Appeal from a decision of the Workmen’s Compensation Board, filed April 17, 1967. The sole issue presented on this appeal is that of causal relationship, in respect of the board’s findings “that the decedent’s activities in working a 2% foot lever, operating a punch .to make holes in 3/16 inch thick angle iron, carrying 20 foot lengths of iron weighing 60 pounds, and placement of a 100 pound cutting machine on the roof, were sufficiently *893strenuous and exerting and caused more than the normal wear and tear of life and so, precipitated the claimant’s myocardial infarction”, the work having been performed in connection with the construction of two large roof signs necessitating the erection of steel and wood framework. Dr. Thompson, an assistant medical examiner, in the proof of death filed with the board and in the official certificate of death stated that the sudden death was the result of an acute myocardial infarction. In addition Dr. Lapedus, predicating his opinion on the cardiac condition diagnosed by the assistant medical examiner, testified that death was causally connected with the work activities; and to the testimony regarding this hypothesis no objection was made regarding the assumptions incorporated therein. Furthermore, these opinions were also expressed by Dr. Lapedus in his two filed reports as well as a recital that the deceased had a pre-existing underlying coronary artery disease. Dr. Gioia called by appellants admitted a myocardial infarction could have been the cause of death and, while at one time stating that he could not relate the work activity with the death, later testified in response to a question as to whether the work could be a competent and producing cause, that “It could be. I ain not saying it couldn’t be. It could be, but we have no proof”. The use of expressions by medical experts of “ could be ” or “ probably was ” or even “ possibly was ” do not tend to defeat establishment of causal relationship, for what the experts are saying is that while there could not be certainty in every case, their respective professional judgments were that “ causality should and could be assumed and acted upon although in the nature of things it could never be scientifically proven or disproven ” (Matter of Ernest v. Boggs Lake Estates, 12 N Y 2d 414, 416); and as further indicated in Ernest, “ Our function is not to reject opinion evidence because nonlawyer witnesses fail to use words preferred by lawyers and Judges but to determine whether the whole record exhibits, as it does here, substantial evidence” of causál relationship. Appellants in contending there was speculative and insubstantial evidence of causal relation, basically and inferentially disagree with .the finding made by the board that the work activity was “ more than the normal wear and tear of life ” which precipitated the myocardial infarction. It is now well settled that the performance of one’s customary duties does not preclude the finding that such activities themselves are sufficiently arduous to entail “greater exertion than the ordinary wear and tear of life” (e.g., Matter of Hudson v. Waddington Constr., 14 A D 2d 463; Matter of Pickhardt v. Heist Ohio Corp., 20 A D 2d 737, mot. for lv. to app. den. 14 N Y 2d 484); and, as we said in Pickatrdt, “Whether given activities constitute sufficient strain is an issue of fact and thus within the province of the board (Matter of Masse v. Robinson Co., 301 N. Y. 34).” Again, in Matter of Lerner v. Terrycab Co. (20 A D 2d 615), the court stated that “While it is true that the ‘usual work’ test has lost most, if not all, of its former significance (Matter of Gioia v. Courtmel Co., 283 App. Div. 40), there still remains a question in each case as to whether the regular job activity itself entails greater exertion than the ordinary wear and tear of life (Matter of Burris v. Lewis, 2 N Y 2d 323, 326) and this question is factual.” Upon the facts in this case it cannot be said that the board, in determining' these factual issues, could not reach the determination it did. Similarly, the question of causal relationship is for the board’s determination (Matter of Pickhardt v. Heist Ohio Corp., supra), which here is supported by substantial evidence and must, therefore, be sustained. Decision affirmed, with costs to the Workmen’s Compensation Board. Gibson, P. J., Herlihy, Staley, Jr., and Gabrielli, JJ., concur in memorandum by Gabrielli, J. Reynolds, J., dissents, and votes to reverse and dismiss in the following memorandum: