EMPLOYEE WAS ATTEMPTING TO SET THE COLLET BACK IN PLACE ON THE LEFT CYLINDER OF A CAT LOADER. HE WAS STANDING ON A LADDER. AS HE WAS DECENDING FROM THE LADDER & REACHED THE 2ND TO LAST STEP FROM THE BOTTOM HE LOST HIS FOOTING & FELL BACKWARD ONTO HIS BACK. THE SELF RESCUER WHICH ATTACHED TO HIS BELT STRUCK HIM ON HIS LOWER BACK CAUSING A BRUISE.