Core strength is super important for runners. This is your powerhouse. Whatever ab exercises you choose, make sure you are doing them correctly, or you could end up doing more damage than good. For women who have had a baby, it is very common to damage the recti muscles. A split actually occurs, called the diastasis recti. Before you start doing more advanced ab exercises like the plank, or seated v as in Pilates, test to make sure your transverse muscles are strong enough to actually perform these exercises. A good way to test the transverse is by performing a head lift: Lay on your back with knees bent. Exhale, bringing your belly button to your spine. Slightly tilt your pelvis to flatten your back to the floor. Tuck your chin, lift your head, and bring it back to the floor. If your abs move at all, your transverse is not quite strong enough. To strengthen your transverse, perform seated isometric abs. Simply tighten your abs bringing belly button to spine in a seated position and let it out slowly. These are awesome because you can do them anywhere anytime. Your body will thank you! Run happy!