Abstract: A harness worn by a golfer while making practice swings restricts the golfer's arm and hand movement so that the hands of the golfer pass through the impact plane before the clubhead strikes the golf ball. In a first embodiment, a flexible strap extends from a point on the shaft of the golf club just above the clubhead to a point on the golfer's forearm. In a second embodiment, a rigid rod replaces the flexible strap. In both embodiments, the effective length of the strap or rod is adjustable to constrain the golfer's movement as needed. The point on the golfer's forearm may be defined by a rigid mounting member that is carried by a base plate that is positioned within a housing and the housing is strapped to the golfer's forearm by a plurality of adjustable straps. It may also be defined by a pivotally mounted mounting member that is secured to an exterior surface of the housing.