EE PICKED UP A POTHEAD W/HIS BACK TOWARDS REAR OF PICKUP TO PUT IT INSIDE. AS HE DID THIS, HE LIFTED & TURNED TO HIS LEFT ALL IN THE SAME MOTION & PLACED THE POTHEAD IN BACK OF P/U. HE FELT A PULL IN LOWER PART OF BACK, RIGHT SIDE, CAUSING SOME DISCOMFORT. HE CONTINUED TO WORK THE REST OF THE DAY, & WORK WEEK, NOTICING HIS BACK WAS A LITTLE STIFF & SORE ON 12/16/03, HE ARRIVED HOME