The plaintiff, Douglas L. Schmidt, appeals from an order of the Industrial Commission denying his application for disability compensation. We reverse the order and remand the matter to the Commission for further proceedings. All statutory references are to Utah Code Annotated, 1953, as amended.
Douglas L. Schmidt began working for the defendant, Kenway Engineering, Inc., October 25, 1976, as a rough-cut sawman. His principal employment duty was the cutting of steel to various sizes for use in the shop. The steel pieces he was required to *694handle varied in weight from a few ounces to as much as 200 pounds. While an overhead crane was present in the shop its use by other employees rendered it unavailable to the plaintiff at various times. When the crane was unavailable the demands of the position required the plaintiff to move the heavy pieces alone or with the aid of fellow employees. The plaintiff testified at the Commission Hearing it was a common occurrence in carrying the larger pieces for one of the individuals involved to suddenly drop the piece. This would result in the other person absorbing the shock of the metal hitting the floor.
The plaintiff, a 21 year old male, had a prior history of back disorders. As an adolescent he had contracted Scheurmann’s disease, which resulted in severe pain in his back involving the Til, T12 and LI vertebrae. This osteochrondrosis was juvenile in nature and the plaintiff testified that from a year to a year and a half prior to his accepting employment at Kenway Engineering he experienced no difficulties or problems with his back.
However, by February 1977, the plaintiff was having significant problems with his back. He testified initial soreness began in December of 1976, increased gradually in intensity and duration through January and into February. He then went to a doctor for care. X-rays taken at that time showed a spondylolysis in the lower lumbar region and a possible appendicolith. Following additional x-rays confirming the existence of the appendicolith the plaintiff underwent an appendectomy. After recovery from the appendectomy the plaintiff returned to work. By June of 1977, he was again experiencing significant pain in his back. He was seen by three different medical doctors, these consultations culminated in a laminectomy and fusion of L5 SI level vertebrae on July 19, 1977.
The plaintiff’s application for workmen’s compensation benefits was denied. Following a hearing the administrative law judge entered findings of fact, conclusions of law and an order denying the benefits requested. After the plaintiff’s submission of a memorandum in support of his motion for review, the Industrial Commission denied the plaintiff’s motion and affirmed the actions of the administrative law judge.
The issues presented on appeal concern the administrative law judge’s conclusion no “accident” occurred for which the plaintiff could be granted compensation, failure of the administrative law judge to refer the medical aspects of the case to a medical panel and the exclusion of certain evidence presented by the plaintiff at the hearing.
Concerning the first issue, the plaintiff candidly explained prior to and at the hearing he could not pinpoint any specific time or occurrence as the origin of his present back problems. The judge explained in his findings of fact:
“The application did not specify a date on which an accident occurred but referred only to February, 1977, and the applicant described the accident by stating: ‘Under the stress of lifting steel daily I developed accute low back pain.’ ”
However, at the-hearing the plaintiff recounted an incident occurring in mid-December, in which he slipped while handling a piece of steel and struck his knee on the saw table. Although the blow was allegedly very painful, the plaintiff testified, because he did not want to create a negative impression on his employer, he did not report it. A short time later he hit the same knee on a piece of scrap metal protruding from a waste can and reported that incident to his supervisor.
The plaintiff also stated generally the above-mentioned problem with the handling of the steel but could not identify a specific instance as adversely affecting his back. While the back pains the plaintiff complained of in February, 1977, allegedly originated contemporaneously with the slipping incident the plaintiff introduced no direct proof he experienced or realized any specific damage to his back because of that incident.
Section 35-1-45 provides compensation for industrial accidents when the employee: “is injured ... by accident arising *695out or or in the course of his employment, wheresoever such injury occurred, provided the same was not purposely self-inflicted.” The administrative law judge concluded the plaintiff was not entitled to compensation, because he failed to establish he sustained an injury as a result of an identifiable accident or accidents. Quoting from Pintar v. Industrial Commission,1 the judge explained:
“It is therefore, a prerequisite for compensation that his disability be shown to result, not as a gradual development because of the nature or condition of his work, but from an identifiable accident or accidents in the course of the employment.”
In this jurisdiction, it is settled beyond question an internal failure brought about by exertion in the course of employment may be an accident within the meaning of 35-1-45, without the requirement that the injury result from some incident which happened suddenly and is identifiable at a definite time and place.2 As this Court explained in Purity Biscuit Co. v. Industrial Commission:3
“In Cherdron Construction Co. v. Simpkins, 61 Utah 493, 214 P. 593, 596, this court held that ‘[t]he underlying principle seems to be that the injury must happen suddenly, undesigned and unexpected, and at a definite time and place.’ In the Dee Hospital [v. Ind. Comm., 109 Utah 25, 163 P.2d 331] case we have relaxed the requirement that it be sudden and at a definite time and place so that the essential requirement now seems to be that it be unexpected and not designed.”
It is equally well settled the injury received may be accidental even though the exertion is that required in the ordinary course of employment.4 If an employee incurs unexpected injuries, including internal failures, caused by the ordinary duties of his employment he is eligible for compensation under 35-1-45.5 Therefore, the administrative law judges conclusion of law was erroneous and did not reflect our contemporary standard.
The existence of an unexpected injury, however, is the beginning rather than the end of the Commission’s inquiry. This Court’s interpretation of 35-1-45 requires the existence of a causal connection between the injury and the employment. Justice Wade explained this requirement in Purity Biscuit:6
“. . . in a case of this kind where the employee suffers an internal bodily failure or breakdown the burden is on the applicant to show that the exertion was at least a contributing cause thereof. In other words, ... in cases where disease or internal failure causes or is the injury there must be a causal connection between the employment and the injury.”
Many times the determination of the existence of a causal connection between the injury and the employment will depend on the production and interpretation of medical evidence. To establish agency expertise in this area the legislature enacted 35-1-77. This section provides:
“Upon the filing of a claim for compensation for injury by accident, or for death, arising out of or in the course of *696employment, and where the employer or insurance carrier denies liability, the commission shall refer the medical aspects of the case to a medical panel . . .
This statute mandates the submission of the medical aspects of the case to the medical panel.7 In the present case, as in most cases involving internal injury, the determination of the existence of the requisite causal connection depends in part on the accumulation and interpretation of medical evidence. The language of the statute is clear. When an accidental injury, such as in the present case, has occurred the submission of the medical aspects of the case, including those involving causation, is mandatory.
At the hearing, the administrative law judge excluded certain evidence presented by the plaintiff because it was hearsay and thus inadmissible. Section 35-1-88 states:
“Neither the commission nor its hearing officers shall be bound by the usual common-law or statutory rules of evidence.”
The hearsay rule has no application in a commission proceeding and the commission and its hearing officers may receive and consider any hearsay evidence presented, to it.8 Therefore the administrative law judge erred in excluding this evidence on the basis of the hearsay rule.
Because the present injury is of a type held by this Court to fall within the purview of Section 35-1-45, the administrative law judge’s conclusion that no accident occurred should not be reached from the facts presented, without submission of the matter to the medical panel. The case is remanded to the Commission for further proceedings. Those proceedings shall include the submission of the medical aspects of this problem to a medical panel.
. Pintar v. Industrial Commission, 14 Utah 2d 276, 382 P.2d 414 (1963).
. Jones v. California Packing Co., 121 Utah 612, 616, 244 P.2d 640, 642 (1952); see also Robertson v. Industrial Comm., 109 Utah 25, 163 P.2d 331 (1945); Thomas D. Dee Memorial Hospital Assoc. v. Industrial Comm., 104 Utah 61, 138 P.2d 233 (1943); Hammond v. Industrial Comm., 84 Utah 67, 34 P.2d 687 (1934).
. Purity Biscuit Co. v. Industrial Commission, 115 Utah 1, 17, 201 P.2d 961, 969 (1949).
.Id., 201 P.2d at 969.
. Justice Wolfe explained in his dissenting opinion in Robertson, supra note 2, 163 P.2d at 338: “Thus where exertion or overexertion in the course of the employment causes disability or death, I agree that compensation should be allowed.”
. Purity Biscuit, supra note 3, 201 P.2d at 969; see also M & K Corp. v. Industrial Comm., 112 Utah 488, 189 P.2d 132 (1948); Robertson v. Industrial Comm., supra note 2; Andreason v. Industrial Comm., 98 Utah 551, 100 P.2d 202 (1940).
. Lipman v. Industrial Comm., Utah, 592 P.2d 616, 618 (1979).
. See Ogden Iron Works v. Industrial Comm., 102 Utah 492, 132 P.2d 376 (1942).