An endurance gene--the haves and have nots.

Scientists have linked sports performance, especially endurance, to a specific gene--the ACE gene (for angiotensin-converting enzyme). This gene is related to how much energy is available to the muscles. Everyone has two ACE genes, either two short versions, or one long and one short, or for the lucky ones, two long ones. As is always the case for genes inherited in this way, 50% of the population has one long and one short; 25% has two short ones; and 25% has two long ones, which give those individuals greater muscular efficiency.

At rest, your particular endowment of these ACE genes won't betray you: each variant is indistinguishable from the other. However, once your muscles are working, those with two of the shorter variant will have a dip in their muscular efficiency while those with both long variants will increase their muscular efficiency by just under 10%.

What does this mean to the average runner? Nothing whatsoever. Genetic endowment has always been recognized as one component to winning, along with discipline, work ethic, nutrition, training, and a huge list of intangibles that distinguish the best from the rest. So, don't fret about genetics: just keep running. What you do with what you've got makes all the difference.

(Nature, 2000. Vol. 403, No. 6770)