Punching bag is an overfed or magnified bag made of leather, canvas, etc., usually suspended so that it can be punched with the fists for exercise. These bags are usually sturdy as they are designed to be repeatedly punched, for use in exercise, physical training or stress relief.

Punching bags are either hung from the ceiling or affixed to a stand and are filled with various materials like grains, sand, rags, water, air, etc.

These bags are designed to take repeated and constant physical abuse without breaking and at the same time absorb the blows without causing harm to the user.

While training on a punching bag it is recommended for young athletes to be cautious as powerful strikes to the heavy bag can damage their still-developing bones. However, the pros can strike it as hard as they like but still they should wear hand wraps and bag gloves to avoid fractures to fingers.