Fatigue mediates the relationship between physical fitness and quality of life in cancer survivors.

In a study just published in the Journal of Science and Medicine in Sports, with Dr. Laurien Buffart as first author, we aimed to investigate whether fatigue mediates the association between physical fitness and quality of life in cancer survivors, i.e. to explore if cancer patients who are physically more fit have higher quality of life because of reduced fatigue .
We used data from an intervention study. The intervention was an 18-week exercise program for cancer patients consisting of high-intensity resistance and interval training. We assessed physical fitness - peak oxygen uptake and peak power output - self-reported fatigue and quality of life. 
We found significant associations between changes in physical fitness and global quality of life, between physical fitness and fatigue, and between fatigue and global quality of life. General fatigue strongly mediated the positive association between physical fitness and quality of life; our analyses further indicated that physical aspects of fatigue were stronger mediators than mental aspects.