ONCE IT WAS THOUGHT to be a matter of physical limitations. Now it seems a matter of calculus: how fast can a human being run the mile? In August two Englishmen, Sebastian Coe and Steve Ovett, combined to break the world record for the mile three times. In 10 days the two took the miles mark from 3:48.8 to 3:47.33. To appreciate these two one need only remember that in 1915 after the mile was run in 4:12.6 it took another 39 years for the mile to be run in under four minutes. And this is only the second time since 1915 that the record has been broken three times in one year. By every conceivable standard what is taking place in running right now ranks as phenomenal.

An added feature of the drama is the rivalry between Mr. Coe and Mr. Ovett. They avoid running against each other. They are from the same country but do not speak to each other. In their only recent joint appearance, brought on by the necessity of running in the Olympics--an opportunity neither would miss even if it meant having to run against each other --Mr. Coe won one race and Mr. Ovett the other. Their personal rivalry has lent an unaccustomed element to what is generally a man-against-himself sport.

There is speculation that today's athletes are able to achieve these miraculous running feats because they are better fed, physically more able than their ancestors and the beneficiaries of improved medical care. With an eye to yet more improvements in the species, there is a theory that in the next 25 years, there will a mile run in three and one-half minutes. Does this mean that in another century a three-minute mile is possible? Keep going--what about three centuries after that?