The genetics of human running: ACTN3 polymorphism as an evolutionary tool improving the energy economy during locomotion

BACKGROUND: Covering long distances was an important trait to human evolution and continues to be highlighted for health and athletic status. This ability is benefitted by a low cost of locomotion (CoL), meaning that the individuals who are able to expend less energy would be able to cover longer distances. The CoL has been shown to be influenced by distinct and even 'opposite' factors, such as physiological and muscular characteristics, which are genetically inherited. In this way, DNA alterations could be important determinants of the characteristics associated with the CoL. A polymorphism in the ACTN3 gene (R577X) has been related to physical performance, associating the X allele with endurance and the R allele with strength/power abilities. AIM: To investigate the influence of ACTN3 genotypes on the CoL. SUBJECTS AND METHODS: One hundred and fifty healthy male individuals performed two constant speed tests (at 10 and 12 km/h) to determine the CoL. RESULTS: Interestingly, the results showed that heterozygous individuals (RX genotype) presented significantly lower CoL compared to RR and XX individuals. CONCLUSIONS: It is argued that RX genotype might generate an intermediate strength-to-endurance phenotype, leading to a better phenotypic profile for energy economy during running and, consequently, for long-term locomotion.