“Ring around the rosie, pocket full of posies. Ashes! Ashes! We all fall down!” It’s a classic nursery rhyme that children often sing on the playground while spinning around. “Ring Around the Rosie,” ...

Ever since the invention of beds, kids have loved to jump on them—the springier the better. Similarly, ever since the invention of beds and the decision for kids to jump on them as high as they can, ...