The Workers' Compensation Board concluded that claimant's repeated lifting while loading and unloading the truck he drove for the employer acted upon his quiescent arthritic back condition and that, on June 18, 1984, it precipitated a disability that had not previously existed. This conclusion was based primarily on the testimony of claimant and his physician and it was within the Board's province to assess the credibility of the witnesses (see, Matter of Smith v Bell Aerospace, 125 A.D.2d 140), as well as the weight, credibility and reasonableness to be accorded the medical evidence (see, Matter of Gaylord v Ronald Gaylord, Inc., 90 A.D.2d 609). In our opinion, the record contains substantial evidence to sustain the Board's finding that claimant sustained a causally related disability (see, Matter of Film v Holmes Transp., 147 A.D.2d 831). Furthermore, date of disablement is a factual question for the Board to resolve and its conclusion that claimant was suffering from a new disability which occurred on June 18, 1984 is also supported by substantial evidence (see, Matter of Falcone v Western Elec. Co., 72 A.D.2d 644, lv denied 48 N.Y.2d 612).
Mikoll, J.P., Levine, Mercure, Crew III and Harvey, JJ., concur. Ordered that the decision and amended decision are affirmed, without costs.