How Cancer Treatment Affects Muscle Strength — and How to Rebuild It
Updated: Oct 14
Written by Rosy Allan, BSc (Hons), ANutr
Registered Associate Nutritionist | Level 3 Personal Trainer | Level 4 Cancer Exercise Rehabilitation Specialist
Cancer treatment can change the way your body feels and functions.
For many people, the effects extend well beyond tiredness. Activities that once felt manageable, such as climbing stairs, carrying shopping or completing a familiar gym workout, can suddenly become challenging.
Chemotherapy and radiotherapy are important cancer treatments, but they can also affect physical strength, mobility and everyday function.
So why does this happen? Can muscle strength be rebuilt? And what role do exercise and nutrition play during recovery?
The research offers some encouraging answers, although recovery will look different for everyone.
Why can cancer treatment affect muscle strength?
Muscle weakness during and after cancer treatment rarely has a single cause.
Several factors may contribute, including:
Reduced physical activity during periods of illness or fatigue
Changes in appetite and nutritional intake
Loss of body weight and skeletal muscle
Inflammation and other effects of cancer or its treatment
Peripheral neuropathy and altered movement patterns
Surgery, hormonal treatments and other treatment-related complications
These factors can interact. For example, someone experiencing fatigue may become less active, which can contribute to deconditioning and make everyday activities feel increasingly difficult.
Importantly, not everyone experiences significant muscle loss, and the effects vary according to cancer type, treatment, previous fitness, age and overall health.
How chemotherapy can affect muscle health
Chemotherapy uses medicines to destroy cancer cells or prevent them from growing and dividing. Different chemotherapy drugs work in different ways, and their effects on healthy tissues vary.
Some treatments may influence skeletal muscle metabolism and contribute to muscle weakness. However, changes in strength during chemotherapy are often influenced by several overlapping factors.
Reduced strength and physical fitness
People undergoing chemotherapy may experience reduced exercise tolerance and physical performance. Even when muscle mass hasn't changed dramatically, fatigue, anaemia, reduced activity and other treatment effects can make physical tasks more demanding.
This distinction matters because muscle weakness doesn't always mean substantial muscle tissue has been lost.
Changes in muscle mass
Some people experience reductions in skeletal muscle during cancer treatment.
Poor appetite, inadequate nutritional intake, inflammation and periods of inactivity may all contribute.
For people experiencing cancer-related malnutrition or cachexia, the situation can be particularly complex and requires specialist medical and dietetic assessment (Muscaritoli et al., 2021). Simply increasing exercise or protein intake may not be sufficient to address these conditions.
Peripheral neuropathy
Certain chemotherapy drugs can damage peripheral nerves, resulting in symptoms such as numbness, tingling, pain or altered sensation.
Neuropathy can interfere with balance, grip strength and the ability to exercise comfortably.
For example, someone who struggles to feel their feet properly may need additional support with balance, while reduced hand sensation can make holding weights difficult.
Exercise programmes may need adapting, with particular attention to footwear, stability, equipment and fall prevention.
How radiotherapy can affect muscles and movement
Radiotherapy uses ionising radiation to damage cancer cells within a defined treatment area.
Unlike many systemic cancer treatments, its direct effects are generally concentrated in the tissues exposed to radiation.
This means the physical consequences depend partly on which area of the body has been treated.
Radiation-induced fibrosis and stiffness
Radiotherapy can sometimes cause longer-term changes in connective tissues, including fibrosis. Fibrosis involves tissue becoming firmer and less flexible. Depending on the treatment area, this may contribute to stiffness, discomfort and restricted movement.
For example, someone who has undergone breast cancer surgery and radiotherapy may experience difficulties with shoulder mobility or tightness around the chest.
However, it is important to distinguish radiotherapy-related changes from complications of surgery, such as axillary web syndrome, also known as cording.
These conditions can occur alongside one another but are not the same thing.
Localised weakness and fatigue
Some people experience weakness or reduced function in areas affected by radiotherapy, particularly when muscles, nerves or surrounding tissues are involved.
Radiotherapy can also contribute to fatigue, making exercise and everyday activities more challenging.
Most people will not experience every possible complication, and some treatment-related effects improve over time.
Persistent or new weakness, pain or restricted movement should be discussed with the treating team rather than assumed to be a normal part of recovery (Cancer Research UK, 2026).
My experience of rebuilding strength after cancer
When I began exercising again after chemotherapy, I was surprised by how much my strength and endurance had changed.
Before treatment, physical activity had been an important part of how I saw myself. Afterwards, I found myself feeling frustrated, self-conscious and disconnected from the body I recognised.
It wasn't simply about lifting less weight in the gym. It was about confidence, independence and wondering whether I would ever feel like myself again.
Returning to exercise wasn't straightforward. Alongside fatigue and reduced strength, I had to manage other treatment-related symptoms that made familiar activities more difficult. Progress was gradual, and it certainly wasn't linear.
That experience became an important part of why I pursued specialist training in cancer exercise rehabilitation.
I understand that rebuilding strength after cancer isn't only a physical process. For many people, it involves learning to trust their body again.
Can exercise help rebuild muscle strength?
Yes. There is good evidence that appropriately prescribed exercise can improve aspects of physical functioning during and after cancer treatment.
The American Society of Clinical Oncology (ASCO) recommends regular aerobic and resistance exercise during active treatment with curative intent, with programmes adapted to the individual's circumstances (Ligibel et al., 2022).
This doesn't mean everybody should follow the same exercise plan or train at the same intensity.
What does the research show?
A 2024 systematic review and meta-analysis examined seven randomised controlled trials involving 561 participants receiving chemotherapy.
Researchers found that resistance training produced improvements in lower-body strength compared with control conditions.
However, findings for fatigue, upper-body strength, physical functioning and quality of life were less certain in this particular review (Metcalfe et al., 2024).
This is an important example of why we should avoid claiming that one type of exercise improves every aspect of cancer recovery.
Broader clinical guidelines also support exercise for managing cancer-related fatigue, although the most suitable approach depends on individual needs (Bower et al., 2024).
What might cancer rehabilitation exercise involve?
A specialist exercise programme should begin with an individual assessment.
Depending on someone's treatment history, symptoms and goals, rehabilitation might include:
Gentle cardiovascular activity
Walking, cycling or other suitable activities can help rebuild exercise tolerance and support cardiovascular health.
The starting point may be only a few minutes, with duration and intensity adjusted gradually.
Resistance training
Strength exercises can help rebuild muscular strength and everyday function.
A programme might incorporate movements such as sit-to-stands, supported rows, step-ups or appropriately selected resistance exercises.
The aim is to create a manageable challenge without exceeding the person's current capabilities.
Mobility and flexibility exercises
After surgery or radiotherapy, some people benefit from exercises designed to improve movement around affected joints and tissues.
Persistent restrictions, cording, lymphoedema or significant pain may require assessment and management by an appropriately qualified physiotherapist or specialist team.
Balance and coordination
For people experiencing neuropathy, weakness or balance difficulties, targeted exercises may help improve confidence and stability.
The programme should account for any sensory changes or increased risk of falling.
Is it safe to exercise during chemotherapy or radiotherapy?
For many people, some physical activity is safe and beneficial during treatment.
However, exercise isn't appropriate in every situation, and intensity may need modifying considerably.
Factors requiring particular attention include:
Fever, infection or feeling acutely unwell
Significant anaemia or low platelet counts
Bone metastases or increased fracture risk
Severe neuropathy or balance difficulties
Cardiac or respiratory complications
Recent surgery or poorly healed wounds
Significant pain, swelling or treatment-related skin reactions
Someone undergoing radiotherapy does not automatically need to stop all vigorous exercise, but the suitability of different activities should be assessed individually.
Macmillan Cancer Support advises people to seek guidance from their cancer team when beginning or changing their activity during treatment.
The goal is not to push through significant symptoms. It is to remain as active as safely possible, with appropriate rest and professional support.
What role does nutrition play in recovery?
Exercise and nutrition work alongside one another in supporting physical function.
Adequate energy intake is important, particularly when someone has experienced unintentional weight loss or reduced appetite.
Protein also provides the amino acids needed to maintain and repair body tissues.
Practical protein sources include eggs, fish, meat, dairy products, tofu, beans and lentils.
However, cancer treatment can make meeting nutritional requirements difficult. Nausea, taste changes, swallowing difficulties and digestive symptoms may all affect intake.
For people who are malnourished, experiencing significant unintentional weight loss or requiring therapeutic dietary support, assessment by an oncology dietitian is important.
ESPEN guidance emphasises individualised nutritional assessment and intervention for people with cancer (Muscaritoli et al., 2021).
It's also worth being cautious about restrictive weight-loss diets during recovery. Someone may have gained body fat during treatment while simultaneously experiencing reduced muscle strength or nutritional inadequacy.
The most appropriate nutritional priorities depend on their overall clinical condition rather than body weight alone.
Recovery isn't always a straight line
One of the most challenging aspects of cancer rehabilitation is that progress can vary from day to day.
You might feel stronger one week and experience significant fatigue the next.
Some people regain function relatively quickly, while others continue managing treatment effects for months or years.
A good rehabilitation programme allows for these fluctuations. Progress might mean walking slightly further, lifting a little more weight, improving shoulder mobility or completing daily activities with less difficulty. All of these can be meaningful outcomes.
And there is no requirement to return to exactly the same level of fitness you had before treatment for your progress to matter.
Final thoughts
Cancer treatment can affect muscle strength through several pathways, including reduced activity, changes in nutritional intake, treatment-related fatigue and complications affecting muscles or nerves.
Chemotherapy and radiotherapy may contribute in different ways, and the impact varies significantly between individuals.
Research supports appropriately tailored exercise as an important part of cancer care, with benefits for strength, physical functioning and aspects of wellbeing.
Nutrition, physiotherapy and specialist clinical support may also be important components of recovery.
For anyone facing these challenges, rebuilding strength isn't about forcing your body back to where it was. It's about finding a safe, sustainable way to move forward.
At ROSY, I provide specialist cancer exercise rehabilitation coaching, including online support for clients throughout the UK, with programmes designed around individual treatment histories, physical capabilities and goals.
Disclaimer: This article is intended for general educational purposes and does not replace personalised medical, physiotherapy or dietetic advice. Cancer treatments and their side effects vary considerably. Always discuss new or changing exercise plans with your oncology team where appropriate, particularly during active treatment or when experiencing complications. Significant nutritional concerns should be assessed by an appropriately qualified healthcare professional.
References
Bower, J.E. et al. (2024) 'Management of fatigue in adult survivors of cancer: ASCO–Society for Integrative Oncology guideline update', Journal of Clinical Oncology, 42(20), pp. 2456–2487. Available at: https://doi.org/10.1200/JCO.24.00541
Cancer Research UK (2026) Side effects of breast cancer radiotherapy. Available at: https://www.cancerresearchuk.org/about-cancer/breast-cancer/treatment/radiotherapy/side-effects
Ligibel, J.A. et al. (2022) 'Exercise, diet, and weight management during cancer treatment: ASCO guideline', Journal of Clinical Oncology, 40(22), pp. 2491–2507. Available at: https://doi.org/10.1200/JCO.22.00687
Macmillan Cancer Support (n.d.) Exercising safely when you have cancer. Available at: https://www.macmillan.org.uk/cancer-information-and-support/treatment/preparing-for-treatment/physical-activity-and-cancer/exercising-safely
Metcalfe, J.W. et al. (2024) 'Effects of resistance training on quality of life, fatigue, physical function, and muscular strength during chemotherapy treatment: A systematic review and meta-analysis', Supportive Care in Cancer, 32, article 593. Available at: https://doi.org/10.1007/s00520-024-08766-y
Muscaritoli, M. et al. (2021) 'ESPEN practical guideline: Clinical Nutrition in cancer', Clinical Nutrition, 40(5), pp. 2898–2913. Available at: https://doi.org/10.1016/j.clnu.2021.02.005
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