with dense material which have little "give" (e.g., packed sand, grains, etc.); in order to avoid injury, hand protection (boxing gloves, bag gloves, training gloves, hand wraps, etc.) is used during practice. Powerful strikes to the heavy bag are not recommended for inexperienced, or younger athletes (<18 female, <21 male), as risk of sprain, strain, or bone-plate damage may adversely affect bone structures. It is highly recommended to carefully focus strikes to reduce chance of injury (such as boxer's fracture). See also Strength tester machine – some of these machines utilize a punching bag References Articles containing video clips Boxing Exercise equipment Martial arts equipment