The teen-agers of today are the Olympic legends of tomorrow. But hard work alone isn't enough to bring home the gold. What sets apart the winners? First and foremost, athletes should thank their parents -- not for their undying support, but for the genetic profile they inherited from them. "Performance" profiles Hank Palmer, who will probably be the world's fastest human by the 2012 games, and Avril Ogrodnick, who at 15 had run the 1,500 meters faster than anyone her age in Canada over the past two decades.

Impressive body of work
Before you can excel at a sport, you must have the proper body. That's why genes -- which influence physical characteristics such as height and limb length -- play such an important role. Palmer, for example, is precisely the right size for a sprinter. A shorter runner can't keep stride with the other competitors, and a taller one wastes precious energy trying to propel a larger frame off the starting block.

It's what's inside that counts
If body type alone were the only requirement for success, sports fans would have many more star athletes to root for. Instead, greatness requires something not readily apparent. Seventy percent of the average person's weight is skeletal muscle. But for Hank Palmer, that total is close to 95 percent. To be a winner also requires a big heart -- literally. Genes also have a hand in heart size and cardiac function. For Ogrodnick, that means pumping 40 liters of blood per minute -- far more than the average person's output -- and having a heart large enough to handle it.

Preventing a power failure
Having the muscles available is one thing. Powering them is quite another. The human body stores a limited quantity of ATP, the molecule that releases the energy to power muscles. But that means little to Hank Palmer, whose genes let his body quickly remanufacture ATP. For someone like Avril Ogrodnick, who relies less on explosiveness and more on endurance, her ability to put oxygen to work in her muscles is key.

Ahead of the pack
Athletes such as Palmer and Ogrodnick also take longer to plateau. While the average person eventually stops improving, these athletes will continue to shave valuable seconds and minutes off their times as they age. But their bodies wouldn't respond so well to training if it weren't for their athlete-friendly genes.