Evidence Search

But I’m exhausted

Fatigue in cancer survivors is a significant issue – it is perhaps the most common side effect. Not everyone calls it fatigue, but tiredness, exhaustion, lack of energy is reported by up to 95% of people with cancer. 


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It varies from person to person of course, but most people find they have low energy. Some have debilitating fatigue that drags on for months. If this is you, you’re not alone.


What causes cancer-related fatigue?

Well, according to Cancer Research UK, almost all of the main forms of treatment can cause it[2]:

  • Surgery: People often underestimate how long it takes to get over surgery. Surgery stresses your body and it needs time to heal. Pain can be exhausting, and the anaesthetic and other drugs may also contribute.
  • Radiotherapy: Most people who have radiotherapy feel increasingly tired as they go through their treatment. Fatigue can last for several weeks and for some people it can last for months after treatment has finished.
  • Chemotherapy: Nearly everyone who has chemotherapy has some fatigue. Your white and red blood cell counts drop midway between treatments. Knowing that you will get tired after each dose of chemo can make you feel anxious and frustrated.
  • Biological and hormone therapies: Biological drugs can cause tiredness as they can affect how the body produces chemicals that it needs in order to work properly. Hormone treatments can disturb the body’s balance and metabolism, and this can lead to many side effects including fatigue. Drugs that block hormones in breast and prostate cancers can cause fatigue as a side effect, like the fatigue that women going through menopause have. Thyroid hormones used to replace hormones after surgery for thyroid cancer can cause weakness, difficulty sleeping and fatigue.


Exercise helps – but how to start?

It’s difficult to motivate yourself to exercise when you’re drained, even though it’ll inevitably make you feel better. The trick is to start with little and often and not let the need to exercise become overwhelming. Be regular – you can always take it easy. Work up until you can be out of breath and warm, for 30 minutes.

Exercise helps – if you do it right

Evidence show that exercise can be used effectively to help overcome fatigue, but it needs to be at a correct, ‘moderate’, level of exertion[3].  Too little and it won’t have as much of an impact as it could. But if you overdo it, you may end up more tired than you were when you started. The best evidence for exercise overcoming fatigue is to work at 70% of your maximum heart rate.

The science bit: 70%HRM and its effect on fatigue

There’s a scale, adjusted for people’s age, that gauges the maximum number of beats that your heart can safely take per minute, known as your Maximum Heart Rate or HRM. It’s thought that exercising at 70% of that level is the most helpful, specifically for tackling tiredness and fatigue.[4] For most people, it’d feel like 7 out of 10 in terms of effort (0 being sitting still, 10 being flat out and you want to stop)

To work out your ‘70% HRM you use this equation:

220 minus your current age, multiplied by 70%. So, for a 60-year-old: 220-60=160 x 70%=112 beats per minute.

What does 70% feel like? It’s working at a level where you’re warm, you might want to take a layer of clothes on, and you’re breathing deeper than usual, but are still able to talk in short sentences. This might, of course, feel like far too much exertion for you, especially in the early days of getting fitter. If that’s the case, don’t worry, just make sure that you continue to push yourself gently to work as hard as you reasonably can.

You can get all sorts of devices and gizmos that measure your heart rate, such as the Fitbit etc. I wear a watch that includes a built-in heart rate monitor. Some people love to have a gadget, and to measure their progress whereas others prefer a simpler life. If this is you, then use the analogy ‘7 out of 10’ in terms of puff. Self-score occasionally, asking yourself how hard you think you’re working.

As you walk, or indeed as you start any cardio-based exercise after cancer, try to get used to maintaining a pace where you are lightly out of puff, 7 out of 10, for as much of the walk as you can.

The importance of strength training

There’s also a role for strength training in overcoming fatigue. Building stronger muscles will help to make daily life – climbing stairs, carrying shopping – less exhausting. Clinical studies show that a combination of cardio exercise and resistance training is your best bet in improving a sense of quality of life after cancer [5]. Your strength training doesn’t need to be complicated or time consuming: do a routine where all of your major muscles work, against resistance. I highly recommend using resistance bands rather than weights at first – they’re easy and adjustable and cheap and you’re less likely to get injured with them.

A good workout would comprise 8-10 different exercises, and you’d aim to do 2-3 sets of 10-12 repetitions each time, taking a break when you need to but ensuring there’s enough resistance so that your muscles are tired after each set. Do them 2-3 times a week, on non-consecutive days.

To nap, or not to nap.

One of the characteristics of fatigue is that night-time sleep can not feel restorative, and you can feel a need to nap during the day. That’s ok. Consensus opinion seems to be that napping for 45-60 minutes during the day should help you get through the day without interrupting night-time sleeping patterns.


There’s a whole, detailed discussion to be had about the impact of nutrition on cancer related fatigue, and there’s some very bad science on the subject. As is often the case with nutritional advice, good science seems to suggest simply good, sensible eating: eat regularly, eat whole foods rather than refined, eat plenty of lean protein, plenty of fruit and veg, keep alcohol, caffeine and sugar under control. Here’s some sensible advice, from Memorial Sloane Kettering’s Cancer Centre

Carolyn Garritt is a personal trainer, based in Central London, aiming to help those living with or after cancer get their oomph back through the power of exercise.

twitter: @carolyngarritt


[1] http://www.cancerresearchuk.org/about-cancer/coping/physically/fatigue/what-is-cancer-fatigue
[2] https://about-cancer.cancerresearchuk.org/about-cancer/coping/physically/fatigue/causes
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3647480/
[4] http://www.journalofphysiotherapy.com/article/S1836-9553(16)00021-7/fulltext
[5] Exercise Recommendations for Cancer-Related Fatigue, Cognitive Impairment, Sleep problems, Depression, Pain, Anxiety, and Physical Dysfunction: A Review
Karen M. Mustian, Ph.D., M.P.H., A.C.S.M, F.S.B.M., Assistant Professor and Director,1 Lisa K. Sprod, Ph.D., A.C.S.M., Research Assistant Professor,1 Michelle Janelsins, Ph.D., Research Assistant Professor,1 Luke J. Peppone, Ph.D., M.P.H., Research Assistant Professor,1 and Supriya Mohile, M.D., M.S., Associate Professor1