This exercise is a variation on toe raises and a pre-curser to the jumping exercises.
Perform this exercise without your vest. Begin on the floor in a standing position with your feet about shoulder width apart. Using a chair for balance as needed, lift both heels off the floor so that you’re standing on your toes and the balls of your feet.
Instead of slowly lowering your heels to the floor as you did with the toe raises, let your heels drop quickly to the floor.
This can feel quite jarring so we recommend that you do a few practice heel drops where you only raise part way up on your toes and drop down more gently. Slowly increase the height of your toe raises and adjust the speed of your heel drops until you are able to raise all the way up on your toes and drop down quickly to your heels.