Feel like you just don’t have much time to exercise? That's no excuse. In fact, high-intensity interval training, or HIIT, makes it easy to squeeze in fitness even when you're short on time. Or perhaps the better word is efficient, since the whole point of HIIT is upping the intensity to get the biggest benefits. You push yourself from one burst of exercise to the next, followed by short rest periods. Several studies have concluded that HIIT workouts help you burn fat and tone muscles effectively. Other research suggests HIIT can often be better than moderate exercise at maximizing your overall health and reducing the risk of disease.