Essential to an award in this class of case is, however, a finding that the claimant was a normal healthy workman before the event. Findon v. Nick Chevrolet, 204 Pa. Super. 99, 203 A.2d 238 (1964); Scannella v. Salerno Importing Co., 2 Pa. Commw. 11, 275 A.2d 907 (1971). Therefore, the Board must consider whether the claimant's previous back injury was disqualifying.