 Numerous studies have shown that the vast majority of patients experience cancer-related fatigue CRF during cancer treatments. Research by our group showed that 71 percent of 84 prostate cancer patients reported CRF during radiation. Unlike fatigue caused by overexertion, CRF is a pervasive, whole-body experience that is not alleviated by rest or sleep and often lingers long after completing standard treatments like radiation therapy. It has a detrimental effect on patients quality of life and can interfere with completion of prescribed treatment regimens. In addition, lasting fatigue for many patients impedes the resumption of normal life following treatments. Unfortunately, effective, well-accepted treatments for CRF are lacking. Although some research suggests that exercise may be a promising intervention for reducing CRF, physicians are still hesitant to prescribe exercise for fatigued patients, and, in fact, often encourage them to rest and conserve energy, which may be in exact opposition to what is needed. 