Association of muscle fiber composition with health and exercise-related traits in athletes and untrained subjects

Skeletal muscle is a heterogenous and metabolically active tissue, the composition of which is associated with multiple traits. The aim of the study was to determine whether there are additional health and exercise-related traits associated with muscle fiber composition in athletes and non-athletes. This study recruited 164 Russian participants (51 endurance and 48 power athletes; 65 controls). Vastus lateralis muscle fiber composition was assessed by immunohistochemistry. Slow-twitch muscle fiber percentage (STMF%) was significantly greater in endurance than power athletes and non-athletes, and in non-athlete females than males. STMF% was positively associated with athletes’ training frequency, non-athletes’ and endurance athletes’ age, endurance athletes’ competition level and chest depth, and power athletes’ training age. STMF% was negatively associated with diastolic blood pressure in power athletes and with systolic blood pressure and reaction time in non-athletes. In all participants, STMF% was positively associated with age, tolerance to long distance exercise, chest depth and fracture incidence, and negatively with systolic blood pressure and resting heart rate. Age, sex and training frequency explained 10.6% and 13.2% of the variance in STMF% in endurance and power athletes, respectively. This is one of the most comprehensive studies involving athletes and untrained subjects and provides novel information concerning associations of increased STMF percentage with lower resting heart rate, better tolerance to long distances, faster reaction time and larger chest depth. On the other hand, the increased percentage of fast-twitch muscle fibers was associated with rare fracture incidence

Is testosterone responsible for athletic success in female athletes?

BACKGROUND: The aim of this study was to determine the interrelationship between the resting serum testosterone (T) levels of female athletes from different types of sporting events and their athletic success. METHODS: The study involved 599 Russian international-level female athletes (95 highly elite, 190 elite, and 314 sub-elite; age: 16-35 years) and 298 age-matched female controls. The athlete cohort was stratified into four groups according to event duration, distance, and type of activity: 1) endurance athletes; 2) athletes with mixed activity; 3) speed/strength athletes; 4) sprinters. Athletic success was measured by determining the level of achievement of each athlete. RESULTS: The mean T levels of athletes and controls were 1.65±0.87 and 1.76±0.6 nmol/L (P=0.057 for difference between groups) with ranges of 0.08-5.82 and 0.38-2.83 nmol/L in athletes and controls, respectively. T levels were positively associated with athletic success in sprinters (P=0.0002 adjusted for age) only. Moreover, none of the sub-elite sprinters had T>1.9 nmol/L, while 50% of elite and highly elite sprinters had T>1.9 nmol/L (OR=47.0; P<0.0001). CONCLUSIONS: Our data suggest that the measurement of the serum T levels significantly correlates with athletic success in sprinters but not other types of athletes and in the future may be useful in the prediction of sprinting ability

Prediction of muscle fiber composition using multiple repetition testing

Direct determination of muscle fiber composition is invasive and expensive, with indirect methods also requiring specialist resources and expertise. Performing resistance exercises at 80% 1RM is suggested as a means of indirectly estimating muscle fiber composition, though this hypothesis has never been validated against a direct method. The aim of the study was to investigate the relationship between the number of completed repetitions at 80% 1RM of back squat exercise and muscle fiber composition. Thirty recreationally active participants’ (10 females, 20 males) 1RM back squat load was determined, before the number of consecutive repetitions at 80% 1RM was recorded. The relationship between the number of repetitions and the percentage of fast-twitch fibers from vastus lateralis was investigated. The number of completed repetitions ranged from 5 to 15 and was independent of sex, age, 1RM, training frequency, training type, training experience, BMI or muscle fiber cross-sectional area. The percentage of fast-twitch muscle fibers was inversely correlated with the number of repetitions completed (r = –0.38, P = 0.039). Participants achieving 5 to 8 repetitions (n = 10) had significantly more fast-twitch muscle fibers (57.5 ± 9.5 vs 44.4 ± 11.9%, P = 0.013) than those achieving 11–15 repetitions (n = 11). The remaining participants achieved 9 or 10 repetitions (n = 9) and on average had equal proportion of fast- and slow-twitch muscle fibers. In conclusion, the number of completed repetitions at 80% of 1RM is moderately correlated with muscle fiber composition

Whole genome sequencing of elite athletes

Whole genome sequencing (WGS) has great potential to explore all possible DNA variants associated with physical performance, psychological traits and health conditions of athletes. Here we present, for the first time, annotation of genomic variants of elite athletes, based on the WGS of 20 Tatar male wrestlers. The maximum number of high-quality variants per sample was over 3.8 M for single nucleotide polymorphisms (SNPs) and about 0.64 M for indels. The maximum number of nonsense mutations was 148 single nucleotide variants (SNVs) per individual. Athletes' genomes on average contained 18.9 nonsense SNPs in a homozygous state per sample, while non-Athletes' exomes (Tatar controls, n = 19) contained 18 nonsense SNPs. Finally, we applied genomic data for the association analysis and used reaction time (RT) as an example. Out of 1884 known genome-wide significant SNPs related to RT, we identified four SNPs (KIF27 rs10125715, APC rs518013, TMEM229A rs7783359, LRRN3 rs80054135) associated with RT in wrestlers. The cumulative number of favourable alleles (KIF27 A, APC A, TMEM229A T, LRRN3 T) was significantly correlated with RT both in wrestlers (P = 0.0003) and an independent cohort (n = 43) of physically active subjects (P = 0.029). Furthermore, we found that the frequencies of the APC A (53.3 vs 44.0%, P = 0.033) and LRRN3 T (7.5 vs 2.8%, P = 0.009) alleles were significantly higher in elite athletes (n = 107) involved in sports with RT as an essential component of performance (combat sports, table tennis and volleyball) compared to less successful (n = 176) athletes. The LRRN3 T allele was also over-represented in elite athletes (7.5%) in comparison with 189 controls (2.9%, P = 0.009). In conclusion, we present the first WGS study of athletes showing that WGS can be applied in sport and exercise science

The GALNTL6 Gene rs558129 Polymorphism Is Associated With Power Performance

The largest genome-wide association study to date in sports genomics showed that endurance athletes were 1.23 times more likely to possess the C allele of the single nucleotide polymorphism rs558129 of N-acetylgalactosaminyltransferase-like 6 gene (GALNTL6), compared with controls. Nevertheless, no further study has investigated GALNTL6 gene in relation to physical performance. Considering that previous research has shown that the same polymorphism can be associated with both endurance and power phenotypes (ACTN3, ACE, and PPARA), we investigated the association between GALNTL6 rs558129 polymorphism and power performance. According to this objective we conducted 2 global studies regarding 2 different communities of athletes in Spain and Russia. The first study involved 85 Caucasian physically active men from the north of Spain to perform a Wingate anaerobic test (WAnT). In the second study we compared allelic frequencies between 173 Russian power athletes (49 strength and 124 speed-strength athletes), 169 endurance athletes, and 201 controls. We found that physically active men with the T allele of GALNTL6 rs558129 had 5.03-6.97% higher power values compared with those with the CC genotype (p< 0.05). Consistent with these findings, we have shown that the T allele was over-represented in power athletes (37.0%) compared with endurance athletes (29.3%; OR = 1.4, p = 0.032) and controls (28.6%; OR = 1.5, p = 0.015). Furthermore, the highest frequency of the T allele was observed in strength athletes (43.9%; odds ratio [OR] = 1.9, p = 0.0067 compared with endurance athletes; OR 5 2.0, p = 0.0036 compared with controls). In conclusion, our data suggest that the GALNTL6 rs558129 T allele can be favorable for anaerobic performance and strength athletes. In addition, we propose a new possible functional role of GALNTL6 rs558129, gut microbiome regarding short-chain fatty acid regulation and their anti-inflammatory and resynthesis functions. Nevertheless, further studies are required to understand the mechanisms involved

Polygenic Profile of Elite Strength Athletes

Strength is a heritable trait with unknown polygenic nature. So far, more than 200 DNA polymorphisms associated with strength/power phenotypes have been identified majorly involving non-athletic populations. The aim of the present study was to investigate individually and in combination the association of 217 DNA polymorphisms previously identified as markers for strength/power phenotypes with elite strength athlete status. A case-control study involved 83 Russian professional strength athletes (53 weightlifters, 30 powerlifters), 209 Russian and 503 European controls. Genotyping was conducted using micro-array analysis. Twenty-eight DNA polymorphisms (located near or in ABHD17C, ACTG1, ADCY3, ADPGK, ANGPT2, ARPP21, BCDIN3D, CRTAC1, DHODH, GBE1, IGF1, IL6, ITPR1, KIF1B, LRPPRC, MMS22L, MTHFR, NPIPB6, PHACTR1, PLEKHB1, PPARG, PPARGC1A, R3HDM1, RASGRF1, RMC1, SLC39A8, TFAP2D, ZKSCAN5 genes) were identified to have an association with strength athlete status. Next, to assess the combined impact of all 28 DNA polymorphisms, all athletes were classified according to the number of ‘strength’ alleles they possessed. All highly elite strength athletes were carriers of at least 22 (up to 34) ‘strength’ alleles, while 27.8% of Russian controls had less than 22 ‘strength’ alleles (P<0.0001). The proportion of subjects with a high (≥26) number of ‘strength’ alleles was significantly greater in highly elite strength athletes (84.8%) compared to less successful strength athletes (64.9%; OR=3.0, P=0.042), Russian (26.3%; OR=15.6, P<0.0001) or European (37.8%; OR=6.4, P<0.0001) controls. This is the first study to demonstrate that the likelihood of becoming an elite strength athlete depends on the carriage of a high number of strength-related alleles

The BDNF-Increasing Allele is Associated With Increased Proportion of Fast-Twitch Muscle Fibers, Handgrip Strength, and Power Athlete Status

The brain-derived neurotrophic factor (BDNF) is involved in neurogenesis and formation of regenerated myofibers following injury or damage. Recent study suggests that the BDNF overexpression increases the proportion of fast-twitch muscle fibers, while the BDNF deletion promotes a fast-to-slow transition. The purpose of this study was to evaluate the association between the BDNF gene rs10501089 polymorphism (associated with blood BDNF levels), muscle fiber composition and power athlete status. Muscle fiber composition was determined in 164 physically active individuals (113 males, 51 females). BDNF genotype and allele frequencies were compared between 508 Russian power athletes, 178 endurance athletes and 190 controls. We found that carriers of the minor A-allele (the BDNF-increasing allele) had significantly higher percentage of fast-twitch muscle fibers than individuals homozygous for the G-allele (males: 64.3 (7.8) vs. 50.3 (15.8)%, P = 0.0015; all participants: 64.1±7.9 vs. 49.6±14.7%, P = 0.0002). Furthermore, the A-allele was associated (P = 0.036) with greater handgrip strength in a sub-group of physically active subjects (n = 83) and over-represented in power athletes compared to controls (7.7 vs. 2.4%, P = 0.0001). The presence of the A-allele (i.e., AA+AG genotypes) rather than GG genotype increased the odds ratio of being a power athlete compared to controls (OR: 3.43, P = 0.00071) or endurance athletes (OR: 2.36, P = 0.0081). In conclusion, the rs10501089 A-allele is associated with increased proportion of fast-twitch muscle fibers and greater handgrip strength, and these may explain, in part, the association between the AA/AG genotypes and power athlete status