another new report?

If you were parent to a 14-year-old American boy with a BMI of 15.5, the neighbors would whisper about neglect, and possibly report you to Child & Family Services. In Kenya, on the other hand, your home might be considered an Olympic Training Camp for distance runners.

That’s one of the striking results from Other Hearst Subscriptions (with free, full text) on daily energy expenditure of Rift Valley teens: The kids are really, really skinny. Which might be one of the reasons they are also so fast in endurance races.

For decades, many observers of the Kenyan success story have guessed that Rift Valley runners are dominant in distance races because they spend their childhood “training” by running/walking to school and working in the fields. American kids ride the school bus, watch TV after school hours, and struggle to keep up in major marathons.

Recently, an experienced team of Kenyan experts including Yiannis Pitsiladis of the University of Glasgow and Daniel Lieberman from Harvard decided to test the early-training theory. They figured that the Kenyan youth who did the most running and walking in their daily lives would have the highest vo2 max scores, a measure of potential running success. However, their testing of 30 young males and females failed to support the hypothesis. In other words, the Kenyans who ran and walked the most didn’t have the highest vo2 max scores. This tends to undercut the early-training theory.

But it doesn't imply that the Kenyan kids are sedentary. Hardly. They averaged 7.5 kilometers a day, trotting to and from school. Still, this doesn’t exactly amount to marathon training, not when they made four trips a day (to school; home for lunch; back to school; back home) for an average of about 1.1 miles each way.

It’s the Kenyans’ low BMIs that really stand out (see table below). When you’re fit and have a low BMI, you also have a high max vo2, as the two are inversely related. The young Rift Valley subjects were tested for vo2 max through a tough, interval-running routine at a makeshift (and undulating) 400-meter track. According to Jack Daniels’s “Oxygen Power” tables, the untrained Kenyan youth who attended a school not known for producing track champions may have the potential to run a 2:18 marathon (males) or a 2:39 (females). And those are the "average" scores; the paper did not report the full range of observed vo2 max scores, so we don't know how the fittest boys and girls performed.

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[New information: The lead author of the paper, Alexander Gibson, just responded to my request for the full range of data by reporting that three of the boys exceeded 80 ml*kg/min, with the top runner hitting 81.6. According to Oxygen Power, 80 confers potential for a 2:07:38 marathon, and 81.9 a 2:05:06. The top girl hit 68.9 ml*kg/min, giving potential for a 2:25:08. Says Gibson: "It was clear early on that we were studying a remarkable population from watching complete the running tests, sometimes at speeds up to 18 km/hour while at altitude and wearing a portable accelerometer. It was also evident from observing the children in their rural, home environment, running to and from school, occasionally carrying books, younger siblings, or water."]

But do skinny kids with high vo2 max scores develop into championship runners? Daniels says it’s quite possible, based on a longitudinal trial he conducted many years ago with teenage runners. He found that they gained weight as they matured, but also gained muscle, with the result that they managed to maintain their high maxes.

Lieberman, who is in Kenya now, working on his next project, says he found the results utterly unsurprising. “We have known that the kids are physically active from an early age, live at high altitude, and get no junk food,” he says.

Pitsiladis believes the study paints a grim picture for future distance efforts by Western world runners. “It is not surprising that Steve Cram, David Moorcroft and Sebastian Coe still hold important running best times in the UK with little or no chance of their records being broken,” he says. “Our young population is simply too unfit in general, so there is little chance of extremely talented athletes emerging. Similarly, this data explains why east Africans (e.g. Kenyans in particular) will continue to dominate middle and distance running, and further perpetuate the unproven idea that Kenyan Great World Race: Results.”

Here's These Are the Worlds Fastest Marathoners on 14 fully-mature but skinny Kenyan marathoners with an average best time of 2:07:16. If I did my math correctly, they have a height (in inches) to weight (in pounds) ratio of .53. You can compare yourself by dividing your height by your weight. Higher is better. If you're anywhere around .5, you might have a chance against the Kenyans. If you're in the .4xs or .3xs, you should challenge them to a bowling match.

On the day when I won the Boston Marathon in 1968, my ratio was .52. But I've sunk into the .4xs now.