Your core deserves your focused effort. 

After all, a lean, tight midsection does so much more than look good shirtless. It prevents back injuries, increases athleticism, boosts strength from head to toe, improves posture, and screams to the world that you’re healthy and fit. 

Related: THE 21-DAY METASHRED From Men’s Health—an At-Home Body-Shredding Program That Strips Away Fat and Reveals Rock-Hard Muscle

(Get fitter faster with an activity or health tracker. Head to Best Buy to find the one that fits your needs and goals.)

The best part: This critical muscle group only requires 15 minutes of your time. That is, if you do The Climb and Crunch from Men’s Health Fitness Director BJ Gaddour shown in the video above. 

The abs workout consists of only two bodyweight exercises—the 3-way jumping mountain climber and the cross crunch—but it hits the more than two dozen muscles between your shoulders and your hips. It’s one of the best ways to strengthen, flatten, and blast your core anytime, anywhere.