The relationship between physical activity and cancer risk has been a subject of extensive research. While regular exercise is widely recognized for its health benefits, recent studies have raised questions about the potential risks associated with extreme forms of exercise, such as long-distance running. This report examines the findings of recent studies on the link between running and cancer, particularly focusing on colorectal cancer.

Overview of Research Findings

Long-Distance Running and Colorectal Cancer

A notable study conducted by oncologists at the Inova Schar Cancer Institute investigated the potential link between marathon running and colorectal cancer risk. The study involved a sample of 100 endurance athletes aged 35 to 50, all of whom had completed multiple marathons or ultramarathons. Key findings from the study include:

• Increased Risk of Advanced Adenomas: The study revealed that 15% of the runners had advanced adenomas, a type of polyp that can develop into colorectal cancer. This rate is significantly higher than the expected 1.2% in the general population of the same age group (Inova Schar Cancer Institute, 2025).
• Mechanisms of Risk: Researchers hypothesize that the intense physical strain associated with long-distance running may lead to reduced blood flow to the intestines, resulting in cellular damage and chronic inflammation, which could contribute to an increased cancer risk (Inova Schar Cancer Institute, 2025).

This study was presented at the American Society of Clinical Oncology conference and is pending formal peer review, indicating that further validation is necessary.

General Benefits of Physical Activity

Despite the concerning findings regarding extreme running, numerous studies have established that regular physical activity is associated with a lower risk of various cancers. Some key points include:

• Breast Cancer: Physically active women have been shown to have a 12-21% lower risk of breast cancer compared to their less active counterparts (World Health Organization, 2023).
• Colorectal Cancer: Regular exercise is linked to improved digestion and reduced inflammation, both of which are protective factors against colon cancer (American Cancer Society, 2023).
• Bladder Cancer: A meta-analysis indicated that individuals with higher levels of physical activity had a 15% lower risk of bladder cancer (National Cancer Institute, 2023).

Conclusion

The emerging evidence regarding the potential risks of long-distance running, particularly concerning colorectal cancer, highlights the complexity of exercise’s effects on health. While regular physical activity is generally beneficial for cancer prevention, moderation may be key, especially for extreme forms of exercise. It is essential for avid runners to balance their training with proper recovery and regular health screenings.

References

• Inova Schar Cancer Institute. (2025). Study on Marathon Running and Colorectal Cancer Risk. [Link to study if available]
• World Health Organization. (2023). Physical Activity and Cancer Prevention. [Link to report if available]
• American Cancer Society. (2023). Exercise and Cancer Risk. [Link to report if available]
• National Cancer Institute. (2023). Physical Activity and Cancer. [Link to report if available]

This report synthesizes current findings and emphasizes the need for further research to understand the implications of extreme exercise on cancer risk.