Prone Quad Stretch

Lie face down and bend one knee, reaching back to grab that ankle or foot and pulling your heel toward your glute. Keep your hips pressed into the floor rather than letting the one on the stretching side lift up, which is what actually isolates the stretch through your quad instead of your hip flexor. Your other leg stays long and relaxed. Lying face down removes balance from the equation entirely and lets gravity help keep your hips square, which makes this the easiest version to actually relax into rather than fight.