Another way to make planks more challenging is to use a Stability Ball.

Be sure that you have mastered Abdominal Bracing and the basic plank before moving on to these more difficult moves!

Elbow Plank on the Ball

Start kneeling with the Ball in front of you. Clasp your hands together and roll out on your forearms until your elbows are on the ball.   If you feel stable enough, go ahead and lift you knees off the floor so that you are perched on your toes. Hold this position for 5-10 seconds, then put knees back on floor, roll back in, rest, repeat!