Sports, or exercise at least, were certainly encouraged in ancient Rome and Greece. With the the Greek [Gymnasium] (http://en.wikipedia.org/wiki/Gymnasium_%28ancient_Greece%29) and their veneration of the human body in various art forms. While in Rome, physical fitness was seen as important to be being a good, moderate Roman. It is likely that most people living in or around Roman cities would have been able to partake in fairly regular exercise, the public bathhouses were more than just swimming pools, they often had designated exercise areas, which most citizens would have had access to. I can't offer much insight into Olympians, but I do know that professional sportsmen existed in Rome. With gladiators often acting almost like ancient celebrities and with some chariot racers being huge stars, able to comfortably live off their earnings (A certain [very successful chariot racer] (http://en.wikipedia.org/wiki/Gaius_Appuleius_Diocles) is thought to have been the best paid sportsman of all time). And of course the infamous [Nika Riots] (http://en.wikipedia.org/wiki/Nika_riots) of Constantinople in AD 532 are closely linked to the chariot races, which I think shows the importance of such sport in the ancient world. If you can find an online source for Matz' 'Greek and Roman Sport: A Dictionary of Athletes and Events from the Eighth Century B.C. to the Third Century A.D.' it might be useful for an insight into the numbers and types of sportsmen and athletes that existed in antiquity.