Super-efficient HIIT is the ideal workout for a busy schedule—whether you want to squeeze in a workout during your lunch break or to get in shape for a fast-approaching event. Research shows you can achieve more progress in a mere 15 minutes of interval training (done three times a week) than the girl jogging on the treadmill for an hour. (Watch and try this video of a 10-minute fat-blasting cardio routine that burns more calories than a half hour on the treadmill!) And according to a 2011 study presented at the American College of Sports Medicine Annual Meeting, just 2 weeks of high-intensity intervals improves your aerobic capacity as much as 6 to 8 weeks of endurance training.
That's not even the best part! Using the Tabata training method, you can complete an effective HIIT workout in just 4 minutes.