Begin in an elbow plank with elbows directly under shoulders, abs engaged toward the spine. Don't let the pelvis sag down or pop up.
Lift your left leg off the ground, bending your knee so the sole of your foot is toward the ceiling. Keep your pelvis square to the floor. Don't let your pelvis twist.
Lift your left heel toward the ceiling as high as you can without moving your pelvis or lower back. The motion will not be huge but rather concentrated on the booty and hamstring. Then lower the knee slightly to complete one rep.
Do as many kicks as you can for 15 seconds on this side, then do another 15 seconds on the other side.