Any HIIT (high-intensity interval training) session has major fat-burning benefits, but a 4x4 workout is tops for improving fitness, per a new study in Medicine and Science in Sports and Exercise.

Tackle this treadmill workout three times a week for the next six weeks to up your cardiorespiratory fitness. Not a fan of the dreadmill? Study author Fredrik Hjulstad Baekkerud says any cardio exercise that uses large muscles (think biking or even burpees) should work, too.

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Get started with this 4x4 HIIT workout:


Looking for more fun ways to get fit? Here's a 10-minute HIIT workout that you can do anywhere.