Planks are a mainstay because they’re so effective: They tax your core and the smaller stabilizing muscles in your hips and shoulders. That there are so many variations on the move is, in large part, because planks are so tedious.
Enter the alligator crawl. It’s unusual in that it’s an active—rather than stationary— plank variation, so there’s no watching the seconds tick by on the wall clock. “This exercise adds work for major shoulder muscles that regular planks don’t hit,” says Matt Pudvah, the head strength coach of the Sports Performance Institute at the Manchester Athletic Club in Manchester-by-the-Sea, Mass. “And it teaches your limbs and core to work better together as you fight to stay tense.”
Start in a high plank wearing socks on a slick floor, or with toes on sliders as shown below, and walk hands forward while maintaining a perfectly straight line between head and feet. Adding in the forward motion forces your abs and glutes to work harder to keep your body in line, while the deltoid muscles at the top of the shoulder get some extra attention, too. Resist the urge to sway your hips as you go—that’s a red flag for a loose core. Your feet should drag in a straight line, not wriggle back and forth. Start with three sets of 20 steps before increasing difficulty or reps. When you’re ready to add intensity, try the alligator crawl in reverse (it’s a challenge not to fall on your chest), or intersperse some pushups as you go. Now snap to it.