TWO MECHANICS WERE MANEUVERING A SINGLE CYLINDER HYDRAULIC JACK (APPROX. 75 LB) INTO POSITION UNDER A FRONT END LOADER. THE EMPLOYEE FELT A STRAIN IN HIS LOWER RIGHT ABDOMENT/GROIN AREA, A REO CCURRENCE OF A HERNIA WHICH HAD PREVIOUSLY BEEN SURGICALLY REPAIRED. THIS INCIDENT BECAME A LOST TIME INJURY ON 5/1/02.