A punching bag (or, British English, punchbag) is a sturdy bag designed to be repeatedly punched. A punching bag is usually cylindrical, and filled with various materials of suitable hardness. History Punching bags have been used in martial arts and swordplay for the entire written history of military training. Similar apparatus in Asian martial arts include the Okinawan makiwara and the Chinese mook jong, which may have padded striking surfaces attached to them. In martial arts and combat sports—such as karate, sanda, taekwondo, and Muay Thai—"heavy" bags, standing bags, and similar apparatuses have been adapted for practicing kicking and other striking maneuvers in addition to developing punching technique. Construction Punching bags are often filled with grains, sand, rags, or other material, and are usually hung from the ceiling or affixed to a stand. Other bags have an internal bladder to allow them to be filled with air or water. The design of a punching bag allows it to take repeated and constant physical abuse without breaking. The bag must also absorb the impact of blows without causing harm to the user. Types There are different types of punching bags, with different names based on their size, use and mounting method. Almost all punching bags are covered with either leather or synthetic materials such as vinyl which resist abrasion and mildew. Canvas can also be used as a bag material where there is lower use and humidity. Speed bags (AKA, speedballs) are small, air-filled bags anchored at the top to a rebound platform parallel to the ground. Speed bags help a fighter learn to keep their hands up, improve hand-eye coordination, and learn to shift weight between feet when punching. They are also known as speedballs or speed ball bags. They are generally filled with air and fitted around a tight PU-based or leather material. They come in various sizes, ranging from the large 13×10″ (33×25 cm) and 12×9″, midsize 11×8″, 10×7″ (25×18 cm) and 9×6″, to the small 8×5″, 7×4″ and 6×4″ (15×10 cm). Generally the larger the bag, the slower it is and the more force is required to keep it going. Large bags are used more for building strength and endurance, while smaller bags allow the training athlete to focus on faster hand speed, timing and coordination. Beginners might view this bag more as a "control bag", not a speed bag, for they will not be able to