What Makes Kenyan Distance Runners the World’s Best?

Kenyan distance runners are known to have exceptionally high endurance for distance running and their performances are well recognized in major global events. Their unique capability has attracted several studies trying to find out possible factors associated with their elite performance. Some of these studies have tried to find a unique genetic make-up or physiology for the Kenyans, but no one study to date has found any clear evidence.

For this reason, researchers from the University of Stellenbosch, South Africa, conducted a systematic review of the present research studies in an attempt to synthesize evidence on biomechanical factors associated with running economy and performance of elite Kenyan distance runners. This systematic review was published in the Journal of Bodywork and Movement Therapies.

Running economy is a complex multi-factorial measure of running efficiency, which reflects the combined functioning of biomechanical, neuromuscular, metabolic, and cardio-respiratory factors, some of which are hereditary and some of which adapt to coaching.

The researchers included eight cross-sectional studies in their review. The overall methodological score of the studies was moderate.

The review found the following regarding elite Kenyan distance runners compared to other elite distance runners around the world:

• No Difference: Shank (lower leg) length is not significantly longer.
• Possible Differences: There is some evidence regarding the Kenyans’ slender and tall body type, low BMI, low body mass, slender and longer lower limbs with mass distributed more proximally, longer Achilles tendon tissue and Achilles moment arm, as well as lower foot levers. However these were classified as “maybe factors” because the authors could not conclusively find these factors in many of the studies.
• Definite Difference: The Kenyans were found to have significantly longer gastrocnemius Achilles tendons compared to their counterparts (other runners about the world). A longer gastrocnemius Achilles tendon “is a factor” associated with running economy and performance.

The authors listed a number of limitations inherent to their review including: low level of evidence, minimal number of included studies, small sample size, and lack of appropriate control subjects.

Nevertheless, the one difference that was conclusively found is that Kenyan distance runners have significantly longer gastrocnemius Achilles tendons compared to other elite distance runners.

This blog post article was created in collaboration with Dr Joe Muscolino

Posterior view of the gastrocnemius. Permission Joseph E. Muscolino. The Muscular System Manual – The Skeletal Muscles of the Human Body, 4th ed. (Elsevier, 2017).