Most people turn this into a leg swing, using momentum to fling their knees toward their chest and back. That skips the muscle you're after. Lie on your back, hands by your sides or tucked under your lower back for support, knees bent at 90 degrees. Curl your hips off the floor by pulling your knees up and in toward your ribs, using your lower abs rather than swinging your legs to get there. Lower slowly until your feet just touch down, then go again without letting your lower back arch off the floor.

PLANS THAT USE IT 4

Upper Body (No Equipment)2× / week · beginner

Core & Mobility — Movement Foundations3× / week · beginner

Upper / Lower ×3 + Arms — 7-Day7× / week · advanced

Bro Split — 7-Day Daily Body Part7× / week · intermediate