This exercise challenges the stability of the shoulder girdle into the core while moving the pelvis and lower spine to activate the oblique muscles around the the myofascial ring of the core. Rolling down as done against the wall in the previous exercise but without the wall and move into a plank. In Pilates, this exercise is known as the Pushup. Hold the plank and alternate reaching one heel back which lengthens the same side waist. The opposite side is contracted hiking the hip upward. The range will be determined by your attention paid to the lower ribcage. The lower ribcage does not shift or translate from side to side. If you feel inclined, throw in a few pushups!