The stability ball plank is a great core exercise to advance you from the plank exercise on the floor.
The ball plank strengthens and stabilizes your deep, foundational core muscles even more than the regular plank. Balancing on the ball while holding the plank position is not easy! Your deep, foundational core muscles are more important than your "six pack abs!"
1. Place your elbows on the ball and balance on your toes while keeping your body in a straight line.
2. Hold the plank position for a count of 5-10 seconds without moving. The ball will move, so it is a challenge to hold the right alignment. This will obviously improve your balance. Your abs and shoulders will also work much harder.
Keep your head in line with your torso and brace your torso (as if taking a punch to the gut).