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The organisation and development strategies of youth soccer differ between Norway and Iceland. Whether this affect physical capacity is unknown. Thus, the first aim of the present study is to compare physical capacity between players fromIceland and Norway. Secondary aim is to assess associations between biological maturity and physical capacity in the Icelandic players since an association previously has been shown among the Norwegians. There were 48 U14 players from Iceland included and 103 players from Norway. Bone age (BA), measured with left-wrist x-ray, was used as an indicator of biological maturity. To measure physical capacity, 40 metre (m) linear sprint, standing long jump (SLJ), countermovement jump (CMJ), the Yo-Yo intermittent recovery test (IR1-test) and a maximal oxygen uptake test (VO2max) were used. Training load was assessed by questionnaire. The results showed that the Norwegian players ran faster (5.90 ± 0.38 vs. 6.37 ± 0.44 s, p < .001), had better intermittent endurance capacity (1,235 ± 461 vs. 960 ± 423 m, p < .001) and higher VO2max, (60.3 ± 6.5 vs. 54.8 ± 5.3 ml·kg-1·min-1, p < .001) than the Icelandic players. The players from Norway reported a higher number of weekly organised soccer training hours than the Icelandic. We also found significant correlations between BA and performance on 40 m linear sprint (r = -.566, p < .001), SLJ (r = .380, p = .008) and CMJ (r = .354, p = .014) among the Icelandic players. Moreover, no correlations were found between BA and VO2max or intermittent endurance capacity. In conclusion, the Norwegian players ran faster and had better VO2max and intermittent endurance capacity than the Icelandic players. Biological maturity level was associated with speed and jumping performance in U14 soccer players in Iceland, but not with VO2max or intermittent endurance capacity. Findings indicate that more research is needed to investigate the influence of different organisation and structure of youth soccer between the two countries on physical capacity. [ABSTRACT FROM AUTHOR]

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Purpose: To evaluate non-specific and ski-specific performance development in male (M) and female (F) peri-pubertal cross-country skiers and to evaluate their relationship with cross-country skiing (XCS) performance and biological maturation within each age category and sex. Methods: Twenty-one and 19 athletes under 14 and 16 years old, respectively (U14 and U16), were tested for biological maturation; non-specific speed, agility, strength, endurance, and balance; ski-specific speed, agility, and endurance. XCS index was considered as average percentage time-gap from the winner in four official races. Sex and age-category effects were verified and a model predicting XCS index was extrapolated for each group. Results: Performance capacities raised across age categories (p < 0.05) except for non-specific speed, agility, balance, and relative arm strength (p > 0.05). F showed advanced biological maturation and greater balance than M (p < 0.05), while M showed higher performance capacities (p < 0.05). XCS index was not related to biological maturation within each group (p > 0.05); its variance was explained by non-specific speed and ski-specific upper-body endurance in M-U14 (p = 0.014), lower-limb strength and ski-specific agility in M-U16 and F-U14 (both p = 0.001), ski-specific upper-body endurance in F-U16 (p = 0.002). Conclusion: Ski-specific performance capacities still develop during peri-puberty, with peri-pubertal M overperforming with respect to F of comparable performance level. XCS index was not influenced by biological maturation withing each age category, but it was rather explained by specific parameters that commonly undergo the "adolescent spurts", accordingly to the average biological maturation level of M and F athletes of each age category. [ABSTRACT FROM AUTHOR]

During puberty, the biological maturity of children of the same chronological age differs. To generate equal opportunities for talent selection in youth sports, the athlete's biological maturity should be considered. This is often assessed with a left hand and wrist radiography. Alternatively, ultrasound (US) could be advantageous, especially by avoiding ionizing radiation. This pilot study aimed to assess intrarater and interrater reliability of an experienced and a non-experienced examiner in an US-based examination of the knee in 20 healthy females (10–17 years). Epiphyseal closure at five anatomical landmarks was staged (stages 1–3) and its interrater and intrarater reliabilities were analyzed using Cohen's kappa (k). Interrater reliability of the calculation of the ossification ratio (OssR) was analyzed using the Bland-Altman method and intraclass correlation coefficients (ICCs). Interrater reliability for the stages was almost perfect for four landmarks. Interrater reliability ranged from k = 0.69 to k = 0.90. Intrarater reliability for the stages was almost perfect for four landmarks. Intrarater reliability ranged from k = 0.70 to k = 1.0. For the OssR, ICC was 0.930 and a minimal detectable change of 0.030 was determined. To conclude, experienced and non-experienced examiners can reliably assign individuals to different ossification stages and calculate an OssR using US-based imaging of the knee. [ABSTRACT FROM AUTHOR]

The organisation and development strategies of youth soccer differ between Norway and Iceland. Whether this affect physical capacity is unknown. Thus, the first aim of the present study is to compare physical capacity between players from Iceland and Norway. Secondary aim is to assess associations between biological maturity and physical capacity in the Icelandic players since an association previously has been shown among the Norwegians. There were 48 U14 players from Iceland included and 103 players from Norway. Bone age (BA), measured with left-wrist x-ray, was used as an indicator of biological maturity. To measure physical capacity, 40 metre (m) linear sprint, standing long jump (SLJ), countermovement jump (CMJ), the Yo-Yo intermittent recovery test (IR1-test) and a maximal oxygen uptake test (VO2max) were used. Training load was assessed by questionnaire. The results showed that the Norwegian players ran faster (5.90 ± 0.38 vs. 6.37 ± 0.44 s, p

Purpose: To examine differences in resistance exercise-induced hormonal responses among young athletes according to their maturity levels. Materials and Methods: A total of 12 collegiate and 32 junior high school male athletes were enrolled. The junior high school participants were divided into pre–peak height velocity (PHV) and post-PHV groups, according to their PHV ages. The salivary testosterone, cortisol, and human growth hormone levels were analyzed before (pre), immediately after (post), and at 15 minutes after performing body weight resistance exercise. Results: The testosterone levels were higher in the collegiate than in the junior high school group (P <.01) and increased after 15 minutes of exercise (P <.01). A significant decrease in the cortisol levels postexercise in the junior high school groups (P <.01) and an increase in the human growth hormone levels at 15 minutes after exercise in the post-PHV group were observed (P <.01). In the collegiate and post-PHV groups, the testosterone-to-cortisol ratio increased post and at 15 minutes after exercise (P <.01). The testosterone-to-cortisol ratio values were higher in the collegiate than in the post-PHV (at preexercise and at 15 min after [P <.01]) and pre-PHV groups (at all times [P <.01]). Conclusion: Exercise-induced acute hormonal responses to resistance exercise may depend on individuals' maturity levels, even in those having the same age. [ABSTRACT FROM AUTHOR]

Background: Adequate body composition is important for health and performance of physically active adolescents; however, some factors can influence body composition. Aim: The purpose of this study was to evaluate the association between body composition and birth weight, skeletal maturity and dietary patterns, in male (n = 124) and female (n = 107) physically active adolescents. Methods: Birth weight was obtained from health booklets. Dual-energy X-ray absorptiometry (DXA) was used to estimate fat mass (FM), fat-free mass (FFM), visceral adipose tissue (VAT) and abdominal adipose tissue (ASAT). Skeletal maturity was assessed by a hand and fist scanner using DXA. Food intake was assessed using a food frequency questionnaire and dietary patterns by factorial analysis. Results: Seventy one percent (male = 16%, female = 55%) of the participants were mature. Two dietary patterns (in natura /minimally processed and processed/ultra-processed) were identified. In males, FM (>15%, P = 0.043) and ASAT (>30%, P = 0.042) were higher in those with low-median compared to high-median birth weight. FFM (>24%) was higher in skeletally mature compared to those immatures (P = 0.001), and VAT (>28%) was higher in processed/ultra-processed compared to in natura /minimally processed dietary patterns (P = 0.015). In females, FFM (>9%) was higher in those with low-median compared to high-median birth weight (P = 0.019); and FFM (>16%), FM (>28%) and ASAT (>45%) were higher in skeletally mature compared to those immatures (P = 0.001). Conclusion: Our results may contribute to a better understanding of the complex association among body composition, birth weight, skeletal maturity and dietary patterns and in physically active adolescents, differently according to sex. [ABSTRACT FROM AUTHOR]

The aim of the study was to compare the status of somatic maturity, anthropometry, strength, speed, and soccer-specific technical skills of players from leading youth soccer academies born in different quarters of the same calendar year. A total of 678 young male soccer players from eight leading Russian soccer academies took part in the study. The following anthropometric measures and physical characteristics were measured: height, weight, body mass index, countermovement jumps (CMJ), 5, 10, and 20 m sprints, speed dribbling, foot and body ball juggling, and short and long pass accuracy. The determination of somatic maturity as a percentage of projected adult height was collected. All subject dates of birth were divided into four quartiles according to the month of birth. The analysis of all data obtained was conducted both within the total sample and by quartiles of birth, according to the age group categories of 12–13 years, 14–15 years, and 16–17 years and the degree of somatic maturity. There was a widespread relative age effect, with 43.5% of early-born players and only 9.6% of late-born players representing the sample. Early-born players were more mature than late-born players (p < 0.001 and p < 0.001) but had no statistically significant differences in strength, speed, or soccer-specific skills. [ABSTRACT FROM AUTHOR]

Featured Application: Coaches and sport managers in charge of talent identification processes in sprint canoeing might take into considerations these findings not only to select potential successful paddlers but also to enhance their attributes during early stages. Elite kayakers are characterized by robust somatotypes and a high degree of technical skills acquired from early ages along the biological maturity process. This study aimed to analyze the interdependence of anthropometric attributes, maturity status, and new stroke kinematics variables such as long- and short-term stroke steadiness in young sprint paddlers. Twenty-two elite young male canoeists, aged 13.5 ± 0.4 years, volunteered for the investigation. A battery of anthropometric measurements was obtained for each individual while stroke kinematics were determined by lateral recordings in an all-out 200 m test. Frame-to-frame analysis of consecutive strokes allowed the determination of short-term and long-term steadiness. Significant and positive correlations (p < 0.05) between maturity status, canoeing experience, and stroke steadiness were identified, especially in long-term steadiness (r = 0.60–0.83). In addition, upper-body dimensions in the chest and arms exhibited strong associations with both short- and long-term steadiness (p < 0.05). These findings suggest that biological maturity, but particularly experience, are key factors for a higher stroke efficiency. Therefore, early identification of morphological characteristics and maturity status along with specific practice in canoeing should be taken into consideration for ideal talent development in young canoeists. [ABSTRACT FROM AUTHOR]

During puberty, the biological maturity of children of the same chronological age differs. To generate equal opportunities for talent selection in youth sports, the athlete’s biological maturity should be considered. This is often assessed with a left hand and wrist radiography. Alternatively, ultrasound (US) could be advantageous, especially by avoiding ionizing radiation. This pilot study aimed to assess intrarater and interrater reliability of an experienced and a non-experienced examiner in an US-based examination of the knee in 20 healthy females (10–17 years). Epiphyseal closure at five anatomical landmarks was staged (stages 1–3) and its interrater and intrarater reliabilities were analyzed using Cohen’s kappa (k). Interrater reliability of the calculation of the ossification ratio (OssR) was analyzed using the Bland-Altman method and intraclass correlation coefficients (ICCs). Interrater reliability for the stages was almost perfect for four landmarks. Interrater reliability ranged from k = 0.69 to k = 0.90. Intrarater reliability for the stages was almost perfect for four landmarks. Intrarater reliability ranged from k = 0.70 to k = 1.0. For the OssR, ICC was 0.930 and a minimal detectable change of 0.030 was determined. To conclude, experienced and non-experienced examiners can reliably assign individuals to different ossification stages and calculate an OssR using US-based imaging of the knee.

Bone maturity is an indicator for estimating the biological maturity of an individual. During adolescence, individuals show heterogeneous growth rates, and thus, differences in biological maturity should be considered in talent identification and development. Radiography of the left hand and wrist is considered the gold standard of biological maturity estimation. The use of ultrasound imaging (US) may be advantageous; however, its validity and reliability are under discussion. The aims of this scoping review are (1) to summarize the different methods for estimating biological maturity by US imaging in adolescents, (2) to obtain an overview of the level of validity and reliability of the methods, and (3) to point out the practicability and usefulness of ultrasound imaging in the field of youth sports. The search included articles published up to November 2022. The inclusion criteria stipulated that participants had to fall within the age range of 8 to 23 years and be free of bone disease and fractures in the region of interest. Nine body regions were investigated, while the hand and wrist were most commonly analyzed. US assessment methods were usually based on the estimation of a bone maturity stage, rather than a decimal bone age. Furthermore, 70% of the assessments were evaluated as applicable, 10% expressed restraint about implementation, and 20% were evaluated as not applicable. When tested, inter- and intra-rater reliability was high to excellent. Despite the absence of ionization, low costs, fast assessment, and accessibility, none of the US assessments could be referred to as a gold standard. If further development succeeds, its application has the potential to incorporate biological age into selection processes. This would allow for more equal opportunities in talent selection and thus make talent development fairer and more efficient. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the methodology for selecting sports talent in the Chilean Promising Athletes Program (CPAP)., Methods: The standing broad jump (SBJ), medicine ball chest throw (MBCT), thirty-meter running sprint (RS-30), Agility-T (T-test), and height were analyzed in 3060 schoolchildren from Chile, grouped by sex, age, geographical area (north, central and south) and maturity status at peak height velocity (PHV) in pre-, circa- and post-PHV., Results: Superior differences were found in boys for all age ranges in SBJ, RS-30, T-test, and MBCT ( p < 0.05). Girls were taller than boys until the age of 12 years ( p < 0.01) with a reversal of this trend after 13 years old ( p < 0.001). In geographical grouping, higher scores in SBJ, RS-30, and T-test were found in the central zone for boys and girls ( p < 0.05). In both sexes, higher scores for the northern zone in MBCT ( p < 0.01) and height ( p < 0.05) are observed. Among selected talents, when comparing post-PHV vs. pre-PHV the differences are superior in all tests for post-PHV in girls and for MBCT and height ( p < 0.05) in boys. In circa-PHV vs. post-PHV in MBCT, T-test, and RS-30 only girls ( p < 0.05) were superior in post-PHV. For pre-PHV vs. circa-PHV, RS-30, and height ( p < 0.05), both sexes were superior in circa-PHV. There are differences between talents selected by physical tests and technical aspects ( p < 0.05)., Conclusions: The results show variations in physical and anthropometric tests in schoolchildren by age, sex, geography, and maturity status that should be considered for talent selection.

The aim of the study was to compare the status of somatic maturity, anthropometry, strength, speed, and soccer-specific technical skills of players from leading youth soccer academies born in different quarters of the same calendar year. A total of 678 young male soccer players from eight leading Russian soccer academies took part in the study. The following anthropometric measures and physical characteristics were measured: height, weight, body mass index, countermovement jumps (CMJ), 5, 10, and 20 m sprints, speed dribbling, foot and body ball juggling, and short and long pass accuracy. The determination of somatic maturity as a percentage of projected adult height was collected. All subject dates of birth were divided into four quartiles according to the month of birth. The analysis of all data obtained was conducted both within the total sample and by quartiles of birth, according to the age group categories of 12–13 years, 14–15 years, and 16–17 years and the degree of somatic maturity. There was a widespread relative age effect, with 43.5% of early-born players and only 9.6% of late-born players representing the sample. Early-born players were more mature than late-born players (p < 0.001 and p < 0.001) but had no statistically significant differences in strength, speed, or soccer-specific skills.

In the present study, we examined the biological maturity of young Japanese football players. In Japan’s football training system, players are selected at a young age. However, relatively early maturing players might be selected if the selection is based solely on technical and physical fitness factors. To eliminate this drawback in player selection, we believe that it is necessary to determine the players’ biological maturity accurately. Accordingly, the present study aimed to investigate the biological maturity of football players during the selection process. We included 475 young Japanese football players (mean age: 12.4 ± 0.6 years) affiliated with the Japan Professional Football League between 2007 and 2015. According to an unpaired t-test, there was no significant difference between the Tanner-Whitehouse 2 (Japan) skeletal age and the chronological age of the affiliated players. The difference in biological maturity between the junior youth (Jy) group (mean age: 12.9 ± 0.4 years [12.0–13.9]) and the junior (Jr) group (mean age: 11.8 ± 0.3 years [11.0–12.4]) was examined using a chi-squared test. The results of the residual analysis revealed a significant difference between the Jy and Jr groups (χ2 = 22.552, degree of freedom = 3, p < 0.01). We evaluated the biological maturity of young football players and examined the relationship between the differences in maturity and the timing of player selection. In the player selection process in this study, it was speculated that early maturing players may not always be easy to identify.

Elite kayakers are characterized by robust somatotypes and a high degree of technical skills acquired from early ages along the biological maturity process. This study aimed to analyze the interdependence of anthropometric attributes, maturity status, and new stroke kinematics variables such as long- and short-term stroke steadiness in young sprint paddlers. Twenty-two elite young male canoeists, aged 13.5 ± 0.4 years, volunteered for the investigation. A battery of anthropometric measurements was obtained for each individual while stroke kinematics were determined by lateral recordings in an all-out 200 m test. Frame-to-frame analysis of consecutive strokes allowed the determination of short-term and long-term steadiness. Significant and positive correlations (p < 0.05) between maturity status, canoeing experience, and stroke steadiness were identified, especially in long-term steadiness (r = 0.60–0.83). In addition, upper-body dimensions in the chest and arms exhibited strong associations with both short- and long-term steadiness (p < 0.05). These findings suggest that biological maturity, but particularly experience, are key factors for a higher stroke efficiency. Therefore, early identification of morphological characteristics and maturity status along with specific practice in canoeing should be taken into consideration for ideal talent development in young canoeists.

Substantial differences in the biological maturity of children of the same chronological age during puberty lead to inequalities in talent selection in youth sports, emphasizing the importance of considering the athlete's biological maturity.1,2 Biological maturity is most commonly assessed on the basis of a radiography of the left hand and wrist, but ultrasound (US) could be advantageous, especially by avoiding ionizing radiation. The aims of this study were to assess the intra- and interrater reliability of two examiners with different expertise levels in an US-based assessment of five anatomical landmarks at the knee joint and the interrater reliability of an US-based calculation of the ossification ratio (OssR) of the distal medial femur. For the purpose of this pilot study, a cross-sectional design with two measurement time points was chosen. Twenty healthy female handball players between 10 and 17 years of age were recruited. Adolescents were excluded if they had any form of growth, musculoskeletal or neurological disorder. Epiphyseal closure at the landmarks was staged (stages 1-3). The reliability of the stages was analyzed using Cohen's kappa (k). The OssR was calculated by dividing the diameter of the ossification center by the epiphy-seal diameter. The interrater reliability of the OssR was analyzed using the Bland-Altman method and intraclass correlation coefficients (ICC). Interrater and intrarater reliability for the stages ranged from k=0.69 to k=0.90 and from k=0.70 to k=1.0, respectively. For the OssR, an ICC of 0.930 and a minimal detectable change (MDC) of 0.030 were determined. In conclusion, the overall high inter- and intrarater reliability shows that US-based imaging has a high potential for use in youth sports. Due to several limitations, further research with a larger number and higher heterogeneity of subjects is needed for possible implementation of US in the field of sports. [ABSTRACT FROM AUTHOR]

In last two decades a problem for determination of optimal rotation ages when considering not only wood production but carbon uptake has had big importance. The coppice stands in Bulgaria occupy approximately 47% of the forest area. The biggest part of it consists of species of genus Quercus which are managed by two silvicultural systems: traditional coppicing and conversion from coppice to high forest. The aim of this paper is to propose optimal rotation ages based on biological and technical maturity for two types of coppice oak stands: for compulsory conversion to high forest and for mixed coppice-seed management. Based on data obtained from forest management plans and temporary sample plots we propose different rotation ages from official regulations for main oak species and recommend some guidelines for forest management of coppice oak stands. [ABSTRACT FROM AUTHOR]

The health benefits of physical activity (PA) are widely recognized; however, biological maturation contributions are a subject that has been little studied, which is why the aim of this study was to analyze the effect of a six-week training program at moderate-intensity on the muscular strength and aerobic capacity in children between nine and 13 years (13 ± 1.0 years) according to their maturation state. Twenty-six schoolchildren (15 girls) participated in a six-week physical exercise program based on aerobic/anaerobic capacity and coordination skills. Maximal oxygen uptake (VO2max), trunk-lift, push-ups, curl-ups, and handgrip strength (both hands) were measured as response variables. Body mass index (BMI), skeletal maturity indicator (SMI), peak height velocity (PHV), age on peak height velocity (APHV) and sex were considered as covariates. The results of VO2max, push-ups, curl-ups, and handgrip strength were higher after the exercise program in the whole group (p < 0.05). The VO2max showed a greater increase in the normal-weight than in the overweight-obesity children (p = 0.001). Higher results in dominant handgrip strength were observed in girls (p = 0.003). The PHV before intervention presented a positive correlation with the dominant handgrip strength in all kids (r = 0.70, p = 0.001). As a conclusion, the six-week training program improved the physical fitness of children independent of the maturation state. Somatic maturation increases the physical abilities in schoolchildren. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess test-retest reliability, discriminative and criterion-related validity of the modified Illinois change-of-direction (CoD) test with ball dribbling-speed (ICODT-BALL) in young soccer players of different biological maturity and playing levels. Sixty-five young male soccer players (11.4 ± 1.2 years) participated in this study. The participants were classified according to their biological maturity (pre- and circum peak height velocity [PHV]) and playing-level (elite and amateur players). During the test-retest time period of two weeks, the following tests were performed during week one and as retest during week two: ICODT-BALL, ICODT, 4 × 9-m shuttle-run, countermovement-jump, triple-hop-test, maximum-voluntary isometric-contraction of back-extensors, Stork, Y-Balance, 10 and 30-m sprints. The ICODT-BALL showed excellent relative (r = 0.995, p < 0.001; ICC = 0.993) and absolute (SEM < 5%; SEM < SWCs(0.2, 0.6, 1.2)) reliability. The circum-PHV (22.8 ± 1.7-s) and elite (22.5 ± 0.9-s) players showed better ICODT-BALL performance than their pre-PHV (24.2 ± 2.5-s) and amateur (25.1 ± 2.8-s) counterparts (p = 0.028 and p < 0.001, respectively). The ICODT-BALL showed “very good” (AUC = 0.81) discriminant validity when comparing the elite and amateur players, and “moderate” (AUC = 0.67) discriminant validity when compared to pre-PHV and circum-PHV boys. ICODT-BALL demonstrated “large” positive associations with the ICODT (r = 0.65; 41.8% shared-variance) and sprint tests (r ≥ 0.52; 27.3 to 34.8% shared-variance). In addition, results showed “moderate” negative associations between ICODT-BALL and strength, and power measures, as well as a “small” negative relationship with balance tests. In conclusion, the ICODT-BALL is a valid and reliable test to evaluate the ability to quickly change directions while ball dribbling in young soccer players. Therefore, practitioners can use the ICODT-BALL as a tool for talent identification.

The purpose of this study was to assess test-retest reliability, discriminative and criterion-related validity of the modified Illinois change-of-direction (CoD) test with ball dribbling-speed (ICODT-BALL) in young soccer players of different biological maturity and playing levels. Sixty-five young male soccer players (11.4 ± 1.2 years) participated in this study. The participants were classified according to their biological maturity (pre- and circum-peak height velocity [PHV]) and playing-level (elite and amateur players). During the test-retest time period of two weeks, the following tests were performed during week one and as retest during week two: ICODT-BALL, ICODT, 4 x 9-m shuttle-run, countermovement-jump, triple-hop-test, maximum-voluntary isometric-contraction of back-extensors, Stork, Y-Balance, 10 and 30-m sprints. The ICODT-BALL showed excellent relative ( r = 0.995, p < 0.001; ICC = 0.993) and absolute (SEM < 5%; SEM < SWCs(0.2, 0.6, 1.2)) reliability. The circum-PHV (22.8 ± 1.7-s) and elite (22.5 ± 0.9-s) players showed better ICODT-BALL performance than their pre-PHV (24.2 ± 2.5-s) and amateur (25.1 ± 2.8-s) counterparts (p = 0.028 and p < 0.001, respectively). The ICODT-BALL showed "very good" (AUC = 0.81) discriminant validity when comparing the elite and amateur players, and "moderate" (AUC = 0.67) discriminant validity when compared to pre-PHV and circum-PHV boys. ICODT-BALL demonstrated "large" positive associations with the ICODT ( r = 0.65; 41.8% shared-variance) and sprint tests ( r ≥ 0.52; 27.3 to 34.8% shared-variance). In addition, results showed "moderate" negative associations between ICODT-BALL and strength, and power measures, as well as a "small" negative relationship with balance tests. In conclusion, the ICODT-BALL is a valid and reliable test to evaluate the ability to quickly change directions while ball dribbling in young soccer players. Therefore, practitioners can use the ICODT-BALL as a tool for talent identification. [ABSTRACT FROM AUTHOR]

Purpose: To examine longitudinal changes in exercise-induced hormonal responses in adolescent male basketball players., Methods: Fifteen adolescent males were assigned to prepeak height velocity (pre-PHV) and post-PHV groups according to the predicted age at PHV. Salivary testosterone, cortisol levels, and the testosterone-to-cortisol ratio were evaluated before (PRE), immediately after (POST), and 15 minutes after a bodyweight resistance training session, which was repeated after 1 year to analyze longitudinal changes in testosterone and cortisol levels., Results: Resting testosterone levels and acute testosterone responses after bodyweight resistance training increased in both groups after 1 year at all measurement points. The POST testosterone levels at initial measurement and PRE and 15-minute postexercise levels at 1 year in the post-PHV group were significantly higher than those in the pre-PHV group. Cortisol levels significantly decreased in the post-PHV group at baseline and 1 year later. In the post-PHV, the testosterone-to-cortisol ratio after bodyweight resistance training was significantly increased at baseline and 1 year later., Conclusions: Although testosterone levels increase with age, no acute response to bodyweight resistance training was observed after 1 year. The change in anabolic status indicated by the testosterone-to-cortisol ratio was due to a decrease in cortisol levels.

Bone maturity is an indicator for estimating the biological maturity of an individual. During adolescence, individuals show heterogeneous growth rates, and thus, differences in biological maturity should be considered in talent identification and development. Radiography of the left hand and wrist is considered the gold standard of biological maturity estimation. The use of ultrasound imaging (US) may be advantageous; however, its validity and reliability are under discussion. The aims of this scoping review are (1) to summarize the different methods for estimating biological maturity by US imaging in adolescents, (2) to obtain an overview of the level of validity and reliability of the methods, and (3) to point out the practicability and usefulness of ultrasound imaging in the field of youth sports. The search included articles published up to November 2022. The inclusion criteria stipulated that participants had to fall within the age range of 8 to 23 years and be free of bone disease and fractures in the region of interest. Nine body regions were investigated, while the hand and wrist were most commonly analyzed. US assessment methods were usually based on the estimation of a bone maturity stage, rather than a decimal bone age. Furthermore, 70% of the assessments were evaluated as applicable, 10% expressed restraint about implementation, and 20% were evaluated as not applicable. When tested, inter- and intra-rater reliability was high to excellent. Despite the absence of ionization, low costs, fast assessment, and accessibility, none of the US assessments could be referred to as a gold standard. If further development succeeds, its application has the potential to incorporate biological age into selection processes. This would allow for more equal opportunities in talent selection and thus make talent development fairer and more efficient.

One method of determining a person’s biological maturity involves evaluating their bone maturity. Differences in physical abilities among athletes during the growth period are thought to be strongly influenced by differences in bone maturity. Thus, it is necessary to understand biological maturity when selecting athletes. Accordingly, this study looks at the biological maturity of young Japanese soccer players in the Japan Professional Soccer League. In total, subjects included 282 male soccer players (mean age, 12.4 ± 0.7 years; mean height, 154.0 ± 9.1 cm) in the J-League Academy, 2007–2012. Results show that the TW2-RUS method (Japan) revealed no significant difference (t = 1.012, df = 277, ns); however, the TW3-RUS method revealed a significant difference (t = -4.075, df = 281, p < 0.05) for chronological age vs skeletal age in t-test. The breakdown of biological maturity according to the TW2-RUS method (Japan) was as follows: mature, 3 persons; early maturing, 45 persons; average, 196 persons; and late maturing, 38 persons. The breakdown of biological maturity according to the TW3-RUS method was as follows: mature, 3 persons; early maturing, 53 persons; average, 132 persons; and late maturing, 94 persons. The chi-square test revealed a significant difference (p < 0.001) between the TW2-RUS method (Japan) and the TW3-RUS method. Our results suggest that it is appropriate to use the TW2-RUS method (Japan) to evaluate skeletal age. With regard to biological maturity, contrary to prior research in Europe and America, a high proportion of our athletes had average biological maturity.

The aim of this study was to examine the impact of the relative age on the power, speed and agility of young U13 and U14 players. The study was conducted on a sample of 60 young soccer players born in 2001 and 2002. Within both age groups, players are divided into two categories according to relative age, whether they were born in the first or second half of the year. Anthropometric measurements and measurements of motor abilities were made to assess explosive power, speed and agility using the tests: standing long jump, vertical jump, sprint at 30 meters with passing time at 10 meters, zig-zag running without a ball and Ajax test 5x10m. Statistically significant differences were found in body height and weight, as well as in tests to assess power in a sample of U13 players. In U14 group, differences were found in tests of power and running speed, while there were no statistically significant differences in anthropometric variables. According to the results obtained, it can be said that the relative age is an important factor that leads to the appearance of differences in the test results of motor skills of young U13 and U14 soccer players. Therefore, the effect of relative age must be taken into account when selecting young soccer players during adolescence.

The health benefits of physical activity (PA) are widely recognized; however, biological maturation contributions are a subject that has been little studied, which is why the aim of this study was to analyze the effect of a six-week training program at moderate-intensity on the muscular strength and aerobic capacity in children between nine and 13 years (13 ± 1.0 years) according to their maturation state. Twenty-six schoolchildren (15 girls) participated in a six-week physical exercise program based on aerobic/anaerobic capacity and coordination skills. Maximal oxygen uptake (VO2max), trunk-lift, push-ups, curl-ups, and handgrip strength (both hands) were measured as response variables. Body mass index (BMI), skeletal maturity indicator (SMI), peak height velocity (PHV), age on peak height velocity (APHV) and sex were considered as covariates. The results of VO2max, push-ups, curl-ups, and handgrip strength were higher after the exercise program in the whole group (p < 0.05). The VO2max showed a greater increase in the normal-weight than in the overweight-obesity children (p = 0.001). Higher results in dominant handgrip strength were observed in girls (p = 0.003). The PHV before intervention presented a positive correlation with the dominant handgrip strength in all kids (r = 0.70, p = 0.001). As a conclusion, the six-week training program improved the physical fitness of children independent of the maturation state. Somatic maturation increases the physical abilities in schoolchildren.

The aim of the present study was to investigate prospectively the role of biological maturity status, anthropometric percentiles, and core flexion to extension strength ratios in the context of traumatic and overuse injury risk identification in youth ski racing. In this study, 72 elite youth ski racers (45 males, 27 females) were prospectively observed from the age of 10 to 14 years. Anthropometric parameters, biological maturity status, and core flexion to extension strength ratios were assessed twice per year. Type and severity of traumatic and overuse injuries were prospectively recorded during the 4 years. Generalized estimating equations were used to model the binary outcome (0: no injury; 1: ≥1 injury). Factors tested on association with injury risk were sex, relative age quarter, age, maturity group, puberty status, core flexion to extension strength ratio, height percentile group, and weight percentile group. In total, 104 traumatic injuries and 39 overuse injuries were recorded. Age (odds ratio (OR) = 3.36) and weight percentile group (OR = 0.38) were significant risk factors for traumatic injuries (tendency: pubertal status). No significant risk factor for overuse injuries was identified (tendency: maturity group, puberty status, height percentile group). Future studies should focus on identifying risk factors for overuse injuries; growth rates might be of importance. [ABSTRACT FROM AUTHOR]

(1) To study the reliability of quantifying rear-chain stabilization capacity during deadbug bridging (DBB), (2) to provide reference values for competitive alpine skiers, and (3) to study associations with age, anthropometrics, maturation, skiing performance and back overuse complaints. Cross-sectional. Biomechanical field experiment including questionnaires. 12 healthy subjects (reliability experiment); 133 skiers of the U16 category and 38 of the elite category (main experiment). DBB performance was quantified using 3D motion capture as the maximum amplitude of the relative vertical displacement of two pelvis markers (DBB displacement). Additionally, in U16 skiers, age, anthropometrics, maturation, skiing performance, and back overuse complaints were assessed. The reliability experiment revealed an ICC(3,1) and 95% CI of 0.81 [0.61, 0.93]. Within-subject SEM was 3.89 mm [3.16 mm, 5.12 mm]. Depending on sex and category, medians of DBB displacement in skiers ranged between 29 mm and 45 mm. DBB displacement differed between elite and U16 skiers (p < 0.001), but not between sexes. In U16 skiers, DBB displacement was independent of age, anthropometrics, and biological maturation, however, associated with skiing performance and back overuse complaints (p < 0.05). The proposed approach may be considered an adequate method to quantify athletes' rear-chain stabilization capacity. • Our approach to quantify athletes' rear-chain stabilization capacity during DBB is objective, reliable, and relevant. • It could potentially be used for monitoring athletic long-term development and screening injury-relevant athletic deficits. • However, its predictive validity needs to be further investigated by longitudinal studies. [ABSTRACT FROM AUTHOR]

This study aimed to examine longitudinal age-related changes in muscle morphology and jump and sprint performances of youth athletes. The subjects of this longitudinal study were 41 youth male basketball players who were assigned to late, mid, and early groups based on differences regarding the estimated age at peak height velocity. The vastus medialis, vastus intermedius, rectus femoris, vastus lateralis, biceps brachii, and triceps brachii thicknesses were assessed using ultrasonography. The subjects' anaerobic capacities were evaluated based on Abalakov jumps and 20- m sprint time. After 1 year, the vastus medialis and biceps brachii thicknesses increased significantly in all groups, and the rectus femoris, vastus intermedius, and vastus lateralis thicknesses increased significantly in the late and mid groups, but not in the early group. The Abalakov jumps and 20-m sprint time improved significantly in all groups. The early group's 10-m sprint time improved significantly. Cross-sectional comparisons showed that after 1 year, the early group's Abalakov jumps and 20-m sprint time at baseline, its Abalakov jumps, and 10-m and 20-m sprint times were significantly better than those in the mid and late groups. Hence, significant muscle growth occurred before the athletes reached the age at peak height velocity. During puberty, late maturers' sprint times and jump performances may not catch up with those of early maturers. The speed and tempo of the morphological growth and anaerobic ability of athletes in the same age category depend on athletes' biological maturity. [ABSTRACT FROM AUTHOR]

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Copyright of German Journal of Exercise & Sport Research is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of the present study was to investigate prospectively the role of biological maturity status, anthropometric percentiles, and core flexion to extension strength ratios in the context of traumatic and overuse injury risk identification in youth ski racing. In this study, 72 elite youth ski racers (45 males, 27 females) were prospectively observed from the age of 10 to 14 years. Anthropometric parameters, biological maturity status, and core flexion to extension strength ratios were assessed twice per year. Type and severity of traumatic and overuse injuries were prospectively recorded during the 4 years. Generalized estimating equations were used to model the binary outcome (0: no injury; 1: ≥1 injury). Factors tested on association with injury risk were sex, relative age quarter, age, maturity group, puberty status, core flexion to extension strength ratio, height percentile group, and weight percentile group. In total, 104 traumatic injuries and 39 overuse injuries were recorded. Age (odds ratio (OR) = 3.36) and weight percentile group (OR = 0.38) were significant risk factors for traumatic injuries (tendency: pubertal status). No significant risk factor for overuse injuries was identified (tendency: maturity group, puberty status, height percentile group). Future studies should focus on identifying risk factors for overuse injuries; growth rates might be of importance.

Abstract Aims: To investigate the presence of a relative age effect (RAE) and the influence of birth quarters (BQ), semesters (S) as well as skeletal maturation on anthropometric characteristics and aerobic peak speed (PST-CAR) in youth male soccer players. Methods: One hundred players were recruited to participate in this study. Players were allocated into 4 BQ’s and 2 S. Skeletal maturity status was assessed using the Fels method. Assessments for players included determination of body size and composition and PST-CAR. Results: Overall, more players were born in BQ1 (38 %) and S1 (75%). The likelihood of players born in BQ1 and BQ2 being selected was 3.61 to 4.96 times higher than players in BQ3 and BQ4. Players in BQ4 maturing earlier were biologically older than their peers in BQ1. The players in BQ3 and S2 displayed higher PST-CAR compared with players in BQ2 and S1, respectively. However, players of contrasting skeletal maturity status did not differ in aerobic performance. Conclusion: Our findings indicate that coaches and talent scouts are systematically retaining average and early maturing players born in S1 and excluding late maturing players born in BQ4. However, aerobic performance appeared to be dependent on the relative age, but independent of skeletal maturation during puberty.

Belsky, Steinberg, and Draper's sociobiological theory suggests that early family context influences an individual's developmental trajectory in adolescence. A key hypothesis derived from the developmental model is that females growing up in a home without a father will have an earlier onset of puberty and may reach pubertal maturity sooner than their peers who grow up in homes with a father present. The current study uses a nationally representative sample of American youth (Add Health) to examine the association between having an absent biological father and female biological maturity, controlling for additional theoretically informed covariates. The current study contributes to the literature by utilizing a lifetime measure of absent biological father and a biological maturity scale (measured in adolescence) that taps into multiple aspects of pubertal development. Results from multivariate regression analysis revealed no significant association between absent biological father and female biological development. This finding suggests that, contrary to the sociobiological model, having an absent biological father in childhood is not predictive of advanced pubertal development among female adolescents. [ABSTRACT FROM AUTHOR]

Abstract AIMS The purpose of present study was verify if the RPE-training session differs between females and males during the track and field training and if biological maturity (BM) has interference on this response. METHODS Seventy-five athletes (13-15 years old) have participated of study, with 38 male 37 female. Five training sessions of track and field were prescribe and monitoring by RPE-training session (intensity) and Total Quality Recovery (TQR) (recovery). RESULTS There was no statistical difference between males and females on 75-meters run, long jump and shot put. Otherwise, for training of 250 and 1000-meters females related higher RPE-values than males 3.68 ± 0.79, 3.26 ± 0.56, p < 0.01 and 4.14 ± 0.94, 3.72 ± 0.89, p < 0.05; respectively. Even when controlling the effect of biological maturity the same results were observed to 250-meters F1,73 = 2.060; p = 0.002 and 1000-meters F1,73 = 0.997; p = 0.036. There was no difference for TQR between genders. CONCLUSION The comparison the RPE-training session of females and males indicated there were difference to 250 and 1000-m training sessions, females have more RPE-training sessions than males. Additionally, there were no differences between genders for recovery parameters, even controlling BM.

The purpose of this study was to develop equations to predict body fat percentage in young Chilean soccer players. Ninetyfour footballers 13.0 to 17.9 yrs of age were studied. The anthropometric variables that were recorded included weight, height, sitting height, and five skinfolds (bicipital, tricipital, subscapular, iliac crest, and abdominal). The reference method used was the dual-energy X-ray absorptiometry. Biological maturity was estimated by age peak height velocity (APHV). Three body fat percentage equations were generated for young soccer players: (a) 7.86 + (0.51*TR) + (0.165*SB) + (0.56*I) - (1.33*APHV); (b) 8.834 + (0.47*TR) + (0.017*SB) + (0.29*I) + (0.27*AB)(1.21*APHV); and (c) 8.677 - (0.008*BI) + (0.502*TR) + (0.051*SB) + (0.24*I) + (0.28*AB) - (1.29*APHV). All three equations displayed similar results when compared with the reference method (P>0.001). The correlations varied between (R = 0.85 - 0.86). The results indicate that skinfolds along with APHV can help estimate accurately the percentage of body fat in young Chilean soccer players. The results suggest that these equations may be used to predict the percentage of body fat in other young soccer players with similar characteristics. [ABSTRACT FROM AUTHOR]