“Your goal is to ride effectively,” Vakalis said. “And just like in speed dating — I’ve never gone on a speed date, but what I imagine you need to do is the same thing you need to do in your 20-minute warm-up: to really quickly figure out what the horse’s personality is.” And as in dating, she said, “you are not there to fix them.”

The 100-year-old sport of modern pentathlon is itself something of an unfamiliar horse to most Americans, though it is quite popular in Eastern Europe. Legend has it that Baron Pierre de Coubertin, the father of the modern Olympics and an ardent romantic, selected the five sports based on what any self-respecting soldier would do if he were behind enemy lines — that is, repel his antagonists in a fencing match, swim across something, run a certain distance, shoot at some people and ride away on whatever horse he happened to come across.

“That’s nonsense, really,” said Andy Archibald, a historian of the pentathlon and a member of Britain’s gold-winning team in 1976. “His selection of sports was quite random.”

In the first pentathlon, in 1912, the athletes were allowed to use horses with which they were acquainted. That is the case in other equestrian events, in which the long-forged symbiosis between rider and horse can be the deciding factor and the course is designed to test the horse as well as the rider.

But de Coubertin believed from the beginning that the real test of athletes’ mettle was their ability to handle a horse that they had never met — or, in the usual lingo, the unfamiliar horse. And from 1920 onward, that is how the event has been conducted.