Stand tall with your back straight, abs engaged, shoulders relaxed, arms at your sides, elbows bent and feet spaced wider than your hips. Make fists with your hands and bring your hands up in front of your chin as if in "defense."
Breathe deeply and keep both feet on the floor at all times as you punch your right arm (in line with the shoulder) across the midline of your body (toward the left), while pivoting toward the left on the ball of your right foot. Pull your arm back in to the starting position, returning to face the front. Repeat on this arm OR alternate arms with each punch (not pictured). After several repetitions with this arm, switch sides.
Every punch should have two phases: the punch itself and the retraction, where you pull the arm back in with as much effort as you took to punch it across your body. Punch in line with your shoulder, crossing the midline of the body. Try to remain relaxed in your shoulders. Punch with greater force and/or speed to increase your overall intensity.