Kathmandu, March 22 -- Arjun Kulung Rai stepped onto the course of the 2013 Everest Marathon with worn-out shoes and socks. Rai, then 18, had no professional training or prior experience on the race track. He was working as a full-time porter around the Everest Base Camp. Before the race, his first ever, he was a nobody for other racers at the marathon-just another face in the crowd.

But he raised eyebrows at the end of the 42-km Full Marathon after he finished sixth, a remarkable feat for an absolute beginner. He was a somebody now, a force to be reckoned with.

"It felt like I was one with the air when I had no weights on my back," Rai, now 30, recalls that race, seated at the runner-themed 888 Cafe near Bauddha in Kathmandu.

"I decid...