What does the phrase "split the beam" mean?

Splitting the beam is when you do something on a balance beam and you fall with the beam between your legs. it hurts.

The beam is a small, thin beam which is typically raised from the floor on a leg or stand at both ends. The balance beam is only performed by female gymnasts.

It came into existence in the late 1700s, Friedrich Ludwig Jahn of Germany developed the side bar, the horizontal bar, the parallel bars, the balance beam, and jumping events. He, more than anyone else, is considered the "father of modern gymnastics."

Originally, the beam surface was plain polished wood. In earlier years, some gymnasts competed on a beam made of basketball-like material. However, this type of beam was eventually banned due to its extreme slipperiness. Since the 1980s, beams have been covered in leather or sued.