Meb Keflezighi, Bernard Lagat, and the Secret to Running Forever

In 2001, a professional runner named Gregory Jimmerson headed up to Mammoth Lakes, California, to spend a couple of weeks running with his old friend and rival Meb Keflezighi. The two were born three months apart, and they’d been roughly as good when younger. Both had come in second at the national high-school cross-country championships as seniors—Jimmerson in 1992 and Meb in 1993. As a senior at Stanford, in 1996, Jimmerson had been the fastest American in the N.C.A.A. cross-country championships. Meb, who attended U.C.L.A, finished a few places behind. The next year, Meb, who is universally known in the running world by his first name, won the race.