For starters, Olympians generally train between 30 and 50 hours a week. They start young and seem to gravitate toward one sport in particular. From that moment, they work single-mindedly toward a goal, sometimes training for a decade to compete in a race that lasts only seconds. Some of an elite athlete's skill is genetic. Sprinters are believed to have a higher proportion of fast-twitch muscle fibers than regular people.
Gymnasts are naturally more flexible, and swimmers usually have a remarkable lung capacity.
But even if you have a natural gift, it can only get you so far. In high school, I knew a boy who was possibly the most gifted natural athlete I have ever seen. After watching him run in a touchdown for the football team, our track coach convinced him to try out for the team. But Jimmy leaned too heavily on his talent and wasn't willing to put in the hard work. He became something of a prima donna, showing up late for practice and sometimes skipping it altogether.