Two sprinters can cross the same finish line seconds apart, yet their strides may look nothing alike. One might stretch long, elastic steps across the track.

At only 16, Cooper Lutkenhaus from Texas was the youngest US athlete to compete at a World Athletics Championship when he stepped onto the track in Tokyo. But he never made it past the first round.

There’s an elusive feeling that some runners get when out clocking miles. Your mood lifts, you feel like you could run forever, and you’re in a near euphoric state. There’s a name for this feeling—the ...