Strength Training and Cancer: Why Your Muscles Matter During Treatment
If you're being treated for cancer, chances are someone has told you to rest. For years that was the standard advice. Today we know that, for most people, staying still doesn't protect you: inactivity speeds up the loss of strength and increases fatigue.
That's why international guidelines recommend exercise during treatment, and strength training is one of its key pieces. In this article I explain what happens to your muscle during cancer treatment, what benefits training it has, and how to do it safely.
What happens to your muscle during treatment?
Chemotherapy, radiotherapy, surgery and some hormonal treatments are often accompanied by less movement, less appetite and more days on the sofa. The result is a progressive loss of muscle mass and strength.
That loss shows up in daily life: it becomes harder to get up from a chair, climb stairs or carry the shopping. And a vicious circle appears that I see often: I get tired, I move less, I lose muscle, and I get even more tired.
Strength training is the most direct tool for breaking that circle, because it's the stimulus that tells the muscle it needs to maintain itself.
What does the scientific evidence say?
In 2019, the American College of Sports Medicine (ACSM) brought together international experts to review the evidence on exercise and cancer. Their conclusions were clear: exercise is generally safe for people with cancer, everyone should avoid inactivity, and aerobic training, strength training, or a combination of both improve fatigue, anxiety, depressive symptoms, physical function and quality of life.
In 2022, the American Society of Clinical Oncology (ASCO) went a step further, recommending that oncology professionals advise regular aerobic and strength exercise during active cancer treatment. Their review found improvements in physical condition, muscle strength and cancer-related fatigue.
A concrete example: in a trial with 242 women with breast cancer undergoing chemotherapy, the group that did supervised strength training improved their strength, muscle mass and self-esteem. They also completed the planned chemotherapy at a higher rate than the group that didn't train. Improvements in fatigue and quality of life were favourable, although they didn't reach statistical significance in that study. And the exercise didn't cause lymphoedema or adverse effects.
Benefits of strength training during cancer treatment
Maintaining strength and muscle mass, which are the foundation for everything else.
Helping reduce cancer-related fatigue, one of the most common and limiting symptoms.
Preserving independence: getting up, walking, climbing stairs or getting dressed without relying on anyone.
Improving emotional wellbeing: exercise is associated with less anxiety and fewer depressive symptoms.
Feeling like you're doing something for yourself: many people tell me that training gives them back some of the control the diagnosis took away.
Is it safe to do strength training during chemotherapy?
Yes, as long as the training is adapted to you. No two treatments are the same, and no two days within the same treatment are the same. That's why there are three non-negotiable rules:
Medical clearance. Your oncology team needs to give you the green light to exercise.
Initial assessment. Before lifting any weight, we need to know your starting strength level and how you move.
Professional supervision. An exercise professional trained in oncology adjusts the load to how you feel each day.
Some situations call for adapting or pausing training: fever, very low white blood cell or platelet counts, marked anaemia, recent surgery, a venous port, or bone metastases. They don't mean you can never train; they mean the plan has to take them into account.
What strength training looks like in practice
Forget the image of lifting as much weight as possible. Training strength during treatment means giving the muscle enough stimulus to maintain itself, without overdoing it. That's what we explain in the article on how exercise can help you or injure you: the key is the dose.
As a general reference, ACSM guidelines suggest two strength sessions per week that work the major muscle groups. From there, everything is individualised: the number of exercises, the load and the rest depend on your assessment, your treatment and how you're doing that day.
On good days, you progress. On bad days, you lower the intensity or change the exercise. What matters is consistency, not the perfect session.
Our oncology exercise programme at KINEO Benidorm
At KINEO Benidorm we've created an oncology exercise programme for people undergoing treatment. We train in groups of up to 3 people, in 60-minute sessions, and I supervise every session.
Before starting, we assess your strength with objective tools, such as the VALD DynaMo dynamometer or a linear encoder, and we repeat the assessment every quarter to adjust the goals. If you'd like to know whether the programme is right for you, you can find out about the oncology exercise programme and get in touch with no obligation.
Frequently asked questions
Can I lift weights during chemotherapy?
In most cases, yes, with medical clearance and adapted, supervised training. Loads are adjusted to your situation and how you feel each day.
Which is better, strength training or cardio?
Both provide benefits, and the guidelines recommend combining them. Strength training is the most specific for maintaining muscle mass and independence.
What if I'm very tired one day?
Training doesn't mean pushing through. On that day, intensity is reduced or the session is adapted. Often, a gentle session helps you feel better than staying at home.
Do I need my doctor's authorisation?
Yes. Before starting any exercise programme during treatment, your oncology team needs to give you the green light.
When can I start?
The sooner the better, as long as you have medical clearance. Starting at the beginning of treatment helps slow the loss of strength from the outset.
This article is for information only and does not replace assessment by your medical team.
Sources
Campbell KL, et al. Exercise Guidelines for Cancer Survivors: Consensus Statement from International Multidisciplinary Roundtable. Med Sci Sports Exerc. 2019;51(11):2375-2390. https://doi.org/10.1249/MSS.0000000000002116
Ligibel JA, et al. Exercise, Diet, and Weight Management During Cancer Treatment: ASCO Guideline. J Clin Oncol. 2022;40(22):2491-2507. https://doi.org/10.1200/JCO.22.00687
Courneya KS, et al. Effects of aerobic and resistance exercise in breast cancer patients receiving adjuvant chemotherapy: a multicenter randomized controlled trial. J Clin Oncol. 2007;25(28):4396-4404. https://doi.org/10.1200/JCO.2006.08.2024
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