EE NOTIFIED PLANT MANAGER DURING LUNCH PERIOD THAT HIS LOWER BACK WAS HURTING. SORE BACK - NOTHING SERIOUS & FINISHED SHIFT OPERATING A HITACHI EX300 BACKHOE-EXCAVATOR. NEXT MORNING WED. JULY 17 BACK WAS STILL SORE. REQUESTED TO SEE DOCTOR. SENT TO DOCTOR.