Sit with your feet slightly wider than shoulder-width apart and with an upright posture.
Hold light dumbbells (or weights of your choice) up at your chin in a "fighting position."
Without locking your elbow, extend your left arm forward to throw a punch, and rotate your hand so that the palm is facing downward at the end of the movement. Bring your hand back toward your face.
Punch with your right arm, then bring your hand back toward your face.
This counts as two reps.
Repeat for a total of 20 punches (10 on each arm).
Rest for 30 seconds, then repeat this four-move circuit for one more round.
After round two, rest for 30 seconds before going into the cardio circuit.