In Chung v. Animal Clinic, Inc., 63 Haw. 642, 636 P.2d 721 (1981), the claimant, a veterinarian, suffered a heart attack after office hours while jogging around the track at Kalani High School. At the time of his attack, he was employed as the president of Animal Clinic, Inc. and was also the sole director and stockholder of the corporation. Conflicting evidence was presented as to the cause of the claimant's heart attack. One doctor, who attributed the claimant's heart attack to pre-existing arteriosclerosis and physical exertion from jogging, stated that the cause of the claimant's heart disease was unknown and opined that work stress did not contribute to the claimant's heart attack. 63 Haw. at 651, 636 P.2d at 727. Another doctor testified that the claimant's employment activities, which the claimant engaged in "for long hours, as well as the claimant's other business-related activities, generated a substantial amount of mental and emotional stress which is strongly linked to the production of heart disease." Id. In Chung, the Hawai'i Supreme Court noted that it first "moved towards adoption of the liberal, unitary concept of work-connection for interpreting the workers' compensation statutory requirement" in Royal State Nat'l Ins. Co., where it held that workers' compensation is awardable "if the injury reasonably appears to have flowed from the conditions under which the employee is required to work," 63 Haw. at 648-49, 636 P.2d at 725. In Chung, the Hawai'i Supreme Court stated that HRS 386-85(1) creates a presumption in favor of the claimant that the subject injury is causally related to the employment activity. . . . This presumption imposes upon the employer both the heavy burden of persuasion and the burden of going forward with the evidence. The claimant must prevail if the employer fails to adduce substantial evidence that the injury is unrelated to employment. The term "substantial evidence" signifies a high quantum of evidence which, at the minimum, must be "relevant and credible evidence of a quality and quantity sufficient to justify a conclusion by a reasonable man that an injury or death is not work connected." The statute nowhere requires . . . some preliminary showing that the injury occurred "in the course of employment" before the presumption will be triggered. Rather, HRS 386-85 clearly dictates that coverage will be presumed at the outset, subject to being rebutted by substantial evidence to the contrary. This is so in all claims proceedings, regardless of the existence of conflicting evidence, as the legislature has determined that where there is a reasonable doubt as to whether an injury is work-connected, it must be resolved in favor of the claimant. Chung, 63 Haw. at 650-51, 636 P.2d at 726-27