Fox was a distance runner and basketball player who had his right leg amputated in 1977 after he was diagnosed with osteosarcoma, a cancerous condition.

In 1980, on an artificial leg, Fox began the "Marathon of Hope," a cross-country run across Canada intended to raise money for cancer research. He started at Saint John's and made it as far as Thunder Bay, just outside Ontario, before his worsening condition forced him to stop.