Khloé Kardashian, who's 7 months pregnant, recently wrote an ode to an arm exercise she practiced before getting pregnant: push-ups on a Swiss ball.
If you've had a glance at Khloe's body lately you'd know she's a fit woman so her workouts are clearly working!
"Doing push-ups on an exercise ball totally changed my arms," she writes on her blog.
To try it, begin in a hands plank with your palms on the ball slightly wider than shoulder-width apart, and press your heels against a wall for stability. Keeping your body in a straight line, bend your elbows to lower your belly to the ball with momentum, and use the resulting bounce to help you extend your arms and return to a full plank. Continue without breaks — Khloé does 30 to 50 reps at a time, but you can start with sets of 8 to 10. "Your arms will feel like Jell-O when you're done".
It's why Crockford suggests first-timers slow things down — and, while you're at it, point your fingers toward the ground, and stick with a firm ball to protect your wrists.