It took repeated home visits and quiet persistence from the coach before the family finally agreed to let Sonam try.

The first months of training were filled with hesitation. Sonam ran with his eyes half-closed, unsure of the space ahead, only feeling secure when his feet struck the ground.

Everything changed, however, when Thubten gave Sonam his first pair of sunglasses.

"With them on, every run felt safe,"Sonam said. "That's when I began to trust myself."

Over five years, one pair of sunglasses broke after another. The skin around his eyes, protected by the frames, grew noticeably lighter than the rest of his face, a visible record of countless hours under the plateau sun.

Like many teenagers, Sonam sometimes wavered. Once, after missing a local horse racing festival, he stopped training for a week.

The setback was immediate and sobering.

"That's when I understood," he said. "If I stop, I fall behind."

"Horses can run fast," Sonam added, thinking of home, "but they may only run on the grasslands. If I keep going, I can run beyond the plateau."

His persistence earned him a place on the Xizang team and, eventually, a ticket to the National Games.