The Sports Gene: Inside the Science of Extraordinary Athletic Performance (42 page)

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Brown has seen partial 21-hydroxylase deficiency in men as well, but the effects are less dramatic. Overall, Brown says that the endocrine systems of elite athletes differ noticeably from those of most adults. “There are all sorts of things peculiar to athletes,” he says. “They are not made like me in terms of their hormonal milieu.”

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Christian J. Cook, a British scientist who studies athletes and testosterone, says: “One pattern that’s emerging is that top-level elite female power athletes are often closer to men in their testosterone levels . . . what those females tend to have is a great ability to garnish power from training.” In a small 2013 study, Cook found that female athletes with higher testosterone self-selected more strenuous strength workouts than lower-testosterone peers.

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I first talked with Harper as part of the 2012
Sports Illustrated
article “The Transgender Athlete,” which I cowrote with Pablo S. Torre. Pablo and I also met Kye Allums, a former George Washington University women’s basketball player and the first openly transgender NCAA Division I athlete in history. Allums had recently started testosterone injections in order to physically transition to male. He said that his hands, feet, and head had grown, his voice had become deeper, he had started growing light facial hair, and that he could run faster. Medical studies have found a dose-dependent relationship in patients between the amount of testosterone administered and the increase in muscle mass and strength.

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To be fair, VO
₂
max is not the sole predictor of endurance, but it is important. While knowing the VO
₂
max of runners in a marathon will not nearly tell you the finishing order, it may tell you which runners are professionals, which are collegians, which are weekend warriors, and which will still be running when the cleanup crews arrive. In other sports, aerobic capacity might be even more predictive. According to Swedish physiologist Björn Ekblom, data from the 1970s showed VO
₂
max to be a decent predictor of Olympic medals in cross-country skiing.

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A decline in myostatin is actually a normal adaptation among people who lift weights regularly, apparently part of the body’s way of clearing the road for muscle building.

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In a famous gene-therapy trial in France, twelve boys were successfully treated for X-linked severe combined immunodeficiency—colloquially known as Bubble Boy syndrome—but several of the boys subsequently developed leukemia.

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It’s important to keep in mind that the harder the training, the less likely there are to be “nonresponders.” The harder the work, the more likely a subject will get at least some response, even if it is less than her peers.

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Slow-twitch muscle fibers require abundant oxygen, and thus are surrounded by blood vessels, which makes them appear dark. At Thanksgiving dinner, you can tell that turkeys are predominantly walkers, not fliers, because the dark meat is in the legs, and white, fast-twitch meat is in the breast. The slow-twitch fibers are iron-rich, so if you’re looking to add iron to your diet, go for the turkey legs.

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A 2009 study of 1,423 Russian endurance athletes and 1,132 nonathletes found a moderately strong and highly statistically significant correlation between the proportion of slow-twitch fibers a subject had and the subject’s versions of ten different genes that independent studies had associated (albeit often tenuously) with endurance. Little is known, though, about the specific genes that influence fiber-type proportions.

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The global search for increasingly suitable athletic bodies has been wildly successful in just about every sport. For centuries, Japanese competitors dominated Sumo wrestling because, well, only Japanese people were competing. From the seventeenth century until 1990, only Japan-born wrestlers had attained the top rank of Yokozuna. But in the global sports marketplace, athletes from countries with generally larger residents have infiltrated Sumo in a big way. To the dismay of some Sumo traditionalists, five of the last seven Yokozuna have been Mongolian or Hawaii-born Americans.

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One reason why amphetamines are so good, albeit illegal, for enhancing endurance performance is that they appear to remove the brain’s inhibition from overheating, allowing an athlete to continue beyond 104 degrees. Great for performance, but it has also led to heat stroke deaths during competition. In 2009, a Kentucky high school football coach was tried for murder when one of his players collapsed and died in a practice in extreme heat. The coach was acquitted, and it was revealed that the player was taking prescribed amphetamines to treat ADHD.

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In sports like swimming, kayaking, and lacrosse, athletes tend to have a very high “brachial index.” That is, the forearm is relatively long compared to the upper arm, which makes the arm better suited to propulsion. Weight lifters and wrestlers, who need stability and strength, have very low brachial indices.

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The limit Holway has documented for women is closer to 4.2 to 1. And both limits are sans steroids. Athletes on steroids have been able to surpass the 5 to 1 upper bound.

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Many of the men who NBA rosters claim are seven feet tall prove to be an inch or even two inches shorter when measured at the combine with their shoes off. Shaquille O’Neal, however, is a true 7'1" with his shoes off.

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Accomplished boxers often have long arms as well, but the trend is nowhere near as ubiquitous as in the NBA, even among the greatest heavyweights. Rocky Marciano was the J. J. Redick of his boxing era, standing 5'11" with a reported 5'7" reach. Meanwhile, Sonny Liston was 6'0" with a reach of 7'0".

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Because people with recent African ancestry tend to have longer limbs, the traditional diagnostic criteria for Marfan syndrome have been updated such that they are different for African Americans and white Americans. For African Americans, a trunk-to-legs ratio of less than 0.87 may be indicative of Marfan, whereas in white Americans the diagnostic ratio is 0.92.

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Data on the ethnicity of NBA players was matched with data generously shared by Brigham Young University economist Joseph Price, who has done fascinating work analyzing racial bias among NBA referees as it pertains to foul calls.

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The measurements from the NBA combine used for this chapter speak only to a very specialized sample of athletes, but, based on that data, the average standing vertical jump for a white NBA player at the combine was 27.29 inches, and for a black player 29.64 inches.

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It’s important to remember that these are average statements. We can all agree, for example, that men are taller than women on average. And yet, there is enough individual variation that it is easy to find a woman who is taller than many men.

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An important exception is that scientists have recently found that humans who ventured out from Africa must have interbred with Neanderthals, as the DNA of modern people in North Africa and outside of Africa—but not in sub-Saharan Africa—contains a small amount of Neanderthal DNA. While the picture of humanity outside of Africa as a subset of immigrants from a single African population is a general model, the more geneticists sample, the more complex is the story of genetic mixing that occurred both before and after humans traveled out from Africa.

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It should be noted, however, that African Americans are predominantly from a specific swath of Africa.

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A separate genetic study of African Americans found that those in South Carolina tended to hail from the “Grain Coast”—Senegal to Sierra Leone—probably because rice plantation owners in South Carolina wanted slaves skilled in a particular kind of agricultural work that was desirable in South Carolina.

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In fairness, several studies that tested elite endurance and sprint/power athletes for a set of genes associated with either endurance or power found, in general, that a gene panel could distinguish the endurance athletes from the sprint athletes. (But any coach worth her salt could do this with greater accuracy.) A 2009 study of Spanish sprinters and jumpers tested athletes for six gene variants associated with explosiveness. Five out of fifty-three of the athletes had all six of the “power” versions of the genes, whereas that should occur in only one in every five hundred normal Spanish men. Interesting for research purposes, but still not very useful for predicting whether a child will become a sprinter or jumper or marathon runner.

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Nanny is so revered in Jamaica that island legend has it she could snatch British bullets out of the air.

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Perhaps the most infamous sprinter of all time, Canada’s Ben Johnson, who won gold in the 100 at the 1988 Olympics only to be stripped days later after he tested positive for steroids, also hails from Trelawny.

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There are white men in the NFL who play safety—the other defensive back position—and some writers, most prominently William C. Rhoden of the
New York Times
, have argued that would-be white cornerbacks are stereotyped as slow and are shuffled to the safety position by narrow-minded coaches. Stereotyping may be a contributing factor, but data from the NFL’s predraft combine also shows that safeties, no matter their ethnicity, perform worse on speed and quickness tests than cornerbacks. As Heisman Trophy winner and Redskins quarterback Robert Griffin III put it on ESPN: “Safeties play safety for a reason, they’re not fast. They’re not as fast as corners, I should say.” A 2011 study in the
Journal of Strength and Conditioning Research
concluded, “cornerbacks would overall appear to be the most, whereas offensive guards would seem to be the least, athletic of the 15 positions examined.”

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The authors noted that black blood donors are sometimes inappropriately turned away because their low hemoglobin levels are assumed to be the result of a health condition.

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Says Bouchard of the finding that subjects with recent West African ancestry had more fast-twitch muscle fibers: “They had a bit more type II [fast-twitch] muscle fibers. Not a difference in kind, a difference in the frequency of events, which means there would be more people with the basic biology who, if selected and trained, might achieve success more readily than the average person of European ancestry. But we do have people of European ancestry with the same profile. That was our conclusion and I have seen no data to make me change my mind.” Bouchard also noted that a small difference in the average means a large difference in people at the end of the curve who have extreme biology.

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Seventeen Ethiopians and Kenyans broke 2:10 in a single race in 2012, the Standard Chartered Dubai Marathon.

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As Manners says, he is actually picking
against
finding running skill, because he invites kids “who have spent all their time in high school studying.”

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Oscar Pistorius, the South African double-amputee known as “the blade runner”—who as of this writing is awaiting trial for the murder of his girlfriend—sprints on carbon fiber crescents that are much lighter than human legs. He has the fastest leg swing time ever recorded in a sprinter, by a lot.

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A small 2012 study in the
European Journal of Applied Physiology
found that a group of Kenyan runners had Achilles tendons that are 2.7 inches longer than nonrunner white control subjects of the same height. That is to be expected, given the Kenyans’ proportionally longer lower limbs. Longer Achilles tendons can store more elastic energy. (Recall: world champion high jumper Donald Thomas.) The next question for scientists: How much do those long tendons influence running ability?

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The Kikuyu, the largest ethnic group in Kenya, account for about 17 percent of the population but are somewhat stockier—indicative of their ancestry in a moist, mountainous region—and produce far fewer pro runners than the Kalenjin, who account for just 12 percent of the population. The Kikuyu are a Bantu people.

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Until recently, married Kenyan women were essentially barred from training. But, as Kenyan women have won major paydays on the international circuit, “there [has been] a total change in the way to imagine the possibility of a woman training in Kenya,” says Gabriele Nicola, an Italian who coaches top Kenyan women. “Before, in Africa, the idea was the girls are weaker than the men.” But that is changing rapidly. Nicola thinks it will take about another decade before Kenyan women have completely banished the perception that they are unfit for rigorous training.

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Rudisha is a member of the Masai ethnic group. (His mother, though, is Kalenjin, and his Olympic medalist father is part Masai.) The Masai are also a Nilotic people and relatively closely related to the Kalenjin. According to data in Jean Hiernaux’s
The People of Africa,
the Masai have extremely long legs in proportion to their height.

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An additional hypothesis, mentioned by physiologists I spoke with, is that Radcliffe’s Achilles tendon had hardened over years of training—like high jumper Stefan Holm’s—improving her running economy.

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I experienced Alaskan husky desire the hard way. On my first and only dogsled trip, in 2010 over the frozen Boundary Waters of Minnesota, my lead husky was a retired racer who was—I later learned—one of Zorro’s sons. I needed about one hundred meters of forceful braking to get the dogs to pause atop a frozen lake. But as soon as I eased up on the brake and looked to the side, the team bolted. I was tossed off the sled and had to chase it for a quarter mile, until the sled got wedged between trees on a tiny frozen island. Lucky for me, as I’m pretty sure I would’ve given up well before Zorro’s progeny.