Abstract: An energy absorbing exercising and training machine for exercising a person's ability to accelerate a portion of his body through a path of motion. The machine comprises a flywheel rotatably connected to a frame by means of a pair of journal bearings. A harness assembly is provided for connection to the portion of the person's body to be exercised. The flywheel and the harness assembly are interconnected to allow the flywheel to rigidly engage relative to the harness assembly upon acceleration of the harness assembly relative to the flywheel in a first direction along a path of motion of the body portion being exercised and to also allow the flywheel to disengage and freely rotate relative to the harness assembly upon deceleration of the harness assembly relative to the flywheel.