This week, equestrian athletes at the Rio Olympics are competing in an event called “dressage,” in which they guide their horses to perform complex combinations of different gaits, including the walk, trot and canter.

One type of footwork (or hoofwork, if you will) you likely won’t see is an “amble,” a sometimes comical four-beat gait that’s faster than a walk, slower than a gallop and well-suited for smooth, long rides.

Most horses can walk, trot, canter and gallop, but only certain breeds can amble. In a study published on Monday in Current Biology, scientists have proposed a hypothesis for how horses with this ability came to be found around the world. They suggest that ambling horses arose in Medieval England and then were brought to Iceland by Vikings, who subsequently spread the animals across Eurasia by trade.