New research, appearing in the Journal of Physiology, suggests that short bursts of intense, physical activity may reduce the growth of colorectal tumor cells.
two men exercising
Could short bursts of high-intensity exercise immediately reduce the growth of colorectal cancer cells?

According to the American Cancer Society, doctors will diagnose more than 100,000 new cases of colon cancer and in excess of 44,000 cases of rectal cancer in 2019.

Colorectal cancer may also cause over 50,000 deaths this year, researchers predict. Treatment options for colorectal cancer vary from localized therapies to systemic, drug-based treatments.

However, new research suggests there is an additional factor that may contribute to reducing colorectal cancer growth and improving patient outcomes: high-intensity exercise.

James Devin, from the School of Human Movement and Nutrition Sciences at The University of Queensland in Brisbane, Australia, is the lead author of a team of scientists who set out to investigate the effects of a short burst of exercise on colon cancer cells.

As Devin and colleagues explain, previous research has pointed out that repeatedly exercising over a long period of time may help fight off cancer, but the new study suggests that even short bursts may have a similarly positive effect.

Additionally, while some studies have found associations between exercise and “significant reductions in colorectal cancer mortality,” the mechanism behind this potentially therapeutic effect of exercise remains unclear.

High-intensity exercise has immediate effects

To elucidate these mechanisms, Devin and team recruited individuals with colorectal cancer and asked them to complete either an acute session of high-intensity interval training (HIIT) or 12 sessions of HIIT over a 4-week period.

HIIT is a training method that aims to make the person who exercises do more physical work at a high intensity, during a single session, by “alternating high-intensity exercise intervals with low-intensity exercise or rest intervals.”

In the acute session group, the researchers collected blood serum samples from the participants at baseline, immediately after finishing the HIIT session, and 120 minutes after the workout. In the 4-week group, the scientists collected and analyzed blood serum before the intervention and 4 weeks after.

The “[s]erum obtained immediately following [HIIT], but not 120 minutes post‐[HIIT], significantly reduced colon cancer cell number,” report the researchers.

Specifically, the scientists found “significant increases” in certain cytokines — that is, in signaling proteins that help modulate the body’s immune and inflammatory responses. These cytokines were interleukin‐6, interleukin‐8, and the tumor necrosis factor‐alpha.

“The acute effects of [HIIT] and the cytokine flux may be important mediators of reducing colon cancer cell progression,” the researchers conclude, adding, “Repetitive exposure to these acute effects may contribute to the relationship between exercise and improved colorectal cancer survival.”

Devin further comments on the findings, saying, “After an acute bout of HIIT there were specific increases in inflammation immediately after exercise, which are hypothesized to be involved in reducing the number of cancer cells.”

“This suggests that a physically active lifestyle may be important in tackling human colorectal tumors,” the lead author adds.

We have shown that exercise may play a role in inhibiting the growth of colon cancer cells.”

James Devin

However, the researchers caution that the method they used to study colon cancer in the lab differs vastly from how these cells grow in the human body. So, they need to do more research to explore the effects of HIIT on human colorectal tumors.

Devin says, “We would now like to look at how these changes in growth occur and understand the mechanisms by which biomarkers in the blood can impact cell growth.”