Kneel on a pad or folded mat, gripping the wheel's handles with your arms extended and the wheel on the floor in front of your knees. Brace your stomach hard before you move, then roll the wheel forward, letting your body extend out into as long a line as you can control. The further out you roll, the harder it is to keep your hips from sagging toward the floor; stop before that happens and pull back to the start using your abs, not by yanking with your arms or your lower back. Keep your hips tucked slightly under throughout rather than letting your back arch.