The popular image of a boxer or other fight sport athlete includes someone who has set of ripped and visible abdominal muscles. Much of that comes from the weight loss practices inherent in combat sports coupled with hours upon hours of cardiovascular training and attention to diet. However, punching bag workouts do engage your abdominal muscles and can help you build a flat stomach with defined muscles.
The Right Bag
If your goal is getting the kind of workout that will help you with your abs, you should avoid working out with a speed bag. That piece of equipment is great for building technique and rhythm, but doesn't tax the body. To work your abs, you'll want a heavy bag -- the large, cylindrical punching bag. A 60 to 80 pound bag is appropriate for most people. Lighter bags swing too much, and heavier bags can put you at risk of injury.
The Right Technique
Properly thrown punches aren't just a matter of swinging your arms. It also involves the very way you stand. Assume the correct stance by standing on an angle; so you're presenting your left shoulder to the bag. Then stand with your left foot at the front and your back, or right foot, about shoulder-width behind the left foot. From this stance, you push your hands forward with motion from your entire body. Push off with your legs, and swing your body from the waist. This technique not only strikes harder, but directly engages the muscles in your abdomen, which will help sculpt and tone the muscles in that area.
Building muscle is only part of the story when it comes to building flat and attractive abs. You also need to burn enough calories to lose the layer of fat on your belly. According to weight loss resource website Nutristrategy.com, an hour of work on a heavy bag will burn over 400 calories in a 155-pound person. This assumes a planned workout alternating between punching drills and rest periods -- in other words, not just fiddling around on the bag.
Your bag work alone isn't likely to produce swimsuit-model abs. Just as combat athletes supplement their bag work with training drills, lifting weights and road work, your ab-building efforts should include support outside of your bag drill. The punching bag workout will certainly help your efforts, but you'll get best results if you combine it with regular cardiovascular training and a healthy diet. Commit to exercising aerobically at a moderately-intense to vigorous intensity at least five to seven days a week for 150 to 300 or 75 to 150 minutes respectively. Eat a healthy, well-balanced diet that includes lean protein and healthy fats along with fresh foods and whole-grain products.