To find an injury compensable, a trial commissioner must determine not just that the claimant sustained an injury, but that this injury was sustained in the course of one's employment. Adriadik Pupuri sought workers' compensation benefits for a claimed back injury allegedly sustained at a quarry on Aug. 13, 2010, while working with Benny, Bislim Djonbalak owner of Benny's Home Service, and his brother, Nazmi, seeking stones for a fireplace for a residential job site. Pupuri testified to hearing a crack in his back and feeling pain. He testified to informing Benny, Nazmi and, later, the homeowner, Gina Gaduk, of his injury and that he laid down in pain before leaving the residence. Pupuri was treated in an emergency room two days later for low back strain and, thereafter, was treated by several doctors. An MRI disclosed moderately severe spondylosis at L4-L5 and L5-SI; with a lateral disc protrusion of L4-L5 and a disc bulge with central disc protrusion at L5-S1. Dr. Dua treated Pupuri opining that Pupuri's lumbar spine symptoms were a direct result of the Aug. 13, 2010 incident. Benny and Nazmi corroborated the quarry visit but denied hearing about or witnessing Pupuri's injury. Gaduk testified that Pupuri never complained to her and she saw no one injured or in obvious pain. The trial commissioner found Pupuri's testimony was not credible and Gaduk's testimony was credible. He found that Pupuri failed to satisfy his burden of proof as to compensability and dismissed the claim. Pupuri's motion to correct was denied. Pupuri appealed contending that the undisputed medical evidence supported compensability and the trial commission was obligated to find the claim compensable. The Compensation Review Board affirmed the judgment. It was the trial commissioner's prerogative to determine that the claimant was not a credible witness. Precedent establishes that if a trial commissioner believes a claimant is not a credible witness, he may determine that any medical opinion reliant on the claimant's narrative is also unreliable. The trial commissioner did not accept the claimant's testimony that he suffered a significant injury lifting rocks at a quarry and was not obliged to accept the treating doctor's opinions based on that testimony.