The Tribe's Luckyboy
As stretching in this tribe is practiced daily and from generation to generation, it is not too rare for some boys to become more limber than ever expected. Such a boy would be called a "luckyboy" as he becomes a symbol of fortune in the village for a year or two when he is the most flexible, until some other boy outbends him.
After offering the therapy to the majority of children of the village, the doctor spends the rest of the day with his special luckyboy. The luckyboy is a very respected position in the tribe and he doesn't take part in hunts and rarely leaves the village. His whole day is dedicated to stretching and his flexibility is the center of attention during evening ritual dances.
As there's not much possibility for privacy in the village, it's also completely normal for his training to be done "in public", letting his stretching exercises be admired by other villagers. The villagers consider it fortunate to be able to watch it. In turn, the luckyboy tries not to disappoint the villagers who gather to watch him.
Even while not actively stretching, he still tries to spend as much time during the day as possible sitting in flexible, "luck-bringing" positions, so that they could be easily admired by other villagers as a symbol of fortune.