This exercise will activate each glute muscle independently, improve your balance and core strength. You can also balance on a chair or another stable surface.

Using an exercise ball, bend over and balance your upper body over the ball.
Slowly lift your leg up and back so that it is parallel to the ground, hold for a moment and then return your leg to start position.
Repeat lifting your leg up and down, holding the ball steady.
Do 8 to 10 repetitions on both legs.