Get in push-up position. Imagine that your body is above a ladder with your hands on the outsides of it and your feet at the bottom. Keep your hands flat on the floor, brace your core and jump the feet forward about 1 foot, as if you were jumping them into the first box of the ladder. Return to start. Jump the feet forward about 2 feet, as if into the second box of the ladder. Return to start. Now jump the feet close to the hands, as if into the third box of the ladder. Jump the feet back to start. Continue, cycling through the three boxes.