All Japanese schools have them. They are called "tobibako" ("jumping boxes"). Anyone who has gone to school in Japan knows what a tobibako is, because schools use them in gym class. It's a vaulting horse put together by stacking wooden frames—each time you add a frame at the bottom of the stack, the higher the horse gets. Tobibako came to Japan from Sweden about 100 years ago, and schools still use them today to promote physical fitness.

You vault over the tobibako with legs apart. First you run towards it, accelerating all the time. You jump onto a springboard to launch yourself up high, body leaning forward. Both hands land on the upper part of the horse, then it's over the far side and onto the mat. Your legs should be open wide on either side of the horse. When you can do all that, you have mastered the tobibako.

An elementary school gym teacher told me, "Vaulting increases muscle strength, and improves balance and posture, so it's very effective as an exercise. Unlike ball games, vaulting is not a competitive school sport. The idea is to get kids to enjoy overcoming an obstacle in front of them."

Schools are about the only place you'd expect to see a tobibako. But recently, a popular TV show segment began broadcasting vaulting competitions. The height of the tobibako is stupendous, and so are the jumpers. The boxes are sometimes piled up to three meters high—much higher than a telephone booth. The competitors might be gymnasts, high jump athletes, professional baseball players, or basketball pros. The TV audience gets wrapped up in the action, because the jumpers try really hard to outdo each other.

Because of the show, many Japanese are now a lot more interested in tobibako vaulting. It offers thrills and some simple surprises, and just about everyone has jumped over a tobibako before. It's an experience almost all Japanese share, no matter what their age.

Could it be that tobibako will one day become an Olympic sport?