Summary: Whitney Neal
Source Article: Buffart, L. M., De Backer, I. C., Schep, G., Vreugdenhil, A., Brug, J., & Chinapaw, M. J. (2013). Fatigue mediates the relationship between physical fitness and quality of life in cancer survivors. Journal of Science and Medicine in Sport, 16(2), 99-104.
Cancer and its treatments (e.g., surgery, radiation therapy, and chemotherapy) often produce significant morbidities that undermine the quality of life of cancer survivors both during and after treatment. Psychosocial and physical symptoms include depression, anxiety, fatigue and decreased physical fitness. Of these, fatigue has been found to be one of the most common symptoms of cancer patients and has a very profound effect on quality of life. Previous research has shown that physical exercise may reduce fatigue, but more insight into how exercise improves quality of life is necessary in order to better inform future exercise-based rehabilitation for cancer survivors. In this study, the relationship between fatigue and physical fitness was examined. The goal was to see if fatigue mediates the association between physical fitness and overall quality of life.
An uncontrolled clinical trial was conducted with a pre-post-test design at a medical center in the Netherlands. Patients who had previously completed chemotherapy treatment for various types of cancer were enrolled in an 18-week exercise program consisting of high-intensity exercise combined with interval training. In total, 119 patients completed the program and provided complete data. Measures of body composition, physical fitness, fatigue, and health-related quality of life were assessed both before and after the 18-week program.
At post-intervention, significant improvements were found for physical fitness, fatigue and health related quality of life compared with pre-intervention except for mental fatigue and pain, which remained unchanged. More specifically, general and physical fatigue, as well as reduced activity and motivation, mediated the positive association between maximum power output and overall quality of life.
However, there were a couple of limitations to this study. First, because the study was not a randomized controlled trial and therefore lacked a non-exercise control group, a true contributing pathway was not established. It is possible that the reverse relation was also present in the study; patients may have improved quality of life over time, causing less feelings of fatigue and becoming more physically active as a result. The second limitation was related to drop-out data. Of the 227 patients who started the exercise program, 48 were unable to complete it due to cancer recurrence or other diseases, while another 60 people did not have complete data for unspecified reasons. This may have limited the power of the study slightly.
Taking into account the limitations mentioned above, this study provided valuable insight into the theory that fatigue mediates the association between physical fitness and overall quality of life. Future studies should address the limitations of this study in addition to looking at more parameters of physical fitness (e.g., aerobic fitness or muscle strength) with respect to fatigue reduction.