Point one arm out straight in front and extend the opposite leg behind you, forming a straight line from your extended hand to the extended foot. Keep your hips squared to the ground. If your low back begins to sag, raise your leg only as high as you can while keeping the back straight. Hold for a few seconds, then return to your hands and knees. Keep your abs engaged throughout the entire exercise and work to minimize any extra motion in your hips during the weight shift. Switch to the other side.