LIFTING 30 LB TUBES FROM ONE TRUCK & PUTTING ON ANOTHER TRUCK 10' AWAY. INJURY CAUSED BY TWISTING WHILE LIFTING. DIDN'T KNOW BACK WAS HURT UNTILTHAT NIGHT. DISCOMFORT ABATED AFTER WALKING FOR A MINUTE. WENT TO DOCTOR AS A PRECAUTION. DOCTORSAID IT SHOULD GO AWAY ENTIRELY IN A WEEK OR TWO