In this video, Matt Numrich of the Elite Defense Systems show you how to do a one-legged and two-legged hamstring curls using a swiss ball. This exercise targets balance, coordination and strength. The initial position involves raising your rear and alternatively having one leg up while using the other leg to push and pull the swiss ball. Shoot for 10-12 repetitions. But if you find the one-legged too difficult, you can start with both your legs pulling and pushing on the swiss ball.