Another surprisingly hard core exercise you should consider adding to your routine for strength is the dead bug.
- Lie on your back with a neutral spine and your hips and knees at right angles with your palms pressed into your thighs just above your knees.
- Pull your abs to your spine, keeping your ribs and pelvis still as you lengthen your right arm and leg out until they are almost parallel to the floor. Keep your torso and spine completely stable as the arm and leg move.
- Return to the starting position, and repeat on the left side to complete one rep.