We note at the outset that plaintiffs have failed to comply with Rule 28(b)(5) of the Rules of Appellate Procedure in that references to pertinent assignments of error and exceptions are not identified by number in their brief. However, in this instance, we will suspend the requirements of Rule 28 pursuant to our residual authority expressed in Rule 2, and discuss the appeal on its merits.
 Plaintiffs contend that the deputy commissioner erred in making findings of fact numbers 13, 14 and 15 and in his conclusions of law, and that the Full Commission incorrectly affirmed them. The findings and conclusions upon which the denial of compensation was based are as follows:
13. There was no emergency regarding the trailer or the contents thereof when decedent and the co-employee arrived at the scene. Extra exertion was not required of decedent in connection with pulling the trailer away from the warehouse.
14. Decedent was performing his assigned duties in the customary fashion without interruptions of unusualness on 21 March 1978 when he experienced sudden cardiac death.
15. Decedent did not experience injury by accident arising out of and in the course of the employment on 21 March 1978.
Based upon the foregoing, the deputy commissioner determined that “[djecedent did not experience sudden cardiac death by accident arising out of and in the course of the employment . . . because he was performing his assigned duties in the customary *541fashion without interruptions of unusualness. N.C.G.S. 97-2(6); . . .” (Citing authority.) The claim was thus denied. The Full Commission, with one dissent, affirmed and adopted the deputy commissioner’s opinion as its own.
Plaintiff argues that findings of fact Nos. 13, 14 and 15 “are not supported by the evidence or by any evidence.” On the contrary, there is plenary evidence from which it may be inferred that no emergency existed and that no extra exertion was required of the decedent. Although there was a fire at the location, Billy Joe Matthews testified that “[t]he fire was under control from where we was at (sic). There was a cement block wall probably eight-foot high (sic) . . . [T]he fire was burning on the back side of the building from where we was at at that time . . . (sic).” He said that “[t]he fire was over on the back side of the building. I would say just roughly speaking the building was something like eighty or a hundred feet wide. It was long. The fire was concentrated on the back side of the building away from us.” The Commission may have concluded from this testimony that the fire was not burning dangerously near the men at that time, and that the remaining flames were isolated from the employees by the concrete block wall. Matthews also testified that decedent drove to the scene of the fire at normal speed. He said that decedent “didn’t seem to be excited or nothing (sic). We got on Wendover and he still, everything was real calm, . . ., (sic).” Although there was evidence that the trailer, possibly containing flammable material, was scorched and blackened, Mr. Matthews testified that firemen had sprayed the trailer with water. Plaintiffs offered no direct evidence that decedent was subjected to any physical or emotional stress. In fact, Matthew’s testimony suggests that decedent was composed and that he employed the customary switching procedure without strain.
Plaintiffs assert that the circumstances surrounding the execution of the task of moving the trailer created an emergency, and espouse, by virtue of the fact that decedent was pulling a trailer labelled “flammable” away from a burning warehouse, that he was subjected to unusual mental and physical strain resulting in death. They introduced medical testimony regarding decedent’s circulatory insufficiency to the heart to bolster this hypothesis. Indeed, this may be a reasonable surmise despite the lack of direct evidence of overexertion. “Evidential facts which cannot be *542established by direct evidence may be proved by reasonable and legitimate inferences drawn from the established facts.” Holloman v. City of Raleigh, 273 N.C. 240, 249, 159 S.E. 2d 874, 880 (1968). The facts would perhaps have allowed the Commission to find that a dangerous, urgent situation existed, as well. However,
if there is any competent evidence to support a finding of fact of the Industrial Commission, such finding is conclusive on appeal, even though there is evidence that would support a finding to the contrary. (Citations omitted.)
Blalock v. Durham, 244 N.C. 208, 212, 92 S.E. 2d 758, 760 (1956), cert. denied, 274 N.C. 378; quoted in Eaton v. Klopman Mills, Inc., 2 N.C. App. 363, 163 S.E. 2d 17 (1968). Our duty goes no further than to determine whether the record contains any evidence tending to support the finding. Anderson v. Construction Co., 265 N.C. 431, 144 S.E. 2d 272 (1965). We find that there was ample competent evidence to support the commissioner’s findings.
 Plaintiffs next assign error to the Commission’s findings of fact and conclusion of law, because, it is argued, “in arriving at those Findings of Fact and Conclusion of Law and Award, the Industrial Commission ignored or disregarded or discounted the evidence of Dr. Theodore Keith, the only medical expert to testify in this case.” Plaintiffs cite Harrell v. J. P. Stevens and Co., Inc., 45 N.C. App. 197, 262 S.E. 2d 830, cert. denied, 300 N.C. 196, 269 S.E. 2d 623 (1980), for the proposition that the Commission must weigh and evaluate the entire evidence. However, the Commission in Harrell specifically stated that it had discounted certain medical testimony. The precedent is therefore inapposite to the case sub judice. Without more, we must reject plaintiffs’ contention that the Commission disregarded the testimony of Dr. Keith or shirked its duty to consider all the evidence in arriving at its findings and conclusion of law.
This is said in Anderson v. Construction Co., 265 N.C. 431, 144 S.E. 2d 272: “The Workmen’s Compensation Act, G.S. 97-86, vests the Industrial Commission with full authority to find essential facts. The Commission is the sole judge of the credibility of the witnesses and the weight to be given their testimony. . . . The court does not have the right to weigh the evidence and decide the issue on the basis of its weight. The court’s duty goes no further than to determine whether *543the record contains any evidence tending to support the finding.”
Holloman v. City of Raleigh, supra at 249, 159 S.E. 2d at 880. There is no showing that Dr. Keith’s testimony was ignored.
In their third assignment, plaintiffs urge that the Industrial Commission erred in failing to find that the heart attack precipitating the death of plaintiffs decedent was an accident arising out of and in the course of employment within the meaning of the North Carolina Workers’ Compensation Act. “The requirement of the Act that an injury to be compensable must be shown to have resulted from an accident arising out of and in the course of the employment is known and referred to as the rule of causal relation; . . .”. Bryan v. Free Will Baptist Church, 267 N.C. 111, 115, 147 S.E. 2d 633, 635 (1966). An “accident” as that word is used in the Workers’ Compensation Act has been variously defined as “an unlooked for and untoward event which is not expected or designed by the injured employee,” “a result from a fortuitous cause,” and “an unexpected or unforeseen event; an unexpected, unusual or undesigned occurrence.” Gabriel v. Newton, 227 N.C. 314, 316-17, 42 S.E. 2d 96, 97 (1947).
We said in Bell v. Dewey Brothers, Inc., 236 N.C. 280, 72 S.E. 2d 680, “ ‘arising out of’ means arising out of the work the employee is to do, or out of the service he is to perform. The risk must be incidental to the employment. Hunt v. State, 201 N.C. 707, 161 S.E. 203; Berry v. Furniture Co., 232 N.C. 303, 60 S.E. 2d 97.”
Adams, J., said in Hunt v. State, supra, “ ‘in the course of refer (sic) to the time, place and circumstances under which the accident occurs, and the words ‘out of to its origin and cause;” ....
Lewter v. Abercrombie Enterprises, Inc., 240 N.C. 399, 403, 82 S.E. 2d 410, 414 (1954). A death does not arise out of employment unless it can be traced to the employment as a proximate cause. Id. “Whether the accident arose out of the employment is a mixed question of law and fact. . . . “Alford v. Chevrolet Co., 246 N.C. 214, 216, 97 S.E. 2d 869, 871 (1957). We have already said that the finding of the Commission as to the factual portion of the question is conclusive here, since supported by competent evidence.
*544  At this point, we must consider plaintiffs’ fourth and final assignment of error, which was that the test which the Industrial Commission should have applied was whether work related strain or exertion was the causing or precipitating factor of the plaintiffs decedent’s heart failure. That the Commission in considering the conclusion of the deputy commissioner should apply this test is accurate, as plaintiffs showed decedent to be suffering from a heart condition and raised the question of overexertion and stress in their evidence. We are not persuaded that the proper standard was not employed, however. “When one is carrying on his usual work in the usual way and suffers a heart attack, the injury does not arise by accident out of and in the course of employment.” Jackson v. Highway Commission, 272 N.C. 697, 701, 158 S.E. 2d 865, 868 (1968). It is well settled in North Carolina that extra exertion by an employee resulting in injury may qualify as an injury by accident. Gabriel v. Newton, supra; King v. Forsyth County, 45 N.C. App. 467, 263 S.E. 2d 283, cert. denied, 300 N.C. 374, 267 S.E. 2d 676 (1980). The findings of fact state that no extra exertion was required of decedent to engage and pull the trailer away from the warehouse. By saying that when stricken decedent “was performing his assigned duties in the customary fashion without interruptions of unusualness,” the deputy commissioner merely indicated that plaintiff failed to establish a causal link, i.e., that decedent was carrying on his usual work in the usual way, and did not meet with an accident arising out of his employment as those words are used in the Workers’ Compensation Act.
We deem that there is competent evidence to support the facts found, and that the findings fully and fairly support the conclusion of law and denial of compensation. The deputy commissioner’s opinion and award is, therefore,
Judges ARNOLD and BECTON concur.