handles. Many pull handles are for lifting, mostly on objects to be carried. Horizontal pull handles are widespread, including drawer pulls, handles on latchless doors and the outside of car doors. The inside controls for opening car doors from inside are usually pull handles, although their function of permitting the door to be pushed open is accomplished by an internal unlatching linkage. Pull handles are also a frequent host of common door handle bacteria such as e-coli, fungal or other viral infections. Two kinds of pull handles may involve motion in addition to the hand-focused motions described: Pulling the starting cord on a small internal-combustion engine may, besides moving the hand toward the shoulder, also exploit simultaneously pushing a wheeled vehicle away with the other hand, stepping away from the engine, and/or standing from a squat. Some throwing motions, as in a track-and-field hammer throw, involve pulling on a handle against centrifugal force (without bringing it closer), in the course of accelerating the thrown object by forcing it into circular motion. Twist handles Another category of hand-operated device requires grasping (but not pulling) and rotating the hand and either the lower arm or the whole arm, about their axis. When the grip required is a fist grip, as with a door handle that has an arm rather than a knob to twist, the term "handle" unambiguously applies. Another clear case is a rarer device seen on mechanically complicated doors like those of airliners, where (instead of the whole hand moving down as it also rotates, on the door handles just described) the axis of rotation is between the thumb and the outermost fingers, so the thumb moves up if the outer fingers move down. Handles for wide-range motion The handles of bicycle grips, club-style weapons, shovels and spades, axes, hammers, mallets and hatchets, baseball bats, rackets, golf clubs and croquet mallets involve a greater range of ergonomic issues. See also Hand truck Shopping trolley (caddy) References Human–machine interaction Door furniture Tools Ergonomics