When You Exercise May Matter During Cancer Treatment, Review Finds
Staying active during cancer treatment can be challenging, especially when fatigue and other side effects make your usual workouts feel out of reach.
But could getting active before treatment begins make a difference?
A new review of 26 clinical trials examined how exercise affects people with colorectal cancer at different stages of care, including when it may offer the greatest benefits.
About the review
Researchers analyzed 26 randomized controlled trials involving 1,731 people with colorectal cancer. In these trials, some participants followed structured exercise programs while others continued their usual routines without a prescribed exercise program.
Researchers compared their health outcomes to see how exercise frequency, intensity, and weekly activity levels influenced six areas, including fitness, body composition, physical function, cancer-related biomarkers, and quality of life.
They also looked at when participants exercised, comparing programs started before treatment (prehabilitation), during active treatment (such as chemotherapy), and after treatment (survivorship).
Exercise improved two key areas of fitness
Exercise was linked to significant improvements in cardiorespiratory fitness (how well the heart and lungs deliver oxygen during activity) and muscular fitness (muscles' ability to produce force).
Muscular fitness showed slightly greater improvements.
The strongest results were associated with programs involving at least 1,400 MET-minutes per week (a measure of activity that accounts for intensity and duration), sessions of 250 MET-minutes or less, and five to seven sessions per week. Supervised programs also tended to outperform unsupervised ones.
Timing made a difference, too.
Prehabilitation produced the strongest overall benefits, followed by exercise during survivorship. Programs during active treatment showed the weakest effects.
RELATED READ: Is This The Best Supplement For Energy?
Why exercise timing matters during cancer care
Treatment side effects may help explain this difference. Chemotherapy and other therapies can cause fatigue and reduce physical capacity, making it harder to exercise consistently and for the body to adapt to training.
Benefits during active treatment also dipped between weeks eight and 20, before increasing again between weeks 20 and 24. Researchers suggest this could reflect participants finishing primary treatment or adjusting to its side effects.
Exercise intensity and volume also mattered differently depending on the treatment stage. Before treatment, higher weekly activity volumes (more than 1,300 MET-minutes) and six to seven sessions per week were associated with better outcomes.
During active treatment, however, increasing intensity, frequency, or total volume didn't provide additional benefits.
In short, pushing harder isn't necessarily better when your body is already managing the demands of treatment.
How to approach exercise at each stage
Your exercise routine should account for your treatment, fitness level, and symptoms. Here's how the findings could inform a conversation with your oncology team:
- Before treatment: If your care team approves, consider starting an individualized exercise program early. This may be the best window to build fitness, with more frequent sessions and higher activity volumes when appropriate for your abilities.
- During treatment: Let your symptoms guide your activity. Reduce exercise intensity and volume when side effects peak, then gradually build back up as you recover. An oncology-trained exercise specialist can help you adjust your routine safely.
- During survivorship: Continuing to exercise can help rebuild and maintain fitness. Gradually increase the challenge as your strength and energy return, with guidance from your care team.
The takeaway
Think of exercise as something to adapt alongside cancer treatment, not another box to tick.
Getting a head start before treatment may pay off, but knowing when to ease up is just as important as knowing when to push.
