New York University's Galvin Kilduff has made a career out of researching rivalry.
Early on in this career, while working on his doctoral dissertation, he made a surprising discovery.
Studying rivalries, and specifically rivalries between runners, he found that "the presence of a rival was associated with a 4.44 second/km increase in pace. Thus, in a 5km race, a runner would be expected to run approximately 22 seconds faster if at least one of their rivals was also participating in the race. Rivalry was also a significant predictor of better race performance when measured by the number of rivals present."
He studied hundreds of running races, categorising the runners according to the level of rivalry between them. He looked at similarities of gender, age and speed, the number of times they raced each other, and margins of victory.
Four seconds each kilometre is a lot: more than enough to have most runners drooling in anticipation. It certainly would have been an easier way for Asbel Kiprop or Rita Jeptoo to take their running to the next level.
Kilduff told Entrepreneur magazine that normally opponents engaged in a competition are focused on the prize rather than who they are competing against.
But, "when the relationship between two players moves to the forefront... and the act of winning becomes more psychologically important than procuring the prize itself? That's when competition morphs into rivalry."
And such rivalry, according to Kilduff, inspires people, or at least some people, to greater success.
Adam Grant, a psychologist at The Wharton School* told the Harvard Business Review that "I tried really hard not to have rivals. I just tried to dismiss it and say, 'I want to be better than that and above that'. And I was totally wrong."
Grant cites New York Marathon champion Shalane Flanagan as one runner who understands the value of rivalry. Flanagan is well-known for training with and supporting her rivals, both during training and in races themselves.
"I never would have expected that, right?" says Grant "Because running is supposed to be zero-sum. And if you’re going to help one of your opponents that should be undermining your own shot at making the Olympics or winning a medal in the Olympics. And yet they really believe that that’s the only way to achieve excellence."
Grant goes on to argue that you should be friends with your rivals. He says that the relationship between friendly rivals makes competition more intrinsically motivating and less like something that you want to avoid.
But Kilduff also warns that rivalries can turn bad. In other studies he has concluded that rivalry can lead rivals to act unethically to gain an advantage. He cites Tonya Harding and Nancy Kerrigan as an example, but runners could easily recognise this behaviour in the Ben Johnson - Carl Lewis rivalry.
At a club level rivalries rarely end with PED busts or steel bars to the kneecap. But for people who see each other on a weekly basis, it is even more important that rivalries are grounded in friendship. There's nothing more awkward than avoiding club runs and Waterfront 5km for the rest of your life because you can no longer bump into that nemesis who you spat on in a fit of rage as you crossed the finish line.
The research appears to show that if you want to get faster, then go shake hands with that person who is constantly a few metres in front of you. Share a cuppa with them and tell them you're coming for them.
* Yes, he has his own business school. Is there no end to the resources he will invest in this feud?