EE HAD A SENSITIVE BACK (WHICH WENT UNREPORTED FROM PACKING FOR 12 HRS STRAIGHT EARLIER IN WEEK. EE WAS PACKING 50 LB BAGS ON 8-11-01 WHEN HE TURNED WITH A BAG AND HEARD A LOUD CRACKING NOISE IN HIS UPPER BACK. EE IMMEDIATELY SENT TO MD. EETOLD TO BED REST FOR 3 DAYS AND THE REVISIT MD ON 8-13-01 @ 1045 HOURS.