The secret of Kenyan success: it’s not the hemoglobin
April’s issue of Medicine & Science in Sports & Exercise brings another in the long line of studies trying to figure out why Kenyan runners are so much better than the rest of the world (other than some of their East African neighbours). As researchers from the universities of Bayreuth and Tubingen in Germany write:
Possible reasons for this performance superiority range from the physiological to the biomechanical, social, and economic, but none of them appears to be exclusively responsible.
Earlier studies have found that elite Kenyan runners have better running economy than elite Caucasian runners — in other words, they require less oxygen to run at a given level of effort. One theory is that Kenyan muscles somehow use oxygen more efficiently, but studies of muscle morphology and function haven’t been able to pick up any significant differences. Another possibility is that, thanks to adaptations from having ancestors living at altitude for 100,000 years, Kenyans are able to transport more oxygen in their blood to fuel the muscles.
To investigate this possibility, the new study measures total hemoglobin mass (tHb-mass) and blood volume (BV), the two factors that predominantly determine oxygen transport. They compared 10 Kenyans with an average 10K time of 28:29 who were staying in Germany for six weeks with a group of 11 German runners with average 10K time of 30:39. Cutting straight to the chase: when the Kenyans arrived in Germany from altitude, their total hemoglobin mass and blood volume per kilogram of body weight were essentially identical to the Germans. As the six weeks in Germany progressed, the Kenyans got fatter (added 3 kg of bodyweight, including 1 kg of fat), and their hemoglobin and blood measures got worse. The conclusion:
The oxygen transport of the blood, that is, tHb-mass and BV, cannot explain the superior endurance performance of Kenyan runners. All of these parameters are in the same range when compared with those of elite German runners, and tHb-mass even deteriorated after adaptation to near sea level.