The study of sports genes has identified specific genes, such as ACTN3, that help explain why some people will probably never run a 4.3 in the 40. Genetic research has also suggested that some athletic phenomena that appear to be entirely genetic may have critical environmental factors, while others that appear to be entirely feats of will may have important genetic components. Scientists are rapidly identifying more performance genes and working to tease apart their subtle influences.
In terms of coaching tips, however, the scientific work has yielded little practical advice beyond what we already knew: Each athlete is an experiment of one, sports are good for all of us, some of us might be more motivated to practice than others, and the only way to find out how good each of us can be is to cross our fingers and train. Even though genes are critically important to an individual's athletic potential, at this point in sports-science history we are left in the position of Greek tragic heroes: circumscribed by nature, but with ill-understood wiggle room to direct our fates.
This may change, of course, as scientists now know that the path between genes and behavior is a two-way street. One study found that when people habitually lifted weights, a gene that codes for a muscle-growth-inhibiting protein became less active. And scientists studying epigenetics are beginning to learn how our behavior might alter the expression of our children's genes.
In the near future the study of genetics promises to tell us more about who we are as individual athletes, how much we can change and how best to go about it. "Genes do not act in a vacuum," notes Bernd Heinrich, a biologist and author and the 1981 North American 100K champion. Heinrich, who grew up running to school, insists that "genes are very plastic. They can be turned on or off. Look at a caterpillar and a butterfly: They've got the same genes. One flies, and one can barely crawl."