PIYO Plank- core stengthening move

One of my favorite PIYO moves. Works on core strength- PIYO Plank. You start in plank position on elbows. Keep core tight and feet together- You should maintain a straight line from your toes to the crown of your head. From plank position you will pull back into a downward dog position - hold and then back to plank. Maintain a tight core. Your arms should line up under your shoulders.