dissenting, with whom RAPER, Justice, joins.
I dissent. I believe the majority opinion is reading into § 27-12-603(b), W.S.1977, something exactly contrary to that which it says. Such section provides:
“(b) Benefits for employment-related coronary conditions except those directly and solely caused by an injury or disease are not payable unless the employee establishes by competent medical authority that there is a direct causal connection between the condition under which the work was performed and the cardiac condition, and then only if the causative exertion occurs during the actual period of employment stress clearly unusual to, or abnormal for, employees in that particular employment, and further that the acute symptoms of the cardiac condition *143are clearly manifested not later than four (4) hours after the alleged causative exertion.” (Emphasis added.)
The majority opinion would have the emphasized words read stress clearly unusual to, or abnormal for, this employee in his particular employment. We cannot invade the legislative prerogative in that fashion. In construing a statute, its words and phrases must be given their plain, ordinary and usual meanings. Jahn v. Burns, Wyo., 593 P.2d 828 (1979); Belco Petroleum Corporation v. State Board of Equalization, Wyo., 587 P.2d 204 (1978); Geraud v. Schrader, Wyo., 531 P.2d 872, cert, denied 423 U.S. 904, 96 S.Ct. 205, 46 L.Ed.2d 134 (1975). The language of § 27-12-603(b) is plain and specific in directing that the required unusual or abnormal employment stress be to, or for, “employees in that particular employment.” These words cannot be twisted to require the stress to be to, or for, the particular individual who has personal attributes or shortcomings which make his stress different from that of the other “employees in that particular employment.”
The majority opinion predicates its interpretation of the statute on language contained in Wyoming State Treasurer ex rel. Wyoming Worker’s Compensation Division v. Schwilke, Wyo., 649 P.2d 218 (1982) (hereinafter referred to as Schwilke). In analyzing that language, two things must be kept in mind.
First, the mandate in § 27-12-603(b), supra, relative to this point is in two distinct areas: (1) there must be “a direct causal connection between the condition under which the work was performed and the cardiac condition,” and (2) “then only if the causative exertion occurs during the actual period of employment stress clearly unusual to, or abnormal for, employees in that particular employment.” The causal connection between the work and the cardiac condition can depend upon the particular individual’s attributes or shortcomings inasmuch as a “cardiac condition” can vary with differences in work capacity and physical makeup between individuals, but the “then only” clause sets forth a requirement that the exertion occur with “employment stress clearly unusual to, or abnormal for, employees in that particular employment.” This requirement cannot be individualized by virtue of its very terms. The two areas are often improperly entwined by courts in addressing the problem.
Second, our position as an appellate court must not be forgotten. Findings of fact by the trial court must be upheld if supported by substantial evidence.
“ * * * We are also mindful that the worker’s compensation law should be liberally construed where reasonably possible so that industry and not the individual worker should bear the burden of injuries suffered under its coverage. [Citation.] We are, however, not free under the guise of liberal construction to extend the beneficial purposes of the compensation law to injuries that do not reasonably fall within the language employed by the legislature. [Citations.]" (Emphasis added.) Mor, Inc. v. Haverlock, Wyo., 566 P.2d 219, 222 (1977) (hereinafter referred to as Mor). See Matter of Haynie, Wyo., 592 P.2d 693 (1979). “ * * * On appeal we assume the evidence in favor of the successful party is true and leave out of consideration entirely the evidence presented by the unsuccessful party in conflict therewith, and we give the evidence of the successful party every reasonable inference that may be reasonably drawn from it. * * * ” Distad v. Cubin, Wyo., 633 P.2d 167, 180 (1981); Brittain v. Booth, Wyo., 601 P.2d 532, 535 (1979).
Turning, then, to Schwilke, we find a recognition that the findings of fact of the trial court must be sustained if based on substantial evidence, and that an analysis of the evidence reflected sufficient medical testimony to sustain the finding of the causative factor. The record also contained sufficient evidence to support the finding that the stress was “unusual to, or abnormal for, employees in that particular employment.” The trial court specifically stated that the award was based on emo*144tional and mental stress and not only on the physical activity of the claimant. The claimant had just completed a non-stop emergency trip, driving a truck from Cas-per to Oklahoma. He spent the night there and again drove twenty hours non-stop to Casper. He drove 1,968 miles in the two days and exceeded the driving time limit authorized by the department of transportation. Also, his truck was having so many mechanical problems that the employer was considering legal action against the manufacturer. There was testimony concerning Schwilke’s exhaustion and of his agitation over the mechanical problems of the truck. His employer testified that the trip to Oklahoma was unusual for his drivers and that the truck trouble was unusual. The evidence was sufficient to support the finding of the trial court that Schwilke was in a “period of employment stress clearly unusual to, or abnormal for, employees in that particular employment” when the causative exertion occurred.
In the next to last paragraph in Schwilke, 649 P.2d at 222-223, we did say:
“Likewise, we are of the opinion that the circumstances of this case establish that the stressful work condition was unusual to, or abnormal for the deceased’s employment. Notwithstanding the fact that the actual physical exertion performed by Mr. Schwilke was within the realm of his normal activity, the record reflects that prior to the performance of these tasks he had experienced heart trouble. Under such circumstances, the once normal activity of his work day indeed became very unusual and abnormal for Mr. Schwilke. Under Mor, Inc. v. Haverlock, supra, 566 P.2d at 222, this is all that need be proven. Other courts have also taken a similar stance — namely, that a normal activity can become unusual after the individual has previously experienced heart-attack symptoms. See: IB Larson’s Workmen’s Compensation Law, § 38.64(c) (1980 ed.); Thornton v. Alaska Workmen’s Compensation Board, Alaska, 411 P.2d 209 (1966); Hanna v. Post & Brown Well Service, 199 Kan. 757, 433 P.2d 356 (1967); Aladits v. Simmons Co., 47 N.J. 115, 219 A.2d 517 (1966) and other cases cited therein.”
To the extent that such language holds that the employment stress must be unusual to, or abnormal for, the individual himself, rather than “unusual to, or abnormal for, employees in that particular employment,” I would overrule. As indicated, the result in Schwilke was proper, but not on the basis that the employment stress was unusual to, or abnormal for, Schwilke. Such was unusual to, or abnormal for, employees in that particular employment. In Schwilke, we did no more than acknowledge the existence of substantial evidence to support the findings of the trial court.
Three of the cases cited in the foregoing citation from Schwilke, supra, are three of the cases summarized and quoted from in the majority opinion. In Mor, supra, 566 P.2d at 221, (another of the cases cited in the majority opinion) we stated that “Wyoming has clearly adopted the unusual-exertion rule for coronary-condition cases.”1 Yet none of the three cases cited in Schwilke and quoted in the majority opinion are from jurisdictions which have adopted such rule, and they concern only the area of causal connection. They do not address the area of “unusual to, or abnormal for, employees.” The thrust in each of them was in the causal connection area, i.e., to establish the proposition that causal connection between work exertion and a cardiac condition could exist if an already existing heart irregularity were aggravated or accelerated. With reference to these three cases, the following is noted:
In Aladits v. Simmons Co., 47 N.J. 115, 219 A.2d 517, 522 (1966), the New Jersey court reviewed the evidence as it bore on such causal connection and concluded that the employment strain “in reasonable probability contributed in substantial measure to his fatal coronary incident.” It addressed the causal connection area only. In cataloging New Jersey with the jurisdic*145tions once adopting the usual rather than the Wyoming unusual-exertion rule, Larson says:
“The displacement of the unusual-exertion requirement in New Jersey by an essentially causal test came about in several stages over a ten-year period. In 1952 the need for unusual exertion was eliminated in all but ‘heart cases.’ In 1958 it was eliminated in ‘heart cases.’ In 1962 the new test of causal relation was confirmed, and refined somewhat by emphasis on the necessity for a causal contribution by the employment greater than de minimis.” IB Larson’s Workmen’s Compensation Law, § 38.64(b), p. 7-185.
At the time the New Jersey case was decided, the usual-exertion rule was followed. The case is not pertinent to Wyoming law.
In Hanna v. Post & Brown Well Service, 199 Kan. 757, 433 P.2d 356 (1967), the Kansas court stated at page 357:
“The issue on appeal is whether there is substantial evidence to support the trial court’s findings that there was a causal connection between the decedent’s work and his death * * *.”
It did not address the area of “unusual to, or abnormal for, employees.” At the time, Kansas was one of the states adopting the usual rather than the unusual-exertion rule. The court directed its inquiry to:
“The crucial question * * * [of] whether the decedent’s work served to aggravate or accelerate an existing disease, intensify the afflication [sic], or contribute to the death of the workman. * * * ” 433 P.2d at 363.
Larson, supra, footnoted § 38.30 of his treatise at page 7-83, that Kansas has now changed to a form of the unusual-exertion rule by statute. See: K.S.A.1981, 44-501, infra. The case is not pertinent to Wyoming law.
In Thornton v. Alaska Workmen’s Compensation Board, Alaska, 411 P.2d 209, 210 (1966), the Alaska court stated that:
“ * * * The question for us to decide is whether in the light of the whole record that finding [that the death was not work-connected — that it was not connected with any of the incidents of his employment] is supported by substantial evidence. * * * ” (Bracketed material added.)
The court’s concern was with causal connection between the worker’s death and his work so as to apply the statute which provided for compensation for “accidental * death arising out of and in the course of employment * * Alaska Stat., § 23.30.-265(13). It did not address the area of “unusual to, or abnormal for, employees” requirement. Again, Alaska applies the usual rather than the Wyoming unusual-exertion rule. Larson, supra, § 38.30, page 7-49.
The majority opinion quotes from two additional cases. They do require “unusual” exertion, but again consider only the causal aspect of the issue. In neither jurisdiction does the statute contain language similar to the Wyoming language requiring “stress unusual to, or abnormal for, employees in that particular employment."
The statute, § 8-41-108(2), C.R.S.1973, interpreted and applied in City and County of Denver v. Industrial Commission, 195 Colo. 431, 579 P.2d 80 (1978), reads:
“(2) ‘Accident’ or ‘injury’ shall not be construed to include disability or death caused by heart attack unless it is shown by competent evidence that such heart attack was proximately caused by an unusual or extraordinary overexertion arising out of and within the course of the employment.”
Section 411, Title 77, Pa.Stat.Ann. (1981 P.P.) (Purdon), to which Borough of Aliquippa v. Workmen’s Compensation Appeal Board, 18 Pa.Cmwlth. 340, 336 A.2d 450 (1975) pertains, provides in pertinent part:
“(1) The terms ‘injury’ and ‘personal injury,’ as used in this act, shall be construed to mean an injury to an employe [sic], regardless of his previous condition, arising in the course of his employment and related thereto * * (Emphasis added.)
*146In Schwilke, we also quoted from the four most recent instances in which this court has considered the effect of the language in § 27-12-603(b), supra.
In Claim of Vondra, Wyo., 448 P.2d 313 (1968), the issue and discussion concerned only the causal connection between the affliction and the employment. The court’s discussion centered on the sufficiency of the evidence. It concluded at page 318 with one of the quotations set out in Schwilke:
“In view of the matters discussed herein, we think that under any reasonable view the burden of the trial court in determining the causal relationship between a heart injury of a workman and his employment is most difficult. Certainly he cannot be satisfied in discharging this upon less than the preponderance of believable evidence that the work effort contributed in a material degree to the precipitation, aggravation, or acceleration of the existing disease.” (Emphasis added.)
The award of the trial court in favor of the workman was affirmed. One of the presented issues concerned the propriety of the trial court adopting the “usual-exertion” rule, but the opinion did not address the question of whether or not obtaining a sheet of metal from an outside scrap pile and dragging it into the shop was a task unusual for employees hired to -fabricate manhole covers.
In Claim of McCarley, Wyo., 590 P.2d 1333 (1979), the presented issues were: (1) whether or not there was “causal connection” between the work activities and the heart injury, and (2) whether or not the symptoms manifested themselves within four hours after the work-related exertion. The employee did not work on the day the injury manifested itself. He was riding snow machines when the injury was manifested. The causal connection was not found and the question of exertion unusual to employees was not discussed. We did set out the four requirements of § 27-12-603(b), one of which was: “The claimant must establish a period of employment stress unusual or abnormal for employees in claimant’s occupations” (emphasis added), 590 P.2d at 1335.
In the other two most recent instances in which we considered the effect of the language in § 27-12-603(b), supra, (also quoted and discussed in Schwilke), we did concern ourselves with the unusual-exertion rule. In each instance, the fact situation was such that substantial evidence supported the trial court’s finding that the worker was in a period of employment stress “clearly unusual to, or abnormal for, employees in that particular employment.”
In Mor, the worker was a cement mason but had to do the work of “helpers” or “hod carriers.” The strenuous activity involved in carrying buckets of cement up stairs to several levels of the project was unusual to and abnormal for cement masons whose tasks were to form and smooth wet cement. Although these facts were sufficient to affirm the trial court’s award in favor of the worker, we did use language unnecessary to the affirmance and at variance with the language of the statute. We said at 566 P.2d, page 222:
“Whether the exertion of work was clearly unusual to, or abnormal for, the individual worker in his particular employment is a question of fact to be determined by the trial court, and its findings will be upheld where supported by substantial competent evidence. See Lentz v. City of Marion, 222 Kan. 169, 563 P.2d 456, 460; and Clayton v. Lease-Way Transportation Corp., Fla., 236 So.2d 765, 766. Cf. Williams v. Northern Development Co., Wyo., 425 P.2d 594; White v. Maverick Production Co., 63 Wyo. 452, 182 P.2d 818. It should be emphasized, however, that the exertion in question must only be unusual to the employee — it need not necessarily be unusual to others engaged in the same employment. Herbert v. Sharp Brothers Contracting Co., Mo.App., 467 S.W.2d 105, 108. See also, Commercial Transfer Company v. Quasny, 245 Md. 572, 227 A.2d 20, 24. To sustain his burden of proof, as to legal causation, the statute requires that the employee show that the causative exertion was clearly something beyond his *147normal routine — something more than the worker’s usual work.” (Emphasis in first sentence added.)
The emphasized portion in the first sentence of the quotation inaccurately states the Wyoming statutory requirement. The statute requires the exertion to be gauged by unusual or abnormal stress for employees in that particular employment, a considerably different standard than one with reference to “the individual worker in his particular employment.” Of the four cases cited in support of the first sentence, the Kansas and Florida cases interpret standards altogether different than the Wyoming statutory standard. The Kansas standard is contained in K.S.A.1981, 44-501:
“ * * * Compensation shall not be paid in case of coronary or coronary artery disease or cerebrovascular injury unless it is shown that the exertion of the work necessary to precipitate the disability was more than the employee’s usual work in the course of the employee’s regular employment.”
The Florida standard is contained in F.S. 1981, 440.02(18):
“(18) ‘Accident’ means only an unexpected or unusual event or result, happening suddenly. * * * ”
The two Wyoming cases cited in the quotation from Mor, supra, concern causal connection and do not address the unusual-exertion rule.
The second sentence in the Mor quotation, supra, is a conclusion at definite odds with the legislative mandate. The legislative standard is specifically set to be “unusual to, or abnormal for, employees in that particular employment.” There is no manner or fashion in which that definite and positive language can be read to apply only to a particular workman and not to “employees in that particular employment.”
The two cases cited in support of the second sentence in Mor are, again, premised on statutes altogether different from the Wyoming statute. Such statutes do not have the plain, definite and clear Wyoming statutory language relative to stress for “employees in that particular employment.” The pertinent part of the statute setting the standard in the Missouri case and under which the holding in the case was predicated reads:
“2. The word ‘accident’ as used in this chapter shall * * *, be construed to mean an unexpected or unforeseen event happening suddenly and violently, with or without human fault and producing at the time objective symptoms of an injury.” Mo.Rev.Stat.1978, § 287.020(2).
The statute setting the standard in the Maryland case and under which the holding in the case was predicated reads in pertinent part:
“Every employer subject to the provisions of this article, shall pay or provide as required herein compensation according to the schedules of this article for the disability or death of his employee resulting from an accidental personal injury sustained by the employee arising out of and in the course of his employment without regard to fault as a cause of such injury, *• * *.” Md.Ann.Code 1957, Art. 101, § 15.
Accordingly, the last sentence of the quotation from Mor, supra, is inaccurate except insofar as the “normal routine” or “worker’s usual work” was also the normal routine and usual work of the other “employees in that particular employment.”
Finally, in Jim’s Water Service v. Eayrs, Wyo., 590 P.2d 1346 (1979), the fourth case quoted and discussed in Schwilke, supra, relative to the language in § 27-12-603(b), supra, the employee truck driver got stuck in a snow drift and had to walk about a mile for help on a cold day with strong winds and deep blowing snow. After he then shoveled snow vigorously for about a half hour in an effort to extricate the truck, he died of heart-related injury.
Again, there was ample evidence to uphold the finding of the trial court that the exertion occurred during employment stress clearly unusual to, or abnormal for, employees in that particular employment. We so found, but worded the opinion in a fashion whereby it could be said that we spoke of the unusual or abnormal exertion as per*148taining to the worker rather than to the worker and all other employees in that particular employment. We said at 590 P.2d, page 1349:
“James was expected to haul water and to maintain his truck. In the event he became snowbound he was expected to use reasonable efforts to extricate himself. The trier of fact had sufficient substantial evidence to find the normal routine was exceeded when James acted to the degree he did and that the stress or exertion, while not different in kind, was greater in degree than normal. It appears from the evidence James was involved in an effort that consumed the entire day of November 20 and involved extensive and strenuous efforts. In Mor, Inc. v. Haverlock, Wyo., 566 P.2d 219 (1977) we found the burden satisfied when the causative exertion was clearly something beyond the worker’s normal and usual routine. We will not disturb the determination of facts here.”
To the extent that such language can be taken to require the exertion to be only that unusual to, or abnormal for, the individual workman rather than unusual to, or abnormal for, the “employees in that particular employment,” I would overrule.
In conclusion, I believe that there was sufficient evidence to support the finding of the trial court that:
“ * * * the employee, Gale A. Yost, did not die of a heart attack as a result of causative exertion during the actual period of employment stress clearly unusual to or abnormal for employees in that particular employment.”
Leaving out of consideration entirely the evidence of the unsuccessful party and assuming the evidence of the successful party to be true together with the reasonable inference therefrom, as we must do2, Brittain v. Booth, supra, the facts are as follows:
Gale Yost’s truck got stuck in a bentonite pile. It was common for the trucks to get so stuck — three or four times a day or even on every other trip if the bentonite was damp. The usual thing for the drivers to do was to “do absolutely nothing but sit and wait” and read. Yost did exactly that. He sat in his truck and read and drank coffee thirty minutes before his death. There is absolutely no evidence that Yost did not perform the same tasks in the same fashion as did he and the other drivers every day. The pit condition was not unusual. There was no evidence of mechanical trouble with the truck. The road conditions were normal. Yost had performed the same routine for over two years. The other drivers regularly performed the same routine.
The trial court had more than substantial evidence upon which to find Yost to not have engaged in exertion “clearly unusual to, or abnormal for, employees in * * * [his] particular employment.”
The holdings of courts construing statutes dissimilar from that of Wyoming are of no value to us in construing the Wyoming statute.
The results reached in Sch wilke and other recent cases involving the application of § 27-12-603(b) are consistent with the requirement of that statute that for benefits for employment related coronary conditions to be paid, the causative exertion must occur during the actual period of employment stress “clearly unusual to, or abnormal for, employees in that particular employment.” The cases themselves need not be overruled but any language in those cases indicating a requirement that the exertion must only be unusual to, or abnormal for, the particular employee should be overruled.
To do otherwise would be to violate that said by Justice Rose in Claim of McCarley, supra, 590 P.2d at 1338, concerning this statute:
“ * * * The statute is not ambiguous and, therefore, we can indulge in no statutory-interpretation exercises. The plain English, understandable language of the statute speaks for itself and, therefore, settles the question.”
I would affirm.
. Mor is analyzed in more detail infra.
. The majority opinion did just the opposite.