Start on all fours with your hands under your shoulders and your knees under your hips.
Keep your right knee at a 90-degree angle and your foot flexed as you slowly raise your leg behind you until your thigh is almost parallel to the floor.
Pulse your right foot a few inches toward the ceiling by squeezing your glutes. Your back should remain still and your spine should be in a neutral position (not arching or rounding).
Lower your right leg without letting it touch the floor, then kick it out to the right side with control. Be sure to keep your foot flexed throughout the entire movement.
Lower your right leg to return to the starting position. That's one rep.