Interaction of ACTN3 gene polymorphism and muscle imbalance effects on kinematic efficiency in combat sports athletes

The Genetic Profile of Combat Sport Athletes: A Systematic Review of Physiological, Psychological and Injury Risk Determinants

This systematic review aims to assess the genetic determinants influencing combat sports performance and address potential gaps in previous reviews. Twenty-four selected studies were analysed, investigating genetic influences on physiological performance, psychological traits, psychophysiological factors like pain perception, and injury susceptibility in combat sport athletes. The systematic literature search, using keywords, encompassed PubMed, Scopus, SportDiscus, Medline, and Google Scholar. The Covidence systematic review management software facilitated the screening process and the creation of the PRISMA flow diagram. The quality assessment complied with the PRISMA guidelines, featuring a custom 10-point scale and the STREGA criteria for more reliable study inclusion. Collectively, the 24 studies incorporated 18,989 participants, of which 3323 were combat athletes of majority European ancestry (71.7%) from various combat sports disciplines. Twenty-five unique genetic variants were significantly associated with combat sports performance across diverse domains. These included physiological performance (nine genetic variants), psychological traits (ten genetic variants), psychophysiological factors (one genetic variant), and injury susceptibility (four genetic variants). In conclusion, this systematic review lays the foundation for a more comprehensive exploration of the association between genetics and athletic performance in the demanding arena of combat sports, offering valuable insights for talent identification, training optimisation, and injury prevention.

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.

An innovative way to highlight the power of each polymorphism on elite athletes phenotype expression

The purpose of this study was to determine the probability of soccer players having the best genetic background that could increase performance, evaluating the polymorphism that are considered Performance Enhancing Polymorphism (PEPs) distributed on five genes: PPARα, PPARGC1A, NRF2, ACE e CKMM. Particularly, we investigated how each polymorphism works directly or through another polymorphism to distinguish elite athletes from non-athletic population. Sixty professional soccer players (age 22.5 ± 2.2) and sixty healthy volunteers (age 21.2± 2.3) were enrolled. Samples of venous blood was used to prepare genomic DNA. The polymorphic sites were scanned using PCR-RFLP protocols with different enzyme. We used a multivariate logistic regression analysis to demonstrate an association between the five PEPs and elite phenotype. We found statistical significance in NRF2 (AG/GG genotype) polymorphism/soccer players association (p < 0.05) as well as a stronger association in ACE polymorphism (p =0.02). Particularly, we noticed that the ACE ID genotype and even more the II genotype are associated with soccer player phenotype. Although the other PEPs had no statistical significance, we proved that some of these may work indirectly, amplifying the effect of another polymorphism; for example, seems that PPARα could acts on NRF2 (GG) enhancing the effect of the latter, notwithstanding it had not shown a statistical significance.

In conclusion, to establish if a polymorphism can influence the performance, it is necessary to understand how they act and interact, directly and indirectly, on each other.

Upper Extremity Strength Imbalance after Mastectomy and the Effect of Resistance Training

The purpose of this non-randomized pre/post comparison trial was to explore the effect of resistance training (RT) on upper extremity strength imbalance in breast cancer survivors. Seventeen right-side dominant female breast cancer survivors (age: 58.2±2.7 years; BMI: 27.8±1.1 kg/m ² ) with right-sided (RSM) or left-sided (LSM) mastectomy completed strength testing (30-second arm curl) before and after an 8-week RT program. At baseline, LSM (n=8) had equal strength bilaterally (right=16.8±1.1 repetitions; left=16.4±1.4 repetitions), whereas RSM (n=9) had impaired strength on the right (16.7±1.3 repetitions) compared to the left (18.6±1.1 repetitions) side ( p <0.01). After RT, RSM increased strength by 25% on the right (initially weaker) side and 19% on the left (initially stronger) side, which resolved the imbalance. By comparison LSM increased 19% on both sides that were initially equal in strength. Based on our findings, breast cancer survivors with dominant-side mastectomy are at risk for upper extremity strength imbalance that can be resolved with a relatively short-term RT program.