Stand up straight facing a high, supportive surface.
Place your hands onto the surface and transfer your weight onto the leg you would like to exercise.
Your other leg can hover away from your stance leg.
Using your arms to assist the movement, rise up onto the ball of your foot.
Your heel should come away from the floor.
You can vary how much or how little your leg does by increasing or decreasing the support of your arms.
Control the movement as you lower back down, and repeat.