Stand up straight facing a wall or supportive surface.
Place a tennis ball between both heels.
Gently squeeze the ball together evenly with both heels.
While maintaining this squeeze, slowly rise up onto the balls of your feet.
Use the supporting surface to help you to balance.
Your knees should be straight.
Control the movement as you lower back to the starting position at the same steady speed and repeat.
Keep your knees straight throughout the movement.