The physical demands of running a marathon every day took their toll on Fox's body. Apart from the rest days in Montreal taken at the request of the Cancer Society, he refused to take a day off, even on his 22nd birthday. He frequently suffered shin splints and an inflamed knee. He developed cysts on his stump and experienced dizzy spells. At one point, he suffered a soreness in his ankle that would not go away. Although he feared he had developed a stress fracture, he ran for three more days before seeking medical attention, and was then relieved to learn it was tendonitis and could be treated with painkillers. Fox rejected calls for him to seek regular medical checkups, and dismissed suggestions he was risking his future health.