Prevalence of the RR genotypes of the locus ACTN3-R577X in Italian Muay Thai elite fighters

BACKGROUND: The α-actinin skeletal muscle isoform 3 ACTN3 p.Arg577X is one of the most frequently genetic variants tested for professional sports and exercise. The aim of this work was to evaluate the prevalence of the ACTN3 p.Arg577X genotypes in a consecutive series of 117 Italian Muay Thai elite fighters enrolled during the agonistic eligibility screening programs. METHODS: One hundred and seventeen professional Muay Thai Italian athletes and 150 controls (all coming from Sardinia) were genotyped for the ACTN3 polymorphisms (SNP ID rs1815739) using real-time polymerase chain reaction. RESULTS: In the two groups, the genotypes' distribution was as per the Hardy-Weinberg principle (P>0.05). Statistically significant differences were observed for the ACTN3 X-allele that was more frequent in the athletes group compared to the controls (32% vs. 29.2%; P=0.012). The association between the genotype (Arg and X alleles) and the athletic status for the participants were statistically different in the Muay Thai group (Arg/Arg 46.2%, Arg/X 43.5% and X/X 10.3%) compared with the controls (Arg/Arg 50%, Arg/X 41.3% and X/X 8.7%). Muay Thai is characterized is a highly demanding sport in terms of both anaerobic and aerobic exercise, due to the powerful strikes and intense resistance training programs. Our results shed light onto a much-debated issue regarding the contribution of genetics to physical performance in the setting of martial arts at elite level in Italy. Since both power and endurance-related phenotypes are needed to excel at elite level, it would be logical that the ArgX genotype played a key role in fighting performance. However, the prevalence of ArgArg+ArgX demonstrates that the R allele is still the "most desirable" genotype. CONCLUSIONS: Although the present study was carried out on a small cohort of professional fighters, it can be concluded that the ACTN3 Arg allele is the "favored genotype".