Ball Leg Curl

Lie on your back with your arms outstretched for balance. Put your ankles on a balance ball and lift your hips high. Keep your body in a straight line by holding core tension. Pull your heels in toward your body, then push them back to the starting position. For more of a challenge, try using only one leg on the ball. Hold the other leg up out of the way.

Harder variation - one leg up	Start with the body flat.	Bring the legs in, keeping the hips up.
Continue to elevate the hips as the legs curl inward.