Three years ago, a Harvard team including evolutionary biologist Daniel Lieberman, Ph.D., published a paper in Nature showing a high percentage of forefoot striking among Kenyan runners, adults and adolescents, who had grown up barefoot. The paper led many to conclude that humans had evolved to be forefoot/midfoot runners, and not rearfoot runners.



Now a research group from George Washington University has conducted a similar analysis of another group of habitually barefoot Kenyans, and reached the opposite conclusion. Among 38 barefoot Daasanach tribe members from northern Kenya (19 men, 19 women), 72 percent landed on their rearfoot when running barefoot at a self-selected, comfortable pace.

The GWU team did confirm one central Lieberman finding. “Our data support the hypothesis that a forefoot strike reduces impact loading,” they wrote. Nonetheless, “the majority of subjects instead used a rearfoot strike at endurance running speeds.”



The GWU data also supported the notion that running speed affects landing. When their Daasanach subjects increased speed, they were more likely to land on the midfoot or forefoot. At the slowest speeds (9:00 to 13:24 per mile), 83 percent of runners landed on their rearfoot. At speeds faster than 5:21 per mile, this decreased to about 43 percent.



Many of Lieberman’s barefoot (and forefoot-striking) Kenyan subjects were running at sub-5:00/mile pace. By contrast, his “habitually barefoot” running U.S. subjects averaged 6:52 pace. See the tables below for data from both studies.



The GWU team believe that many other factors could influence preferred running style. These include “training level, substrate mechanical properties [ie, running surface, hard or soft], running distance and running frequency.”



The question of running speed becomes important because, from an evolutionary perspective, it should answer this question: What running speed would have put the most calories on the dinner table? Did Paleo runners survive by going relatively long and slow, or with shorter, faster bursts? Little is known about this subject.



The Daasanach live on the northern reaches of Lake Turkana in Kenya, bordering Ethiopia and Sudan. They are a small tribe with little or no running history. Lieberman’s study was conducted with Kalenjin runners in and around Eldoret, Kenya, about 300 miles from the homeland of the Daasanach. Many of Kenya’s fastest, most famous runners come from the Kalenjin tribe.

GWU Study, 2013: Percent Rearfoot Strikers (All Barefoot)

Rearfoot % Speed, range (pace per mile) Daasanach 83 8:56-13:24 Daasanach 68 6:42-8:56 Daasanach 73 5:21-6:42 Daasanach 43 4:28-5:21

Harvard Study, 2010: Percent Rearfoot Strikers (All Kenyans barefoot)

Rearfoot % Speed, average (pace per mile) Kenyan adults 9 4:32 Kenyan teens 25 4:52 U.S. barefoot 12 6:52 U.S. shod 83 6:42

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