Nap Time
In the tribe of Benduti contortionism has long become part of the daily chores. It's not at all an art but is the most everyday normal thing taught to every newborn for health purposes, bodily flexibility always serving as the main indication of physical well-being.
A child's first backfold is celebrated almost as a second birth and the whole tribe gathers to watch the child fully folded backwards for the first time. After that day, losing the ability to bend in half backwards is treated as an illness that must be checked by the tribe's doctor. The sick person is prescribed massages and exercises until they're good and bendy again.
Taking hours a day to polish their flexibility to perfection, the Benduti youths are so used to these exercises (which may surprise any outsider with their extremity) that sometimes they just go and take a good nap in all kinds of interesting poses...