BIOHIIT - BIOfeedback High Intensity Interval Training - 5 DVD Workout Complete 5 DVD Workout Program will help you get the results you're looking for. Workout with Personal Trainer David Norton at your own pace and at your own level. Reduce Cortisol, Lose Fat and Build Lean Muscle using scientific heart rate based interval training. Workouts adapt to your current and future fitness level using biofeedback (heart rate) to ensure you're always working out at the appropriate level.