Two popular hammers of size and style to be used in continuous and repetitive fashion are manufactures with the incorporation of the patented "Bennett's bend" in the handle to reduce stress and tension in the forearm which many times leads to worker compensable injury. This very particular bend is based on the scientific study of how the movement of the human hand, wrist (universal joint), and arm interact with tools a person would hold and use to accomplish task.
This handle is specifically designed to utilize the natural angle between the gripping portion of the hand and the axis of the forearm. With the conventional straight handle of striking tools, the user must rotate their wrist to the full extent of its travel, exerting and wasting muscular strength to maintain the wrist applying meaningful striking force through the tool to the object. This is fatiguing ton one's arm, does not make easy the application of maximum force against the object, and causes repeated small stresses or medical terms the injury to the person is known as cumulative trauma disorder, the more commonly known kind of which is carpal tunnel syndrome.
In contrast, the ergonomically engineered handle with its careful manufactured bend allows the user to utilize the natural angle between the gripping portion of their hand and the axis of their forearm. This handle enables the user to grasp the handle with their wrist in a comfortable position so that the axis of the straight portion of the handles is almost perfectly coaxial with the axis of their forearm. All the fore and aft motion in using the striking tool is translated directly into the implement with increased control and force, but reduced rotational stress on the wrist and forearm.
These hammers are very helpful to crafts people using such striking tools continuously, for they reduce the twist of the wrist, the passage of shock vibration through the tools handle to the wrist and resulting injury to forearms and elbows.