FACTS
In March of 1988, Leslie Roberts (“Roberts”) worked as a shipping and receiving clerk for Kit Manufacturing Company (“Kit”). His job involved loading and unloading items Kit used in the manufacture of recreational vehicles. According to Roberts, *947the nature of his job with Kit had not changed for the approximately ten months he worked there before March 22, 1990.
Roberts spent the afternoon of March 22, 1990, unloading windows and refrigerators at Kit. Although Roberts alleges an injury-causing accident took place on this date, he experienced no pain or other symptoms of an injury that day. Roberts testified that when he woke up the following morning, Friday, March 23, 1990, there was some pain between his shoulder blades and in his arm and hand. Despite this, Roberts went to work on that day and performed his normal duties of loading and unloading heavy items.
Because of the pain in his back and arm, Roberts began treatment with Dr. Kranz Monday, March 26, 1990. Dr. Kranz is a chiropractor who previously treated Roberts for back pain in May 1988. Roberts maintains that the earlier injury and the pain he began experiencing on March 23, 1990, are unrelated.
After several apparently unsuccessful attempts at conservative therapy, Roberts began treatment with Dr. Henbest, a Boise neurosurgeon. Dr. Henbest operated on Roberts, noting that Roberts had suffered both an earlier injury and recent trauma to the C5-6 and C6-7 vertebrae. Roberts’ symptoms completely subsided after the operation.
PROCEEDINGS BELOW
Roberts first notified one of his supervisors that he was experiencing back pain on March 26, 1990, when he requested time off to be treated by Dr. Kranz. The first time Roberts declared that he suffered a work related accident was March 30, 1990. On May 7, 1990, Roberts filed a notice of injury and claim for benefits with Kit, which denied his claim. Roberts filed an application for a hearing with the Industrial Commission (“Commission”) on November 27, 1990. Roberts claimed to have suffered an accident while working for Kit on March 22, 1990, which resulted in an injury.
A referee heard Roberts’ claim on December 31, 1991. In his findings of fact, conclusions of law, and proposed order, the referee recommended that the Commission deny Roberts’ claim. The referee concluded that Roberts did not prove that the alleged injury arose out of and in the course of his employment. The referee further concluded that, even if Roberts could have proven his injury was work related, he did not sustain an “accident” within the meaning of I.C. § 72-102(15). The Commission concurred in the referee’s recommended findings of fact and conclusions of law, and adopted them as its own. On appeal, Roberts contends that the Commission’s denial of compensation is not supported by substantial and competent evidence, and that the Commission erred by finding that Roberts did not suffer an accident.
STANDARD OF REVIEW
Whether an injury arose from the course of employment is a question of fact to be decided by the Commission. Koester v. State, 124 Idaho 205, 858 P.2d 744 (1993); Neufeld v. Browning Ferris Indus., 109 Idaho 899, 902, 712 P.2d 600, 603 (1985). This Court reviews the Commission’s findings of fact exclusively to determine whether substantial and competent evidence supports those findings. I.C. § 72-732(1). This Court does not scrutinize the weight and credibility of the evidence relied upon by the Commission, but construes that evidence in the light most favorable to the party prevailing before it. Darner v. Southeast Idaho In-Home Serv., 122 Idaho 897, 900, 841 P.2d 427, 430 (1992). We will disturb the Commission’s findings regarding weight and credibility only if they are clearly erroneous. Koester, 124 Idaho at 208, 858 P.2d at 747; Darner, 122 Idaho at 900, 841 P.2d at 430 (1992).
ANALYSIS
Roberts had the burden of proving that there was a probable causal link between his employment and the injury for which he seeks relief. Proof of a possible causal link is not sufficient to satisfy this burden. Koester, 124 Idaho at 208, 858 P.2d at 747; Neufeld, 109 Idaho at 902, 712 P.2d at 603. In an attempt to prove the existence of this link, Roberts relies heavily upon a *948letter Dr. Henbest wrote to Roberts’ attorney. We cannot conclude that this letter establishes that Roberts’ injury was related to his employment.
Dr. Henbest did not state that he believed to a reasonable degree of medical probability that Roberts’ injury was work related. Several times throughout the letter Dr. Henbest qualified his ability to speculate about what caused Roberts’ injury. Although his conclusions are supportive of Roberts’ claim, Dr. Henbest voiced uncertainty about their merit. Dr. Henbest repeatedly noted that he relied entirely on Roberts’ account of what happened as the basis for his conclusions. Because Dr. Henbest’s conclusions did not use the usual formulation for a medical opinion, i.e., belief to a reasonable degree of medical probability, the Commission did not err by requiring that the opinion rise to the level of plainly and unequivocably conveying the physician’s conviction that the injury is work-related. See Paulson v. Idaho Forest Indus., 99 Idaho 896, 901, 591 P.2d 143, 148 (1979).
The Commission’s superior position from which to judge the weight and credibility of evidence is the cornerstone of our deference to their findings. Neufeld, 109 Idaho at 902, 712 P.2d at 603. Dr. Henbest’s hesitance severely impugned the weight the Commission was willing to afford his conclusions. Roberts has not shown that the rationale the Commission applied to determine the proper weight to afford Dr. Henbest’s conclusions was clearly erroneous. Resolving all reasonable inferences that can be drawn from Dr. Henbest’s testimony in the light most favorable to Kit, we conclude that the Commission’s finding in this regard is not clearly erroneous.
Roberts’ own testimony adds little support for the proposition that he suffered an injury through the course of his employment. Roberts testified that the symptoms first appeared the morning after he allegedly hurt himself at work. He provided the Commission with no evidence showing that anything extraordinary happened to him while working the day before his symptoms appeared. His relevant testimony merely proved that, at some point between when he went to bed and woke up the next morning, he began experiencing pain. Roberts presented no direct evidence that his injury was work related. The Commission’s conclusion that Roberts did not prove a probable causal link between the injury and his employment is supported by substantial and competent evidence.
CONCLUSION
There is substantial and competent evidence to support the Commission’s findings and conclusion that Roberts failed to prove he suffered an employment related injury. The Commission’s order denying Roberts’ claim for compensation is affirmed.
Because we affirm the portion of the Commission’s order that holds Roberts did not suffer a work related injury, this Court need not address the question of whether the injury was the result of an accident within the meaning of I.C. § 72-102(15)(b).
Costs to respondent on appeal.
JOHNSON, TROUT and SILAK, JJ., concur.