Be Warned: This Trainer's Favourite Exercise Ball Move Will Take Your Abs Prisoner

• Start in a plank position with your hands directly under your shoulders and your toes on the ball. Do not allow your lower back to arch. Keep your feet, pelvis, and shoulders in one long line.
• On an exhale, pull your abs deeply to your spine to fold your body in half, pulling the ball forward toward your hands as your pelvis and butt move upward in the air.
• This is a pike position. Allow your head to fall between your arms, keeping your neck long and in line with your spine.
• Lower yourself back into a plank position, keeping your core engaged. Then, push yourself back so your feet are going toward the wall behind you into an extended plank (or push-up position). You can allow the ball to roll onto your shins here.
• Roll forward to your starting plank position with your toes on the ball. This completes one rep.

The more that your legs are on the ball, the closer your hands end up being to it as well and the easier the rollback will be, Paul said. "Having just your feet on the ball will make it much more difficult."

Note: the variation seen here moves straight through your plank positions without stopping, which is another way to add intensity.