EE WAS CLOSING BOTTOM COMPARTMENT OF RAILCAR #CRDX 970232 USING AN IRON ROUND 1"" BAR ABOUT 4' LONG. WHILE TRYING TO TURN THE WHEEL & PULLING WITH FORCE, THE BAR SLIPED OUT THE HOLE ON THE WHEE L & EE LOST HIS BALANCE MOVING IN A BACKWARD MOTION LANDING AGAINST LEG OF PLATFORM THAT'S USED TO GET ON TOP OF RAILCARS. EE STATED HE HIT HIS BACK AGAINST THE PLATFORM LEG & THAT HE FEELS A