REPLACING TAIL PULLEY ON C-25: EE BENT DOWN TO RELEASE THE SLACK ON THE CONVEYOR BELT SO HE COULD LOOSEN THE COME-A-LONG THAT WAS HOLDING THE BELT CLAMPS. AT THIS POINT, EE FELT A SHARP PAIN G O DOWN HIS LEFT LEG, BUT HE DIDN'T MENTION IT, THINKING IT WAS NOTHING SERIOUS. HE COMPLETED HIS SHIFT.