Start: Place your hands in one square of the ladder. Push up into a plank and maintain a neutral spine. Make sure that your hands are stacked under your shoulder and not protruded out past your shoulder girdle.
Movement: move your leading hand over one square followed in tandem with your feet. Then drive one leg into your chest, extend it back out and tuck the next knee into your chest and then extend that knee back out, maintain plank position.
Return: Move your hand following hand next to your leading hand followed with a slight shuffle of the feet.