High-Intensity Interval Training, or HIIT, is a research-backed training system that alternates between high-intensity efforts and periods of rest. HIIT is by far my favorite type of workout due to all the benefits it brings. The system burns more calories in a shorter period of time than traditional, longer duration, steady-state training programs. Just 15 minutes of HIIT can burn more calories than jogging steadily on a treadmill for an hour. Plus, this training method will maximize your calorie burn even when the workout is over! HIIT is not only great for your heart, but research has been shown that HIIT workouts favor fat metabolism, while allowing your body to produce lean muscle mass. In other words, you burn fat while building muscle!