Punching bags are useful training tools for boxers, kickboxers and martial artists. Using a punching bag can have a significant cardiovascular benefit, so individuals interested in general fitness might benefit from a bag as well. But punching bags aren't a one-size-fits-all piece of equipment. Whether you are buying a bag or just planning to use one at a gym, there are several aspects of punching bags that should be compared before making your decision.
There are two primary mounting methods that punching bags use: chain mounting from above and base mounting from below. Chain mounting can be done using either a punching bag frame or a mounting point secured in the ceiling so that the bag hangs down from its mount, and base mounting uses a solid base that enters the bottom of the bag to support it from below. Chain-mounted bags typically move more when punched or kicked but aren't as easy to transport or set up as base-mounted bags. Chain-mounted bags are usually mounted higher than base-mounted bags as well, making chain-mounted bags good for boxing practice and high strikes, and base-mounted bags might be better for kickboxing practice and low strikes.
There are a number of options available when comparing the shells of different punching bags. Leather, nylon, canvas and vinyl are the most common shell materials, though synthetic leather and polycanvas options also are available. Leather shells are more durable than some other options but are also more expensive and require occasional maintenance to keep the leather moist and prevent cracking. Nylon, vinyl and other synthetics might not be quite as durable but cost less and don't require the same maintenance. Canvas shells are durable and economical but have a rougher surface that is not recommended for those training without gloves or other protective padding.
There are three distinct filling types that punching bags use. So-called "hard fill" bags use shredded natural or synthetic fiber to fill the bag inside of a one-inch thick foam liner; the liner provides minimal cushioning so that the bag will offer a large amount of resistance and very little give when you strike it. "Soft fill" bags use the same shredded fiber but encase it in a two-inch foam liner so that the bag has more padding and offers slightly more give when you make contact. Water bags feature a liquid-filled bladder inside of the bag's liner, allowing the bags to have a lot more give than fiber-filled bags while providing you with additional resistance.
The weight of a punching bag determines how much resistance the bag provides and affects when and how the bag begins to sway and move as you punch it. The more weight a bag has, the more resistance it will offer when you make contact with it. But a greater amount of impact will be placed on your joints, hands and feet. Lighter bags don't offer as much resistance but are lower-impact and move more when struck, so you can generally achieve a more aerobic workout.
When considering a punching bag's size, you should look at not only its length but also its circumference. For standard punching bags, the size will depend at least somewhat on the weight, but alternative punching bag designs such as bags with a speed bag-like design that is short but thick are available in different weight amounts as well. Take your available space into consideration when choosing a size and be aware that both you and the bag might need to be able to move in several directions during a workout once the bag starts swinging.
If you are buying a punching bag, you need to consider whether any additional materials will be needed before you can use it. If you purchased a chain-mounted bag you might need chains and mounting equipment if they weren't provided with the bag or if you don't plan on using a mounting frame. Some bag kits require you to fill the bag yourself, either with provided shredded fiber or with materials that you supply or purchase separately. You might need moisturizer for leather shells or additional hand or foot protection for canvas shells.