A fitness and fighting practice accessory, the punching bag has been used for these purposes for a long time. A functionally simple design and build allow for it to be available at many price points. Proving wider access to people.
A fitness accessory that has been used since ancient times, the exact date isn't known but punching bags have been present for the entire written military history. Today used by most athletes, or average people to let off steam regularly. There are a few different types of punching bags, designed for either speed and hand-eye coordination or for developing a heavy blow. The insides are also filled with different materials depending on what the expectant result is from training with one.
Build of a punching bag
Constructed of various materials from different types of plastic-based cloth to leather and faux-leather. The filling inside can be seeds, sand or rags. Sometimes there is a mix to achieve a balance that works for the person training. Also, the materials affect weight which in turn change how the person interacts with the bag and how much they are able to move it. Some hang from the roof or are hung off a bracket that is fixed to a wall, other types come with a metal stand so can be moved around or placed in a more open space. The construction should be tough enough to take repeated blows and not fall apart and at the same time not harm the person punching it.
Cautions while punching one
Even generally while punching it one should cover their hands with cloth wraps or wear gloves as there are many chances of damaging your hands, from skin tears due to friction to the more serious 'Boxer's Fracture'. Wrist sprain and strain is also common, along with bone plate damage. It is advisable to get some basic training and starting slow before going at a punching bag all out. Even kicking wrong can damage the shin or ankle.
Depending on what your goal is you can pick a punching bag that works specifically for you and is within your budget. The most commonly known brand with punching bags and other boxing equipment is Everlast, immortalised by Muhammad Ali!