The plank up will work the deep abdominal muscles and the explosive strength in the forearms, triceps, and chest muscles. This movement is very advanced and takes a good amount of strength to complete.
To begin this movement, get into a plank position with your forearms braced on the ground. Once you are in position, drive your forearms into the ground to lift your arms off the ground to land in the top position of a push-up. One at a time, reset your forearms gently back onto the ground and restart the movement.