Why are the tarahumara amerindians in Mexico such powerful mountain runners?

› The Tarahumara Amerindians in Mexico are extremely potent runners on long mountain trails. We have analyzed publications to find causes. Traditionally the Tarahumara live alternating at altitudes between 2400 m and 800 m. Distances from homes to fields and village centers are large and covered on foot since childhood. Men and women take part in running competitions often with kickballs. › Investigated runs lasted on average 8:42 h (78 km without ascent) and 6:58 h (63km), respectively. The intensity during the short race amounted to 70% of estimated V˙O₂ max (ranging between 41 and 70 ml/(kg*min)), energy expenditure reached 21000 kJ. People run barefoot or with thin sandals resulting in increased forefoot impact and storage of elastic energy. This and the slim frame with little subcutaneous fat reduce energy consumption. The vegetarian nutrition contains many carbohy-drates and plant proteins, little fat and cholesterol. Hemoglobin concentration tends to increased values. Noncoding beta-chain variants possess no importance for oxygen affinity. The hearts are not enlarged like in endurance athletes. Genes show little European admixture. Gene enrichment in musclerelated pathways suggests a contribution to physical resistance. › Conclusions: Explanations for the extreme endurance are fa-vorable biomechanical conditions and physical training begin-ning during childhood. Running on slopes and changing living sites between 800 and 2400 m play an additional role. Standard exercise tests and genetic investigations are necessary in future.