2050 words

Much has been written about the genotypic and phenotypic differences in Jamaicans, Kenyans, and Ethiopians. Why do they dominate these competitions? Is it cultural? Genetic? Does training matter more? Grit? Expertise? There are multiple reasons that they have such an advantage, the most important one being their morphology/somatype. Of course other physiologic and morphologic factors come into play for these three populations, but the greatest physical advantage they have is their somatype which lends itself to running—whether short, medium or long distance.

Back in July, I argued that the wide-hipped Neanderthals were stronger than the recently migrated Homo sapiens, due mostly to pelvic anatomy (along with Neanderthal protein intake). That’s one of the keys to explaining African dominance in running: their long slender bodies with high limb ratios.

Kenyans and Ethiopians

Kenyan distance running is driven by an ethny named the Kalenjin, particularly of the Nandi tribe. Much research has been undertaken on the physiology and morphology of certain subpopulations of Kenyans, with a complex genotype, phenotype, and even SES interaction driving the dominance of this subpopulation (Tucker, Onywera, and Santos-Concejero, 2015). Another important factor is their low BMI. Kenyans have the lowest BMIs in the world at 21.5, which considerably helps in regards to distance running (Radovanovic et al, 2014; Shete, Bute, and Deshmukh, 2014; Sedeaud et al, 2015).

Kenyans—like Jamaicans and Ethiopians—dominate these competitions due to a complex interaction between genes, environment and SES (Tucker, Onywera, and Santos-Concejero, 2015). Though, of course, a lot of what makes certain Kenyan populations dominate is trainable in other populations. Caucasians can have similar trainability in regards to Vo2 max, oxidative enzymes, and running economy. However, Kenyans are more likely to be slender with longer limbs which is a huge advantage in these competitions. So having a good running economy and a high Vo2 max may be the primary causal factors that cause them to be so good at distance running, with, as I’ve noted in the past, a higher genetic ceiling for high Vo2 max, along with high-altitude training (Larsen, 2003). Though Saltin et al (1995) conclude that physical activity during childhood combined with intense training as a teenager explains the higher Vo2 max in Kenyan boys. Other factors such as low blood lactate and ammonia accumulation are also important.

Genetics, though, is the most likely explanation for African distance-running dominance (Vancini et al, 2014; see Scott and Pitsiladis, 2007 for alternative view that as of yet there are no genetic evidence for African running superiority).

Not all studies show that Kenyans have more slow-twitch (type I) fibers than Caucasians, though the oxygen cost of running at a given velocity was found to be lower in elite Kenyan runners compared to non-Kenyans, which may be due to body dimensions. Apparently, there is no indication that Kenyans possess a pulmonary system that confers a physiologic advantage over non-Kenyans (Larsen and Sheel, 2015). Ethiopian diets, however, met the most recommendations for macronutrients, but fluids were lacking (Beis et al, 2011), similar to what is found on similar studies in Kenyans (Onywera et al, 2003).

It is important to note that not all of the literature out there says that there are mainly physiologic/genetic reasons for their success in distance running; other factors that may be at play are somatype which leads to exceptional biomechanical and metabolic efficiency, high-altitude training, and the want to succeed for economic and social advancement (Wilbur and Pitsiladis, 2012). Oxygen transport of the blood doesn’t explain Kenyan dominance either, they have similar oxygen transport as elite German runners (Prommer et al, 2010). Though, women and men from Ethiopia and Kenya, although they only account for <0.1% of the marathons and half-marathons, achieved the fastest times and were the youngest in the half-marathons and full-marathons (Knechtle et al, 2016). Similar results were seen in Switzerland, with male Africans being faster and younger than non-Africans (Aschmann et al, 2013).

From the years 2000-2014, Knechtle et al (2017) analyzed the Boston, Berlin, New York, and Chicago marathon along with the Stockholm marathon. Over this time period, Ethiopian men improved their times, but Ethiopian women didn’t. Age increased in Ethiopian men, but not women. Female and male marathon runners from Ethiopia were the fastest (Knechtle et al 2017). More studies, though, are needed to unravel the complex relationship between environmental and genetic factors that cause East Africans to dominate distance running (Onywera, 2009). However, elite endurance athletes consistently test higher than non-elite athletes on running economy, Vo2 max, and anaerobic threshold (Lorenz et al, 2013), and mechanical work may be able to predict recreational long distance performance (Tartaruga et al, 2013).

Jamaicans

Jamaican sprinting dominance has been chalked up to numerous factors, most recently, symmetry of the knees and ankles (Trivers, Palestis, and Manning, 2013; Trivers et al, 2014). Trivers et al (2014) write in the Discussion:

Jamaicans are the elite sprinters of the world. Why? If symmetry of knees and ankles is a factor, why should Jamaicans be especially symmetrical (there is no knowledge of whether they actually are)? One possibility is heterozygosity for genes important to sprinting. The slave trade greatly increased heterozygosity on the West African side by mixing genes up and down the West coast of Africa from Senegal to Nigeria [15], [16]. Recently a mtDNA haplotype has been isolated that correlates with success in African American–but not Jamaican–sprinters [17]. Since there is a general (if often weak) positive relationship between heterozygosity and body symmetry [18] we are eager to do targeted studies of genomics on areas associated with sprinting, including energy substrate utilization, muscle fibre-type distribution and body composition analyses (with specific reference to the shape and size of the glutei maximi). Fast twitch (anaerobic) muscle fibres are characterized by specific adaptations which benefit the performances of explosive high-intensity actions such as those involved in sprinting. Notably, West Africans appear to have a higher fast twitch muscle fibre content than do comparable Europeans (67.5% vs 59% in one sample [19], as cited in [20]).

It’s interesting to note that the mtDNA haplotype predicts success in African American sprinters, but not Jamaicans. In regards to mtDNA haplotypes, Jamaican sprinters had statistically similar mtDNA haplotypes, which suggests that the elite sprinters arose from the same source population which indicates that there is no population stratification or isolation on sprint performance. African American sprinters and non-sprinters, on the other hand, had statistically significant differences in mtDNA, which implies that maternal ancestry plays a part in sprinting performance (Deason et al, 2011). Studying both maternal and paternal haplotypes to see where source populations originate is important in these fields, since if we know where their population came from, then we can better understand the hows and whys of elite running performance—especially between race. Though demographic studies on Jamaicans show that elite sprinters come from the same demographic population, so genetics cannot possibly account for Jamaican sprinting success, so their sprinting success may be related to environmental and social factors (Irving et al, 2013). We know little about the genomics of elite sporting performance (Pitsiladis et al, 2013), so the physical correlates (somatype) and physiologic correlates will do for now.

Usain Bolt is the current fastest man in the world, due in part to his anthropometric advantage (Krzystof and Mero, 2013). As everyone knows, you cannot teach speed (Lombardo and Deaner, 2014). Bolt himself has a large advantage, in part, to his power development and biomechanical efficiency compared to the people he competes with (Beneke and Taylor, 2010). Though one study has noted that a human may be able to run faster quadrupedally than bipedally–stating that at the 2048 Olympic Games, that the fastest human on the planet may well be a quadrupedal runner (Kinugasa and Usami, 2016). One of the most important factors of acceleration in the 100m sprint is stride frequency (Mackala, Fostiak, and Kowalski, 2015).

In Afro-Caribbean adolescents, body height and stride number to body height ratio were the main determinants of sprint performance (Copaver, Hertogh, and Hue, 2012). Body height being a predictor of sprint performance is nothing new; taller people have longer limbs; longer limbs cover more distance per step. Indeed, sprinters are taller than the American population, there is more variability in men than in women, sprinters have lower body mass and the height range excludes people who are really tall or really short (Uth, 2005).

Fiber typing

I will touch on fiber typing again since I’ve come across new information on it.

East Asians are less likely to have the RR allele of the ‘sprint gene’ (MacArthur and North, 2004) (ACTN3) while Bantus are more likely to have it. Alpha-actinen-3 is a skeletal muscle isoform which is encoded by the ACTN3 gene. Alpha-actinen-3 deficiency is common in the general population (North, 2008; Berman and North, 2010), which means that most people in the general population are XX. Eighteen percent of the population on earth is homozygous for this mutation (Ivarsson and Westerblad, 2015). This allele is the 577X allele, and Bantus are less likely to have it while Eurasians are more likely to have it. The frequency of the RR genotype is also highest in Bantus than in Asians (Mills et al, 2001). This is one very important reason why Eurasians are not faster than Africans (somatype matters too, of course).

Elite sprinters are more likely to be RR and less likely to be XX. Why does this matter? It matters because the RR genotype with the right morphology, fiber type (fast twitch) and contractile properties of the individual fast twitch fibers contribute to heightened performance with an RR genotype (Broos et al, 2016). Jamaicans are also less likely to have the XX genotype (~2 percent) along with Kenyans (Scott et al, 2010). So this shows that since Jamaicans are less likely to be XX, they’re more likely to be RR. So since XX i negatively associated with sprint status, then populations that have a lower frequency will be more likely to have more sprinters, whereas a population that has the genotype will have fewer sprinters.

This is one of many genetic factors that account for elite sprinting performance between populations. So, clearly, the right muscle fiber type combined with the right genotype from the ACTN3 gene infers an advantage, contrary to Daniel MacArthur’s claims that it does not (one of the authors of numerous studies on the ACTN3 gene).

Conclusion

The genetics of sprinting/distance running is currently poorly understood. Though we have a few candidates (and they’re really good, showing variation where they should) like the RR ACTN3 genotype combined with fast twitch fibers. This is very important to note. If you’re missing this, and you’re short with a low Vo2 max and low limb length, there’s an extremely high chance you will not be an elite sprinter/distance runner. I cannot emphasize enough how much the physical factors mean when it comes to this.

It is possible that SES variables combined with other psycho-social factors could explain why these three populations excel so well in these sports. Though, on the other hand, you cannot discount that the individual has to have the right somatype and physical capabilities first. Contrary to popular belief, fiber typing DOES give an advantage, especially if combined with other variables. Low BMI is very important, as are long limbs and a taller than average height.

When it comes to Jamaicans, symmetry of the knees and ankles help considerably, along with a low body mass and taller body. SES factors could be driving the will to compete in these three populations, however, the physical ability needs to be there first, then it needs to be nurtured. Over the next 5 to 10 years, we will have a better understanding of why some populations excel over others and that will largely be due to somatype, physiology, and genetic factors, with SES and other psycho-social factors driving the want to excel in the sport.

The physical differences that underlie the success of these three populations needs more study. Elite athletes of Jamaican, Kenyan, and Ethiopian descent need to be studied more to untangle the physiologic, psychological, physical and social factors that have them excel so well. We know that certain combinations of traits infer a great advantage in certain populations, we now just need enough elite athletes of these populations to study to see how and why they excel so much. The current body of research reviewed here is a good start, though it does leave some questions unanswered.