EE WAS RIDING IN THE BUDDY SEAT OF UNIT #2409 TRAINING A NEW EE. THE TRUCK HIT 3 BUMPS CAUSING THE SUSPENSION TO BOTTOM OUT. THIS INCIDENT, COMBINED WITH OTHER NON WORK RELATED BACK PROBLEMS CAUSED DISCOMFORT WHICH WAS INITIALLY DIAGNOSED AS A LOWER BACK STRAIN. ADDITIONAL MEDICAL TREATMENT REVIEWED DAMAGE TO LOWER BACK DISCS.