Power jacks

Instructions

Stand up, feet together, back straight, arms pointed toward the floor and head facing forward.
Lower your butt as if you are sitting on a chair (squat).
Move back up explosively and make a small jump.
Land by spreading your legs apart and bending your knees, arms above your head.
Lower your butt like for the first squat.
Move back up explosively and make a small jump.
Land with your feet together, bending your knees, arms pointed toward the floor and repeat.

Muscles