Cambodian master classical dancer Penh Yom walks between her teenage students, painstakingly adjusting a bent-back finger here and the tilt of a head there, as she passes on a centuries-old art form.

In women's artistic gymnastics, beam is the third event in the Olympic order. This apparatus is 4 inches wide, 16 ft long and 4.10 ft high. Since the 80s, beams have been covered in leather or suede ...