ACTN3 R577X Genotype Research Articles

The stiffness response of type IIa fibres after eccentric exercise-induced muscle damage is dependent on ACTN3 r577X polymorphism

The aim of the study was to determine the effect of α-actinin-3 (ACTN3) deficiency (XX) on muscle damage induced by an eccentric exercise bout. In this purpose, 4 RR and 4 XX individuals performed an intensive eccentric knee flexion exercise on an isokinetic dynamometer. Muscle biopsies, blood and pain scores were taken before and after the exercise to determine the extent of the exercise-induced damage and the effect of the ACTN3 R577X polymorphism. Maximal isometric strength of the quadriceps and single fibre properties were compared before and after the exercise. The drop in maximal isometric strength of the quadriceps at 45° knee flexion following the eccentric exercise bout was on average 37% 24 h post-exercise. The decrease in force was also apparent in isolated type IIa fibres (8%; P = 0.02), but not in type I fibres (P = 0.88). Creatine kinase and myoglobin plasma levels increased in all participants at least by 55% and 87%, respectively (P < 0.05). In addition, mRNA levels of markers for muscle regeneration and muscle remodelling increased after the eccentric exercise (P < 0.05), however, independently from ACTN3 R577X genotype. The mRNA level of nuclear factor of activated T-cells 1 (NFATc1) decreased after the eccentric exercise only in XX genotypes (P < 0.05). The stiffness of type IIa, but not type I muscle fibres increased only in RR individuals after the eccentric exercise (P < 0.05). While no major effect of α-actinin-3 deficiency on susceptibility to muscle damage was found acutely, the increased stiffness response in fast RR fibres might be a protection mechanism from muscle damage during a subsequent eccentric exercise bout.

More than a 'speed gene': ACTN3 R577X genotype, trainability, muscle damage, and the risk for injuries.

A common null polymorphism (rs1815739; R577X) in the gene that codes for α-actinin-3 (ACTN3) has been related to different aspects of exercise performance. Individuals who are homozygous for the X allele are unable to express the α-actinin-3 protein in the muscle as opposed to those with the RX or RR genotype. α-actinin-3 deficiency in the muscle does not result in any disease. However, the different ACTN3 genotypes can modify the functioning of skeletal muscle during exercise through structural, metabolic or signaling changes, as shown in both humans and in the mouse model. Specifically, the ACTN3 RR genotype might favor the ability to generate powerful and forceful muscle contractions. Leading to an overall advantage of the RR genotype for enhanced performance in some speed and power-oriented sports. In addition, RR genotype might also favor the ability to withstand exercise-induced muscle damage, while the beneficial influence of the XX genotype on aerobic exercise performance needs to be validated in human studies. More information is required to unveil the association of ACTN3 genotype with trainability and injury risk during acute or chronic exercise.

The relationship between ACTN3 R577X gene polymorphism and physical performance in amateur soccer players and sedentary individuals.

The aim of this study was to determine the distribution of ACTN3 R577X gene polymorphism in soccer players and sedentary individuals, and to investigate the relationship of this distribution with performance tests. A total of 100 soccer players and 101 sedentary individuals were enrolled in the study. Standing long jump and countermovement jump (with arm swing, without arm swing and repeated) scores were recorded, using a jump meter. Maximum VO2 levels were measured using a treadmill-connected cardiopulmonary exercise device, Masterscreen CPX. ACTN3 R577X polymorphism was evaluated by real-time PCR. ACTN3 R577X genotype distribution was found to be similar in soccer players and controls (p>0.05). The only statistically significant finding was a shorter countermovement jump with arm swing scores in the RR-genotyped soccer players, compared with their RX genotyped counterparts (p<0.05). In the soccer player group, RX-genotyped subjects were observed to have lower respiratory threshold values compared with RR-genotyped subjects (p<0.05). No significant correlation was detected between this distribution and performance test results. ACTN3 R577X genotype distribution was found to have no effect on sprint and endurance characteristics in amateur soccer players. The ACTN3 R577X polymorphism may not be a specific enough genetic marker to determine athletic performance in soccer.

ACE I/D and ACTN3 R577X genotypes, muscular and cardiovascular fitness in Malay males

ACE I/D and ACTN3 R577X genotypes, muscular and cardiovascular fitness in Malay males

Effects of the ACTN3 R577X Genotype on the Muscular Strength and Range of Motion Before and After Eccentric Contractions of the Elbow Flexors.

The purpose of present study was to examine the association between ACTN3 R577X genotype and functional characteristics of elbow flexors before and after isokinetic eccentric contractions (ECCs). Fifty-two men (age: 20.8±3.8 years, height: 172.5±5.9 cm, body mass: 64.7±6.5 kg, BMI: 21.7±1.7) who had not participated in any regular resistance training for at least 1 year prior to this study were recruited. ECCs consisted of five sets of six maximal voluntary isokinetic (30°/s) ECCs of the elbow flexors with a range of motion (ROM) from 90° flexion to 0° (full extension). Measurements of maximal voluntary isometric contraction (MVC) torque, ROM, and muscle soreness were taken before, immediately after, and 1, 2, 3, and 5 days after ECCs. Genotyping results were analyzed for identifying ACTN3 R577X polymorphism (rs1815739) using TaqMan approach. The genotype frequencies of the ACTN3 R577X polymorphism were RR 26.9% (n=14), RX 50.0% (n=26), and XX 23.1% (n=12). There were no significant differences in MVC torque, ROM, and soreness between three genotype groups of ACTN3 R577X. However, MVC at baseline was greater in RR homozygotes than in X-allele carriers (combined XX and RX; p<0.05). ROM in RR homozygotes at baseline was lower than that of X-allele carriers. Although a significant decrease in ROM was observed in X-allele carriers until 3 days after ECCs, a significant ROM reduction in RR homozygotes was observed only immediately after ECCs. Our data indicated that ACTN3 RR genotype has higher MVC and lower flexibility than X-allele carriers at baseline, but the effect of ACTN3 R577X genotype on these two parameters is limited after ECCs.

Association analysis of the ACTN3 R577X polymorphism with passive muscle stiffness and muscle strain injury.

Passive muscle stiffness is considered to be a major factor affecting joint flexibility and is thought to relate to the occurrence of muscle strain injury. In skinned muscle fiber experiments, the R577X polymorphism of the α-actinin-3 gene (ACTN3) has been associated with passive muscle stiffness. Our primary purpose was to clarify whether the ACTN3 R577X polymorphism influences passive stiffness of human muscle in vivo. We also examined whether the ACTN3 R577X polymorphism is associated with the occurrence of hamstring strain injury. Seventy-six healthy young male subjects were genotyped for the ACTN3 R577X (rs1815739) polymorphism. Shear modulus (an index of stiffness) of each hamstring muscle (biceps femoris, semitendinosus, and semimembranosus) was assessed using ultrasound shear wave elastography, and history of hamstring strain injury was collected via a questionnaire. The muscle shear moduli of the semitendinosus and semimembranosus were significantly higher in R-allele (RR+RX genotype) carriers than in XX genotype carriers, whereas the shear modulus of the biceps femoris did not differ among the ACTN3 R577X genotypes. Frequency of past hamstring strain injury also did not differ between the 3 genotypes nor between the R-allele and XX genotype carriers. This study indicates that RR and RX genotypes of the ACTN3 R577X polymorphism (corresponding to the presence of α-actinin-3 in type II muscle fibers) are associated with increased passive muscle stiffness of the human hamstring in vivo. However, this altered mechanical property might not affect the risk of hamstring muscle strain injury.

ACTN3 R577X Gene Variant Is Associated With Muscle-Related Phenotypes in Elite Chinese Sprint/Power Athletes.

Yang, R, Shen, X, Wang, Y, Voisin, S, Cai, G, Fu, Y, Xu, W, Eynon, N, Bishop, DJ, and Yan, X. ACTN3 R577X gene variant is associated with muscle-related phenotypes in elite Chinese sprint/power athletes. J Strength Cond Res 31(4): 1107-1115, 2017-The ACTN3 R577X polymorphism (rs1815739) has been shown to influence athletic performance. The aim of this study was to investigate the prevalence of this polymorphism in elite Chinese track and field athletes, and to explore its effects on athletes' level of competition and lower-extremity power. We compared the ACTN3 R577X genotypes and allele frequencies in 59 elite sprint/power athletes, 44 elite endurance athletes, and 50 healthy controls from Chinese Han origin. We then subcategorized the athletes into international level and national level and investigated the effects of ACTN3 genotype on lower-extremity power. Genotype distribution of the sprint/power athletes was significantly different from endurance athletes (p = 0.001) and controls (p < 0.001). The frequency of the RR genotype was significantly higher in international-level than that in the national-level sprint/power athletes (p = 0.004), with no international-level sprint/power athletes with XX genotype. The best standing long jump and standing vertical jump results of sprint/power athletes were better in the RR than those in the RX + XX genotypes (p = 0.004 and p = 0.001, respectively). In conclusion, the ACTN3 R577X polymorphism influences the level of competition and lower-extremity power of elite Chinese sprint/power athletes. Including relevant phenotypes such as muscle performance in future studies is important to further understand the effects of gene variants on elite athletic performance.

Evidence for ACTN3 as a genetic modifier of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is characterized by muscle degeneration and progressive weakness. There is considerable inter-patient variability in disease onset and progression, which can confound the results of clinical trials. Here we show that a common null polymorphism (R577X) in ACTN3 results in significantly reduced muscle strength and a longer 10 m walk test time in young, ambulant patients with DMD; both of which are primary outcome measures in clinical trials. We have developed a double knockout mouse model, which also shows reduced muscle strength, but is protected from stretch-induced eccentric damage with age. This suggests that α-actinin-3 deficiency reduces muscle performance at baseline, but ameliorates the progression of dystrophic pathology. Mechanistically, we show that α-actinin-3 deficiency triggers an increase in oxidative muscle metabolism through activation of calcineurin, which likely confers the protective effect. Our studies suggest that ACTN3 R577X genotype is a modifier of clinical phenotype in DMD patients.

ACTN3 R577X genotype and performance of elite middle-long distance swimmers in China.

The ACTN3 gene is one of the genes that have a potential influence on physical performance. Studies have shown that the 577R genotype of ACTN3 is more prevalent in sprint athletes, while the 577X genotype is more prevalent in endurance athletes. In swimming, both power and endurance related phenotypes are equally needed for swimmers to excel at the elite level. Therefore, the ACTN3 R577X polymorphism may become a genetic marker for swimmers. The study aimed to examine the association of the ACTN3 R577X genotype with the performance of elite middle-long distance (MLD) swimmers. The distributions of the ACTN3 R577X (rs1815739) genotype and allele were examined in a general population (206) and a group of elite MLD swimmers (160) in China by using PCR-RFLP and TOF. Compared with the general population, the elite MLD swimmers, especially the females, had a higher frequency of the RR genotype. The swimmers had a higher frequency of the R allele than the general population. However, the difference was not statistically significant. After being stratified by performance, the difference of the R allele frequency between the international master athletes and the general population was statistically significant. The elite MLD swimmers had a higher frequency of the RR genotype than the RX+XX genotype compared with the general population. The ACTN3 R577X polymorphism was associated with the performance of elite MLD swimmers in China. The SNP R577X could be used as a biomarker for selecting elite MLD swimmers in China.

Advances in Exercise, Fitness, and Performance Genomics in 2015.

This review of the exercise genomics literature encompasses the highest-quality articles published in 2015 across seven broad topics: physical activity behavior, muscular strength and power, cardiorespiratory fitness and endurance performance, body weight and adiposity, insulin and glucose metabolism, lipid and lipoprotein metabolism, and hemodynamic traits. One study used a quantitative trait locus for wheel running in mice to identify single nucleotide polymorphisms (SNPs) in humans associated with physical activity levels. Two studies examined the association of candidate gene ACTN3 R577X genotype on muscular performance. Several studies examined gene-physical activity interactions on cardiometabolic traits. One study showed that physical inactivity exacerbated the body mass index (BMI)-increasing effect of an FTO SNP but only in individuals of European ancestry, whereas another showed that high-density lipoprotein cholesterol (HDL-C) SNPs from genome-wide association studies exerted a smaller effect in active individuals. Increased levels of moderate-to-vigorous-intensity physical activity were associated with higher Matsuda insulin sensitivity index in PPARG Ala12 carriers but not Pro12 homozygotes. One study combined genome-wide and transcriptome-wide profiling to identify genes and SNPs associated with the response of triglycerides (TG) to exercise training. The genome-wide association study results showed that four SNPs accounted for all of the heritability of △TG, whereas the baseline expression of 11 genes predicted 27% of △TG. A composite SNP score based on the top eight SNPs derived from the genomic and transcriptomic analyses was the strongest predictor of ΔTG, explaining 14% of the variance. The review concludes with a discussion of a conceptual framework defining some of the critical conditions for exercise genomics studies and highlights the importance of the recently launched National Institutes of Health Common Fund program titled "Molecular Transducers of Physical Activity in Humans."

Progressive Resistance Training Modulates the Expression of ACTN2 and ACTN3 Genes and Proteins in the Skeletal Muscles

Purpose: Mammalian skeletal muscle has the two isoforms of actin binding protein, α-Actinin-2 and α-Actinin-3, which are located in the skeletal muscle Z-line where they cross-link the actin thin filaments. There is a common stop codon polymorphism R577X in the ACTN3 gene. Several association studies have demonstrated that the ACTN3 R577X genotype influences athletic performance. The response of α-Actinins to resistance exercise training is little understood. Methods: Female Sprague-Dawley rats were assigned to control (C; n = 10) and resistance training (T; n = 12) groups. Training consisted of climbing a ladder carrying a load suspended from the tail. After training, fast (Flexor halluces longus, FHL) and slow (Soleus) hind limb muscles from each group was examine to study the effect of resistance training on muscle mass. Gene expression and protein levels of both Actn3, Actn2 were examined. Results: The resistance trained group had a significantly greater absolute muscle mass in FHL (P=0.011). We also found that Actn3 and Actn2 gene expression levels increased significantly in FHL and Soleus muscles by mean factors of 2.16, and 2.91, respectively. α-Actinin-2 protein expression increased significantly in training group (P=0.025) while, α-actinin-3 protein expression remained similar in training & control groups (P=0.130). The most important finding of this study showed that both α-actinin-3 and α-actinin-2 mRNA levels were up-regulated after 8wk of resistance training (P≤0.05). Conclusion: Our results provide a new insight into the impact of progressive resistance training and evaluating the role of α-actinins responsiveness.

ACTN3 R577X genotype and athletic performance in a large cohort of Japanese athletes

Aim: Recent meta-analyses of the literature confirmed the association between the RR+RX genotype of the ACTN3 R577X polymorphism and elite sprint/power athletic status in Europeans but not in Asians and Africans, while the association between the R577X genotype and elite endurance athlete status is less convincing. The aim of the present study was to investigate the association between the ACTN3 R577X genotype and elite athlete status in a large Asian (Japanese) cohort of track and field athletes. Methods: One-thousand fifty-seven Japanese track and field athletes (627 sprint/power athletes and 430 endurance athletes) and 810 Japanese controls were genotyped for the ACTN3 R577X polymorphism (rs1815739) by using the TaqMan® SNP Genotyping Assay. Results: Elite sprint/power athletes had a higher frequency of the RR+RX genotype than the controls (OR: 1.59, 95% CI: 1.16–2.18; P = .003). A significant linear correlation was found between the RR + RX genotype and athlete status (i.e. regional < national < international) in sprint/power athletes (regional: 71%, national: 81%, international: 84%; P = .001 for trend) and long-distance runners (regional: 65%, national: 72%, international: 82%; P = .030 for trend). Conclusions: The data obtained for this large Asian (Japanese) cohort of track and field athletes served to confirm the association between the RR + RX genotype of the ACTN3 R577X polymorphism and elite sprint/power athlete status and also the association between the ACTN3 RR + RX genotype and long-distance running athletic status.

ACE and ACTN3 Genes Polymorphisms and Endurance Performance

ACE I/D and ACTN3 R577X polymorphisms are the most extensively studied genes in recent years in association with human physical performance. VO2max is recognized as one of the major quantitative traits in sports physiology and the most common method to demonstrate cardiorespiratory endurance. The heritability for the VO2max in several studies has been observed up to 51%. PURPOSE: (1) To assess ACE gene ACTN3 genotype frequencies in young male skiers compared to the control group and (2) to analyze the relationships between VO2peak and ACE I/D and ACTN3 R577X polymorphisms in young male skiers. METHODS: Male skiers (n=56; 14 to 21 yrs), 52% of them are current or former junior national team members of Estonia. A standardized exercise test on a treadmill with determination VO2peak was performed. Anthropometric measurements and training characteristics were obtained. The male control group (n=145, 20 to 37 yrs) consisted of healthy sedentary subjects without previous athletic status. Venous blood samples for DNA extraction were collected. Genotyping of rs4343 (ACE, C_11942562_20) and rs1815739 (ACTN3, C_590093_1) was carried out by using the TaqMan SNP 5’ allelic discrimination assay. For statistical analysis, descriptive analysis, χ2-test was used. RESULTS: Frequency of ACE ID and ACTN3 RR genotypes in male skiers was statistically higher (p<0.05) and frequency of RX genotype of ACTN3 was lower (p<0.05) compared with controls. There were no significant differences in distribution of ACE I/D and ACTN3 R577X polymorphisms between the groups with different competing levels. We did not observe significant differences in mean VO2peak between ACE I/D, as well between ACTN3 R577X genotypes in male skiers. CONCLUSIONS: Our study results revealed a statistically higher prevalence of ACE ID and ACTN3 RR genotypes in young male skiers (64% and 40%, respectively) compared with male controls (47% and 18%, respectively). Mean VO2peak did not show significant differences between ACE I/D as well between ACTN3 R577X genotypes in male young skiers.

Association of the ACTN3 R577X polymorphism with glucose tolerance and gene expression of sarcomeric proteins in human skeletal muscle.

A common polymorphism (R577X) in the α-actinin (ACTN) 3 gene, which leads to complete deficiency of a functional protein in skeletal muscle, could directly influence metabolism in the context of health and disease. Therefore, we tested the hypothesis that states of glucose tolerance are associated with the ACTN3 R577X genotype. We analyzed the prevalence of the ACTN3 R577X polymorphism in people with normal glucose tolerance (NGT) and type 2 diabetes (T2D) and measured muscle-specific α-actinin 2 and 3 mRNA and protein abundance in skeletal muscle biopsies. Furthermore, we investigated the protein abundance of the myosin heavy chain isoforms and the components of the mitochondrial electron transport chain in skeletal muscle from people with NGT or T2D. mRNA of selected sarcomeric z-disk proteins was also assessed. Although the prevalence of the ACTN3 577XX genotype was higher in T2D patients, genotype distribution was unrelated to metabolic control or obesity. ACTN2 and ACTN3 mRNA expression and protein abundance was unchanged between NGT and T2D participants. Protein abundance of mitochondrial complexes II and IV was related to genotype and glucose tolerance status. Gene expression of sarcomeric z-disk proteins was increased in skeletal muscle from NGT participants with the ACTN3 577XX genotype. While genetic variation in ACTN3 does not influence metabolic control, genotype does appear to influence gene expression of other sarcomeric proteins, which could contribute to the functional properties of skeletal muscle and the fatigue-resistant phenotype associated with the R577X polymorphism.

The ACTN3 R577X genotype is associated with muscle function in a Japanese population.

Homozygosity for the common nonsense polymorphism R577X in the α-actinin-3 gene (ACTN3) causes complete α-actinin-3 deficiency in fast-twitch skeletal muscle fibers. This study investigated whether the ACTN3 R577X polymorphism affects fitness status using a battery of tests in a large Japanese cohort. In the present study, 1227 subjects (age: 25-85 years) were genotyped for the ACTN3 R577X polymorphism (rs1815739) using a TaqMan SNP genotyping assay (Applied Biosystems). All subjects were divided into 2 groups based on their age (<55 years and ≥55 years). All subjects completed a questionnaire about exercise habits and were subjected to a battery of tests to assess their fitness status (including grip strength test, chair stand test, and 8-foot walking test). A significant association between the ACTN3 R577X genotype and chair stand test performance was observed in the group of men ≥55 using ANCOVA adjusted for age and exercise habits (p = 0.036). The ACTN3 R577X genotype accounted for 2.5% of the variability in the results of the chair stand test among men in the ≥55 age group. Moreover, for the ≥55 age group, performance in the chair stand test was lower among those with the XX genotype than among those with the RR genotype (p = 0.024) or RX genotype (p = 0.005), unlike results for the <55 age group. No significant difference was noted for hand grip strength or 8-foot walking time. Thus, our results suggest that the ACTN3 R577X genotype is associated with lower-extremity muscle function in the Japanese population.

Interaction Between ACE I/D and ACTN3 R557X Polymorphisms in Polish Competitive Swimmers

We hypothesized that the ACE ID / ACTN3 R577X genotype combination was associated with sprint and endurance performance. Therefore, the purpose of the present study was to determine the interaction between both ACE ID and ACTN3 R577X polymorphisms and sprint and endurance performance in swimmers. Genomic DNA was extracted from oral epithelial cells using GenElute Mammalian Genomic DNA Miniprep Kit (Sigma, Germany). All samples were genotyped using a real-time poly- merase chain reaction. The ACE I/D and the ACTN3 R577X genotype frequencies met Hardy-Weinberg expectations in both swimmers and controls. When the two swimmer groups, long distance swimmers (LDS) and short distance swimmers (SDS), were compared with control subjects in a single test, a significant association was found only for the ACE polymorphism, but not for ACTN3. Additionally, four ACE/ACTN3 combined genotypes (ID/RX, ID/XX, II/RX and II/XX) were statistically significant for the LDS versus Control comparison, but none for the SDS versus Control comparison. The ACE I/D and the ACTN3 R577X polymorphisms did not show any association with sprint swimming, taken individually or in combination. In spite of numerous previous reports of associations with athletic status or sprint performance in other sports, the ACTN3 R577X polymorphism, in contrast to ACE I/D, was not significantly associated with elite swimming status when considered individually. However, the combined analysis of the two loci suggests that the co-occurrence of the ACE I and ACTN3 X alleles may be beneficial to swimmers who compete in long distance races.

The ACTN3 R577X Polymorphism Is Associated With Muscle Power in Male Japanese Athletes

In this study, we investigated whether the ACTN3 R577X polymorphism is associated with muscular power in Japanese collegiate athletes by analyzing the mean and peak power results of a 30-second Wingate anaerobic test (WAnT) with respect to the ACTN3 R577X genotype in 253 Japanese athletes (144 men and 109 women). Each athlete performed a 30-second WAnT with a resistance equal to 7.5% of his or her body weight. Genotyping for the ACTN3 R577X (rs1815739) polymorphism was performed using the TaqMan approach. The ACTN3 R577X genotypes exhibited a Hardy-Weinberg equilibrium distribution in our population. The relative and absolute mean power results of the 30-second WAnT did not differ significantly among the genotypes. However, the relative peak power result of the WAnT was significantly higher in the R-allele-dominant model groups than in the XX group in male but not female athletes. These results suggest that the ACTN3 R allele is associated with the relative peak power during the WAnT in male Japanese collegiate athletes.

ACTN3 R577X Genotype is Associated with Sprinting in Elite Japanese Athletes

The ACTN3 R577X genotype has been found to associate with sprint/power phenotypes in all elite athlete cohorts investigated. This association has not been extensively studied in elite Asian athletes. The present study was undertaken to investigate the association between the ACTN3 R577X genotype and elite Japanese track and field athlete status. 299 elite Japanese track and field athletes (134 sprint/power athletes; 165 endurance/middle-power athletes) and 649 Japanese controls were genotyped for the ACTN3 R577X polymorphism. All athletes were of national or international level. Sprint/power athletes showed a higher frequency of RR + RX genotype than controls (111/134 [82.8%] vs. 478/649 [73.7%], P = 0.025 under the R-dominant model), while there was no significant difference between endurance/middle-power athletes and controls (126/165 [76.4%] vs. 478/649 [73.7%], P = 0.48 under the R-dominant model). Sprinters with the RR + RX genotype had significantly faster personal best times for the 100 m than those with XX genotype (10.42 ± 0.05 s vs. 10.64 ± 0.09 s, P = 0.042); no such association was found in the 400 m sprinters (47.02 ± 0.36 s vs. 47.56 ± 0.99 s, P = 0.62). ACTN3 R577X genotype is associated with sprint/power performance in elite Japanese track and field athletes, especially short sprint performance.

No Association Between ACTN3 R577X Polymorphism and Elite Judo Athletic Status

The authors compared ACTN3 R577X genotype and allele frequencies in the majority of all-time-best Spanish judo male athletes (n = 108) and 343 ethnically matched nonathletic men. No between-groups differences were found in allele (P = .077) or genotype distributions (P = .178). Thus, the R577X polymorphism was not significantly associated with the status of being an elite judo athlete, at least in the Spanish population. The contribution of genetics to sports-related phenotype traits is undeniable with some genotypes, of which ACTN3 R577X is currently the leading candidate, partly distinguishing individuals predisposed to either endurance or power sports. However, few athletic events can be categorized as purely power or endurance based. Although genetic testing (ie, for ACTN3 R577X) is already being marketed to predict sports talent and potential of young children, its usefulness is still questionable, at least in competitive judo.

ACTN3 genotype in Spanish elite swimmers: No “heterozygous advantage”

The aim of the present case-control study was to examine the association of the ACTN3 R577X genotype with elite swimming status. We compared a group of Spanish (Caucasian) elite swimmers (n = 88) with other cohorts of the same ethnic origin, i.e., nonathletic controls (n = 343) and other types of athletes who are in both end-points of the sports performance continuum, i.e., world-class power (n = 119) and endurance male athletes (n = 154). Swimmers had a lower odds ratio (OR) of having the RX genotype [1.815, 95% confidence intervals (CI): 0.899-3.664] compared with nonathletic controls, yet the association did not reach statistical significance (P = 0.096). Endurance athletes had greater OR of having the XX genotype (OR: 2.88, 95% CI: 1.162-7.135, P = 0.022), or the RX+XX genotype (OR: 1.903, 95% CI: 1.015-3.567, P = 0.045) compared with swimmers. No other association was found. In summary, we did not observe an association between the ACTN3 R577X polymorphism and elite swimmer's status, suggesting that any influence of this polymorphism is not of sufficient magnitude as to significantly influence elite swimming performance, at least in Spanish athletes.