concurring in the judgment. While I agree with the conclusion adopted by the majority herein as it relates to the facts of this case, I am unable to adopt what I perceive to be the breadth of the syllabus law presented by the majority. It is my position that an injury which gradually develops may qualify under R.C. 4123.01(C) only if such injury is found to have developed over a discernible period of time within which the employee is performing his job-related duties.
When confronted with this issue, most jurisdictions hold that the accidental nature of the injury is not defeated by the fact that the injury is caused by the gradual and cumulative effect of working conditions. See, generally, Prosser & Keeton, Law of Torts (5 Ed. 1984) 575, Section 80. These jurisdictions recognize that as long as the injury is work-related and unexpected, it falls within the term “accidental” under their respective compensation statutes. See 1B Larson, Law of Workmen’s Compensation (1982) 7-277 to 7-304, Section 39.10; Note, Workmen’s Compensation: The Cumulative Injury Doctrine (1979), 81 W.Va. L. Rev. 435. It is the claimant’s particular susceptibility to the continual working condition which is compensable.
Under the “sudden mishap” test as previously recognized by this court, the determinative factor was the ability of the employee to isolate a specific event upon which to rest his claim. The practical result of this distinction was to preclude recovery in those instances where the employee could not point to an isolated, traumatic external event as the cause of his disability. In the area of injuries occasioned oyer a period of time while acting in the course of his employment, the burden was insurmountable in most cases for the employee as there was not a sudden occurrence but, rather, a continual degenerative condition.
*135An accidental injury need not result suddenly from the immediate application of external force. It has been my position that injuries may be accidental although the definite time of their beginning is not precisely determined.1 The onset of disability may be somewhat gradual and progressive, and the ultimate injury may result from the cumulative impact of activities occurring in employment which operate on the employee’s body or a particular physical weakness. However, the rule has its limits. The accrual of the disability must relate to a discernible time which is reasonably definite and not remote.
It is the time factor relative to the physical condition which is crucial. The court’s duty will be to distinguish between a gradual work-related condition and one that is the consequence of natural aging. It will be the claimant’s burden to establish, by way of expert testimony, that his injury was caused by a working condition within a definite time span.
It is conceded by this writer that many difficult questions will be presented in the application of this principle. One perplexing area for future litigation will certainly be that of heart-related cases. There, the essence of the problem is causation, which must be broken down into legal causation as well as medical causation. Coday v. Willamette Tug & Barge Co. (1968), 250 Ore. 39, 47, 440 P. 2d 224. This distinction is set forth by Professor Larson as follows:
“Under the legal test, the law must define what kind of exertion satisfies the test of ‘arising out of the employment.’
“Under the medical test, the doctors must say whether the exertion (having been held legally sufficient to support compensation) in fact caused this collapse.” Larson, supra, at 7-235, Section 38.83.
A heart attack brought on by a sudden and dramatic stimulus, such as a severe muscular strain, is clearly compensable under our statute. However, closer questions are involved when the employment contribution is a more protracted burden such as worry, frustration, overwork, anxiety, and other stressful conditions. In this situation, medical testimony can never be certain that the heart failure or cerebral hemorrhage was entirely due to the employee’s working environment. Thus, the factual issue of causal relationship is generally for the medical experts and the triers of fact.
In addition, the claimant or his representative has a more difficult burden of proof in this type of case. That person must initially present substantial evidence that the resultant heart attack arose from conditions in the course of employment. See 1A Larson, supra, at 5-375 to 5-381, Section 29.22, and cases cited therein. Further medical testimony must establish a causal connection between the employee’s heart failure and the unusual strenuous exertion, either physical or emotional, due to his oc*136cupation. New Hampshire Supply Co., Inc. v. Steinberg (1979), 119 N.H. 223, 400 A. 2d 1163; City and County of Denver v. Indus. Comm. (1978), 195 Colo. 431, 579 P. 2d 80; Wirth v. Indus. Comm. (1974), 57 Ill. 2d 475, 312 N.E. 2d 593; Mississippi Research & Dev. Center v. Shults (Miss. 1973), 287 So. 2d 273; see, generally, Larson, supra, at 7-199 to 7-222, Section 38.65, and cases cited therein. Finally, the unusual strenuous exertion must be fixed in a definite time period.
In the present case, there is no question that the injury was occasioned in the course of the claimant’s employment. In addition, the time element is readily ascertainable in that the injuries were sustained within a five-day period. Therefore, appellant is entitled to compensation under R.C. 4123.01(C).
In the foregoing I have attempted to alleviate some of the practical problems which will arise due to our recognition that a gradual injury is compensable under this state’s workers’ compensation law. In my view, analysis must proceed on a case-by-case basis, leaving discretion in the trier of the fact to determine whether the gradual condition was work-related or the product of aging.
I was a member of the Tenth Appellate District which was reversed in Bowman v. National Graphics Corp. (1978), 55 Ohio St. 2d 222 [9 O.O.3d 159],