balls of feet
balls of the/(one's) feet
The bottom part at the front of the feet that the toes connect to. For this dance move, you'll need to stand on the balls of your feet. When you're running, pay close attention to where the balls of the feet strike the ground.
balls of one's feet
the bottom part of the feet just behind the toes. Mary got blisters on the balls of her feet from playing tennis. The dancer balanced on the balls of his feet.