Last week for planks! This will be our most challenging plank exercise yet. It will require some balance but once you get the hang of it, it's a lot of fun and effective.
Plank to pike (on stability ball)
Start in plank position on the stability ball. Using abs and legs, lift your hips and keep your head down. Hold for a second and roll back out. Start with 5 reps to start and work your way up to 10 reps.