This is a whole body exercise that also has the added benefits of being able to push your body's aerobic performance (if you do it fast enough) and increase stamina (if you do it long enough). As a matter of fact you could spend an hour doing just this, to different tempos and it's all the workout you would need.
What's involved: Quads, lower back, shoulders, triceps, calves, lower abs, biceps, cardiovascular system, aerobic performance (VO2 Max).
Powered by: Like all punches the power comes from the legs and hips.
Tip: The classic mistake in this exercise is to duck using your lower back. Duck using your legs, instead and keep your trunk upright and eyes focused on your target. This minimizes the risk of pulling a muscle in your lower back (which can happen when your muscles get tired) and it gives you greater control over the movement.