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Traditionally, sports participation has been based on the chronological age of the individual with year of birth determining participation grouping. However, grouping by chronological age can result in individuals who are nearly a full year different in age competing within the same age group. Moreover, during the pubertal years, age grouping may provide physical (size) advantage to early maturers and disadvantage to late maturers. These advantages/disadvantages could impact talent selection, psychosocial aspects of sport participation, technical and tactical skill development, competitiveness, and injury risk. Biobanding is an alternative method for determining sport participation categorization and uses factors of growth and/or maturation, rather than traditional chronological age, for grouping athletes. Implementation of biobanding in sports may be advantageous to both early and late-maturing athlete development. [ABSTRACT FROM AUTHOR]

Introduction: 3 × 3 basketball is becoming more and more professionalized, which is leading to a growing interest in talent development and talent selection. Different studies have demonstrated relevant factors in the talent selection process of 5v5 basketball but not in 3 × 3 basketball. Therefore, this study investigated the main predictors in the talent selection process in 3 × 3 basketball athletes. Methods: A total of 192 athletes (M age = 16.11 ± 0.45 years; n = 85 were female) 3 × 3 basketball athletes were assessed for various anthropometric and motor performance variables as well as maturity status. All assessments were carried out during selection camps for the German "under 17" youth national team. Binomial logistic regression was conducted to determine which variables predicted selection (either 'selected', n = 30 female and n = 34 male, or 'non-selected', n = 55 female and n = 73 male). Results: The regression model was statistically significant in female athletes (χ ² (3) = 26.86, p <.001). It explains 37.9% (Nagelkerke's R 2) of the variance in selection status and suggests that the general motor-performance component (p <.001) and the anthropometric- and maturation-related component (p =.004) seem to be relevant for being selected. In male athletes, the binomial logistic regression model was also statistically significant (χ ² (3) = 11.38, p =.010) with explaining 14.2% (Nagelkerke's R 2) of the variance in selection status but only the anthropometric- and maturation-related component (p =.004) predict selection. Discussion: Anthropometric conditions (such as body height, body weight, and wingspan) and the maturity status are particularly important in talent selection in 3 × 3 basketball for both sexes. Regarding motor-performance variables, we found a predictive value for talent selection only in females (without sprinting), but not in males which means that more 'athletic' female athletes seem to be favoured in talent selection. The results suggest that the talent selection process might be biased by maturation status even in middle adolescence. Therefore, coaches who decide on athletes' selection should be aware of the temporal advantages induced by earlier maturation when evaluating talented athletes and should consider strategies such as bio-banding to evaluate the real and potential value of talented athletes. [ABSTRACT FROM AUTHOR]

Introduction: 3 × 3 basketball is becoming more and more professionalized, which is leading to a growing interest in talent development and talent selection. Different studies have demonstrated relevant factors in the talent selection process of 5v5 basketball but not in 3 × 3 basketball. Therefore, this study investigated the main predictors in the talent selection process in 3 × 3 basketball athletes. Methods: A total of 192 athletes (Mage = 16.11 ± 0.45 years; n = 85 were female) 3 × 3 basketball athletes were assessed for various anthropometric and motor performance variables as well as maturity status. All assessments were carried out during selection camps for the German "under 17" youth national team. Binomial logistic regression was conducted to determine which variables predicted selection (either 'selected', n = 30 female and n = 34 male, or 'nonselected', n = 55 female and n = 73 male). Results: The regression model was statistically significant in female athletes (χ² (3) = 26.86, p < .001). It explains 37.9% (Nagelkerke's R²) of the variance in selection status and suggests that the general motor-performance component (p < .001) and the anthropometric- and maturation-related component (p = .004) seem to be relevant for being selected. In male athletes, the binomial logistic regression model was also statistically significant (χ² (3) = 11.38, p = .010) with explaining 14.2% (Nagelkerke's R²) of the variance in selection status but only the anthropometric- and maturation-related component (p = .004) predict selection. Discussion: Anthropometric conditions (such as body height, body weight, and wingspan) and the maturity status are particularly important in talent selection in 3 × 3 basketball for both sexes. Regarding motor-performance variables, we found a predictive value for talent selection only in females (without sprinting), but not in males which means that more 'athletic' female athletes seem to be favoured in talent selection. The results suggest that the talent selection process might be biased by maturation status even in middle adolescence. Therefore, coaches who decide on athletes' selection should be aware of the temporal advantages induced by earlier maturation when evaluating talented athletes and should consider strategies such as bio-banding to evaluate the real and potential value of talented athletes. [ABSTRACT FROM AUTHOR]

Background Motor performances of youth are related to growth and maturity status, among other factors.Aim To estimate the contribution of skeletal maturity status per se to the motor performances of female athletes aged 10–15 years and the mediation effects of growth status on the relationships.Subjects and methods Skeletal age (TW3 RUS SA), body size, proportions, estimated fat-free mass (FFM), motor performances, training history and participation motivation were assessed in 80 non-skeletally mature female participants in several sports. Hierarchical and regression-based statistical mediation analyses were used.Results SA per se explained a maximum of 1.8% and 5.8% of the variance in motor performances of athletes aged 10–12 and 13–15 years, respectively, over and above that explained by covariates. Body size, proportions, and hours per week of training and participation motivation explained, respectively, a maximum of 40.7%, 18.8%, and 22.6% of the variance in performances. Mediation analysis indicated specific indirect effects of SA through stature and body mass, alone or in conjunction with FFM on performances.Conclusion SA per se accounted for small and non-significant amounts of variance in several motor performances of female youth athletes; rather, SA influenced performances indirectly through effects on stature, body mass and estimated FFM.

This study was designed to evaluate the influence of maturity status in the inter- and intra-session reliability of curvilinear sprinting (CS) and compare the reliability of the half-CS trials with the complete CS trials. Forty-two youth basketball players from an elite academy (13.1 ± 1.7 years; 166.7 ± 16.2 cm; 57.2 ± 17.0 kg) performed two sessions of three CS trials each on both right and left sides with seven days of separation between sessions. The predicted peak height velocity (PHV) was used to establish players’ maturity status (pre-PHV, n = 14; mid-PHV, n = 14; post-PHV = 13). Mid- and post-PHV groups showed a high relative (interclass correlation coefficient [ICC] ≥ 0.75) and absolute (coefficient of variation [CV] < 5%) reliability inter- and intra-session, and pre-PHV showed high relative and absolute reliability in the left trials and in the CS right trial, but moderate (ICC = 0.73) relative reliability in the half-CS right side. Based on these findings, it is recommended that practitioners consider players’ maturity status to ensure accurate and reliable assessments of CS performance.

This study aimed to investigate the effect of maturity status on force-velocity relationships in a ballistic lower limb (BLL) test in high-level soccer adolescents and young adults. The population was 61 adolescents (13.0–17.9 years) and 23 young adults (18.0–26.2 years). Subjects completed the BLL test on a ballistic ergometer equipped with two force plates and a linear encoder. Following Samozino's method, maximal power output (Pmax), force (F0) and velocity (v0) were determined. An allometric model was applied to Pmax and F0 with body mass (BM) and fat-free mass (FFM). Significant effects of maturity status were found for absolute Pmax, F0, relative Pmax to BM and FFM, relative F0 to FFM and F0 allometrically scaled to BM and FFM (p = 0.02 to p < 0.001; $\eta $ η = 0.10 to $\eta $ η = 0.49). There was no significant effect for Pmax allometrically scaled to BM and FFM, F0 relative to BM and v0. Body dimensions explain group differences in Pmax whereas for F0, qualitative factors explain the differences between the groups. As maturity status and body dimensions influence Pmax, these factors should be considered when assessing explosive short efforts. This could help to better identify potential athletic talent and adapt training content. [ABSTRACT FROM AUTHOR]

Introduction3 × 3 basketball is becoming more and more professionalized, which is leading to a growing interest in talent development and talent selection. Different studies have demonstrated relevant factors in the talent selection process of 5v5 basketball but not in 3 × 3 basketball. Therefore, this study investigated the main predictors in the talent selection process in 3 × 3 basketball athletes.MethodsA total of 192 athletes (Mage = 16.11 ± 0.45 years; n = 85 were female) 3 × 3 basketball athletes were assessed for various anthropometric and motor performance variables as well as maturity status. All assessments were carried out during selection camps for the German “under 17” youth national team. Binomial logistic regression was conducted to determine which variables predicted selection (either ‘selected', n = 30 female and n = 34 male, or ‘non-selected’, n = 55 female and n = 73 male).ResultsThe regression model was statistically significant in female athletes (χ² (3) = 26.86, p

The aim of this study was to examine the effect of various contextual factors on the 30-15 Intermittent Fitness Test (30-15 IFT) in young male football players.30-15 IFT was evaluated in U-14 and U-16 football teams (n=229). The sample was categorized by relative age, biological maturation, playing position and competitive level (CL). The results revealed a trend in the overall sample towards an overrepresentation of players born in the early months of the year. Significant differences were found when comparing vIFT (maximal intermittent running velocity) values across age categories (U13: 17.73 ± 1.24; U14: 18.14 ± 1.56; U15: 18.99 ± 1.31; U16: 18.81 ± 1.55; F = 9.93; p < .001) and between maturity groups, in favor of the more mature players (PrePHV: 17.77 ± 1.38; MidPHV: 18.53 ± 1.37; PostPHV: 18.83 ± 1.48). There were some minor differences in the vIFT between players from different field positions (F = 2.96; p = .014; ηp2 = 0.078). As well as players who compete at higher levels of competition reached higher results for the vIFT (CL: F = 9.01; p < .001; ηp2 = 0.238 and CL2: F = 15.44; p < .001; ηp2 = 0.184). This study showed the complexity of factors influencing the 30-15 IFT of young football players and suggest that maturity may play a more influential role than RA in physical performance which could influence the selection process at early ages.

Background: Motor performances of youth are related to growth and maturity status, among other factors. Aim: To estimate the contribution of skeletal maturity status per se to the motor performances of female athletes aged 10–15 years and the mediation effects of growth status on the relationships. Subjects and methods: Skeletal age (TW3 RUS SA), body size, proportions, estimated fat-free mass (FFM), motor performances, training history and participation motivation were assessed in 80 non-skeletally mature female participants in several sports. Hierarchical and regression-based statistical mediation analyses were used. Results: SA per se explained a maximum of 1.8% and 5.8% of the variance in motor performances of athletes aged 10–12 and 13–15 years, respectively, over and above that explained by covariates. Body size, proportions, and hours per week of training and participation motivation explained, respectively, a maximum of 40.7%, 18.8%, and 22.6% of the variance in performances. Mediation analysis indicated specific indirect effects of SA through stature and body mass, alone or in conjunction with FFM on performances. Conclusion: SA per se accounted for small and non-significant amounts of variance in several motor performances of female youth athletes; rather, SA influenced performances indirectly through effects on stature, body mass and estimated FFM. [ABSTRACT FROM AUTHOR]

The handgrip strength is used as a means of individual's health prediction during life. It is used as an indicator of the nutrition status, bone fragility, presence of sarcopenia and it correlates with certain diseases and clinical complications. The research goal was to analyze the results of the hand dynamometry test, based on the chronological and biological age, and to offer normative and referent standards about children and adolescents from the Republic of North Macedonia. The study was conducted on a sample of 4031 respondents of both sexes at the age 6-14 years. In order to achieve the research goals, the measured characteristics were of the weight, height, sitting height and handgrip strength. The body mass index and biological maturity values (APHV) were obtained by using formulas. On the basis of the obtained results, it can be concluded that statistically significant differences in handgrip strength are established between the boys and girls of all age categories. Also, statistically significant differences between boys and girls are established in the hand dynamometry test of all APHV levels. In general, the use of the APHV allows a better categorization of the performance of the studied children and adolescents. With boys, the correlation between the chronological age and test was 68 %, and with girls - 77 %. The normative referent standards of the hand dynamometry test are presented in percentiles for both sexes. Thye hand dynamometry test's results during childhood and adolescence should be analyzed and interpret on the basis of biological age, and not on the chronological age. These tools can help specialists who work with children and adolescents in ethnic and epidemiological context. [ABSTRACT FROM AUTHOR]

Estimated ages at take-off (TO) and at peak height velocity (PHV) based on two models and maturity status based upon age at PHV and skeletal age (SA) were compared in a longitudinal sample of male soccer players. In addition, estimated ages at PHV in 13 longitudinal samples of soccer players were compared. The longitudinal height records of 58 players of European ancestry, measured annually on four or five occasions between 11 and 16 years, were modeled with Superimposition by Translation and Rotation (SITAR) and Functional Principal Component Analysis (FPCA) to estimate ages at TO and PHV. SAs were assessed with the Fels method. Ages at PHV in 13 longitudinal samples of soccer players (Europe 7, Japan 6) were evaluated with meta-analysis. Estimated ages at TO, 11.2 ± 0.8 (SITAR) and 11.0 ± 0.8 (FCPA) years, and at PHV, 13.6 ± 0.9 (SITAR) and 13.7 ± 0.0 (FCPA) years, were similar. An earlier age at PHV was associated with advanced skeletal maturity status (rho = -0.77 at ~14 years). Ages at PHV among European players indicated a north (later) -- south (earlier) gradient, and were later than ages at PHV among Japanese players. In summary, ages at TO and PHV were similar with SITAR and FPCA, and ages at PHV were most strongly correlated with SA at ~14 years. Mean ages at PHV showed a north-south gradient among European samples, and were later compared to Japanese samples. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the effect of various contextual factors on the 30- 15 Intermittent Fitness Test (30-15 IFT) in young male football players.30-15 IFT was evaluated in U-14 and U-16 football teams (n=229). The sample was categorized by relative age, biological maturation, playing position and competitive level (CL). The results revealed a trend in the overall sample towards an overrepresentation of players born in the early months of the year. Significant differences were found when comparing vIFT (maximal intermittent running velocity) values across age categories (U13: 17.73 ± 1.24; U14: 18.14 ± 1.56; U15: 18.99 ± 1.31; U16: 18.81 ± 1.55; F = 9.93; p < .001) and between maturity groups, in favor of the more mature players (PrePHV: 17.77 ± 1.38; MidPHV: 18.53 ± 1.37; PostPHV: 18.83 ± 1.48). There were some minor differences in the vIFT between players from different field positions (F = 2.96; p = .014; ηp2 = 0.078). As well as players who compete at higher levels of competition reached higher results for the vIFT (CL: F = 9.01; p < .001; ηp2 = 0.238 and CL2: F = 15.44; p < .001; ηp2 = 0.184). This study showed the complexity of factors influencing the 30-15 IFT of young football players and suggest that maturity may play a more influential role than RA in physical performance which could influence the selection process at early ages. [ABSTRACT FROM AUTHOR]

Abstract Background Generally, Body surface area (BSA) changes significantly during growth and maturation. These increases portend a possible relationship between body size as determined by BSA with maturational status in children and adolescents. Objective To determine the relationship between maturity status (MS) obtained by non-invasive anthropometric methods and body surface area (BSA) in children and adolescents of both sexes in a regional population of Chile. Additionally, we sought to verify the type of linear or nonlinear relationship between MS and BSA in both sexes. Methods A descriptive (cross-sectional) study was designed in 950 children and adolescents of both sexes (539 males and 411 females). The age range ranged from 6.0 to 17.9 years. Anthropometric measurements were evaluated: body weight, standing height, sitting height. MS was assessed by means of two non-invasive anthropometric techniques. Both techniques predict peak years of growth velocity (APHV) through a regression equation for each sex. BSA (m2) was estimated by means of the Haycock equation. Results The R2 in the linear model is relatively lower (R2 = 0.80 to 0.89 in males and 0.74 to 0.66 in females) in relation to the nonlinear quadratic model (R2 = 0.81 in males and 0.76 to 0.69). The quadratic nonlinear quadratic model reflected an adequate fit (RMSE) for the data set, being in men (RMSE = 1.080 and 1.125), while in women (RMSE = 1.779 and 1.479). Conclusion BSA is positively associated with MS determined by two non-invasive methods in Chilean children and adolescents: The nonlinear quadratic model was a better fit to the data distribution. The results suggest the use of BSA as a possible predictor of maturity status in Chilean youth.

Estimated ages at take-off (TO) and at peak height velocity (PHV) based on two models and maturity status based upon age at PHV and skeletal age (SA) were compared in a longitudinal sample of male soccer players. In addition, estimated ages at PHV in 13 longitudinal samples of soccer players were compared. The longitudinal height records of 58 players of European ancestry, measured annually on four or five occasions between 11 and 16 years, were modeled with Superimposition by Translation and Rotation (SITAR) and Functional Principal Component Analysis (FPCA) to estimate ages at TO and PHV. SAs were assessed with the Fels method. Ages at PHV in 13 longitudinal samples of soccer players (Europe 7, Japan 6) were evaluated with meta-analysis. Estimated ages at TO, 11.2± 0.8 (SITAR) and 11.0± 0.8 (FCPA) years, and at PHV, 13.6± 0.9 (SITAR) and 13.7±0.0 (FCPA) years, were similar. An earlier age at PHV was associated with advanced skeletal maturity status (rho = -0.77 at ~14 years). Ages at PHV among European players indicated a north (later) – south (earlier) gradient, and were later than ages at PHV among Japanese players. In summary, ages at TO and PHV were similar with SITAR and FPCA, and ages at PHV were most strongly correlated with SA at ~14 years. Mean ages at PHV showed a north-south gradient among European samples, and were later compared to Japanese samples.

The aim of this study was to examine the effect of various contextual factors, such as relative age, biological maturation, or competitive level, on the jumping performance of young football goalkeepers. Vertical jump performance was evaluated in a selection of goalkeepers (n = 110) from U-14 and U-16 category teams. The sample was categorized by relative age, biological maturation, and competitive level. The results revealed a trend in the overall sample towards an overrepresentation of goalkeepers born in the early months of the year. Maturity status influenced the most in jumping performance of young goalkeepers (SJ: F = 11.27, p < .001, ηp2 = 0.187; CMJ: F = 8.72, p < .001, ηp2 = 0.162; AJ: F = 8.37, p < .001, ηp2 = 0.146), while the birth quartile had no effect on the jumping performance in the sample. Statistical differences were significant for SJ and CMJ between competitive level groups in the U-14 group only. (F = 5.37, p = .008, ηp2 = 0.186) and CMJ (F = 4.54, p = .016, ηp2 = 0.159). This study showed a greater association between maturation and jumping performance in young football goalkeepers rather than with relative age, which could influence the selection process in this field position at early ages.

Volleyball is an intermittent team sport that requires specific anthropometrical and physical characteristics for winning performance. The present study aimed to evaluate the maturity status of the young male players of eight volleyball teams, and to observe differences in anthropometric characteristics and body composition. Ninety-four male adolescent volleyball players were recruited during a national tournament carried out in Treviso (Italy). Anthropometric characteristics such as weight, stature, skinfold thicknesses, circumferences and diameters, and bioelectrical impedance were measured. The biological maturation was estimated for all players. Each team was classified as a higher or lower lever according to its tournament ranking. A two-way ANOVA compared team levels and players' maturity status. Considering the maturity offset, 62 boys were classified as "on time", 20 as "late", and 12 as "early". Three clubs presented many boys with "early" as the maturity offset, and two of these finished the tournament in the first position. Young volleyball players classified as "early" seemed to show anthropometric characteristics linked to better performance at the tournament (higher height, upper arm and calf muscle area, fat mass percentage, and total fat-free mass). The results of the present study could have practical implications for talent selection, but further studies are needed to better evaluate the effect of maturity status on the characteristics of volleyball players. [ABSTRACT FROM AUTHOR]

Abstract Background Skeletal age (SA) is an estimate of biological maturity status that is commonly used in sport-related medical examinations. This study considered intra-observer reproducibility and inter-observer agreement of SA assessments among male tennis players. Methods SA was assessed with the Fels method in 97 male tennis players with chronological ages (CA) spanning 8.7–16.8 years. Radiographs were evaluated by two independent trained observers. Based on the difference between SA and CA, players were classified as late, average or early maturing; if a player was skeletally mature, he was noted as such as an SA is not assigned. Results The magnitude of intra-individual differences between repeated SA assessments were d = 0.008 year (observer A) and d = 0.001 year (observer B); the respective coefficients of variation were 1.11% and 1.75%. Inter-observer mean differences were negligible (t = 1.252, p = 0.210) and the intra-class correlation coefficient was nearly perfect (ICC = 0.995). Concordance of classifications of players by maturity status between observers was 90%. Conclusion Fels SA assessments were highly reproducible and showed an acceptable level of inter-observer agreement between trained examiners. Classifications of players by skeletal maturity status based on assessments of the two observers were highly concordant, though not 100%. The results highlight the importance of experienced observers in skeletal maturity assessments.

Objectives: The objective of the study was to verify whether (FFM), maturity status (MS) and chronological age (CA) are determinants of physical fitness performance, and to analyze FFM and physical performance aligned by CA and MS in children and adolescents. Methods: A descriptive correlational study was carried out in 863 schoolchildren. Weight, height, and waist circumference (WC) were evaluated. Body mass index (BMI), FFM, fat mass (FM), MS (Age at peak height velocity, APHV) were calculated. The physical tests of velocity 20 m, agility 5 m x 10rep, and horizontal jump (HJ) were evaluated. Results: The APHV was estimated in boys at 14.0 ± 0.36APHV and in girls at 11.96 ± 0.49APHV. The relationships between CA and APHV with FFM was r = 0.80 in boys and r = 0.44 to 0.45 in girls. The relationships between FFM and physical tests in boys were [HJ (r = 0.70), agility 5m x 10rep (r = -0.68), velocity (r = -0.61)] and in girls [HJ (r = 0.42), agility 5m x 10rep (r = -0.52), velocity (r = -0.20)]. The differences in FFM and physical fitness tests were more pronounced when aligned by APHV than by CA. Conclusion: It was verified that both FFM, CA, and APHV are determinants of physical fitness performance. In addition, the APHV should be introduced in physical education as a means of ranking physical performance among schoolchildren.

Background: Generally, Body surface area (BSA) changes significantly during growth and maturation. These increases portend a possible relationship between body size as determined by BSA with maturational status in children and adolescents. Objective: To determine the relationship between maturity status (MS) obtained by non-invasive anthropometric methods and body surface area (BSA) in children and adolescents of both sexes in a regional population of Chile. Additionally, we sought to verify the type of linear or nonlinear relationship between MS and BSA in both sexes. Methods: A descriptive (cross-sectional) study was designed in 950 children and adolescents of both sexes (539 males and 411 females). The age range ranged from 6.0 to 17.9 years. Anthropometric measurements were evaluated: body weight, standing height, sitting height. MS was assessed by means of two non-invasive anthropometric techniques. Both techniques predict peak years of growth velocity (APHV) through a regression equation for each sex. BSA (m2) was estimated by means of the Haycock equation. Results: The R2 in the linear model is relatively lower (R2 = 0.80 to 0.89 in males and 0.74 to 0.66 in females) in relation to the nonlinear quadratic model (R2 = 0.81 in males and 0.76 to 0.69). The quadratic nonlinear quadratic model reflected an adequate fit (RMSE) for the data set, being in men (RMSE = 1.080 and 1.125), while in women (RMSE = 1.779 and 1.479). Conclusion: BSA is positively associated with MS determined by two non-invasive methods in Chilean children and adolescents: The nonlinear quadratic model was a better fit to the data distribution. The results suggest the use of BSA as a possible predictor of maturity status in Chilean youth. [ABSTRACT FROM AUTHOR]

Purpose: To investigate peak oxygen uptake ( V ˙ O 2 ) in relation to sex, age, body mass, fat-free mass (FFM), maturity, and overweight status. Methods: Multiplicative, allometric models of 10- to 18-year-olds were founded on 1057 determinations of peak V ˙ O 2 supported by anthropometry and estimates of maturity status. Results: Baseline models with body mass controlled for showed age to exert a positive effect on peak V ˙ O 2 , with negative estimates for age2, sex, and a sex-by-age interaction. Sex-specific models showed maturity status to have a positive effect on peak V ˙ O 2 in addition to the effects of age and body mass. Introducing skinfold thicknesses to provide, with body mass, a surrogate for FFM explained maturity effects and yielded a significantly (P <.05) better statistical fit in all models compared with those based on FFM estimated from youth-specific skinfold equations. With girls only, the introduction of overweight, defined by body mass index, resulted in a small but significant (P <.05) negative effect, with an age-by-overweight status interaction. Conclusions: FFM has a powerful influence on peak V ˙ O 2 in both sexes. Interpretation of the development of youth aerobic fitness and its application to health should reflect the sex- and maturity-associated variation in FFM. [ABSTRACT FROM AUTHOR]

Study purpose. The research goal was to establish if the fat-free mass, chronological age and maturity status are determinants of physical fitness, and to analyze the development changes of fat-free mass and physical fitness in concordance with chronological age and maturity status in schoolchildren aged 6 to 14. Materials and methods. The research was conducted on a sample of 9106 students aged 6 to 14 years. In order to reach the research goals, the following variables were measured: height, weight, sitting height, fat mass, fat-free mass and various components of the physical fitness (lower limbs explosive strength, handgrip strength, abdominal muscle repetitive strength, speed and agility). The values of body mass and biological maturation indexes (APHV) were obtained by using formulas. Results. The boys' age at peak height velocity was estimated at 13.00±0.82, and the girls' one at 11.57± 0.68. The relationships between chronological age and age at peak height velocity with fat-free mass was r=0.82 to 0.94 in the boys and r=0.83 to 0.92 in the girls. The relationships between fat-free mass and physical fitness tests in the boys were: standing long jump (r=0.55), 30 sec sit-ups (r=0.37), handgrip strength (r=0.75) and shuttle run 4 x 10 meters (r=-0.40); and in the girls - standing long jump (r= 0.45), 30 sec sit-ups (r= 0.36), handgrip strength (r= 0.74) and shuttle run 4 х 10 meters (r= -0.43). The differences in fat-free mass and physical fitness tests were more prominent when the comparison was done with relation to the biological maturation (APHV) and chronologic age. Conclusions. On the basis of the obtained results, it can be concluded that maturity status and fat-free mass determinate the physical fitness performances in the schoolchildren of both genders. Also, the age at peak height velocity should be used in Physical Education as a tool of monitoring, ranging and classification of physical performances in children and adolescents. [ABSTRACT FROM AUTHOR]

Background: Skeletal age (SA) is an estimate of biological maturity status that is commonly used in sport-related medical examinations. This study considered intra-observer reproducibility and inter-observer agreement of SA assessments among male tennis players. Methods: SA was assessed with the Fels method in 97 male tennis players with chronological ages (CA) spanning 8.7–16.8 years. Radiographs were evaluated by two independent trained observers. Based on the difference between SA and CA, players were classified as late, average or early maturing; if a player was skeletally mature, he was noted as such as an SA is not assigned. Results: The magnitude of intra-individual differences between repeated SA assessments were d = 0.008 year (observer A) and d = 0.001 year (observer B); the respective coefficients of variation were 1.11% and 1.75%. Inter-observer mean differences were negligible (t = 1.252, p = 0.210) and the intra-class correlation coefficient was nearly perfect (ICC = 0.995). Concordance of classifications of players by maturity status between observers was 90%. Conclusion: Fels SA assessments were highly reproducible and showed an acceptable level of inter-observer agreement between trained examiners. Classifications of players by skeletal maturity status based on assessments of the two observers were highly concordant, though not 100%. The results highlight the importance of experienced observers in skeletal maturity assessments. [ABSTRACT FROM AUTHOR]

Study purpose. The research goal was to establish if the fat-free mass, chronological age and maturity status are determinants of physical fitness, and to analyze the development changes of fat-free mass and physical fitness in concordance with chronological age and maturity status in schoolchildren aged 6 to 14. Materials and methods. The research was conducted on a sample of 9106 students aged 6 to 14 years. In order to reach the research goals, the following variables were measured: height, weight, sitting height, fat mass, fat-free mass and various components of the physical fitness (lower limbs explosive strength, handgrip strength, abdominal muscle repetitive strength, speed and agility). The values of body mass and biological maturation indexes (APHV) were obtained by using formulas. Results. The boys’ age at peak height velocity was estimated at 13.00±0.82, and the girls’ one at 11.57±0.68. The relationships between chronological age and age at peak height velocity with fat-free mass was r=0.82 to 0.94 in the boys and r=0.83 to 0.92 in the girls. The relationships between fat-free mass and physical fitness tests in the boys were: standing long jump (r=0.55), 30 sec sit-ups (r=0.37), handgrip strength (r=0.75) and shuttle run 4 х 10 meters (r=-0.40); and in the girls – standing long jump (r= 0.45), 30 sec sit-ups (r= 0.36), handgrip strength (r= 0.74) and shuttle run 4 х 10 meters (r= -0.43). The differences in fat-free mass and physical fitness tests were more prominent when the comparison was done with relation to the biological maturation (APHV) and chronologic age. Conclusions. On the basis of the obtained results, it can be concluded that maturity status and fat-free mass determinate the physical fitness performances in the schoolchildren of both genders. Also, the age at peak height velocity should be used in Physical Education as a tool of monitoring, ranging and classification of physical performances in children and adolescents.

Objectives: The objective of the study was to verify whether (FFM), maturity status (MS) and chronological age (CA) are determinants of physical fitness performance, and to analyze FFM and physical performance aligned by CA and MS in children and adolescents. Methods: A descriptive correlational study was carried out in 863 schoolchildren. Weight, height, and waist circumference (WC) were evaluated. Body mass index (BMI), FFM, fat mass (FM), MS (Age at peak height velocity, APHV) were calculated. The physical tests of velocity 20 m, agility 5 m x 10rep, and horizontal jump (HJ) were evaluated. Results: The APHV was estimated in boys at 14.0 ± 0.36APHV and in girls at 11.96 ± 0.49APHV. The relationships between CA and APHV with FFM was r = 0.80 in boys and r = 0.44 to 0.45 in girls. The relationships between FFM and physical tests in boys were [HJ (r = 0.70), agility 5m x 10rep (r = -0.68), velocity (r = -0.61)] and in girls [HJ (r = 0.42), agility 5m x 10rep (r = -0.52), velocity (r = -0.20)]. The differences in FFM and physical fitness tests were more pronounced when aligned by APHV than by CA. Conclusion: It was verified that both FFM, CA, and APHV are determinants of physical fitness performance. In addition, the APHV should be introduced in physical education as a means of ranking physical performance among schoolchildren. [ABSTRACT FROM AUTHOR]

Volleyball is an intermittent team sport that requires specific anthropometrical and physical characteristics for winning performance. The present study aimed to evaluate the maturity status of the young male players of eight volleyball teams, and to observe differences in anthropometric characteristics and body composition. Ninety-four male adolescent volleyball players were recruited during a national tournament carried out in Treviso (Italy). Anthropometric characteristics such as weight, stature, skinfold thicknesses, circumferences and diameters, and bioelectrical impedance were measured. The biological maturation was estimated for all players. Each team was classified as a higher or lower lever according to its tournament ranking. A two-way ANOVA compared team levels and players’ maturity status. Considering the maturity offset, 62 boys were classified as “on time”, 20 as “late”, and 12 as “early”. Three clubs presented many boys with “early” as the maturity offset, and two of these finished the tournament in the first position. Young volleyball players classified as “early” seemed to show anthropometric characteristics linked to better performance at the tournament (higher height, upper arm and calf muscle area, fat mass percentage, and total fat-free mass). The results of the present study could have practical implications for talent selection, but further studies are needed to better evaluate the effect of maturity status on the characteristics of volleyball players.

Papaya (Carica papaya) is a tropical fruit having commercial importance because of its high nutritive and medicinal value. The packaging of papaya fruit as per its maturity status is an essential task in the fruit industry. The manual grading of papaya fruit based on human visual perception is time-consuming and destructive. The objective of this paper is to suggest a novel non-destructive maturity status classification of papaya fruits. The paper suggested two approaches based on machine learning and transfer learning for classification of papaya maturity status. Also, a comparative analysis is carried out with different methods of machine learning and transfer learning. The experimentation is carried out with 300 papaya fruit sample images which includes 100 of each three maturity stages. The machine learning approach includes three sets of features and three classifiers with their different kernel functions. The features and classifiers used in machine learning approaches are local binary pattern (LBP), histogram of oriented gradients (HOG), Gray Level Co-occurrence Matrix (GLCM) and k-nearest neighbour (KNN), support vector machine (SVM), Naïve Bayes respectively. The transfer learning approach includes seven pre-trained models such as ResNet101, ResNet50, ResNet18, VGG19, VGG16, GoogleNet and AlexNet. The weighted KNN with HOG feature outperforms other machine learning-based classification model with 100% of accuracy and 0.099 5 s training time. Again, among the transfer learning approach based classification model VGG19 performs better with 100% accuracy and 1 min 52 s training time with consideration of early stop training. The proposed classification method for maturity classification of papaya fruits, i.e. VGG19 based on transfer learning approach achieved 100% accuracy which is 6% more than the existing method.

The aim of this study was to determine what kind of performance characteristics distinguish between different skill levels at different development stages in field hockey using a multi-dimensional testing battery. A total of 100 players identified as "talented" (51.0% girls) and 105 recreational level players (41.0% girls) divided over three age groups (U13/U15/U18) performed anthropometric, physical capacity, sport-specific technical skill and decision-making tests and completed self-regulation and sport history questionnaires. Gender specific multivariate analysis with playing level and age group as factors and age as a covariate were performed. Results revealed that experienced selectors and coaches select players for representative teams predominantly based on their dribbling skills, passing/hitting skills and speed and endurance. Furthermore, it is clear that selection for such a representative team is strongly influenced by maturational status and accumulated field hockey specific training hours. Interestingly, no differences were found between the self-regulatory skills of state and club level players for either gender. This study highlighted the performance characteristics deemed to be important by selectors and coaches and emphasized the need to consider the strong influence of maturational status and practice history when selecting "talented" players as these factors don't translate to future sporting success. [ABSTRACT FROM AUTHOR]

Baseline characteristics of 31 healthy male U15 soccer players who were classified as select or non-select at the end of the season were compared. Players were 14.4 ± 0.54 years (13.6–15.3 years) at baseline; characteristics included body size, proportions and composition, estimated maturity status, several functional capacities, and coach classifications of potential in the sport. Decisions regarding selection or nonselection were made about two months after baseline. Select and non-select U15 soccer players differed significantly in estimated maturity status, body size, proportions and estimated muscle mass, functional tests related to speed, power and strength, and coach evaluation of potential, specifically tactical skills on offense and skills associated with creativity and decision making. When age and biological maturity status were statistically controlled, select and non-select players differed significantly only on the vertical jump, grip strength, and coach ratings of tactical skills on offense and of creativity and decision making. Results of stepwise discriminant analysis highlighted the importance of coach evaluation of tactical skills associated with offense, and of power and strength in distinguishing select from non-select players. The results highlight the dvantages of advanced biological maturity status among adolescent male soccer players and also the importance of oach perceptions of talent. The latter implies a need for further study of the basis of coach perceptions, specifically how they are influenced by and perhaps interact with player characteristics at different ages, and how the perceptions influence playing time and player behaviors and interactions.

Relative age selection bias persists within all major soccer leagues and youth soccer academies across the globe, with the relative age effect (RAE) being typically characterized as the over selection of relatively older players (who have sometimes also been shown to be early maturing). The aim of this study was to examine if a new allocation method (i) eliminates the RAE, and (ii) reduces the presence of any additional maturity-related differences in anthropometric and physical fitness characteristics which may exist between players within the same selection category. In the first phase, 1,003 academy soccer players [under (U) 9–16] from 23 UK professional soccer clubs were sampled and a clear RAE per birth quarter (Q) was observed for the overall sample (Q1 = 45.0% vs. Q4 = 9.8%) as well as for the different age categories. Using the newly suggested reallocation method, youth players were divided by allocation date which was defined as the midway point between the chronological age and the estimated developmental (ED) birthdate. Stature was used as an anthropometric reference point on the P50 of the growth curve to determine the developmental birthdate for this new method. After the reallocation of the players using ED, the distribution of players was more equally spread (Q1 = 25.3%, Q2 = 25.6%, Q3 = 22.4%, Q4 = 26.7%). After reallocation, the mean delta stature was reduced by 16.6 cm (from 40.3 ± 7.08 to 23.7 ± 4.09 cm, d = 2.87). The mean delta body mass difference after allocation was reduced by 6.7kg (from 33.2 ± 6.39 to 26.5 ± 4.85 kg, d = 1.18). The mean age difference increased from 1.8 to 3.9 years. A total of 42.7% of the sample would have been reallocated to a different age group compared to the current one. After reallocation, 45% of the anthropometric and physical fitness comparisons showed reductions in the within-group variation expressed as a percentage of coefficient of variation (CV%). The U10 players demonstrated the largest reduction in CV% (−7.6%) of the anthropometric characteristics. The U10 squad also showed the largest reduction in CV% for various physical fitness characteristics (−7.5%). By both eliminating the RAE and reducing temporary maturity-related anthropometric and physical fitness differences, soccer academies across the world may diversify and increase the size of the talent pool both for clubs and national youth teams. In conclusion, this study provides further evidence that the newly proposed allocation method shows the potential to remove the RAE and to create a more “leveled playing field” by reducing the within-group variation of anthropometric and physical fitness characteristics affording relatively younger, and eventually, late-maturing players the opportunity to develop their talent fairly.

Yáñez-García, JM, Rodríguez-Rosell, D, Mora-Custodio, R, and González-Badillo, JJ. Changes in muscle strength, jump, and sprint performance in young elite basketball players: the impact of combined high-speed resistance training and plyometrics. J Strength Cond Res 36(2): 478–485, 2022—This study aimed to compare the effect of a combined resistance training (RT) and plyometrics on strength, sprint, and jump performance in basketball players of different ages. Thirty three elite basketball players from the same academy were categorized into 3 groups by chronological age: under-13 (U13, n = 11); under-15 (U15, n = 11); and under-17 (U17, n = 11). Players participated in a 6-week strength training program that included 2 sessions each week and consisted of full squats with low loads (45–60% 1 repetition maximum) and low volume (2–3 sets and 4–8 repetitions), jumps, and sprint exercises. All repetitions were performed at maximal intended velocity. In addition to strength training sessions, subjects performed 4 on court basketball training sessions plus 2 official matches per week. After training program, all 3 experimental groups resulted in significant improvements (p < 0.05–0.001) in maximal strength (Δ: 9.2–27.3%; effect size [ES]: 0.38–0.82), countermovement jump height (Δ: 6.6–11.6%; ES: 0.37–0.95), and sprint time in 10 and 20 m (Δ: −3.9 to −0.3%; ES: 0.09–0.69) for all experimental groups. Comparison between groups showed that training program was more effective in inducing improvements in most variables assessed for U13 compared with U15 (ES: 0.11–0.42) and U17 (ES: 0.20–0.43), whereas differences between U15 and U17 were relevant in jump and strength parameters (ES: 0.20–0.35). Therefore, these findings suggest that high-speed RT combined with plyometrics produces increments in several important variables, including strength, jump, and sprint, to yield high performance during a match in young basketball players. However, training program used seems to be generally less effective as the age of the basketball players increased. [ABSTRACT FROM AUTHOR]

Baseline characteristics of 31 healthy male U15 soccer players who were classified as select or non-select at the end of the season were compared. Players were 14.4 ± 0.54 years (13.6-15.3 years) at baseline; characteristics included body size, proportions and composition, estimated maturity status, several functional capacities, and coach classifications of potential in the sport. Decisions regarding selection or non- selection were made about two months after baseline. Select and non-select U15 soccer players differed significantly in estimated maturity status, body size, proportions and estimated muscle mass, functional tests related to speed, power and strength, and coach evaluation of potential, specifically tactical skills on offense and skills associated with creativity and decision making. When age and biological maturity status were statistically controlled, select and non-select players differed significantly only on the vertical jump, grip strength, and coach ratings of tactical skills on offense and of creativity and decision making. Results of stepwise discriminant analysis highlighted the importance of coach evaluation of tactical skills associated with offense, and of power and strength in distinguishing select from non-select players. The results highlight the advantages of advanced biological maturity status among adolescent male soccer players and also the importance of coach perceptions of talent. The latter implies a need for further study of the basis of coach perceptions, specifically how they are influenced by and perhaps interact with player characteristics at different ages, and how the perceptions influence playing time and player behaviors and interactions. [ABSTRACT FROM AUTHOR]

Introduction: Introduction: during childhood and adolescence there is great individual variability in growth and biological maturation, resulting in differences in size, shape and body composition in children and adolescents of similar age. Objective: to propose percentiles to assess physical growth and body adiposity as a function of maturity status (SM) in Chilean children and adolescents. Methods: a descriptive (cross-sectional) study was designed in 7,292 children and adolescents (4214 boys and 3084 girls) from the Maule region (Chile). The age range was 6.0 to 17.9 years. Weight, height and waist circumference (WC) were evaluated. Body mass index (BMI), waist-height index (WHtR) and SM were calculated through a non-invasive anthropometric technique based on chronological age and standing height. The LMS method was used to calculate percentiles. Results: the SM calculated in boys was observed at 13.7 ± 0.6 APHV (years of peak growth speed) and in girls at 12.1 ± 0.6 APHV. Percentiles were created for weight, height, WC, BMI, and WHtR. All anthropometric variables increase as MS increases in PHV years. Conclusion: the proposed percentiles are an alternative to evaluate physical growth and body adiposity as a function of SM in Chilean children and adolescents. The results suggest the use of this non-invasive technique to be applied in clinical and epidemiological contexts. [ABSTRACT FROM AUTHOR]

Despite various solutions proposed to solve the relative age effect (RAE), it is still a major problem confounding talent identification and selection processes. In the first phase, we sampled 302 under 7–21 academy soccer players from two Belgian professional soccer clubs to explore the potential of a new approach to solve the inequalities resulting from relative age- and maturity-related bias. This approach allocates players into four discrete quartile groups based on the midway point of their chronological and estimated developmental (ED) birth dates (calculated using the growth curves for stature of Belgian youth). With the use of chi square analyses, a RAE was found (p < 0.01) for the overall sample (Q1 = 41.4% vs. Q4 = 14.9%) that completely disappeared after reallocation (Q1 = 26.5%; Q2 = 21.9%; Q3 = 27.5%; Q4 = 24.2%). According to the new allocation method, the stature difference was reduced, on average, by 11.6 cm (from 24.0 ± 9.9 to 12.4 ± 3.4 cm, d = 1.57). Body mass difference between the two methods was 1.9 kg (20.1 ± 11.3–18.2 ± 13.1 kg, respectively, d = 0.15). The new method created a maximum chronological age difference of 1.9 vs. 0.8 years for the current method. With the use of this method, 47% of the players would be reallocated. Twenty-three percent would be moved up one age category, and 21% would be moved down. In the second phase, we also examined 80 UK academy soccer players to explore if reallocating players reduces the within-playing group variation of somatic and physical fitness characteristics. The percentage coefficient of variation (%CV) was reduced (0.2–10.1%) in 15 out of 20 metrics across U11–U16 age categories, with the U13 age category demonstrating the largest reductions (0.9–10.1%) in CV. The U12 and U13 age categories and associated reallocation groupings showed trivial to small (ES = 0.0–0.5) between-method differences and trivial to moderate (ES = 0.0–1.1) differences within the U14–U16 age categories. A reduction in RAE may lead to fewer dropouts and thus a larger player pool, which benefits, in turn, talent identification, selection, and development.

The aim of this cohort study is to estimate the influence of position, category, and maturity status on the incidence and pattern of injury in handball players, across two seasons. Injury registration from 164 players per season (12-27 years) was conducted, and players were categorized into youth (133) and adults (31), and per position: 27 goalkeepers, 67 backs, 70 wings and pivots. Maturity status in youth players was also measured by testicular volume on clinical examination (32 immature, 101 mature). 190 injuries occurred during 34 221 hours of exposure. Injury incidence in youth was 6.0 per 1000 total hours [CI 95%, 4.8-7.2] (14.9 match [9.7-20.1] and 3.7 training hours [2.7-4.6]; n= 142 injuries), and in adults 6.5 per 1000 total hours [4.4-8.6] (22.2 match [8.8- 35.6] and 3.0 training hours [1.3-4.6]; n=48 injuries). There were significant differences in knee (P=0.01) and cartilage injury (P=0.05) according to playing position. There were significant differences according to age category in ankle (P=0.03), head (P=0.01), thigh (P=0.05) and muscular injury (P= 0.02), and apophysitis (P=0.04) for biological maturity state. Adult handball players had more ankle and muscle injuries than youths. Backs and centre backs (2nd line) had more knee and cartilage problems. A higher incidence of apophysitis was found in immature youth players.

Because age-groups in soccer often comprise children born within a 2-year time frame, characteristics that define the profile of a successful player may not be appropriate for the oldest or youngest players of the same age-group. Therefore, this study aimed to determine to what extent performance was influenced by age, maturation, and body size in elite soccer players with barely 1-year age gap. Anthropometry, 15-m sprint test, modified Barrow's agility test, Yo-Yo intermittent recovery test level 1, countermovement jump, and handgrip test were conducted in players aged 12 years and under (n = 82; age, 11.1 ± 0.6 years) and between 12 and 13 years (n = 79; age, 12.8 ± 0.6 years). A total score of performance, chronological age, and age at peak height velocity were calculated. Descriptive statistics, Student's t-tests, and multiple linear regressions were performed. The explained variance in composite score was greater in the older (54%) than in the younger (30%) players. Sum of skinfolds was the primary predictor of 15-m sprint and countermovement jump in the younger group, whereas in the older group, chronological age and body size appeared as predictors of performance (41%). Body size explained the variance in most tests in older players. In the younger group, biological maturity status explained the variance in endurance (35%) and handgrip (59%) tests. In summary, chronological age and sum of skinfolds influenced the most tests; however, predictors differed between age groups. These findings highlight the importance of assessing individual differences in young male soccer players regardless of their similarity in age. [ABSTRACT FROM AUTHOR]

Traditionally, physical and anthropometrical profiles of the most successful kayak athletes have been identified in male kayakers. This study attempted to identify the differences in morphology and fitness level of 2 performance-based groups of young elite female paddlers. Eighty-six female kayakers, aged 13.62 ± 0.57 years (mean ± SD), were allocated in 2 groups (Top-10 and Rest) depending on their ranking in the 3 Olympic distances (200, 500, and 1,000 m). All subjects underwent a battery of anthropometrical (heights, mass, girths, and sum of skinfolds), physical fitness (overhead medicine ball throw, countermovement jump, sit-and-reach test, and 20-m multistage shuttle run test), and specific performance assessments (200, 500, and 1,000 m). Best paddlers presented significantly greater anthropometrical values in muscle mass percentage, maturity status, and chronological age (p ≤ 0.05), whereas physical fitness comparison only revealed significant differences in countermovement jump (p ≤ 0.05). Furthermore, aerobic power and muscle mass percentage seem to be crucial in achieving optimal performances at long (1,000 m) and short duration races (200 and 500 m). These findings confirm the importance of a larger and compact morphology, as well as superior fitness level, for success in female kayakers. The current results not only identify the weak areas on body composition and physical fitness depending on the maturity status but also the development of specific training programs for females. [ABSTRACT FROM AUTHOR]

Background: Preterm birth is associated with various risks, including delayed or atypical language development. The prenatal start of prosodic tuning may affect the processing of word stress, an important suprasegmental feature of spoken utterances.Aim: Our study focused on the expected contribution of intra-uterine experience to word stress processing. We aimed to demonstrate the hypothesized effect of intra-uterine sound exposition on stress sensitivity.Method: We recorded ERP responses of 34 preterm infants elicited by bisyllabic pseudo-words in two oddball conditions by switching the stress pattern (legal vs. illegal) and role (standard vs. deviant).Results: The mismatch responses found were synchronized to each syllable of the illegally stressed stimuli with no difference between pre- and full-term infants. However, the clear role of the preterm status was demonstrated by the exaggerated processing of the native stress information. The impact of intra-uterine exposure to prosody was confirmed by our finding that moderate-late preterm infants outperformed the very preterm ones.Conclusion: Intra-uterine exposition to prosodic features appears to contribute to the emergence of stable long-term stress representation. When this tuning is missing it is considered a risk for the language acquisition process. [ABSTRACT FROM AUTHOR]

The aim of this cohort study is to estimate the influence of position, category, and maturity status on the incidence and pattern of injury in handball players, across two seasons. Injury registration from 164 players per season (12-27 years) was conducted, and players were categorized into youth (133) and adults (31), and per position: 27 goalkeepers, 67 backs, 70 wings and pivots. Maturity status in youth players was also measured by testicular volume on clinical examination (32 immature, 101 mature). 190 injuries occurred during 34 221 hours of exposure. Injury incidence in youth was 6.0 per 1000 total hours [CI 95%, 4.8-7.2] (14.9 match [9.7-20.1] and 3.7 training hours [2.7-4.6]; n= 142 injuries), and in adults 6.5 per 1000 total hours [4.4-8.6] (22.2 match [8.8- 35.6] and 3.0 training hours [1.3-4.6]; n=48 injuries). There were significant differences in knee (P=0.01) and cartilage injury (P=0.05) according to playing position. There were significant differences according to age category in ankle (P=0.03), head (P=0.01), thigh (P=0.05) and muscular injury (P= 0.02), and apophysitis (P=0.04) for biological maturity state. Adult handball players had more ankle and muscle injuries than youths. Backs and centre backs (2nd line) had more knee and cartilage problems. A higher incidence of apophysitis was found in immature youth players. [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the role of the relative age effect (RAE) and to investigate the influence of the biological maturity status on the RAE in international under-9 soccer. The birth dates of 222 male participants of the U9 Eurochampionship Soccer Tournament in Vienna in 2016 were analyzed and divided into four relative age quarters (Q1-Q4) and the biological maturity status was assessed with the age at peak height velocity (APHV) method. Based on the mean±standard deviation of the APHV, the athletes were divided into three groups of maturity: early, normal and late maturing. Chi-Square-tests were used to assess the difference between the observed and the expected even relative age quarter distribution and to evaluate the difference between the observed distribution of early, normal and late maturing athletes and the expected normal distribution. A univariate analysis of variance was performed to assess differences in the APHV between the relative age quarters. A RAE was present (χ² = 23.87; p < 0.001; ω = 0.33). A significant difference was found in APHV between the four relative age quarters (F = 9.906; p < 0.001); relatively older athletes were significantly less mature. A significant difference was found between the distribution of early, normal and late maturing athletes and the expected normal distribution for athletes of Q1 (high percentage of late maturing athletes: 27%; χ² = 17.69; p < 0.001; ω = 0.46) and of Q4 (high percentage of early maturing soccer players: 31%; χ² = 12.08; p = 0.002; ω = 0.58). These findings demonstrated that the selection process in international soccer, with athletes younger than 9 years, seems to be associated with the biological maturity status and the relative age. Relatively younger soccer players seem to have a better chance for selection for international tournaments, if they enter puberty at an earlier age, whereas relatively older athletes seem to have an increased likelihood for selection independent of their biological maturity status. [ABSTRACT FROM AUTHOR]

The aim of the present study was to compare the effectiveness of low-load, low-volume weight training combined with plyometrics on strength, sprint, and jump performance in soccer players of different ages. Eighty-six soccer players from the same academy were categorized into 3 groups by age (under 13 years, U13, n = 30; under 15, U15, n = 28; and under 17, U17, n = 28) and then randomly assigned into 2 subgroups: a strength training group (STG) and a control group (CG). The strength training program was performed twice a week for 6 weeks and consisted of full squats (load: 45-60% 1 repetition maximum; volume: 3 set of 8-4 repetitions), jumps, and straight line sprint exercises. After training intervention, the STGs showed significant improvements in maximal strength (7.5-54.5%; p < 0.001), jump height (5.7-12.5%; p <0.01-0.001), and sprint time (-3.7 to -1.2%; p ≤0.05-0.001), whereas no significant gains were found for any variable in the CGs. Comparison between experimental groups resulted in a greater magnitude of change for U13 compared with U15 (effect sizes [ES]: 0.10-0.53) and U17 (ES: 0.14-1.41) soccer players in most variables, whereas U15 showed higher improvements in jump and strength parameters than U17 (ES: 0.25-0.90) soccer players. Thus, although our results indicates that a combined weight training and plyometrics program may be effective in eliciting gains in strength, jump, and sprint in soccer players of different ages, the training program used appears to be generally less effective as the age of the soccer players increased. Therefore, it appears that training characteristics (mainly volume, intensity, and type of exercise) should be modified in relation to maturity status and initial strength level. [ABSTRACT FROM AUTHOR]

A robust understanding of habitat usage by coastal shark species, and how it overlaps with human presence in denselypopulated regions is needed to inform the development of efficient conservation strategies for these important top predators. An intensive longline survey conducted in nearshore waters off northeastern Brazil from 2004 through 2014 caught a total of 18 bull sharks (Carcharhinus leucas) (male-female ratio = 0.63:1), which can be dangerous to humans. Although most sharks were sexually mature, there was no evidence that this region could be used as a parturition or nursery area. Prey items identified in the guts of the sharks comprised teleosts, mollusks and elasmobranchs. Additionally, one satellite-tagged bull shark covered a great distance (> 3,000 km) in 75 days at liberty, making most use of shallow waters (< 20 m depth) and presumably also entering an estuarine area. Although bull sharks are not an important fishery resource in this region, such a reduced abundance coupled with its affinity for coastal and inshore habitats highlights the potential vulnerability of C. leucas to deleterious anthropic interferences off northeastern Brazil. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether average growth tempo influenced longitudinal relationships between maturity status and coordination capability using a 15-s hopping task (Aim 1). To investigate how differences in absolute growth tempo were associated with change in coordination capability within and across peak growth (Aim 2).Methods: Participants were N1 = 110 (Aim 1) and N2 = 71 (Aim 2) Australian male competitive swimmers, aged 10-15 years, exposed to repeated-measures tracking (2-years, and 12-months respectively) of maturity status, growth tempo and movement coordination capability. Coordination capability was estimated via vertical stiffness (KV) in a hopping task, reflected by participant mean KV and between-jump coefficient of variation (CV).Results: For Aim 1, log-linear mixed model trends identified maturity status and growth tempo were significantly associated with KV mean and KV CV. For a given maturity status, mean KV was 9% lower in the 'High' average growth tempo group than the 'Low' average tempo group. For Aim 2, mixed repeated-measures analyses of variance identified how time points of increased growth tempo were significantly associated with 7-11% reductions in mean KV, with similar mean KV decrements irrespective of growth tempo group. Meanwhile, KVCV only illustrated progressive longitudinal reductions.Conclusions: Within maturational progression, short-term accelerations in growth tempo corresponded with short-term decreases in KV mean, suggesting temporary disruptions to movement coordination capability. Measuring growth tempo and applying hopping tasks in specific movement contexts could help consistently identify disturbances in motor coordination. [ABSTRACT FROM AUTHOR]

We investigated the evolution and stability of anthropometric and soccer-specific endurance characteristics of 42 high-level, pubertal soccer players with high, average and low yo-yo intermittent recovery test level 1 (YYIR1) baseline performances over two and four years. The rates of improvement were calculated for each performance group, and intra-class correlations were used to verify short- and long-term stability. The main finding was that after two and four years, the magnitudes of the differences at baseline were reduced, although players with high YYIR1 baseline performance still covered the largest distance (e.g., low from 703 m to 2126 m; high from 1503 m to 2434 m over four years). Furthermore, the YYIR1 showed a high stability over two years (ICC = 0.76) and a moderate stability over four years (ICC = 0.59), due to large intra-individual differences in YYIR1 performances over time. Anthropometric measures showed very high stability (ICCs between 0.94 to 0.97) over a two-year period, in comparison with a moderate stability (ICCs between 0.57 and 0.75) over four years. These results confirm the moderate-to-high stability of high-intensity running performance in young soccer players, and suggest that the longer the follow-up, the lower the ability to predict player's future potential in running performance. They also show that with growth and maturation, poor performers might only partially catch up their fitter counterparts between 12 and 16 years. [ABSTRACT FROM AUTHOR]