If you are superior at sprints, or you are a star performer at endurance, besides your training and intrinsic motivation, your genetics may be giving you that edge.
There is a gene called alpha-actinin3 (ACTN3) that has been identified in elite athletes that compete in power sports. The gene is responsible for promoting fast twitch fiber growth, metabolizing glucose and reducing damage during eccentric contractions.
Not everyone has this gene, but of over 400 hundred elite Australian power athletes tested for it, every female had it and 92% of the males had it. Athletes from track, swimming, track cycling and Judo were included in the study (Yang et al. 2003).
There is another gene associated with elite athletes. It is called Angiotensin-converting Enzyme (ACE). It is basically a hormone that assists with amino acids and it promotes cell growth and vasoconstriction. There are two variations, or alleles called I and D. The first has lower levels of ACE and is found in endurance athletes while D has higher levels of ACE and is found in sprint & power athletes (Myerson et al. 1999; Nazarov et al. 2001; Woods et al. 2001).
Most athletes, whether at an elite level (defined in the research as competing at international levels) or those who compete for fun, know what distances and events in which they are able to excel because genetics does give us 45% of our muscle fiber typing (Simoneaux and Bouchard, 1995) and that makes certain events easier than others. The good news here is that what we are left with even if these special genes are not present in our DNA is 55% training specificity, hard work and desire. We still have the ability to mold our bodies into the kind of athletes we wish to be.
The genes identified in elite athletes are also in the general population, it is just that those at elite levels have tapped into their talents. We never know what is just below the surface, until we go searching. Keep training and encourage your couch potato friends that they might be pleasantly surprised by their own genetics if they get out there and give fitness and sport a try!