Stand in a staggered stance with one foot in front and your chest tall, fists up by your chin and your elbows against your ribs.
Rotate at your hips, and punch upward with one fist to meet the punching bag (as if you are making contact with someone's jaw), keeping your core tight.
Bring your fist back to the starting position.
Bending your knees and keeping your chest lifted, sit back into a squat like you're sitting into an imaginary chair. Press your weight back into your heels.
Push through your heels to bring yourself back to the starting position.
Repeat this same uppercut with the other arm, then do another squat.