Exercise: The Wonder Drug?

Powerful treatments for those with Cancer

Sir Chris Hoy at Speed (Courtesy of Chris Hoy)

Cyclist Sir Chris Hoy, the winner of six Olympic gold medals, has terminal cancer. He was diagnosed with prostate cancer in September 2023 and was told that he had between two and four years to live.

He is an important role model, fundraiser and advocate for those living with cancer and a hero of mine both for his sporting achievements and his current stance on absurd government cuts to PSA testing.

He has been in the news recently, talking about the ‘wonder drug’ and the remarkable role that exercise is playing in keeping him well.

Exercise isn’t a replacement for cancer treatment, but the evidence for the benefits of physical activity in preventing cancer and during and after cancer treatment is increasingly compelling.

And the good news is that even relatively small amounts of exercise can make a significant difference, particularly for people who have previously been inactive. UK guidelines make it clear. There is no minimum amount of exercise required to achieve some health gains. (1)

Let’s look at the research.

One study found that men diagnosed with localised prostate cancer who had undertaken vigorous exercise at least once a week before diagnosis were significantly less likely to experience disease progression than men who did less vigorous exercise.(2)

In women diagnosed with breast cancer, studies have found that physical activity after diagnosis is associated with better overall survival and lower breast-cancer mortality. (3,4)

The numbers are startling.

Large academic reviews have found that higher levels of physical activity are associated with substantially lower risks of developing several cancers.

Compared with people doing very little physical activity, those reporting the highest levels had approximately the following reductions in risk: (5)

Breast cancer: 12–21%

Bladder cancer: 15%

Colon cancer: 19%

Oesophageal cancer: 21%

Kidney cancer: 12%

Stomach cancer: 19%

The consistency of the evidence across different cancers is remarkable and a lack of physical activity is now recognised as an important risk factor for several cancers.(5,6)

Another fascinating study by Professor Janet Lord and colleagues at the University of Birmingham sheds more light on how lifelong physical activity may affect how we age.(7)

The thymus is an organ that plays a crucial role in producing T-cells, key parts of our immune system. It begins to shrink after puberty, with its function generally declining as we get older.

The researchers compared older adults who had maintained high levels of physical activity through cycling with inactive older adults and much younger adults.

The results were striking.

The older cyclists had T-cell production levels that were comparable with those seen in much younger adults.

This provides fascinating evidence that maintaining high levels of physical activity may help preserve aspects of immune function as we age.

T-cells play a significant role in the detection and destruction of infected or abnormal cells, including cancer cells.

Another type of immune cell is appropriately called a Natural Killer (NK) cell. The clue really is in the name. Exercise can temporarily mobilise immune cells, including NK cells. These can recognise and destroy certain infected and abnormal cells too. (8)

There is another fascinating line of research.

In one small study of colorectal cancer survivors, participants completed a single high-intensity interval training (HIIT) session.

Blood serum collected immediately after HIIT temporarily reduced the growth of colon cancer cells in laboratory experiments. One possible mechanism involves the physical forces generated by exercise.

As blood flows faster as a result of exercise, the fluid shear stress increases. Experimental research has shown that sufficiently high shear stress can damage or destroy some circulating tumour cells.(9)

Chris Hoy is right about one thing: exercise really is remarkable. So why don’t Doctors prescribe exercise more often?

For people with cancer, prescribed exercise can help manage some of the consequences of both the disease and its treatment. Yet medical education has historically devoted little attention to exercise prescription compared with its importance to health.

Research suggests that many medical students and doctors receive limited formal training in physical-activity counselling. (10)

Why isn’t exercise routinely prescribed when up to one in four adults in both the United States and England is physically inactive? (11,12)

Perhaps the problem is partly cultural.

We are accustomed to thinking of medicine as something that comes in a packet or a bottle. Exercise doesn’t. There is no pharmaceutical company promoting it.

Yet the evidence suggests that we don’t need to become elite athletes to benefit. For someone who is currently inactive, simply starting to move more can be an important first step.

I cannot finish this article without mentioning the often-quoted concerns about cycling and prostate cancer, particularly among people who cycle very long distances for extended periods.

The evidence is considerably more complicated than some headlines suggest.

There is currently no established causal relationship between cycling and an increased risk of prostate cancer.(13)

Cycling can, however, cause temporary changes in PSA levels in some circumstances, particularly after prolonged rides. However, the evidence is mixed. I made the mistake of having a PSA test some years ago after my usual morning run. The results were initially alarming.

The overall picture is considerably more reassuring than some media coverage suggests.

Exercise provides substantial benefits to cardiovascular fitness, metabolic health and cognitive decline. For most people, those benefits are likely to outweigh the potential risks.

If you have prostate symptoms, or you are worried about your PSA level, speak to your GP.

Exercise isn’t a miracle cure for cancer. But the evidence increasingly shows that physical activity can play an important role in preventing cancer, supporting health during treatment and improving outcomes afterwards.

Best wishes. Keep taking the medicine.

Mike

Here are the links to the research cited in this article:

1. UK Chief Medical Officers. Physical Activity Guidelines: UK Chief Medical Officers’ Report. UK Government, 2026. UK Chief Medical Officers’ Physical Activity Guidelines

2. Bonn et al. Physical activity and risk of metastatic-lethal prostate cancer progression. Journal of Clinical Oncology. The study found an association between vigorous physical activity and lower risk of metastatic-lethal progression. PubMed — Prostate cancer and physical activity research

3. Ibrahim EM, Al-Homaidh A. Physical activity and survival after breast cancer diagnosis: meta-analysis of published studies. Medical Oncology. 2011. PubMed — Physical activity and breast cancer survival

4. Cannioto et al. Physical activity before, during, and after breast cancer diagnosis and survival. Research supporting associations between physical activity and outcomes following breast-cancer diagnosis. https://academic.oup.com/jnci/article/113/1/54/5814214

5. Friedenreich CM, Ryder-Burbidge C, McNeil J. Physical activity and cancer prevention: systematic review of the evidence. Medicine & Science in Sports & Exercise. 2021. PMC — Physical activity and cancer prevention evidence

6. Campbell KL et al. Exercise guidelines for cancer survivors: consensus statement from an international multidisciplinary roundtable. Medicine & Science in Sports & Exercise. 2019. PubMed — Exercise guidelines for cancer survivors

7. Duggal NA et al. Major features of immunesenescence, including thymic atrophy, are ameliorated by high levels of physical activity in adulthood. Aging Cell. 2018. PubMed — Janet Lord cycling and immune ageing study

8. Valenzuela PL et al. Effects of exercise training on natural killer cells in cancer survivors: systematic review and meta-analysis. PMC — Exercise, NK cells and cancer survivors

9. Brown JC et al. Acute high-intensity interval exercise reduces colon cancer cell growth. The Journal of Physiology. 2019. PubMed — HIIT and colon cancer cell growth

10. Systematic review of exercise-related education among medical students and residents. PMC — Exercise education in medical training

11. US Centers for Disease Control and Prevention. Physical inactivity data and research. CDC — Physical inactivity data

12. UK Government. Physical activity and inactivity statistics for England. UK Government — Physical activity statistics

13. Jiandani D et al. The effect of bicycling on PSA levels: a systematic review and meta-analysis. Prostate Cancer and Prostatic Diseases. Nature — Cycling and PSA systematic review