* He has proportionately short legs relative to his long, powerful trunk; this large upper body is the engine that powers his long arms. Moreover, his unique physique reduces drag through the water and allows for maximum propulsion.
* Phelps has a greater-than-average lung capacity allowing him to execute his underwater dolphin kicks longer than the competition.
* He has a genetic advantage that cause his muscles to produce 50% less lactic acid than other athletes. This means he can work at higher work loads for longer periods.
* With a low body fat of 4%, he is better able to convert his effort into speed.

Looking at this list it’s as if Phelps was designed to swim.

Which leads to an interesting question: Given the potential for genetic modification and gene doping, should it be acceptable for other athletes to acquire the same physiological endowments through artificial means?

If not, what makes it so acceptable to come by these traits ‘naturally?’ And how

Aqua-man

Look at any of the other competitive swimmers at the elite Olympic level, both men and women, and you will find they all have long trunks in relationship to their height -- not all can recover as Phelps does from the lactic acid buildup, lung capacity can be enhanced by the work during training. But swimming coaches look for the long trunk in swimmers at age 8, 9 to pick the next Olympic swimmers. They know from tests in the endless pools, the easiest body type to streamline are those with long trunks whether stationary or swimming. Swimming at the Olympic level is all about streamlining the body through the water as one displaces it by moving the arms & legs.