One which comes to mind is the philosopher Epictetus. He seems to have admired athletes and frequently used them to describe aspects of being a philosopher.

'I wish to conquer at the Olympic games.'

'And I too, by the gods: for it is a fine thing. But consider here what precedes and what follows; and then, if it is for your good, undertake the thing. You must act according to rules, follow strict diet, abstain from delicacies, exercise yourself by compulsion at fixed times, in heat, in cold; drink no cold water, nor wine, when there is opportunity of drinking it. In a word you must surrender yourself to the trainer as you do to a physician. Next in the contest, you must be covered with sand, sometimes dislocate a hand, sprain an ankle, swallow a quantity of dust, be scourged with the whip; and after undergoing all this, you must sometimes be conquered. After reckoning all these things, if you have still an inclination, go to the athletic practice. If you do not reckon them, observe you behave like children who at one time play as wrestlers, then as gladiators, then blow a trumpet, then act a tragedy, when they have seen and admired such things...

According to Epictetus they had very specialised training regimes, based upon what event they competed in:

Those who follow athletic exercises first determine what they wish to be, then do accordingly what follows. If a man is a runner in the long course, there is a certain kind of diet, of walking, rubbing and exercise; if a man is a runner in the stadium, all these things are different; if he is a Pentathlete, they are still more different.

Of course, Epictetus is talking about philosophy, but the parallels he draws with athletes and fitness can be interesting. He stresses again and again how training is important to an athlete (and to a philosopher), but the actual competition is what really matters:

It is as if an athlete, on entering the stadium, were to complain that he's not outside exercising. This was the goal of your exercise, of your weights, your practice ring and your training partners. You want them now that the time to exploit them has arrived?