Over-under training sessions are structured interval workouts that alternate between specific effort peaks and valleys either side of an athlete’s functional threshold power (FTP). Exercising just above (over) FTP builds lactate, limiting performance. Reducing the intensity to just below (under) FTP conditions the body to process the lactate, even when the effort is still relatively high. Over-unders are an effective means of building FTP and simulating the sensations of racing.