In this clinical trial, the authors attempt to answer the question of whether a high-intensity interval training program can improve cardiorespiratory fitness and delay the biochemical progression of prostate cancer in patients who are undergoing active surveillance. One group was asked to complete 12 weeks of thrice-weekly, supervised aerobic sessions on a treadmill at 85% to 95% of peak oxygen consumption (V̇o2). The usual care group maintained their normal exercise levels.