John Knudson had never been very interested in regular exercise. "I played a little soccer and did a little cross-country skiing, but I never did enough in between to be in very good shape," he said.

But after undergoing a routine colonoscopy, Knudson's doctor told him about a Fred Hutchinson Cancer Research Center study called APPEAL (A Program Promoting Exercise and Active Lifestyles). The four-year study, led by Dr. Anne McTiernan of the Center's Public Health Sciences Division, examined why moderate to vigorous exercise apparently lowers the risk of developing colon polyps and colon cancer.

"It sounded interesting to me," Knudson said. "I have a family history of polyps. Plus the exercise program was a big attraction. It's hard to get out there and do it on your own on a regular basis."

APPEAL recruited healthy but sedentary men and women and randomly assigned them either to an exercise group or to a control group. The exercisers engaged in moderate to vigorous physical activity six days a week for one year. Those in the control group were asked to simply maintain their current activity level for a year.

As a member of the exercise group, Knudson used various exercise machines during supervised sessions, but he preferred to run whenever he could. "I just liked being outdoors and in the neighborhood," he said.

Participants underwent flexible sigmoidoscopies at the start and end of the program to examine the balance of cell growth and cell death in the lining of the colon. The goal was to determine how exercise affects this balance since too much growth and too little death can result in polyps and/or cancer.

While study findings have yet to be announced, Knudson already feels the benefits of his participation. "I feel great," he said. "I lost 10 pounds, and I gained fitness, strength and confidence."

Read more about Colorectal Cancer >

Learn more about how you can Join a Research Study >