How To: Lying on your side, position your elbow directly below your shoulder and perpendicular to your body. Rest your upper leg directly on top of the lower leg. Straighten your legs out, no bend in the knee. Contract your abdominals. Keep a straight line from your head to your toes, meaning your hips should not be too low or too high. Repeat for the opposite side.
Beginner Version: Start with your knees resting on the ground/mat, keeping your knees bent and feet behind. Rest your upper knee directly on top of the lower knee and contract your abdominals.
Main Muscles: Obliques, Rectus Abdominus
Secondary Muscles: Erector Spinae, Adductors, Glutes