Cyclist riding fast on an open road

Hard Cycling and Colon Cancer Cells: What a 2026 Lab Study Found

9 min read

A 2026 study from Newcastle University took blood from 30 adults before and after a cycling test that got harder every minute until they could not go on. The scientists then added the blood to colon cancer cells in a dish. Cells exposed to the after-exercise blood cleared DNA breaks faster.

This guide covers what the study did, what it found, why faster DNA repair might matter, how it fits with other lab research, what it does not show, and how to add hard efforts to your week safely. The study was done on cells in a lab, not in people with cancer, so it points to a possible mechanism rather than a proven effect on cancer risk.

16.8%
Fewer DNA break markers at 6 hours in irradiated cells exposed to after-exercise blood, with no clear difference at 1 or 24 hours
Orange et al. 2026, blood from 30 adults
10-12
Minutes of cycling, after a 3-minute warm-up, rising in effort every minute until exhaustion
Orange et al. 2026, adults aged 50 to 78
1,364
Genes whose activity changed in colon cancer cells, most by small amounts
Orange et al. 2026, blood from 12 adults
4.5x
Activity of the DNA repair gene PNKP in irradiated cells, against before-exercise blood
Orange et al. 2026, blood from 11 adults
Sources: Orange et al. 2026, International Journal of Cancer. All results are from colon cancer cells grown in a lab dish.

What the Newcastle team did

Samuel Orange and colleagues recruited 30 apparently healthy adults aged 50 to 78 who were overweight or obese. People with heart, metabolic or kidney disease, high blood pressure, a past stroke or past cancer treatment were excluded. Each did a cycling test on a static bike in the lab. After a 3-minute warm-up with no resistance, the work rate rose every minute until each person could not continue, which took 10 to 12 minutes. The effort started easy and rose by 15 to 25 watts each minute, so it was hardest at the end, when each person reached maximal effort. Blood was taken before and straight after.

Serum is the liquid part of blood left after it clots. In serum from 12 of the participants, the team measured about 249 proteins. Thirteen rose after exercise, including interleukin-6 (IL-6), a signalling protein released during exercise, and its receptor. The team then grew a colon cancer cell line called LoVo in a dish, added either the before-exercise or the after-exercise serum, and gave the cells a dose of radiation to damage their DNA.

What the study found

The team counted small spots inside each cell, called gamma-H2AX foci, which mark places where DNA strands have broken. They counted them at several points over 24 hours after radiation. Fewer spots over time means the breaks were being repaired faster.

Cells exposed to after-exercise serum had 16.8% fewer break markers 6 hours after radiation than cells exposed to before-exercise serum. The likely range of that effect was wide, from about 4% to 30%. There was no clear difference at 1 hour or at 24 hours, but across the full 24 hours the breaks cleared faster overall. In serum from 11 participants, the activity of PNKP, a gene involved in repairing breaks in DNA, was 1.9 times its level with before-exercise serum in cells without radiation, and 4.5 times in cells with radiation. With only 11 people, the exact size is uncertain.

Gene activity here means how much of each gene's message the cells made. In serum from 12 participants, the after-exercise serum changed the activity of 1,364 genes, 627 up and 737 down, and most of the changes were small. Genes linked to energy production in mitochondria, the parts of the cell that make energy, went up. Genes linked to cell division went down, though one growth-related pathway went up a little. The authors concluded that exercise might shift colon cancer cells in a dish towards a pattern of gene activity linked to slower growth. The study did not measure cell growth directly.

DNA repair gene PNKP in colon cancer cells Times higher with after-exercise serum than before-exercise serum (1.0) With radiation 4.5x Without radiation 1.9x 1.0 = before-exercise serum
Source: Orange et al. 2026, International Journal of Cancer. LoVo colon cancer cells grown in a lab dish, exposed to serum from 11 of the 30 participants, overweight or obese adults aged 50 to 78, taken before and after a cycling test to exhaustion.

Why faster DNA repair might matter

Faster repair in cancer cells can sound like bad news. The authors argue the opposite. They explain that when DNA damage is repaired slowly or with errors, damaged cells can pick up more mutations, and unstable cells can survive and spread. Faster, accurate repair might keep these cells more stable. This is their theory. The study did not test it, and it did not look at how cancer cells respond to cancer treatment.

How this fits with other lab research

A 2024 narrative review by Francesco Bettariga and colleagues in the Journal of Sport and Health Science gathered lab studies that grew cancer cells in serum taken after exercise. Studies with breast, prostate, colorectal and lung cancer cells often found that after-exercise serum reduced cancer cell growth, though results were mixed, and for colorectal cancer the review says there is not yet enough evidence to say which type, amount or intensity of exercise matters. The review reports that a single bout of moderate to vigorous aerobic exercise may have suppressive effects in the lab, and that these might come from substances released into the blood, such as hormones and myokines (signalling proteins released by working muscle).

The review says it remains unclear how the type, amount and intensity of exercise change these effects. The 2026 authors also say it is unclear whether lower-intensity exercise would have a similar effect. In our reading, the lab evidence does not yet show that hard exercise works better than moderate exercise for this purpose.

What this study does not show

The authors list the limits themselves. The study used a single type of colon cancer cell grown flat in a dish, which does not capture the complexity of a real tumour. The blood came from healthy overweight and obese adults, not from people with cancer. The cycling test involved maximal effort, which the authors note might not be suitable for some people with cancer, especially during treatment. In our view, it is also worth knowing that the blood was taken straight after exercise, and cells in a dish do not show what happens in the body over the following hours.

The study did not measure cancer risk, cancer growth in people, or survival. In our view, it adds a plausible mechanism to the case for regular exercise, but it does not show that a hard cycling session prevents colon cancer.

How to add hard efforts to your week

The NHS advises adults aged 19 to 64 to do at least 150 minutes of moderate activity or 75 minutes of vigorous activity a week, plus strength activities on at least 2 days. It describes "very vigorous" activities as short bursts of maximum effort broken up with rest, and says several short sessions of them count towards the weekly target. The test in the study was a supervised lab test in screened volunteers. The steps below are ours, not a tested programme.

1
Start with a base
If you are new to hard exercise, build up regular moderate activity for a few weeks before adding harder efforts.
2
Add short hard sessions
Once or twice a week, try about 10 minutes on a bike or rower that builds from easy to hard, where talking is difficult, with a warm-up and cool-down. You do not need to go to exhaustion.
3
Count them towards the target
Short hard sessions count towards the NHS weekly target. Keep your two days of strength work as well.
4
Check with your GP first
If you are over 50 and inactive, have a heart condition, high blood pressure or diabetes, are managing a long-term illness or are having cancer treatment, speak to your GP or care team before trying hard efforts.

Stop at once if you feel chest pain or pressure, faintness, dizziness or a racing or irregular heartbeat during exercise. Call 999 if chest pain does not settle with rest.

Frequently asked questions

Does a hard cycling session prevent cancer?
This study does not show that. It found that blood taken after a cycling test to exhaustion changed how colon cancer cells behaved in a lab dish. It did not measure cancer risk in people.
Does this apply to other cancers?
This study only used colon cancer cells. The 2024 Bettariga review reports that after-exercise blood slowed the growth of several cancer cell types in the lab, though not every study found an effect.
Is moderate exercise still worth doing?
Yes. The NHS target is met by moderate or vigorous activity. The 2024 review suggests a single bout of moderate to vigorous exercise may have effects in the lab, but the 2026 authors say it is unclear whether lower intensity works the same way.
Who took part in the study?
Thirty adults aged 50 to 78 who were overweight or obese and described as apparently healthy. None had been treated for cancer, and their blood was tested on cells in a dish.
I am having cancer treatment. Should I try this?
The authors note that maximal efforts might not be suitable during cancer treatment. Follow the exercise advice from your care team.

The bottom line

In a 2026 lab study, blood taken from 30 overweight or obese adults after a cycling test to exhaustion sped up DNA repair in colon cancer cells at one time point, and in blood from 12 of them, changed the activity of 1,364 genes. Other lab studies report that after-exercise blood slowed the growth of several cancer cell types, though results were mixed. These are lab results, not evidence that hard cycling prevents cancer. In our view, they add one more reason to meet the NHS activity target, and short hard efforts are one way to do it if your health allows.

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Sources

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