As sports other than running go, basketball is excellent training for the mile. Wrestling is also excellent, as is soccer. In soccer, you're going to be running longer distances at once in games and especially practices--where coaches usually make you run around the athletic fields once or more. In wrestling, you'll typically do a lot of very steep hill repeats every day, ours was about 150 meters per rep, as well as longer hill/stair circuits, plus a lot of situps and pushups, and just an overall endurance element from long, exhausting practices and repeated practice of moves and matches and encouragement to run for conditioning. In basketball practice, you're going to have a lot of wind sprints and a lot of running up and down the court in games. So, you're not talking about untrained guys running sub 5 their first time. The UNC record for 1600m is 4:36 and those big guys run sub 5. Williamson could well have done it. He is an absolute freak of an athlete.