CAMBRIDGE — Mark Pollock was accustomed to facing challenges most people would never dream of when he suffered a setback three years ago that left him broken in body, if not in spirit.
Blind since the age of 22, Pollock, a native of Northern Ireland, had conquered one frontier after another as an extreme adventure athlete. He’d run marathons in the Gobi Desert, in the shadow of Mt. Everest, and by the banks of the Dead Sea. In 2009, he became the first blind man to race to the South Pole on skis, a 22-day trek in temperatures that dipped into the minus-50s. A year later, Pollock co-skippered a boat in the Round Ireland Yacht Race, a grueling, 1,400-mile test of physical endurance and seamanship.