EE WAS REMOVING TOOLS FROM A HOISTING CAGE AFTER COMPLETING A JOB. HE LEANED OVER THE HANDRAIL TO RETRIEVE THE 5 GALLON PLASTIC BUCKET OF TOOLS (APPROX. 10-15 LBS.), LIFTED IT AND TURNED TO SE T IT ON THE GROUND. AT THAT POINT HE FELT A PAIN IN HIS LOWER BACK.