text:  Track sprinters have had high-stakes rivalries for years, particularly between the U.S. and Jamaica. The Kerr-Ingebrigtsen pairing brings that dynamic to the longer races. In some ways, they have similar origin stories, with both athletes starting out as prodigies. Kerr began running with one of Scotland's top clubs at age eight, and Ingebrigtsen seems to have the sport in his blood. You may have noticed it.