A fire department member slightly injured his back during a stretcher lifting procedure. There were four crew members involved in this operation. Due to the positions he had to use in assisting with maneuvering this patient, he felt a pain in his lower back upon exertion. The pain increased while transporting the patient to the hospital. He notified his officer after the incident was complete about his injury. He later was evaluated at the ER and was relieved from duty for the remainder of the shift.