Start in a push-up position with your body in a straight line from head to heels. Squeeze your glute and raise one straight leg up behind you until it's level with your torso - no higher - hold for a moment, then lower it back down and raise the other. Your hips are the test: they stay square to the floor and dead level while the leg lifts, so the work lands in your glutes and core instead of your lower back.

Works: glutes, abs, lower back, shoulders

Breathing: Exhale as the leg raises, inhale as it lowers.

Common Mistakes: Kicking the leg above torso height and arching the lower back, letting the hips tilt toward the raised leg, and rushing the switches instead of pausing at the top.

Make Easier: Raise the leg only halfway, or drop to a forearm plank for a steadier base - or start with Plank Arm Raises.

Make Harder: Hold each raise for a slow three-count with the glute squeezed hard, or move on to Alt Arm / Leg Raises or Plank Rotations.