Workouts first thing in the morning or last thing at night could be most effective for staving off cancer, research suggests.
Those who were more active at the start or end of the day had the lowest chances of developing bowel cancer, a study found.
Experts say the findings suggest there are peak times for physical activity which could be used to design targeted cancer prevention strategies.
Researchers used data from the UK Biobank to assess 86,252 people aged 42 to 79, who tracked physical activity by wearing a device on their wrist known as an accelerometer.
They highlighted four activity patterns; continuous day-long activity, activity late in the day, activity in the morning and evening, and activity at midday and at night.
During the 5 year follow-up, 529 people were diagnosed with bowel cancer.
Two daily peaks in activity – at around 8am and 6pm – were ‘associated with reduced colorectal cancer risk, beyond the benefits of overall physical activity’.
Those who exercised at these time slashed their chances of getting it by 11 per cent, compared with those similarly active during other parts of the day.
Lead investigator, Professor Dr Michael Leitzmann, of the University of Regensburg in Germany, said: ‘Our study highlights that not only is physical activity important for reducing colorectal cancer risk, but the timing of peak activity throughout the day could play a crucial role.
‘By identifying specific times – early morning and late day – when physical activity is most beneficial, our findings open new avenues for targeted prevention strategies.
‘If confirmed by future research, this could provide a simple yet impactful way for individuals to further reduce their cancer risk through the timing of their exercise.’
Bowel cancer is the fourth most common cancer in the UK, with an estimated 44,000 people each year diagnosed with the disease.
Between the early 1990s and 2018, the number of adults aged 25 to 49 being diagnosed with bowel cancer increased by a fifth (22 per cent) in the UK.
Dr Helen Croker, assistant director of research and policy at the World Cancer Research Fund, which funded the study published in BMC Medicine, said it was further evidence exercise was one of the best forms of prevention.
She said: ‘Being physically active is one of our cancer prevention recommendations, and we know that this cuts cancer risk.
‘These intriguing new findings offer potential for developing more specific recommendations, including patterns and timing of physical activity, for reducing cancer risk.’