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.
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.