‘The Sports Gene: Inside the Science of Extraordinary Athletic Performance’ by David Epstein (Current Hardcover; August 1, 2013)
Table of Contents:
i. Introduction/Synopsis
PART I: PHYSIOLOGY: BONES, MUSCLES AND CARDIO
Section A. Height and Skeletal Structure (and an Introduction to Heritability and Genetics)
1. Nature and Nurture in Height and Skeletal Structure
2. An Introduction to Heritability and Genetics
3. Height and Skeletal Structure in the NBA
a. Height in the NBA
b. Skeletal Structure in the NBA (the Power of Wingspan)
4. Skeletal Structure in Long-Distance Running
5. Skeletal Structure in Sprinting and Swimming (and Other Sports)
a. Sprinting and Swimming
b. Skeletal Structure in Other Sports
Section B. Muscle
6. Muscle Mass
a. Muscle Mass Potential
b. Muscle Mass and Strength Increase through Weight Training
7. Fast-Twitch and Slow-Twitch Muscle Fibers
Section C. Aerobic Capacity (VO2max)
8. Baseline Aerobic Capacity
a. Blood Volume (and Blood Doping)
b. Red Blood Cell and Hemoglobin Volume (and More Blood Doping)
9. Increasing Aerobic Capacity through Exercise (and Altitude)
a. Exercise
b. Altitude
PART II: WHY DISTANCE RUNNERS ARE FROM EAST AFRICA AND SPRINTERS ARE FROM WEST AFRICA
Section D. East Africa
10. Why So Many Elite Distance Runners Hail from East Africa (Part I): Altitude and Latitude
a. The Elevation Sweet Spot
b. The Equator (and the Nilotic Body Type)
11. Why So Many Elite Distance Runners Hail from East Africa (Part II): The Kalenjin and the Oromo Tribes (Thin Lower Legs and Cattle-Raiding Ancestors)
a. Thin Lower Legs
b. Cattle-Raiding Ancestors
12. Cultural Practices and Values in Kenya and Ethiopia
Section E. West Africa
13. Why So Many Elite Sprinters Have Origins in West Africa
14. Jamaican Sprinters
a. The Sprinting Culture in Jamaica
b. The Trelawny Population
PART III: MOTIVATION, PAIN AND INJURY
15. Motivation
16. Pain and Injury
a. Pain
b. Injury
17. Conclusion
i. Introduction/Synopsis
What does it take to become an elite athlete? The intuitive answer for most of us is that it probably takes some lucky genes on the one hand, and a whole heck of a lot of hard work on the other. Specifically, that we may need to be blessed with a particular body type to excel at a particular sport or discipline (after all, elite marathon runners tend to look far different than elite NFL running backs, who in turn tend to look far different than elite swimmers), but that beyond this it is practice and diligence that paves the way to success. When we look at the science, though—as sports writer David Epstein does in his new book The Sports Gene: Inside the Science of Extraordinary Athletic Performance—we find that the story is much more complicated than this. In general terms we find that nature and nurture interact at every step of the way in the development of an elite athlete, and that biology plays far more of a role (and in far more ways) than we may have expected.
To begin with, when it comes to physiology, we find that genetics not only has a large role to play in influencing our height and skeletal structure (as we would expect), but that genes also influence physiology in many other ways that are important when it comes to elite sports. For example, we find that people naturally vary widely in all of the following ways: the size of our heart and lungs, and the amount of red blood cells and hemoglobin that pumps through our veins; the specific type of muscle fibers that are most prevalent in our bodies (and the specific number of each); as well as our visual acuity—and again, all of these factors play a significant role in determining just how athletic we will be (and in what sports we will excel).
Second, when it comes to training, we find that hard work is not all there is to it. For genetics not only shapes our physiology, but also how our physiology responds to training (including how much muscle mass and aerobic capacity we are able to build through exercise). The fact is that we naturally vary widely in just how much we respond to exercise (to the point where some of us improve dramatically through exercise, whereas others of us respond hardly at all). And we also respond differently to different training regimens (to the point where a training regime that works well for one person may in fact harm another).
And while we may wish to take credit for just how hard we train, here too genetics is found to play a role. For it turns out that we differ widely in just how naturally disposed we are to push ourselves. And over and above this, genes also influence how much we experience pain, such that even among those who experience the same desire to push themselves (both in training and in competition), one may find it much easier to handle the pain involved than the other—which, of course, can have a big impact on results.
And speaking of pain, our genes even influence how easily we injure and how well we recover from our injuries—which, once again, has a significant impact on performance.
As an added bonus, Epstein not only covers which biological factors have an impact on sports performance, but the evolutionary story behind these biological factors (including why different populations that have adapted to different environments have come to acquire traits that make them well-disposed to different sports and disciplines [for example, why many elite marathoners have origins in East Africa, many elite sprinters have origins in West Africa, and many elite swimmers and weight-lifters have origins in Europe]).
In short, then, biology plays much more of a role in elite athletic performance that we may have realized. Not that the point of the book is to say that athletic performance is all in our genes. Just the contrary, as mentioned above the book makes the point that genes always interact with the environment to produce athletic outcomes. Genes are essential in shaping the athlete, but just as essential is the athlete’s upbringing and culture, and that they do in fact get the training that is needed to make the most of their natural talents.
Here is David Epstein discussing his new book:
*To check out the book at Amazon.com, or purchase it, please click here: The Sports Gene: Inside the Science of Extraordinary Athletic Performance. The book is also available as an audio file from Audible. com here: Audio Book
What follows is a full executive summary of The Sports Gene: Inside the Science of Extraordinary Athletic Performance by David Epstein
PART I: PHYSIOLOGY: BONES, MUSCLES AND LUNGS
Section A. Height and Skeletal Structure (and an Introduction to Heritability and Genetics)
1. Nature and Nurture in Height and Skeletal Structure
Height and skeletal structure is one area where it is easy to see that genetics plays a dominant role. Just compare yourself with your parents and/or children, and chances are the apple hasn’t fallen too far from the tree. If you want to get scientific, though, it has been shown that about 80% of the variability in height in industrialized nations, for example, may be attributed to genes (loc. 2015). As Epstein explains, “repeatedly, studies of families and twins find the heritability of height to be about 80 percent. That means that 80 percent of the difference in height between people in the group that is being studied is attributable to genetics, and around 20 percent to the environment” (loc. 2015).
When it comes to the length (and girth) of particular bones in the body, this too is largely determined by genetics (as we would expect). However, it is interesting to note that both the length and girth of bones can be modified through training. For example, the exercise and nutrition researcher Francis Holway “measured the forearms of a group of tennis players ranked in the top twenty in the world and found that their racket arms grew slightly differently from their nonracket arms. The racket-side forearm bones of the players grew around a quarter-inch longer than the forearm bone of the nonracket arm. And the elbow joint widened a centimeter. Like muscle, bone responds to exercise. Even nonathletes tend to have more bone in the arm they write with simply because they use it more, so the bone becomes stronger and capable of supporting more muscle. ‘It’s just amazing how the bone can adapt to repeated stress,” Holway says. Those tennis pros literally served and volleyed their ways to longer forearms” (loc. 1850). Still, the degree to which bones can be lengthened (or strengthened) through exercise and training is fairly limited.
2. An Introduction to Heritability and Genetics
Returning to height now, while the influence of genes on height is well-established, what is not so well established is just what genes are responsible for this. Studies that compare the heights of individuals and their genes have found an enormous number of genes that seem to contribute to height, but researchers are still far from identifying all of the genes at play here. As the author explains, “a 2010 study in Nature Genetics needed 3,925 subjects and 294,831 single nucleotide polymorphisms—spots of DNA where a single letter can vary between people—to account for just 45 percent of the variance in height between adults, and that’s the best any study has done. Finding all the height genes will take much larger and more complex studies than scientists presumed a decade ago [when the human genome was first sequenced]” (loc. 2031).
The difficulty of identifying the precise gene(s) that are responsible for a given physiological (or even behavioral) trait is a theme that shall be revisited time and time again throughout the text. The reason for this is that genetics is quite simply overwhelmingly complex, with each gene coding for multiple traits, and capable of being influenced both by other genes as well as the environment—thus making genetics notoriously difficult to study, and unravel. As Epstein explains, “imagine the genome as a 23,000-page recipe book that resides at the center of every human cell and provides directions for the creation of the body. If you could read those 23,000 pages, then you would be able to understand everything about how the body is made. That was the wishful thinking of scientists, anyway. Instead, not only do some of the 23,000 pages have instructions for many different functions in the body, but if one page is moved, altered, or torn out, then some of the other 22,999 pages may suddenly contain new instructions… Unfortunately… single genes usually have effects so tiny as to be undetectable in small studies. Even most of the genes for easily measured traits, such as height, largely elude[] detection. Not because they don’t exist, but because they [are] cloaked by the complexity of genetics” (loc. 79).
Again, though, despite the fact that scientists are not yet able to identify all of the genes that are responsible for most physiological traits, the heritability of these traits can be studied (through family and twin studies), and thus the biological basis of most physiological (and even behavioral) features can be brought to light.
Now, the fact that height and skeletal structure is highly heritable (as we have seen above) is significant, of course, because, as is fairly plain to see, certain body types tend to excel in certain sports and athletic disciplines (for example, as mentioned in the introduction, elite marathon runners tend to look far different than elite NFL running backs, who in turn tend to look far different than elite swimmers). Nevertheless, it is easy for us to under-appreciate just how specialized bodies confer an advantage in different sports (and why), and so that is where we shall begin.
3. Height and Skeletal Structure in the NBA
a. Height in the NBA
One place where it is very easy to see that specialized bodies confer and advantage (and why) is in the NBA. Indeed, when you take a sport where the focus of attention is a tiny hoop 10 feet above the ground—whereas the average height of a man is between 5’7” and 6’1” (loc. 1937)—it’s no small surprise that the most elite basketball players on the planet are going to be well above-average in height.
And they are—and how! Just consider that “fewer than 5 percent of American men are 6’3” or taller, while the average height of an NBA player perennially hovers around 6’7”” (loc. 1938). Elsewhere, the author adds that “there is such a premium on extra height in the NBA that the probability of an American man between the ages of twenty and forty being a current NBA player rises nearly a full order of magnitude with every two-inch increase in height. For a man between six feet and 6’2”, the chance of his currently being in the NBA is five in a million. At 6’2” to 6’4”, that increases to twenty in a million. For a man between 6’10” and seven feet tall, it rises to thirty-two thousand in a million, or 3.2 percent” (loc. 1951). And when we get into the stratosphere of the 7-footers, the statistics really go nuts. As Epstein points out, “the CDC’s data suggest that of American men ages twenty to forty who stand seven feet tall, a startling 17 percent of them are in the NBA right now. Find six honest seven-footers, and one will be in the NBA” (loc. 1955).
Of course, being 7 feet tall does not guarantee that you will play in the NBA, just as being under 6 feet does not guarantee that you will not (in fact some very notable NBA players have been below average in height, such as “Muggsy Bogues (5’3”), Nate Robinson (a shade under 5’8”), and Spud Webb (5’7”, with thick socks)” [loc. 1981]). The point is just that the statistics (as well as common sense) indicate that being taller carries with it an enormous advantage.
What’s more, when we look at those players who have managed to make the NBA despite being below average in height, we find that they invariably make up for this with other athletic advantages that make up for it (loc. 1985), such as long arm span (which we shall get to in a moment), and jumping ability (Spud Webb, for instance, at 5’7”, could not only dunk a basketball, but actually won the 1986 slam dunk competition). Here is Spud Webb in the 1986 slam dunk competition:
(Interestingly, jumping ability has also been shown to be highly influenced by genetics. Jumping ability has much to do with the length and stiffness of one’s Achilles tendons [since they act like springs in jumping (loc. 487)], and though one can stiffen one’s Achilles tendons through repeated jumping [loc. 487], some people are just born with longer, stiffer Achilles tendons. A good case in point is Donald Thomas. Thomas, a basketball player, discovered that he had a hidden talent in the high-jump in 2006 when he took a bet that he could not clear 6’6” on a high-jump bar [loc. 515]. When he cleared the height with ease he was quickly welcomed onto the track team. A year later, with just 8 months of legitimate training [and a jumping form that drew ridicule (loc. 559)] Thomas shocked the world by winning the World Championship with a jump of 7’8 ½” [loc. 556]. One of Thomas’ closest competitors, long-time long-jumping great Stefan Holm, displayed flawless jumping form, and had practiced the high-jump religiously for over 20 years [Holm acknowledges that “it would be a fair bet that he has taken more high jumps than any human being who has ever lived” (loc. 468)]. When Thomas’ body was later examined, it was discovered that he had incredibly long Achilles tendons for his height [loc. 563].)
Here is Donald Thomas’ winning high jump from the 2007 World Championships:
b. Skeletal Structure in the NBA (the Power of Wingspan)
Now, in addition to height, there is one other aspect of skeletal structure that represents a significant advantage in basketball, and that’s having a long arm span (or wingspan). For most people, the arm span (meaning the distance from finger tip to finger tip with arms outstretched to the sides) is exactly the same measurement as one’s height (or very close) (loc. 1987). However, there are exceptions to the rule, as some people have an arm span that is less than their height, while others have an arm span that exceeds their height. And if you are in the NBA, chances are you are in the latter camp. As Epstein explains, “the average arm-span-to-height-ratio of an NBA player is 1.063. (For medical context, a ratio of greater than 1.05 is one of the traditional diagnostic criteria for Marfan syndrome, the disorder of the body’s connective tissues that results in elongated limbs.) An average-height NBA player, one who is about 6’7”, has a wingspan of seven feet” (loc. 1989).
What having long arms does, of course, is increase one’s reach and range—effectively making one taller than one’s actual height (for all intents and purposes) on the basketball court (loc. 1987). Accordingly, arm span is actually just as important as height (and sometimes more important than height) when it comes to several basketball skills, as is reflected in the statistics. As Epstein explains, “an NBA general manager who wants to increase his team’s blocked shots would be better off signing a player with an extra inch of arm than an inch of height. The New Orleans Pelicans’ Anthony Davis, the shot-swatting first pick of the 2012 draft, is 6’9 ¼” with a 7’5 ½” wingspan. A player with Davis’ build will be predicted to get ten more blocks per season than a 7’1” giant who plays an equal number of minutes but has arms that match his height. If the GM wanted offensive rebounds, he would do equally well to sign a player with an extra inch of reach as an extra inch of height. And while height is a slightly better predictor of defensive rebounds than is wingspan, both are important and together account for half of an NBA player’s defensive boards, without even considering characteristics like jumping ability, weight, position, or general rebounding skill” (loc. 2002).
Given that wingspan acts as stand-in for height, it is no surprise that many of the players in the NBA that are undersized for their position have exceptional wingspan (if they do not already have exceptional speed and/or jumping ability to boot). As the author explains, “NBA players who are labeled as ‘undersized’ for the position they play based on stature generally have the extra arm span to make up for it. Elton Brand, the first pick of the 1999 NBA Draft, at 6’8 ¼” is unremarkable for a power forward. But Brand is actually a giant among power forwards if you consider his 7’5 ½” of reach. John Wall, the point guard who was the first pick in the 2010 draft, is only 6’2 ¾” with his shoes off, but has 6’9 ¼” worth of reach” (loc. 1993). Elsewhere, Epstein adds that “three seasons ago, the rockets used the shortest starting center in NBA history, Chuck Hayes, who is just 6’5 ½”. Fortunately, his arms are 6’10”” (loc. 2006).
4. Skeletal Structure in Long-Distance Running
As you may have guessed, basketball is not the only sport wherein it is advantageous to come pre-packaged with a particular skeletal structure. Indeed, specialized body types can be identified in most sports and disciplines (loc. 1801).
Take long-distance running, for instance. In distance running, long legs and a short, thin torso (and thin pelvis) are favored (loc. 2883-2904). The value of long legs in distance running has to do with the fact that “all other factors being equal, maximum running speed scales with the square root of leg length” (loc. 2590). A short, thin torso, in the meantime, is favored due to the fact that this leaves less weight for the legs to carry. Also, a thin pelvis is valued due to the fact that this reduces the amount of energy that is lost due to the compression of the hip joint (loc. 1021).
Interestingly, having long limbs and a short, thin torso (known as the Nilotic body type [loc. 2923]) not only improves running economy through mechanics, but also through thermodynamics. Specifically, having a Nilotic body type helps with heat dissipation, which is a major advantage in distance running. As Epstein explains, “one reason that marathon runners tend to be diminutive is because small humans have a larger skin surface area compared with the volume of their body. The greater one’s surface compared with volume, the better the human radiator and the more quickly the body unloads heat. (Hence, short, skinny people get cold more easily than tall, hefty people.) Heat dissipation is critical for endurance performance, because the central nervous system forces a slowdown or complete stop of effort when the body’s core temperature passes about 104 degrees” (loc. 1788).
It is no small wonder, then, that the vast majority of accomplished marathon runners do in fact sport a Nilotic body type. Pictured below are 3 of the best marathoners in the world right now: Patrick Makau (the official world record holder), Geoffrey Mutai (the unofficial world record holder), and Tsegay Kebede.
Now, as it turns out, where your ancestors lived in the deep past has a big impact on your likelihood of having a Nilotic body type. As Epstein explains, “a 1998 analysis of hundreds of studies of native populations from around the world found that the higher the average annual temperature of a geographic region, the proportionally longer the legs of the people whose ancestors had historically resided there. Men and women from dozens of native populations on every inhabited continent were included, and when it came to leg length, they grouped by geography. Low-latitude Africans and Australian Aborigines had the proportionally longest legs and shortest torsos. So this is not strictly about ethnicity so much as geography. Or latitude and climate, to be more precise. Africans with ancestry in southern regions of the continent, farther from the equator, do not necessarily have especially long limbs. But whether an African person in the study was from a population in Nigeria or from a genetically and physically distinct population in Ethiopia, so long as he was from low latitude his legs were likely longer than those of a height-matched European. And certainly longer than those of an Inuit from northern Canada, as Inuit tend to be short and stocky with compact limbs and a wide pelvis” (loc. 2086).
And just why would having ancestors that resided closer to the equator increase one’s chances of having a Nilotic body type? For the same reason that the Nilotic body type excels in long-distance running: heat-dissipation. The closer one’s ancestors lived to the equator, the hotter it was, and the more evolution favored a Nilotic body type to handle the heat through an efficient heat-dissipation system (loc. 2923). Whereas the further one’s ancestors lived from the equator the colder it was, and the more evolution favored a body type that preserved heat (loc. 2923).
Nowadays, most of us are not nearly as exposed to the elements as our ancestors were, and yet we retain their body types. And it just so happens that the Nilotic body type, which is designed to be good at heat-dissipation, works just right for long-distance running. Revisit the pictures above of the marathon runners and you will notice that they all represent countries that hover on or near the equator (of course, there are other reasons why certain countries in particular [including Kenya and Ethiopia] are especially over-represented when it comes to marathoning excellence, but we shall have to wait until a further section to found out why).
5. Skeletal Structure in Sprinting and Swimming (and Other Sports)
a. Sprinting and Swimming
While the Nilotic body type may be ideal in the marathon, it is less so in the sprint, for here the benefits of having a longer stride have to be weighed against the benefits of accelerating quickly, which is accomplished better by way of shorter legs. As the author explains, “the height of a sprinter is often critical to his best event. The world’s top competitors in the 60-meter sprint are almost always shorter than those in the 100-, 200, and 400 meter sprints, because shorter legs and lower mass are advantageous for acceleration. (Short legs have a lower moment of inertia, which essentially means less resistance to starting to move.) Sprinters hit the highest top speeds in the 100- and 200-meter races, but the 60-meter race has a proportionally longer acceleration period” (loc. 1776). (The advantage of short legs in acceleration is also reflected in the relative shortness of NFL running backs and cornerbacks. As Epstein explains, “NFL running backs and cornerbacks, who make their living starting and stopping as quickly as possible, have gotten shorter on average over the last forty years, even while humanity has grown” [loc. 1780]).
(Usain bolt is an interesting case in sprinting. Bolt is taller [and has longer legs] than many sprinters [especially 100-meter sprinters, where acceleration is at a premium], and thus he is at a disadvantage when it comes to early acceleration. Bolt makes up for this, though, when he hits top speed, where his longer legs do give him an advantage. Here is Usain Bolt winning the 100-meter sprint at the 2012 Olympics in Beijing [the final begins at the 50 second mark]).
And while the Nilotic body type may not be ideal in the sprint, it is positively disastrous in the swimming pool. Here, the exact opposite body type (short legs, and a long torso [with long arms]) rules the day. As Epstein explains, the most comprehensive study of the bodies of elite Olympic athletes ever found that “the male swimmers were, on average, more than 1.5 inches taller than the sprinters, but nonetheless had legs that were a half-inch shorter. Longer trunks and shorter legs make for greater surface area in contact with the water, the equivalent of a longer hull on a canoe, a boon for moving along the water at high speed” (loc. 1813). The author adds that “Michael Phelps, at 6’4”, reportedly buys pants with a 32-inch inseam, shorter than those worn by Hicham El Guerrouj, the Moroccan runner who is 5’9” and holds the world record in the mile. (Like other top swimmers, Phelps also has long arms and large hands and feet. That elongated body type can be indicative of a dangerous illness called Marfan syndrome. According to Phelps’ autobiography, Beneath the Surface, his unusual proportions led him to get checked annually for Marfan)” (loc. 1813).
Here is Michael Phelps winning the 100-meter butterfly at the 2012 Olympics in Beijing in dramatic fashion:
And it is in no coincidence that Phelps, with his short legs (and corresponding low center of mass), has European (as opposed to African) ancestry. As the author explains, “in 2010, a racially diverse research team from Duke and Howard universities confronted the issue of body types as it pertains to ancestry and sports performance… the researchers reported that, compared with white adults of a given height, black adults have a center of mass—approximately the belly button—that is about 3 percent higher. They used engineering models of bodies moving through fluids—air or water—to determine that the 3 percent difference translates into a 1.5 percent running speed advantage for athletes with the higher belly buttons (i.e., black athletes) and a1.5 percent swimming speed advantage for athletes with a lower belly button (i.e., white athletes)” (loc. 2101).
So, is it the case that black athletes tend to outperform white athletes on the running track, whereas white athletes tend to outperform black athletes in the swimming pool? For anyone who has paid even scant attention to the Olympics in recent years, this question will seem absurd. And, not surprisingly, the statistics bare out the optics, as black athletes have, indeed, owned the track, whereas white athletes have owned the pool (loc. 2603). And while body type may not be the only thing that explains this phenomenon (we shall encounter other factors below), it surely cannot be discounted as contributing to the clear trend.
b. Skeletal Structure in Other Sports
Over and above running and swimming, skeletal structure plays a role in many other (in fact, most) sports and athletic disciplines. Weight lifters, for instance, tend to have shorter arms, “—and particularly shorter forearms—relative to their height than normal people, giving them a substantial leverage advantage for heaving weights overhead” (loc. 1768). By contrast, athletes that use their arms to throw an object (often a ball), or power a boat of some sort tend to have longer arms relative to their height, for this increases the necessary leverage required in these disciplines (loc. 1768).
Athletes that need to rotate in the air, such as gymnasts and divers, tend to be short and have narrow pelvises (loc. 1070, 1748). This helps explain why elite women gymnasts (whose pelvises naturally widen after puberty) tend to peak in their teens, whereas elite male gymnasts (who do not have to deal with widening pelvises) tend to peak much later in life. As Epstein explains, “if elite female gymnasts go through a significant growth spurt in height or hips, their career at the top level is essentially over. As they increase in size faster than strength, the power-to-weight ratio that is so critical to aerial maneuvers goes in the wrong direction, as does their ability to rotate in the air. Female gymnasts are pronounced over the hill by twenty, whereas male gymnasts are still early in their careers” (loc. 1071).
To take just one final example, consider boxers, whose skeletal structure is influenced by two competing needs—the need to reach their opponent, and the need to remain stable on their feet. As the author explains, “professional boxers come in an array of shapes and sizes, but many have the combination of long arms and short legs, giving greater reach but a lower and more stable center of gravity” (loc. 1775).
I could go on and on, but you get the picture: skeletal structure matters in elite sports and athletics, and it matters a lot.
Section B. Muscle
6. Muscle Mass
a. Muscle Mass Potential
Bones aren’t the only aspect of physiology that matter in elite sports, though. Also high on the list is muscle, and once again genetics plays a big role here. To begin with, the amount of muscle one is able to pack onto one’s body is limited by the size and strength of one’s bones (which, as we have seen above, is largely determined by genetics). As Epstein explains, “in measurements of thousands of elite athletes from soccer to weight lifting, wrestling, boxing, judo, rugby, and more, Holway has found that each kilogram (2.2 pounds) of bone supports a maximum of five kilograms (11 pounds) of muscle. Five-to-one, then, is a general limit of the human [body]” (loc. 1866).
Thus those who are born with larger (and heavier) bones are capable of packing on comparatively more muscle than those with smaller (and lighter) bones, and are therefore given a big advantage in sports and athletic disciplines that require great strength (no small number). Take shot-put and discuss, for example. As the author explains, “male Olympic strength athletes whom Holway has measured, like discus throwers and shot putters, have skeletons that are only about 6.5 pounds heavier than those of average men, but that translates to more than 30 pounds of extra muscle that they can carry with the proper training” (loc. 1870). And that, of course, gives them a huge advantage in these sports. (Epstein does not mention the bone mass of NFL lineman, or the strong-men of other sports, but I think we can safely assume that they would be well above normal as well).
b. Muscle Mass and Strength Increase through Weight Training
In addition, while the five-to-one ratio of muscle to bone may be a general limit for humans, not all of us are able to achieve this maximum—even with all the training in the world. The fact is that people differ dramatically in just how much muscle they are able to build through training. For example, in one study “sixty-six people of varying ages were put on a four-month strength training plan—squats, leg press, and leg lifts—all matched for effort level as a percentage of the maximum they could lift. (A typical set was eleven reps at 75 percent of the maximum that could be lifted for a single rep.) At the end of the training, the subjects fell rather neatly into three groups: those whose thigh muscle fibers grew 50 percent in size; those whose fibers grew 25 percent; and those who had no increase in muscle size at all. A range from 0 percent to 50 percent improvement, despite identical training” (loc. 1631).
And when it comes to improvements in strength through training, the differences are even more dramatic. As the author explains, “in Miami’s GEAR study, the strength gains of 442 subjects in leg press and chest press ranged from under 50 percent to over 200 percent. A twelve-week study of 585 men and women, run by an international consortium of hospitals and universities, found that upper-arm strength gains ranged from zero to over 250 percent” (loc. 1640).
Part of the reason for the discrepancy in muscle growth (and strength) between individuals (as a response to exercise) has to do with the fact that there are 2 types of muscle fibers (slow-twitch, and fast-twitch [loc. 1655]), and they differ in just how much they grow in response to strength-training. As Epstein explains, “fast-twitch fibers… grow twice as much as slow-twitch fibers when exposed to weight training. So the more fast-twitch fibers in a muscle, the greater its growth potential” (loc. 1660). And it just so happens that one’s relative proportion of slow-twitch to fast-twitch muscle fibers is largely determined by genetics. As Epstein explains, “no training study ever conducted has been able to produce a substantial switch of slow-twitch to fast-twitch fibers in humans, nor has eight hours a day of electrical stimulus to the muscle. (That caused a fiber type switch in mice, but failed to do so in people.)” (loc. 1666). Thus the author concludes that “some athletes have greater muscle growth potential than others because they start with a different allotment of muscle fibers” (loc. 1654).
7. Fast-Twitch and Slow-Twitch Muscle Fibers
Now, slow-twitch and fast-twitch muscle fibers differ from one another not only in their responsiveness to weight-training. As their names indicate, slow-twitch fibers contract more slowly than their fast-twitch counterparts (though they tire less quickly as a result), and each is used in different types of body movements. As the author explains, “fast-twitch fibers contract at least twice as quickly as slow-twitch fibers for explosive movements—the contraction speed of muscles has been shown to be a limiting factor of sprinting speed in humans—but they tire out very quickly” (loc. 1658).
The different capabilities of the different muscle fibers is significant, of course, because it means that people with different proportions of each will differ not only in the degree to which they are able to add muscle mass, but they will also differ in just what kinds of athletic disciplines they will be best suited for. For example, those with a higher proportion of fast-twitch muscle fibers will be best suited for those athletic disciplines that require quick movements and short bursts of activity (i.e., sprinting and power sports), whereas those with a higher proportion of slow-twitch muscle fibers will be best suited for those disciplines that require slower muscle movements and more stamina (i.e., distance-running and endurance sports).
It should come as no surprise, then, that long-distance runners and sprinters (for example) differ not only in their skeletal structures, but in their muscle mass (which is partly the result of their very different training regimens, but also partly the result of their relative proportion of slow-twitch to fast-twitch muscle fibers—which more than likely steered each into their respective disciplines to begin with). As Epstein explains, “most people have muscles comprising slightly more than half slow-twitch fibers. But the fiber type mixes of athletes fit their sport. The calf muscles of sprinters are 75 percent or more fast-twitch fibers. Athletes who race the half-mile, as I did, tend to have a mix in their calves closer to 50 percent slow-twitch and 50 percent fast-twitch, with higher fast-twitch proportions at the higher levels of competition. Long-distance runners are skewed towards slow-twitch muscle fibers that can’t produce explosive force as quickly, but which tire very slowly. Frank Shorter, the last American man to win the Olympic marathon, was found to have 80 percent slow-twitch muscle fibers in a leg muscle that was sampled” (loc. 1664). (And again, all of the evidence indicates that one’s proportion of muscle fibers is entirely determined by genetics. As the author explains, “aerobic training can make fast-twitch fibers more endurant and strength-training can make slow-twitch fibers stronger, but they don’t completely flip. (Save for extreme circumstances, like if one’s spinal cord is severed, in which case all fibers revert to fast-twitch.)” [loc. 1670].)
Section C. Aerobic Capacity (VO2max)
8. Baseline Aerobic Capacity
In addition to skeletal structure and muscle mass (and muscle composition), one other physiological factor that plays a significant role in many sports and athletic disciplines (though to wildly different degrees) is aerobic capacity, otherwise known as VO2max. VO2max is defined as “a measure of the amount of oxygen a person’s body can use when he or she is running or cycling all out” (loc. 1233). Essentially, the more oxygen a person’s body can take in and use, the better they are able to keep their muscles fed, which results in better endurance (loc. 1237).
Several factors go into determining one’s VO2max. As Epstein explains, “it is determined by how much blood the heart pumps, how much oxygen the lungs impart to that blood, and how efficient the muscles are at snatching and using the oxygen from the blood as it hurtles past” (loc. 1237). These determinants of V02max are themselves influenced by several factors, including the size of the heart and lungs (loc. 3153, 3214, 3426), the amount of blood coursing through the veins (loc. 1400), and the amount of hemoglobin and red blood cells in the blood (loc. 4003).
Now, all of these factors can be enhanced through aerobic training (though to differing degrees in each of us, as we shall see in a moment), but all are also factors wherein we differ naturally to a degree (and sometimes quite a lot). These natural differences mean that people can differ quite a bit in terms of their base-line aerobic capacity. For example, tests involving largely inactive people show that “between one in ten and one in twenty people start with elevated aerobic capacity” (loc. 1481).
What’s more, a very small percentage of people (about 0.3%) actually naturally have the aerobic capacity of a trained athlete (loc. 1397, 1461). For example, Norm Gledhill, a sports researcher out of York University in Toronto conducted one study wherein he tested 1900 young men for VO2max and discovered that “among them were six men with absolutely no history of training whatsoever who nonetheless had aerobic capacities on par with collegiate runners. The ‘naturally fit six,’… had VO2max scores more than 50 percent higher than the average untrained young man, despite being inclined to couch-bound activities” (loc. 1397).
a. Blood Volume (and Blood Doping)
As mentioned above, several factors go into determining one’s VO2max. However, one of the most significant factors here is just how much blood one has pumping through one’s veins. When it came to the naturally fit six, for example, it was this factor that stuck out. As Epstein explains, “when the York researchers examined their ‘hidden talents,’ as they call them, they saw that the naturally fit men had a crucial gift, through no discipline or effort of their own: massive helpings of blood. They were endowed with blood volumes that could have been mistaken for those of endurance-trained athletes. ‘It’s the increased diastolic filling,’ explains Gledhill, referring to the part of the heartbeat when the heart muscle relaxes to allow blood back in. ‘When you fill up the right side of the heart with more blood, then it pumps more blood into the left side, and the left side pumps it out into the body. The [return of blood to the heart] is enhanced because of the extra blood volume.’” (loc. 1401).
So blood volume, which can be enhanced through training, is also something wherein we differ in terms of our base-line amount, and this has a big impact in terms of our VO2max potential (as it turns out, blood volume can also be increased artificially through a certain kind of blood doping; and, though illegal, this procedure is not unheard of in elite endurance sports [loc. 1405]).
b. Red Blood Cell and Hemoglobin Volume (and More Blood Doping)
Over and above the amount of blood coursing through one’s veins, another factor that influences VO2max is the amount of red blood cells that this blood contains, and the amount of hemoglobin in these red blood cells.
Hemoglobin is the oxygen-carrying protein in red blood cells, thus the more red blood cells you have, and the more hemoglobin these red blood cells contain, the more oxygen your blood will carry, and the higher VO2max you will have (loc. 2613, 3904); and, once again, these are both areas in which we differ by nature. On the extreme high end, for example, some individuals come equipped with 65% more red blood cells than the average person (this is true of Eero Mantyranta, one of Finland’s greatest cross-country skiers of all time [loc. 4007, 4106]).
(Again, there are artificial ways of increasing ones levels of both red blood cells and hemoglobin [the drug called EPO, for example]). And if you are caught with high levels of hemoglobin, you will be assumed to be a cheater in sport—unless you can prove that this is natural, which it is possible to do. For example, “Italian cyclist Damiano Cunego was granted a medical exemption by the International Cycling Union and at twenty-three years of age became the youngest road cyclist ever to be ranked number one in the world. Frode Estil, a Norwegian cross-country skier who was given an exemption by the International Ski Federation, won two golds and one silver medal at the 2002 Winter Olympics in Salt Lake City. Neither of these men had hemoglobin levels as high as Eero’s… but Cunego and Estil nonetheless had elevated levels that they could prove were natural and that were higher than those of their teammates and competitors who trained in similar manners. Like the naturally fit six from the York University study, there was just something innately different about them” [loc. 4109]).
9. Increasing Aerobic Capacity through Exercise (and Altitude)
a. Exercise
Now, as mentioned above, virtually all of the factors that go into one’s VO2max can be improved through aerobic training, but here too there are great natural differences between us in terms of just how much we can improve. For example, in the HERITAGE Family Study, which looked at subjects in four centers—Indiana University, University of Minnesota, Texas A&M, and Laval University (loc. 1247)—it was discovered that “despite the fact that every member of the study was on an identical exercise program, all four sites saw a vast and similar spectrum of aerobic capacity improvement, from about 15 percent of participants who showed little or no gain whatsoever after five months of training all the way up to the 15 percent of participants who improved dramatically, increasing the amount of oxygen their bodies could use by 50 percent or more” (loc. 1251). And when it came to the latter group, the highest responders improved by as much as 100%! (loc. 1242).
Interestingly, the study also revealed that there was no correlation between one’s baseline aerobic capacity, and the amount one was able to improve through aerobic training. As the author explains, “amazingly, the amount of improvement that any one person experienced had nothing to do with how good they were to start. In some cases, the poor got relatively poorer (people who started with a low aerobic capacity and improved little); in others, the oxygen rich got richer (people who started with higher aerobic capacity and improved rapidly); with all manner of variation between—exercisers with a high baseline aerobic capacity and little improvement and others with a meager starting aerobic capacity whose bodies transformed drastically” (loc. 1254).
b. Altitude
Interestingly, aside from aerobic training, there is one other environmental factor that can help improve your VO2max, and that is exposing your body to high altitude. The higher up you go, the less oxygen is present in the air (loc. 3093), and the body responds to this by way of producing more red blood cells and hemoglobin so that more oxygen can be accessed (loc. 3093). As we have seen above, increased red blood cells and hemoglobin improves VO2max, so you can improve your aerobic capacity just by acclimatizing yourself to higher and higher altitudes (loc. 3097).
There’s a limit here, though, for eventually the increased level of red blood cells and hemoglobin thickens the blood to the point where it substantially slows its flow, and this is very bad for aerobic capacity (loc. 3097). Thus there is said to be a ‘sweet spot’ for maximizing VO2max; which, it has been discovered, “is around six to nine thousand feet” (loc. 3148).
Many elite endurance athletes take advantage of the sweet spot phenomenon by way of heading to climes in the sweet spot to train. For example, “in the United States, pro endurance athletes hunting for the sweet spot train in mammoth lakes, California; 7,880 feet. Or Flagstaff, Arizona: 7,000 feet” (loc. 3153).
What’s even better for upping VO2max, though, is being born and raised in the sweet spot. For this results not only in increased red blood cells and hemoglobin, but larger lungs as well. As the author explains, “preferable to moving to altitude to train is being born there. Altitude natives who are born and go through childhood at elevation tend to have proportionally larger lungs than sea-level natives, and large lungs have large surface areas that permit more oxygen to pass from the lungs into the blood. This cannot be the result of altitude ancestry that has altered genes over generations, because it occurs not only in natives of the Himalayas, but also among American children who do not have altitude ancestry but who grow up high in the Rockies. Once childhood is gone, though, so too is the chance for this adaptation. It is not… alterable after adolescence” (loc. 3156).
PART II: WHY DISTANCE RUNNERS ARE FROM EAST AFRICA AND SPRINTERS ARE FROM WEST AFRICA
Section D. East Africa
10. Why So Many Elite Distance Runners Hail from East Africa (Part I): Altitude and Latitude
a. The Elevation Sweet Spot
One fairly large stretch of land that lies smack dab in the middle of the sweet spot is the highlands of East Africa, which is located primarily in Kenya and Ethiopia. Now, if you are at all familiar with the world of long-distance running, you know that Kenya and Ethiopia are the world’s two leading superpowers here (loc. 3052). Take Kenya, for instance, the unquestioned leader of the pack. As Epstein explains, “Anthropologist Vincent Sarich used world cross-country championship results to calculate that Kenyan runners outperformed all other nations by 1,700 fold. Sarich made a statistical projection that about 80 out of every 1 million Kenyan men have world-class running talent, compared with about 1 out of every 20 million men in the rest of the world… A 1992 Runner’s World article noted, based purely on population percentages, the statistical chances of Kenyan men having won the medals they did at the 1988 Olympics was 1 in 1,600,000,000” (loc. 2967).
The fact that large parts of Kenya and Ethiopia are located in the long-distance running sweet spot is no doubt part of the reason why these countries dominate on the international running scene, but there’s more to it than that. It turns out that there is a perfect storm of factors that explain this phenomenon.
b. The Equator (and the Nilotic Body Type)
To begin with, one thing you will notice about the map above is that the Equator runs straight through the middle of Kenya, and Ethiopia isn’t too far away. Recall what was said above about those with ancestors who hail nearer the Equator: the closer to the Equator your ancestors are from the more likely you are to have longer limbs and a short, thin torso, the exact body type that is built for long distance running.
11. Why So Many Elite Distance Runners Hail from East Africa (Part II): The Kalenjin and the Oromo Tribes (Thin Lower Legs and Cattle-Raiding Ancestors)
One more thing, though. It turns out that the vast majority of elite long-distance runners from Kenya and Ethiopia come from two particular tribes (one in each county). In Kenya it is the Kalenjin tribe, and in Ethiopia it is the Oromo tribe. With regards to the Kalenjin, as Epstein explains, “the 4.9 million Kalenjin people represent about 12 percent of Kenya’s population, but more than three quarters of the country’s top runners” (loc. 2790). When it comes to the Oromo, “the Oromo people make up about one third of the country’s population but the vast majority of its international runners” (loc. 2807).
a. Thin Lower Legs
What is it about these tribes in particular that makes them stand out? Well, studies have been done on the Kalenjin that indicate there is one more aspect of their physiology that makes them particularly well-suited for distance running; and that is that their lower legs are especially thin. For example, in one study that compared Kalenjin boys with Danish boys it was found that “the volume and average thickness of the lower legs of the Kalenjin boys was 15 to 17 percent less than in the Danish boys” (loc. 2888).
Why would this matter? Because the leg is akin to a pendulum, and the less weight there is at the end of a pendulum, the less energy is required to swing it (loc. 2888). In other words, thin lower legs make for excellent running economy (just as long legs, and a short, thin torso do—which the Kalenjin also have). As Epstein explains, “compared with the Danish runners, the Kalenjin runners tested by the Danish scientists had nearly a pound less weight in their lower legs. The scientists calculated the energy savings at 8 percent per kilometer” (loc. 2900). Stretch that energy savings out over 42 kilometers and you can see why the Kalenjin dominate the international marathon scene.
b. Cattle-Raiding Ancestors
What might explain why the Kalenjin have inordinately thin calves? It could be a genetic fluke (say a result of genetic drift), but it might also be the result of sexual selection. You see, the Kalenjin were traditionally a pastoralist culture. Now, as it turns out, pastoralist cultures in East Africa are known to have practiced cattle raiding. Take the Kalenjin cattle-raids, for instance. As the author explains, these raids involved “stealthily running and walking into the land of neighboring tribes, rounding up cattle, and escorting them back to Kalenjin land as quickly as possible… The raids were conducted largely at night… and sometimes ranged over distances as great as 100 miles!” (loc. 2799). The raiders worked together, but each man was allowed to keep the cattle that he had personally rounded up (loc. 2799).
Now, in the Kalenjin tribe, the number of cattle one owned was a marker of prestige, and could be used to acquire more wives—which, of course, translated into more children. All of this has led at least one theorist, Anthropologist Robert Manners, to offer an evolutionary account of why an inordinate number of the world’s elite runners come from the Kalenjin tribe. Here’s Esptein to explain: “Manners wrote that, insofar as successful cattle raiders had to be strong runners to hustle captive herds to safety, and the best cattle raiders accumulated more wives and children, then cattle raiding could serve as a mechanism of reproductive advantage that favored men with superior distance running genes” (loc. 2802).
Could it be that some random mutation(s) led to certain Kalenjin developing physiological traits that were good for long-distance running (including, perhaps, thinner lower legs), and that these traits conferred an advantage in cattle raids (which conferred a benefit in terms of acquiring wives and children) to the point where these traits came to dominate the population? It’s a speculative theory, but a very intriguing one. And adding to the intrigue is that the Oromo—the tribe from Ethiopia that is responsible for the vast majority of running prowess in that country—is also a traditionally pastoralist tribe that took part in cattle-raids (loc. 2805).
12. Cultural Practices and Values in Kenya and Ethiopia
All the reasons we have mentioned thus far for why Kenyans and Ethiopians (and particularly the Kalenjin and Oromo people) are the world’s greatest long-distance runners are biological in nature. But Kenya and Ethiopia also feature certain cultural practices and values that make them the best candidates to fulfill this role.
For one thing, the vast majority of young people living in these countries run virtually everywhere they need to go—including school. And this early exposure to running makes a big difference in terms of later success in the discipline. As Epstein explains, it has been found that “Kenyan kids who rely on their feet to get to and from school have 30 percent higher aerobic capacities on average than their peers. World-class athletes [are] also more likely than lesser athletes to have had to run or walk six miles or more to school” (loc. 3043). Elsewhere the author adds that “as in Kenya, Ethiopian runners… are also much more likely to have had to run to school than nonrunners, and professional Ethiopian marathon runners are more likely to have had to run long distances to school than professional Ethiopian 5K and 10K runners” (loc. 3043).
Also, when Kenyan and Ethiopian children grow up, they find that long-distance running is one of the quickest ways to get rich, or at the very least remove themselves from poverty—and one of the surest ways too, considering how many runners from these countries have gone on to great success. As Epstein explains, “given Kenya’s annual per capita income of $800, according to the World Bank, the potential payoff for running success is greater, relatively speaking, than even an NBA contract is for an inner-city American boy. Winning a single marathon brings a six-figure payday. Even earning a few thousand dollars in smaller road races in America and Europe is a relative windfall for most rural Kenyans” (loc. 3018). Thus virtually anyone who shows the least bit of promise in running in Kenya and Ethiopia is willing to stick with it long enough to see if it might be a viable option for them (loc. 3009-30). For the vast majority it is not, but the few who do make it tend to become very successful.
Section E. West Africa
13. Why So Many Elite Sprinters Have Origins in West Africa
It is difficult to imagine a population being better-adapted to excel at a particular athletic discipline than the Kalenjin, and yet there is a second example on the very same continent; only this time the sport is sprinting, and the location is West Africa.
To begin with, it is important to recognize just how dominant runners with ancestry from West Africa are when it comes to elite sprinting. As Epstein explains, “at every Olympics after the U.S. boycott of 1980, every single finalist in the men’s Olympic 100-meters, despite homelands that span from Canada to the Netherlands, Portugal, and Nigeria, has his recent ancestry in sub-Saharan West Africa. (The same has been true for women at the last two Olympics, and all but one female winner since the U.S.-boycotted 1980 Games has been of recent western African descent.)” (loc. 2603).
In order to explain this dominance on the part of West African sprinters it is important to first appreciate what West Africa has in common with East Africa. And that is that both locales straddle the equator. As we have seen, people who have ancestors that lived nearer the equator tend to have longer legs relative to their torso than those with ancestors who resided further from the equator; and this carries an advantage in terms of top running speed (loc. 2590).
Where West Africans differ from East Africans, though, is that whereas the latter have had to adapt to high elevation, the former have had to adapt to a different challenge (this one associated with low elevation): malaria. It is now widely accepted that West Africans have evolved two traits that act as protection against the scourge that is malaria. The first is the sickle cell trait, and the second is lower levels of hemoglobin (loc. 2625). Both of these traits protect against malaria by way lessening the potential number of hosts in the blood that the malaria parasite latches on to (loc. 2661-81).
However, both traits also have a negative effect, and that is they leave the individual with less oxygen in their blood (loc. ). Interestingly, though, it appears that 2 other physiological featu
