Objective is to keep core tight during the entire motion of walking feet from back to front. When extending legs into plank, its important that legs, back and neck stay aligned to achieve the most from the exercise. Brace your core muscles by tightening midsection as you extend legs back.
Keep back upright and brace your midsection as you lean back and forth. Keep neck in line with your spine
Tighten and draw in your belly button as you bring your knee up, causing a “crunch” motion putting tension on your mid section