EE WAS OPENING AND CLOSING BOTTOM DOORS ON RAILCARS WHEN HE FELT A SLIGHT PAIN IN LOWER BACK. EE REPORTED THE INCIDENT ON 5-7-02 BUT DID NOT THINK MEDICAL TREATMENT WAS NEEDED. EE WAS SENT TO PHYSICIAN ON 5-20-02 AFTER COMPLAINING OF PAIN AND DIAGNOSED WITH A MILD STRAIN AND PUT ON LIGHT WORK RESTRICTION. EE WAS RELEASED TO FULL DUTIES AFTER 3 RESTRICTED WORK DAYS. THE INCIDENT BEC