, around low blood counts, or where cancer affects the bone. That is a reason to get the right advice, not a reason to do nothing.
What "exercise" actually means here It doesn't mean a gym, or a class full of people half your age; it doesn't mean a set duration or intensity, and it doesn't mean sport.
In the research, "moderate intensity" means working hard enough that your breathing has picked up and you could talk but not sing. Walking qualifies, so does a stationary bike. Resistance training means loading your muscles in a controlled way, which for many people starts with bodyweight or a resistance band rather than anything you'd recognise from a gym floor.
Macmillan makes the point that a lot of ordinary life counts: walking around the house, gardening, playing with your grandchildren, doing the housework. Starting gently and building up is the method, not a lesser version of it.
Who should be guiding it Someone who knows both exercise and cancer. The international guidance is specific about this. Where a person needs modification or medical clearance, it names rehabilitation professionals: physiatrists, physical therapists, clinical exercise physiologists, nurses, occupational therapists, and certified clinical exercise physiologists as the people to refer to. Across anxiety, depression, physical function and quality of life, supervised programmes consistently produced greater improvements than unsupervised ones.
In the UK, a Clinical Exercise Physiologist is the profession trained to prescribe exercise as clinical treatment for people with complex conditions, reading your treatment plan, screening for the things above, and building a programme around your chemotherapy cycles rather than around a template.
How to raise it with your oncology team You may need to start the conversation, and that is a reasonable thing to do. International guidance actually asks oncology clinicians to assess, advise and refer on physical activity — while acknowledging that they aren't expected to write the exercise prescription themselves. Asking gives them the opening.
Questions worth taking to your next appointment: "Is there any reason I shouldn't be exercising at this point in my treatment?" "Are there specific movements or activities I should avoid — because of my surgery, my bloods, or where the cancer is?" "Are there points in my cycle when I should ease off?" "Is there an exercise or prehab service I can be referred to locally?" "If there isn't one, is there any reason I shouldn't work with a Clinical Exercise Physiologist privately?"
Your Clinical Exercise Physiologist will know this and guide you through what you are able to do at different stages of your treatment plan.
Provision across the UK is uneven: well-resourced services like Prehab4Cancer exist in some regions, but most trusts have no equivalent to refer into. That gap is the reason this page exists.
Ready to talk to someone? Tell us about your diagnosis, where you are in treatment, and where you're based. We'll match you with a Clinical Exercise Physiologist who specialises in cancer — AHCS-registered and personally verified by our team. Free to use, and you won't be left searching a directory yourself.
This article is general information and is not a substitute for advice from your oncology team. Always speak to them before starting or changing physical activity during cancer treatment.
Sources
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- Macmillan Cancer Support. Tiredness (fatigue) and cancer. https://www.macmillan.org.uk/cancer-information-and-support/impacts-of-cancer/tiredness
- Macmillan Cancer Support. Being active during cancer treatment. https://www.macmillan.org.uk/cancer-information-and-support/treatment/preparing-for-treatment/physical-activity-and-cancer/during-treatment
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- Prehab4Cancer, Greater Manchester. https://prehab4cancer.co.uk/