"You Are Not Wrong About Getting Strong:" An Insight Into the Impact of Age Group and Level of Competition on Strength in Spanish Football Players.

OBJECTIVE: This study aimed to compare the maximum and rapid force production of Spanish football players and explore the differences between age group and level of competition. METHODS: A cross-sectional study was developed to evaluate the peak force (PF), relative PF, and rate of force development over 250 ms (RFD0-250) during the isometric midthigh pull between groups of football players based on age group (senior vs junior) and level of competition (national vs regional). Using a portable isometric rig, 111 football players performed 2 isometric midthigh-pull trials on a force plate. Two-way analysis of variance with Bonferroni post hoc correction was applied, and statistical significance was set at P ≤ .05. The PF, relative PF, and RFD0-250 0, 25, 50, 75, and 100 percentiles were also calculated and descriptively reported, separated by age group and level of competition. RESULTS: The analysis of variance revealed a significant main effect of the level of competition for the PF (P < .001), relative PF (P = .003), and RFD0-250 (P < .001). There was a significant main effect of age group for the PF (P < .001). There was a significant interaction effect of the age group × level of competition for relative PF (P = .014). National players were stronger than regional players on the PF and RFD0-250 (P < .001). Senior players were stronger than junior players for the PF (P < .001). CONCLUSIONS: Maximum and rapid force production are crucial for Spanish football players as they progress in both level of competition and age group. Practitioners should encourage young football players to prioritize strength development to improve their athletic performance.

The 8:1:1 Supplementation of Branched-Chain Amino Acids in High-Intensity Training: A Case Study of the Protective Effect on Rhabdomyolysis.

INTRODUCTION: The increasing prevalence of high-intensity sports activities, notably the burgeoning popularity of CrossFit, underscores the contemporary significance of such physical pursuits. The discernible protective impact of branched-chain amino acids on muscle fatigue and injuries is emerging as a noteworthy area of investigation. Within the realm of sports, integrating BCAA supplementation into dietary practices holds promise for aiding athletes in their recovery, particularly in mitigating Delayed-Onset Muscle Soreness. METHODOLOGY: This study adopted an experimental pilot design with repeated measures, employing a controlled and randomized approach through double-blind procedures. The participant engaged in high-intensity activity, specifically the CrossFit Karen® test, which entailed executing 150 wall ball throws (9 kg) to a height of 3 m. The trial incorporated three randomized supplementation conditions: BCAAs in an 8:1:1 ratio or a 2:1:1 ratio or a placebo condition. The participant consumed 15 g daily for 7 days, commencing 72 h prior to the initial blood sample and the first Karen® test. RESULTS: In this study, BCAA supplementation at an 8:1:1 ratio demonstrated a discernible protective effect against muscular damage, as evidenced by creatine kinase values and ratings of perceived exertion.

Prospective and Retrospective Analysis of the Sporting Success of Elite Spanish High and Long Jumpers.

The aim of the present study was to analyze the sporting progression from U14 to senior categories of elite Spanish high and long jumpers. For prospective analysis, 300 athletes ranked top 20 at U14 were analyzed (153 female and 147 male). For retrospective analysis, 64 athletes ranked in the top 20 in the senior category were included (21 female and 43 male). Ranking positions were registered in each of the seasons where they presented records. Only 6.3% (19) of athletes who reached the top 20 at U14 became successful senior athletes [4.7% (14) of athletes maintained top 20 status throughout their sporting careers from U14 to senior]. The transition rate from U14 to U16 (35.7%) was the most severe drop down in consecutive categories (after this, it ranged from 47.8 to 66.7%). Of the senior top 20 athletes (64), most of them were already ranked top 20 at U16 (59.4%, 38), at U18 (62.5%, 40), at U20 (70.3%, 45) and at U23 (78.1%, 50). Nevertheless, only 34.4% (22) were top 20 when they were U14 athletes. Transition rates in the top 20 senior athletes ranged from 86.7 to 95.5%. Around one out of four (26.6%, 17) of the top 20 senior athletes maintained top 20 status throughout their sporting careers from U14 to the senior category. Although early success is not a good predictor of senior success, successful senior athletes excelled early on and were able to remain in top rankings throughout their sporting careers of national elite jumpers.

Change of Direction Performance in Young Tennis Players: A Comparative Study Between Sexes and Age Categories.

ABSTRACT: Fernandez-Fernandez, J, Loturco, I, Pereira, LA, Del Coso, J, Areces, F, Gallo-Salazar, C, and Sanz-Rivas, D. Change of direction performance in young tennis players: a comparative study between sexes and age-categories. J Strength Cond Res 36(5): 1426-1430, 2022-The aim of this study was to examine the differences in linear sprint, change of direction (COD) performance, and COD deficit in a large sample of under-13 (U13) and under-15 (U15) male and female tennis players. One hundred and twenty-eight junior tennis players grouped into 2 age-groups (U13 years [32 boys and 28 girls] and U15 [36 boys and 32 girls]) participated in this study. Tests included anthropometric measurements, sprints (5-, 10- and 20-m), and a modified version of the 505 COD test. The differences in performance between age-categories and sex were assessed via an independent t-test. The differences in the physical tests between U13 and U15 players were tested using a univariate analysis, with age and anthropometric variables as covariates. Effect sizes (ESs) were calculated for pairwise comparisons. Results showed that boys presented lower 20-m sprint times than girls in the U13 (ES: 0.54; p < 0.05), and lower linear sprint (5-20-m) and COD times than girls in the U15 category (ES varying from 0.67 to 1.60; p < 0.05). Comparing age-groups, U15 girls demonstrated a higher COD deficit than the U13 (p < 0.05), whereas no differences were found in the other variables. In boys, no significant differences were observed in any variable when comparing both categories. These results could be of great interest for coaches and researchers involved in the development and training of elite tennis players, suggesting the need to include strategies able to improve sprint and COD performance throughout the players' specialization process.

Endurance running prevents the age-related decline of calcaneal bone stiffness.

This investigation presents a comparison of calcaneus bone stiffness of endurance runners of different ages and age-matched controls. We found that there was an age-associated decline in calcaneus bone stiffness in the control group while endurance runners prevented this decline, with a higher effect as the participants increased their age. PURPOSE: Previous investigations have found that endurance runners have higher bone mineral density and other bone quality variables in mechanically loaded bones. However, it is unknown if endurance running might counteract the decline in bone stiffness that occurs with age. The purpose of this study was to compare calcaneus bone stiffness of endurance runners of different ages to age-matched controls. METHODS: In a descriptive cross-sectional study, 182 endurance-trained male runners and 116 healthy untrained male controls underwent an ultrasonographic assessment of the calcaneus bone in the right and left heels. Calcaneal bone stiffness was calculated from assessments of the broadband ultrasound attenuation and the speed of sound. RESULTS: The line of best fit for the association between age and calcaneus stiffness was different between marathoners and controls (Z = - 2.1, P = 0.02). A two-way ANCOVA (condition × age) with body mass, and body mass index as covariates, revealed that there were main effects of condition (F = 26.8, P < 0.01) and age (F = 4.2, P < 0.01) for calcaneus stiffness, with a significant interaction between these two factors (F = 2.8, P = 0.03). The post hoc analysis revealed that calcaneus stiffness was significantly higher in marathoners of 40-44 years (121.5 ± 18.2 vs 101.1 ± 21.3 arbitrary units [A.U.], P = 0.01), 45-49 years (121.5 ± 19.7 vs 104.3 ± 13.4 A.U., P = 0.04), and > 50 years (111.2 ± 17.9 vs 92.4 ± 16.0 A.U., P < 0.01) than their untrained counterparts of the same age with no statistically significant differences in the remaining age groups. CONCLUSION: Endurance runners of > 40 years had higher values of calcaneus stiffness than controls, providing evidence to support the potential effect of endurance running to reduce the age-related decline on calcaneus bone stiffness.

Thickness and cross-sectional area of the achilles tendon in marathon runners: a cross-sectional study / Espessura e área transversal do tendão de aquiles em maratonistas: um estudo transversal / Espesor y área transversal del tendón de aquiles en maratonistas: un estudio transversal

ABSTRACT Introduction: This study aimed to measure thickness and cross-sectional area of the Achilles tendon (AT), and the range of motion of the ankle joint in dorsiflexion of amateur marathon runners compared to non-active people. Objectives: To analyze the relationship between cross-sectional area and thickness of the Achilles tendon in marathon runners and age, anthropometric characteristics (height and body mass), training habits, running experience, marathon performance, and range of motion in the ankle joint. Methods: Achilles tendon thickness and cross-sectional area were measured using ultrasound images of the left leg in 97 male amateur marathon runners (age 42.0 ± 9.6 years; height 175 ± 6 cm; and body mass 73.7 ± 8.6 kg), and 47 controls (39.9 ± 11.6 years; 176 ± 7 cm; 79.6 ± 16.1 kg). Results: Achilles tendon thickness (4.81 ± 0.77 vs. 4.60 ± 0.66 mm; p = 0.01) and cross-sectional area (60.41 ± 14.36 vs. 53.62 ± 9.90 mm2; p < 0.01) were greater in the marathon runners than in non-active people. Achilles tendon thickness has been correlated, in a weak but significant manner, with years of running experience. Moreover, marathon runners showed increased ankle range of motion (81.81 ± 6.93 vs. 77.86 ± 7.27 grades; p<0.01). Conclusion: Male amateur marathon runners have hypertrophy of the Achilles tendon compared to non-active people, and this enlargement is mediated by running experience. In addition, range of motion in ankle dorsiflexion is favored by marathon training. Level of evidence III; Retrospective study.

RESUMO Introdução: Este estudo visou medir a espessura e a área transversal do tendão de Aquiles (TA) e a amplitude de movimento da articulação do tornozelo em flexão dorsal em maratonistas amadores, em comparação com indivíduos não ativos. Objetivos: Analisar a relação entre a área transversal e a espessura do tendão de Aquiles em maratonistas e idade, características antropométricas (estatura e massa corporal), hábitos de treinamento, experiência de corrida, desempenho em maratona e amplitude de movimento da articulação do tornozelo. Métodos: A espessura do tendão de Aquiles e a área transversal foram medidas por meio de imagens de ultrassom da perna esquerda em 97 maratonistas amadores do sexo masculino (idade 42,0 ± 9,6 anos; altura 175 ± 6 cm; massa corporal 73,7 ± 8,6 kg) e 47 controles (39,9 ± 11,6 anos; 176 ± 7 cm; 79,6 ± 16,1 kg). Resultados: A espessura (4,81 ± 0,77 vs. 4,60 ± 0,66 mm; p = 0,01) e a secção transversal (60,41 ± 14,36 vs. 53,62 ± 9,90 mm2; p < 0,01) do tendão de Aquiles foram superiores nos maratonistas do que nos indivíduos não ativos. Verificou-se correlação fraca, mas significativa, entre espessura do tendão de Aquiles com os anos de experiência em corrida. Além disso, os maratonistas tiveram aumento da amplitude de movimento da articulação do tornozelo (81,81 ± 6,93 vs. 77,86 ± 7,27 graus; p < 0,01). Conclusão: Os maratonistas amadores do sexo masculino têm hipertrofia do tendão de Aquiles em comparação com indivíduos não ativos e esse aumento é mediado pela experiência em corrida. Além disso, a amplitude de movimento na flexão dorsal da articulação do tornozelo é favorecida pelo treinamento de maratona. Nível de evidência III; Estudo retrospectivo.

RESUMEN Introducción: Este estudio buscó medir el espesor y el área transversal del tendón de Aquiles (TA), y la amplitud de movimiento de la articulación del tobillo en flexión dorsal en maratonianos amateur en comparación con individuos no activos. Objetivos: Analizar la relación entre el área transversal y el grosor del tendón de Aquiles en maratonianos y edad, características antropométricas (estatura y masa corporal), hábitos de entrenamiento, experiencia en carrera, desempeño en maratón y amplitud de movimiento de la articulación del tobillo. Métodos: Fueron medidos el grosor y el área transversal del tendón de Aquiles por medio de imágenes de la pierna izquierda a 97 maratonianos amateur del sexo masculino (edad 42,0 ± 9,6 años; altura 175 ± 6 cm; masa corporal 73,7 ± 8,6 kg), y 47 controles (39,9 ± 11,6 años; 176 ± 7 cm; 79,6 ± 16,1 kg). Resultados: El grosor (4,81 ± 0,77 vs. 4,60 ± 0,66 mm; p = 0,01) y la sección transversal (60,41 ± 14,36 vs. 53,62 ± 9,90 mm2; p < 0.01) fueron superiores en los maratonianos que en los individuos no activos. Se verificó correlación débil, aunque significativa, entre grosor del tendón de Aquiles con los años de experiencia en carrera. Además, los maratonianos tuvieron aumento de la amplitud de movimiento de la articulación del tobillo (81,81 ± 6,93 vs. 77,86 ± 7,27 grados; p<0,01). Conclusión: Los maratonianos amateur del sexo masculino tienen hipertrofia del tendón de Aquiles en comparación con individuos no activos, y ese aumento es mediado por la experiencia en carrera. Además, la amplitud de movimiento en la flexión dorsal de la articulación del tobillo es favorecida por el entrenamiento de maratón. Nivel de evidencia III; Estudio retrospectivo.

The influence of a badminton competition with two matches in a day on muscle damage and physical performance in elite junior badminton players.

To investigate the effects of a badminton competition with 2 matches in a day on hip strength and range of motion (ROM) and exercise-induced muscle damage in elite junior badminton players. Twenty players (age: 17±0.8 years; body mass: 62.9±6.5 kg, height: 173.8±8.9 cm) participated in this study. Passive hip internal (IR) and external rotation (ER), abduction (ABD) and adduction (ADD) hip ROM, isometric hip ADD and ABD muscle strength, countermovement vertical jump (CMJ) height and blood creatine kinase concentration (CK) were measured before and after a badminton competition during an international tournament. Blood samples were collected 24 h after the end of the last match. Compared to baseline values, hip IR and ER ROM were significantly decreased at post-competition in the dominant (IR=-9.0%; p=0.007 and ER=-15.2%; p=0.002) and non-dominant limbs (IR=-9.08%; p=0.004 and ER=-19.4%; p<0.001). In contrast, hip ADD (13.5%; p<0.001) and ABD (14.6%; p<0.001) strength increased significantly after the competition in the dominant limb and ABD strength increased significantly in the non-dominant limb (9.2%; p=0.001). From baseline values, CK increased after the competition (430.1%) and values remained elevated over baseline values 24 h later (160.4%). Although hip muscle strength increased, a badminton competition with two consecutive matches reduced hip ROM and increased blood CK concentration. This study suggests the necessity of investigating recovery strategies after a badminton competition to return hip ROM to basal values before the next day of the competition.

Polygenic Profile and Exercise-Induced Muscle Damage by a Competitive Half-Ironman.

Del Coso, J, Salinero, JJ, Lara, B, Gallo-Salazar, C, Areces, F, Herrero, D, and Puente, C. Polygenic profile and exercise-induced muscle damage by a competitive half-ironman. J Strength Cond Res 34(5): 1400-1408, 2020-To date, it is still unknown why some individuals develop higher levels of muscle damage than other individuals, despite participating in exercise with comparable levels of physical intensity. The aim of this investigation was to analyze 7 single-nucleotide polymorphisms (SNPs) that are candidates to explain individual variations in the level of muscle damage attained during a half-ironman competition. Using the model of Williams and Folland (2, 1, and 0 points for optimal, intermediate, and suboptimal genotype), we determined the total genotype score from the accumulated combination of 7 SNPs (ACE = 287bp Ins/Del; ACTN3 = p.R577X; creatine kinase, muscle type = NcoI; insulin-like growth factor 2 = C13790G; interleukin-6 = 174G>C; myosin light chain kinase = C37885A; and tumor necrosis factor-α = 308G>A) in 22 experienced triathletes. Before and after the race, a sample of venous blood was obtained to measure serum markers of muscle damage. Two groups of triathletes were established according to their postcompetition serum CK concentration: low CK responders (n = 10; 377 ± 86 U·L) vs. high CK responders (n = 12; 709 ± 136 U·L). At the end of the race, low CK responders had lower serum myoglobin concentrations (384 ± 243 vs. 597 ± 293 ng·ml, p = 0.04). Although the groups were similar in age, anthropometric characteristics, and training habits, total genotype score was higher in low CK responders than in high CK responders (7.7 ± 1.1 vs. 5.5 ± 1.1 point, p < 0.01). A favorable polygenic profile can contribute to reducing the level of muscle damage developed during endurance exercise.

Age and sex-related upper body performance differences in competitive young tennis players.

OBJECTIVE: The aims of this study were to analyze the shoulder functional profile of young male and female tennis players and to establish the relationship among physical variables and serve speed. METHODS: A total of 128 Spanish tennis players (Under-13 (n = 32/32 males/females) and Under-15 (n = 36/28 males/females), were tested during National training camps. Tests included passive shoulder range of motion (ROM) for both internal (IR) and external rotation (ER) and isometric strength (i.e., IR and ER) of the dominant/non-dominant shoulders, medicine ball throws (MBT), and serve speed. Age and sex pairwise comparisons were carried using the Hedges' g index (dg). RESULTS: Results showed age and sex effects on serve speed and all MBT, with males showing greater changes (1.51≤dg≤1.98) with age than females (0.92≤dg≤1.35; p<0.05). U15 males showed higher (p<0.05) absolute shoulder IR and ER strength than U13, with only significant differences between males and females in the U15. Regarding ROM, U15 males showed a decreased IR ROM compared to U13 (dg = -0.84; p<0.05) and higher significant IR bilateral deficit (dg = 0.51; p<0.05). The distances obtained in the different MBT were the variables more correlated to serve speed. CONCLUSION: The present results suggest that shoulder strength, medicine ball throws and serve speed increased along with age in young elite tennis players of both sexes. However, a decreased range of motion and bilateral deficit for glenohumeral internal rotation is evident in male under-15 tennis players. Muscle strength, power and shoulder range of motion are key factors for serve speed in young tennis players.

The effects of playing two consecutive matches in the shoulder rotational profiles of elite youth badminton players.

OBJECTIVE: The aim of the present study was to analyse the effects of playing two badminton matches on the same day on the shoulder profile (i.e., range of motion (ROM) and strength) of young badminton players. DESIGN: Cross-sectional study. SETTING: Indoor sports facility. PARTICIPANTS: Thirty-one elite junior badminton players (age 16.6 ±â€¯1.0 years, body mass 63.9 ±â€¯6.1 kg, height 174.8 ±â€¯6.1 cm), including 19 boys and 12 girls. MAIN OUTCOME MEASURES: Shoulder passive internal rotation (IR) and external rotation (ER) ROM as well as shoulder IR/ER maximal isometric strength were measured before and after a competition including two competitive matches. RESULTS: Significant decreases (p < 0.05) were found in the shoulder ROM (i.e., dominant and non-dominant ER ROMs as well as in the dominant and non-dominant total arc of motion [TAM]) in boys, while in girls, significant increases (p < 0.05) were found in the non-dominant ER absolute strength, with significant decreases were found in the non-dominant ER ROM and the non-dominant TAM. CONCLUSION: Playing two badminton matches on the same day led to gender-specific changes on the shoulder profile (i.e., ROM and strength) of young elite badminton players, with more impact on the shoulder profile of boys compared to girls.

Game Activity and Physiological Responses of Young Tennis Players in a Competition With Two Consecutive Matches in a Day.

PURPOSE: This study aimed to determine whether the game activity and physiological responses of young tennis players differed depending on the session of play (e.g., morning (MOR) vs. afternoon (AFT)) and the final match outcome (e.g., winners vs. losers), during a simulated competition with two matches on the same day. METHODS: Twelve well-trained male tennis players (14.5±0.8 years) took part in a simulated competition of two 3-set matches separated by 3 h. All the matches were video-recorded and the participants were monitored using 10 Hz global positioning (GPS) units including a heart-rate (HR) monitor. Effect size (ES) statistics were used to investigate the magnitudes of the differences. RESULTS: During the AFT matches, in absolute terms, players covered longer total distance (ES=moderate), ran more distance between 0 and ≤ 4m·s-1 (ES=small-to-large) compared to MOR matches. Total duration was also longer (ES=large) in the AFT, where the rest time between rallies was also longer (ES=very large). HR was similar during both AFT and MOR matches, but higher rates of perceived exertion (RPE) (ES=moderate) were reported in the AFT. Only peak running velocity was observed to be likely higher for losers compared to winners (ES=small). CONCLUSIONS: Game activity and physiological responses of young tennis players differ when two consecutive matches are played on the same day. These data might help to elucidate the need for specific pre-competition training loads and/or in-between match/session recovery strategies when facing overloaded competitions.

CYP1A2 Genotype Variations Do Not Modify the Benefits and Drawbacks of Caffeine during Exercise: A Pilot Study.

Previous investigations have determined that some individuals have minimal or even ergolytic performance effects after caffeine ingestion. The aim of this study was to analyze the influence of the genetic variations of the CYP1A2 gene on the performance enhancement effects of ingesting a moderate dose of caffeine. In a double-blind randomized experimental design, 21 healthy active participants (29.3 ± 7.7 years) ingested 3 mg of caffeine per kg of body mass or a placebo in testing sessions separated by one week. Performance in the 30 s Wingate test, visual attention, and side effects were evaluated. DNA was obtained from whole blood samples and the CYP1A2 polymorphism was analyzed (rs762551). We obtained two groups: AA homozygotes (n = 5) and C-allele carriers (n = 16). Caffeine ingestion increased peak power (682 ± 140 vs. 667 ± 137 W; p = 0.008) and mean power during the Wingate test (527 ± 111 vs. 518 ± 111 W; p < 0.001) with no differences between AA homozygotes and C-allele carriers (p > 0.05). Reaction times were similar between caffeine and placebo conditions (276 ± 31 vs. 269 ± 71 milliseconds; p = 0.681) with no differences between AA homozygotes and C-allele carriers. However, 31.3% of the C-allele carriers reported increased nervousness after caffeine ingestion, while none of the AA homozygotes perceived this side effect. Genetic variations of the CYP1A2 polymorphism did not affect the ergogenic effects and drawbacks derived from the ingestion of a moderate dose of caffeine.

Optimum polygenic profile to resist exertional rhabdomyolysis during a marathon.

PURPOSE: Exertional rhabdomyolysis can occur in individuals performing various types of exercise but it is unclear why some individuals develop this condition while others do not. Previous investigations have determined the role of several single nucleotide polymorphisms (SNPs) to explain inter-individual variability of serum creatine kinase (CK) concentrations after exertional muscle damage. However, there has been no research about the interrelationship among these SNPs. The purpose of this investigation was to analyze seven SNPs that are candidates for explaining individual variations of CK response after a marathon competition (ACE = 287bp Ins/Del, ACTN3 = p.R577X, CKMM = NcoI, IGF2 = C13790G, IL6 = 174G>C, MLCK = C37885A, TNFα = 308G>A). METHODS: Using Williams and Folland's model, we determined the total genotype score from the accumulated combination of these seven SNPs for marathoners with a low CK response (n = 36; serum CK <400 U·L-1) vs. marathoners with a high CK response (n = 31; serum CK ≥400 U·L-1). RESULTS: At the end of the race, low CK responders had lower serum CK (290±65 vs. 733±405 U·L-1; P<0.01) and myoglobin concentrations (443±328 vs. 1009±971 ng·mL-1, P<0.01) than high CK responders. Although the groups were similar in age, anthropometric characteristics, running experience and training habits, total genotype score was higher in low CK responders than in high CK responders (5.2±1.4 vs. 4.4±1.7 point, P = 0.02). CONCLUSION: Marathoners with a lower CK response after the race had a more favorable polygenic profile than runners with high serum CK concentrations. This might suggest a significant role of genetic polymorphisms in the levels of exertional muscle damage and rhabdomyolysis. Yet other SNPs, in addition to exercise training, might also play a role in the values of CK after damaging exercise.

ACTN3 genotype influences exercise-induced muscle damage during a marathon competition.

PURPOSE: Exercise-induced muscle damage has been identified as one of the main causes of the progressive decrease in running and muscular performance in marathoners. The aim of this investigation was to determine the influence of the ACTN3 genotype on exercise-induced muscle damage produced during a marathon. METHODS: Seventy-one experienced runners competed in a marathon race. Before and after the race, a sample of venous blood was obtained and maximal voluntary leg muscle power was measured during a countermovement jump. In the blood samples, the ACTN3 genotype (R577X) and the changes in serum creatine kinase and myoglobin concentrations were measured. Data from RX heterozygotes and XX mutant homozygotes were grouped as X allele carriers and compared to RR homozygotes. RESULTS: At the end of the race, X allele carriers presented higher serum myoglobin (774 ± 852 vs 487 ± 367 U L-1; P = 0.02) and creatine kinase concentrations (508 ± 346 vs 359 ± 170 ng mL-1; P = 0.04) than RR homozygotes. Pre-to-post-race maximal voluntary leg muscle power reduction was more pronounced in X allele carriers than RR homozygotes (-34.4 ± 16.1 vs -27.3 ± 15.4%; P = 0.05). X allele carriers self-reported higher levels of lower limb muscle pain (7 ± 2 vs 6 ± 2 cm; P = 0.02) than RR homozygotes at the end of the race. CONCLUSIONS: In comparison to RR homozygotes, X allele carriers for the R577X polymorphism of the ACTN3 gene presented higher values for typical markers of exercise-induced muscle damage during a competitive marathon. Thus, the absence of a functional α-actinin-3 produced by the X allele might induce higher levels of muscle breakdown during prolonged running events.

A comparison of the physiological demands imposed by competing in a half-marathon vs. a marathon.

BACKGROUND: While there is widespread scientific information about the physiological challenges imposed on elite endurance runners during competitions, the information regarding the amateur population is scarce. The aim of this study was to compare the physical and physiological load imposed by competing in a real half-marathon vs. a marathon race. METHODS: From a larger group of participants, we selected 22 experienced runners who were matched in pairs (11 marathoners and 11 half-marathoners) for age and anthropometric data. Participants completed their respective distances on the same day and circuit while race time was measured by means of chip timing. Sweat samples were obtained during the race using sweat patches. Before and after the race, a sample of venous blood was obtained and jump height was measured during a countermovement jump. Participants also rated their perception of leg muscle pain at the end of the race. RESULTS: Running pace was similar for half-marathoners vs. marathoners (3.3±0.4 vs. 3.1±0.4 m·s-1; P=0.36). At the end of the race, jump height reduction (-11±12% vs. -25±19%; P=0.03), serum myoglobin concentration (186.1±93.6 vs. 564.1±370.7 µg·mL-1; P<0.01) and self-reported muscle pain (3.0 ±2.3 vs. 5.5 ±1.0 A.U.; P<0.01) were lower in half-marathoners vs. marathoners. Sweat rate (~1.0±0.3 L·h-1; P=0.79) and sweat sodium concentration (47.8±29.4 and 39.3±24.1 mmol·L-1; P=0.47) were similar for both groups but body mass reduction (-1.9±0.8% vs. -3.3±0.8%; P<0.01) and electrolyte imbalance were higher in marathoners. CONCLUSIONS: Completing a marathon induces higher muscle fatigue, greater muscle fiber damage and perceived muscle pain levels and higher body water and electrolyte deficits than finishing a half-marathon with a similar running speed. This information could be valuable to improve physical training for endurance running disciplines.

Impact of a competition with two consecutive matches in a day on physical performance in young tennis players.

The purpose of this study was to analyze the effects of playing 2 tennis matches on the same day on physical performance in young tennis players. Twelve well-trained young tennis players took part in a simulated tennis competition consisting of 2 tennis matches on the same day (morning and afternoon sessions). Before and the day after the competition, physical performance was measured using a battery of countermovement jumps; a 10 m sprint; the 5-0-5 agility test; hip, grip and shoulder maximal isometric strength; shoulder range of motion; and a serve velocity test. Postcompetition results showed reduced performance in 10 m (-3.3%, effect size (ES) = small), dominant and nondominant 5-0-5 agility test (-4.6%, ES = moderate; -4.2%, ES = moderate, respectively), bilateral (-5.2%, ES = small), and unilateral countermovement jumps (dominant leg: -7.2%, ES = small; non-dominant leg: -9.1%, ES = small). Both dominant and nondominant shoulder external rotation range of motion increased (12.2%, ES = moderate; 5.6%, ES = small), whereas internal rotation decreased (-4.2%, ES = small; -3.3%, ES = small) in the postcompetition tests, together with the dominant shoulder external rotation (-10.7%, ES = moderate) and internal rotation (-9.3%, ES = small) strength. Physical impairments occurred in neuromuscular performance variables involving lower (e.g., jumping, sprinting, and change of direction) and upper (e.g., isometric strength and range of motion) limbs the day after playing a competition with 2 consecutive matches on the same day. These alterations in neuromuscular and sport-specific performance need to be taken into consideration when planning tournament schedules for young tennis players, as well as preparing match and recovery strategies.

Predicting race time in male amateur marathon runners.

BACKGROUND: The aim of the study was to analyze the relationship between anthropometry, training characteristics, muscular strength and effort-related cardiovascular response and marathon race time in male amateur runners. METHODS: A total of 84 male amateur marathon runners aged between 23 and 70 years took part in this study (41.0±9.5 years). All of them competed in the 2013 edition of the Madrid Marathon with a finish time between 169.8 and 316 minutes (226.0±28.5 minutes). Age, running experience, number of marathon races finished, mean kilometers run weekly in the last three months, and previous personal best time in the 10 km, half marathon and marathon were recorded. Moreover, anthropometric characteristics, and the results from the Ruffier Test and a whole-body isometric force test were measured. After the marathon, the race time was registered. RESULTS: Training volume (r=-0.479; P=0.001), previous running milestones (marathon r=0.756; half-marathon r=0.812; 10-km r=0.732; P<0.001), cardiovascular fitness (r=0.371; P=0.001) and anthropometric variables (body mass, Body Mass Index, body fat percentage, skinfolds and lower leg volume) were correlated to marathon performance (P<0.05). Two regression models appeared from the data with r2>0.50. The best, including body fat percentage, heart rate change during the recovery after the Ruffier Test and the half-marathon race time, was strongly correlated with real marathon performance (r=0.77; P<0.001). A second regression model was proposed replacing the half-marathon performance with the 10-km race time, reducing the correlation to 0.73 (P<0.001). CONCLUSIONS: Marathon performance could be partially predicted by two different equations, including body fat percentage, recovery heart rate in the Ruffier Test and a half-marathon or 10-km performance.

ACTN3 X-allele carriers had greater levels of muscle damage during a half-ironman.

PURPOSE: Alpha-actinin-3, encoded by the ACTN3 gene, is an actin-binding protein with an important role in myofibril contraction and muscle force output. In humans, there is a relatively common deficiency of the α-actinin-3 due to homozygosity in a polymorphism of the ACTN3 gene (R577X, rs1815739), that has been related to decreased resistance to strain during voluntary muscle contractions. The purpose of this study was to investigate the influence of the ACTN3 genotype on the level of exercise-induced muscle damage attained by 23 experienced triathletes during an official half-ironman competition. METHODS: Before and after the race, a sample of venous blood was obtained and jump height was measured during a countermovement jump. The changes in serum creatine kinase (CK-MM isoform) were measured in the blood samples and muscle pain was measured with a visual analogue scale (0-10 cm). Data from RX heterozygotes and XX mutant homozygotes were grouped as X-allele carriers (n = 13) and compared to RR homozygotes (n = 10). RESULTS: Race time was very similar between groups (313 ± 31 vs. 313 ± 25 min; P = 0.45); however, pre-to-post-competition reduction in jump height was greater in X-allele carriers than RR homozygotes (-18.4 ± 11.4 vs. -8.2 ± 6.9%; P = 0.04). At the end of the race, X-allele carriers presented higher serum CK-MM concentrations (682 ± 144 vs. 472 ± 269 U/L; P = 0.03), and there was also a tendency for higher self-reported values of lower limb muscle pain (7.7 ± 1.1 vs. 6.3 ± 2.3 cm; P = 0.06). CONCLUSIONS: X-allele triathletes in the ACTN3 R577X polymorphism presented greater signs of exercise-induced muscle damage during a half-ironman race than RR homozygotes.

Correction: Myosin Light Chain Kinase (MLCK) Gene Influences Exercise Induced Muscle Damage during a Competitive Marathon.

[This corrects the article DOI: 10.1371/journal.pone.0160053.].