Grand Kenyans

By Tom Hummer | 4.16.07

On the third Monday of each April, the citizens of Boston celebrate the uniquely New England holiday of Patriot’s Day. The day is a celebration of the opening salvo of the American Revolution at the nearby towns of Lexington and Concord. So naturally, the day belongs to Kenyans. There’s no interesting historic tale here – the day’s festivities center around the running of the annual Boston Marathon, one of the most prestigious of the world’s 26.2-mile events. The Republic of Kenya has produced 14 of the last 16 overall winners, with another champion originating from nearby Ethiopia. This marked dominance extends throughout the realm of distance running, perhaps most profoundly demonstrated by a recent string of 18 straight team championships at the world cross country championships. At this point, we can probably rule out luck.

Quite a range of possibilities have been posited for Kenyan dominance, a few of which are more myth than reality. One legend for Kenyan superiority is that children from the country’s small villages develop their abilities as they run enormous distances to school each day. A nice story, but research has found no difference in activity levels between Danish and Kenyan schoolchildren (we’ll leave lazy Americans out of it for now). Plus, discussions with a group of elite Kenyan runners found that 14 of the 20 interviewed had no such childhood transportation issues.

Another idea we can mostly dismiss is that the Kenyan diet is the secret, which is akin to attributing The Rolling Stones’ popularity to their looks. If anything, the Kenyans probably succeed despite their diet. While rich in carbohydrates and protein, the typical East African diet is in the low range for essential amino acids and fats. The low amount of fat may be disadvantageous for distance runners because it acts as a secondary source for muscular energy. While running extensive distances, muscle glycogen stores diminish, limiting the amount of energy produced. When this happens – around mile 20 – the body must turn to fat, which provides a necessary but slower alternative source of metabolism.

The key to competing in marathons at an elite level is maximizing the efficiency of energy metabolism. Adenosine triphosphate (ATP), the body’s cellular fuel, is most efficiently produced via aerobic metabolism. If oxygen is not readily available due to muscle overuse, anaerobic metabolism takes place; glucose is burned to generate ATP, but in a way that is much less efficient. Several studies have taken a look at the possibility that East African runners have superior oxygen. “VO₂max,” despite sounding like a cheap shampoo, is instead a measure of maximal oxygen usage during intense aerobic exercise (measured in liters/minute or, when taking body mass into account, ml/kg/min). Essentially, the higher VO₂max, the better muscle cells utilize oxygen in the bloodstream for energy, which is particularly beneficial for performance in endurance events. There are genetic differences in VO₂max, but it also improves with training. But here’s the thing – among elite athletes with VO₂max values in a similar high range, the measure isn’t the best predictor of running speed, which means I don’t even have to bother explaining that Kenyans don’t even have a genetic or with-training advantage in VO₂max.

But there must be some reason why I spent the last paragraph harping on the wonders of VO₂max. It wasn’t just to take up space. If I wanted to do that, I would mention the rough finish of Kenya’s Robert Cheruiyot at the 2006 Chicago marathon. Or I would express astonishment about the disturbingly large number of studies that discuss rectal temperature of marathoners, and wonder whether runners were faster when someone was trying to stick a thermometer up their butt.

No, the reason VO₂max is important is that elite Kenyan runners actually demonstrate a greater ability to sustain performance at a high percentage of their VO₂max. In other words, the Kenyans can maximize their oxygen efficiency for a longer period of time than other runners. The primary reason for this advantage is a more economical running stride due to the Kenyan body structure. The thinner calves of Kenyan runners – about 400 grams lighter in each leg compared to Danes – result in less consumption of energy on each stride. The amount of energy saved is accentuated due to the distance of the lower leg from the center of gravity, for the same reason that it is tough to hold a phone book at arms’ length (necessary, I suppose, if you are extremely farsighted): the farther an object is from the center of mass, the greater the force required to move it. With lighter calves, the Kenyans are able to use about 8% less energy than other runners.

In addition to this advantages, another theory posits that lower lactate production benefits the Kenyans’ fuel economy, due in part to differences in activity level of a couple enzymes (citrate synthase and 3-hydroxyacyl-CoA dehydrogenase, but you knew that). Lactate is produced during intense muscle use, and the traditional idea has been that it leads to an acidic intramuscular environment, causing muscle soreness and impairing performance. However, new evidence has challenged this view. Though your gym teacher was right – working those muscles does build up lactate levels – we’re no longer sure that it is the cause of diminishing returns during your workout. So the Kenyans’ lower plasma lactate levels may be more reflective of their efficient muscular performance than a direct cause of their dominance.

Two additional factors may play a role in the perpetuation of Kenyan superiority, if not its origination. First, the mind games that come into play during long-distance competitions make runners particularly susceptible to psychological factors. If a competitor believes that a Kenyan athlete is superior, then, come mile 20, when muscle fatigue and harmful thoughts creep in (e.g. is it just me or are my nipples starting to bleed?), the Kenyan will have an advantage even with equal talent. Next, the continued success of Kenyan runners inspires future generations to carry on the tradition. The best Kenyan athletes become runners, just like the best Canadian athletes develop into hockey players (usually), while the youth in other countries are more likely to partake in less noble pursuits. So despite a small population of 35 million, Kenya maintains a large talent pool from which to continue their excellence.

You were probably told as a young child that you can do anything, as long as you put your mind to it. That is a lie. You can train everyday of your adult life, with an intense, unrivaled single-minded pursuit. You can give up all social engagements, eat right and follow the strictest training regiment. Then, you can find yourself on a Wheaties box for winning the Boston Marathon – if only your calves weren’t half a pound too big. Oh well...maybe they need someone to hold the thermometer.

References

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Holden C. 2004. Peering under the hood of Africa’s runners. Science. 305(5684), 637-39.

Larsen HB. 2003. Kenyan dominance in distance running. Comp Biochem Physiol A Mol Integr Physiol. 136(1), 161-70.

Noakes TD, Myburgh KH, Schall R. 1990. Peak treadmill running velocity during the VO2 max test predicts running performance. J Sports Sci. 8(1), 35-45

Weston AR, Karamizrak O, Smith A, Noakes TD, Myburgh KH. 1999. African runners exhibit greater fatigue resistance, lower lactate accumulation, and higher oxidative enzyme reactivity. J Appl Physiol. 86(3), 915-23.