A ball hitting training device has a ball hitting implement such as a
baseball bat or golf club, a shoulder harness or anchoring device for
wearing on a player's leading shoulder when taking a swing with the
hitting implement, and an elongate tether of flexible, non-extensible
material having a first end secured to the shoulder harness and a second
end secured to a location at or adjacent the ball striking end of the
hitting implement. By maintaining the tether taut during a practice
swing, the player can establish a so-called magic triangle between the
hands, the ball hitting end of the hitting implement, and the leading
shoulder, and can maintain this triangular relationship throughout the
swing.