HOW: Start in a side plank position on your knees. Next perform a clamshell exercise with your top leg. This is the starting position. Slowly close the clamshell while at the same time lowering your hips to the ground behind you. You can reach your top arm out at the same time.
FEEL: Drive your bottom knee into the ground to raise your hips. You should feel your glutes, sore, and shoulder all working.
COMPENSATION: None. Make sure you have strong enough shoulders to perform this variation of the plank first.