Validation of maturity offset in a longitudinal sample of Polish girls

Fat-free mass predictive equation using bioelectrical impedance and maturity offset in adolescent athletes: Development and cross-validation

OBJECTIVES

This is a cross-sectional study, aimed to develop and cross-validate a fat-free mass (FFM) predictive equation using single-frequency bioelectrical impedance (BIA), considering the predicted age at peak height velocity (PHV) as a variable. Additionally, the study aims to test the FFM-BIA obtained using a previous predictive equation that used skeletal maturity as a variable.

METHOD

The participants (n = 169 male adolescent athletes) were randomly divided into two groups: development of a new predictive equation (n = 113), and cross-validation (n = 56). The concordance test between the FFM values obtained by Koury et al. predictive equation and DXA data was determined (n = 169). Bioelectrical data was obtained using a single-frequency analyzer.

RESULTS

Among the models tested, the new predictive equation has resistance index (height2/resistance) and predictive age at PHV as variables and presented R2 = 0.918. The frequency of maturity status using skeletal maturity and PHV diagnosis was inadequate (Kappa = 0.4257; 95%CI = 0.298-0.553). Bland-Altman plots and concordance correlation coefficient showed substantial concordance between the FFM-DXA values (48.8 ± 11.2 kg) and the new predictive equation (CCC = 0.960). The results showed that the new equation performed better than the equation developed by Koury et al. (CCC = 0.901).

CONCLUSIONS

Our results show that it is feasible to predict FFM in male adolescent athletes using predictive age at PHV, with moderate concordance. The calculation of FFM using more economical and less complex variables is viable and should be further explored.

Estimating Maturity Status in Elite Youth Soccer Players: Evaluation of Methods

PURPOSE

The objective of this study is to evaluate the concordance of predicted maturity status classifications (pre-, circa-, or post-peak height velocity (PHV)) relative to observed age at PHV in youth soccer players.

METHODS

Longitudinal height records for 124 male soccer players were extracted from academy records spanning the 2000 to 2022 seasons. Age at PHV for each player was estimated with the Superimposition by Translation and Rotation model. Players were classified as pre-, circa-, or post-PHV using both ±1- and ±0.5-yr criteria to define the circa-PHV interval. Maturity status was estimated with several prediction protocols: maturity offset (Mirwald, Moore-1, Moore-2), maturity ratio (Fransen), and percentage of predicted adult height (PAH%) using the Khamis-Roche and Tanner-Whitehouse 2 equations using several bands: 85% to 96%, 88% to 96%, 88% to 93%, and 90% to 93% for the circa-PHV interval, and visual evaluation of individual growth curves alone or with PAH% based on Khamis-Roche and Tanner-Whitehouse 2. Concordance of maturity status classifications based on complete growth curves and predicted estimates of maturity status was addressed with percentage agreement and Cohen's kappa.

RESULTS

Visual evaluation of the growth curves had the highest concordance (≈80%) with maturity status classifications (pre-, circa-, post-PHV) based on longitudinal data for individual players. Predicted maturity offset with the Mirwald, Moore-1, and Fransen equations misclassified about one-third to one-half of the players, whereas concordance based on PAH% varied with the band used, but not with the method of height prediction.

CONCLUSIONS

Visual assessment of the individual growth curves by an experienced assessor provides an accurate estimate of maturity status relative to PHV. Maturity offset prediction equations misclassify the majority of players, whereas PAH% provides a reasonably valid alternative.

Age at peak height velocity in Polish adolescents: Effect of socioeconomic factors

Age at peak height velocity (APHV) is an indicator of maturity timing which is applicable to both sexes, and which is influenced by environmental factors. The objective of this study was to assess variation in APHV associated with several indicators of socioeconomic status (SES) in a longitudinal sample of Polish adolescents. The sample included 739 boys born in 1983 and followed annually from 12 to 16 years, and 597 girls born in 1985 and followed annually from 9 to 13 years. The height records were fitted with the SITAR model to estimate APHV. SES was estimated using principal component analysis of indicators of familial status based on parental education, family size, living conditions and household possessions. Statistical analyses included analysis of variance (one-way for general SES and three-way for parental education and family size) and Tukey post-hoc tests for unequal samples. General SES (p <.001) and family size (p < .05) significantly influenced APHV among boys, while only maternal education (p < .05) significantly influenced APHV among girls. Among youth from families of higher SES, as defined by the respective indicators, APHV was attained significantly earlier, on average, than in peers from families of lower SES. Overall, the results showed a sex-dependent effect of SES on APHV, and highlighted the influence of favorable socioeconomic conditions for optimal growth and maturation during adolescence.

Influence of Maturation and Determinants of Repeated-Sprint Ability in Youth Basketball Players

ABSTRACT

Gonzalo-Skok, O, and Bishop, C. Influence of maturation and determinants of repeated-sprint ability in youth basketball players. J Strength Cond Res 38(2): 325-333, 2024-The main aims of the current study were (a) to determine the main predictors of general and specific repeated-sprint ability (RSA) tests, (b) to analyze the relationships between RSA tests and independent measures of physical performance, (c) to examine whether between-age differences exist, and (d) to assess whether maturation affects those mentioned above in young basketball players. Thirty-five young (U-14 to U-16), highly trained basketball players performed a linear sprint test (5, 10, and 25 m), an incremental running test, and 2 repeated-sprint tests (general [RSG]: 6 × 25 m; specific [RSS]: 6 × 5 + 5 m with a 45° change of direction and 20 seconds of passive recovery in both tests). Anthropometric variables were measured and used to calculate age at peak height velocity (APHV), which was used to determine maturation. The main determinants of RSA tests were aerobic performance and linear sprinting for RSS ( R2 = 0.84) and adding the percentage of body fat for RSG ( R2 = 0.94). Almost perfect relationships ( r = 0.93-0.99) were found between all RSA variables (i.e., the best [RSG b and RSS b ] and mean time [RSG m and RSS m ]). As age increased, performance in RSA was evident, as shown by improved best and mean scores. When APHV was controlled for, no significant differences were apparent in the comparison from U-14 and U-16 in 25 m, RSG b , and RSG m . By contrast, significant differences ( p < 0.05) were still evident with APHV controlled between U-14 and U-16 in 5 m, 10 m, RSS b , and RSS m . In conclusion, maturation positively affects linear sprinting and linear RSA performance, whereas specific (multidirectional) RSA seems to be related to other factors.

What Factors Discriminate Young Soccer Players Perceived as Promising and Less Promising by Their Coaches?

Purpose: This study aimed to verify whether there are differences in physical, technical, and tactical assessment outcomes derived from field-based tests and small-sided games (SSG) in addition to anthropometric and maturational characteristics between players classified as promising and less promising as per the coaches' perception. Method: A total of 53 male U-15 youth soccer players (age: 14.8 ± 0.2 years, weight: 61.7 ± 6.9 kg, height: 171.8 ± 6.7 cm) and three experienced coaches from three distinct sports clubs were enrolled in this study. Based on the coaches' perception, players were split into three group levels for both short- and long-term success ranking: (i) promising (PL; top 5 players; n = 15), (ii) intermediate (IL; n = 23) and (iii) less promising (LPL; 5 bottom players; n = 15). The following measures were determined: anthropometry, maturity offset, vertical jump, and aerobic-anaerobic running performance, soccer- specific skills tests, GPS-based running metrics, technical and tactical actions during SSG, and minutes played throughout the season. Results: There were no differences between groups for anthropometrical, maturational, and physical outcomes. PL players in both rankings covered more distances at sprinting and presented more offensive technical and tactical actions during SSG than their LPL peers. PL and IL presented more minutes played in competitive seasons than LPL of short-term ranking. Conclusion: The biggest differences between the players ranked by their coaches were apparent only during a representative game task, emphasizing the importance of SSG as a tool to assess the players' technical-tactical awareness. In addition to the SSG, the coach's eye plays a key role during the talent identification and selection process.

Survey of the current practices of German football academies towards biological maturation assessment

OBJECTIVES

This study aimed to examine the importance assigned to assessing and considering biological maturation in thematic areas of player development and provide an overview of current practices in German football academies regarding its consideration in training and competition.

METHODS

An online survey was sent to 56 elite German football academies. A total of 46 responded to the questionnaire (82% response rate). Six participants provided incomplete information resulting in a total of 40 completed surveys in the period from March to May 2022.

RESULTS

Only 20 of participants regularly carried out maturation assessments, despite 95% recognizing its importance for load management, 90% for player development, and 85% for injury prevention. There was no consistent approach to modifying training and competition formats based on maturity status, with a primary focus on gym-based sessions for load management.

CONCLUSION

The survey results highlight limited implementation of maturation assessment and training modification based on maturity status in German elite youth football academies. Despite recognizing the importance of load monitoring, reporting to parents, and long-term player development in considering biological maturation, practices are not widespread. The predominant use of the maturity offset method suggests an opportunity to improve accuracy by exploring alternative measurement methods and increasing assessment frequency. Moreover, a lack of established procedures for incorporating maturity status into training and competition exists, hindering comprehensive consideration of biological maturation and injury risk prevention. Further research is needed to understand the reasons for inconsistent approaches in maturation assessment and load modification during training and competition.

Change of direction speed and deficit over single and multiple changes of direction: Influence of biological age in youth basketball players

The study analysed the difference in change of direction (COD) deficit among young male basketball players of different age groups and biological ages and analysed the relationships in COD performance (time and deficit) across single and multiple CODs depending on their biological age. Fifty-four highly-trained male players (U-13 and U-17) were tested on sprinting (25-m) and COD ability over single and multiple CODs through total times and the percentage-based COD deficit (CODD). Results showed that older age groups performed significantly (ES = 0.43-2.32, p < 0.05) better in linear and COD times, especially those players with post-peak height velocity (PHV) (ES = 0.89-1.90). Controlling for age at PHV, no significant differences were found in any group or inter-limb asymmetries. Moderate relationships were found between CODD in the pool data (r = 0.36 to 0.50). All CODD and time relationships in any test (i.e., 180º COD and V-cut) were considerably lower (r= -0.27 to 0.32) across individual biological groups. The study highlights the impact of maturation on COD performance, whereas CODD seems to be not affected. Interestingly, the CODD is independent, highlighting this measurement's specific nature. Practitioners should use common distances, angles, and the number of CODs linked to biological status to create a COD profile.

Motor Competence Among Irish Adolescents: An Investigation of Sex Differences and Relatedness Between Fundamental Movement Skills and Functional Movement

In prior research, Irish youth displayed poor motor competence across fundamental movement skills (FMS) and functional movements (FM). Our purpose in this study was to compare FMS and FM across male and female Irish adolescents and to determine whether there are associations between these movement domains. We collected data on 373 adolescents (178 females; M age = 14.38, SD = 0.87 years) from six Irish secondary schools, including motor competence testing of 10 FMS, and 7 FM. Overall levels of motor competence of both FMS and FM were low, and certain levels of dysfunctional movement were high. We observed significant sex-based differences in both FMS and FM, and there was a moderate association between FMS and FM that warrants further investigation. There is a need for societal intervention and policy changes to address low levels of motor competence among adolescent youth.

Maturation-based Corrective Adjustment Procedures (Mat-CAPs) in youth swimming: Evidence for restricted age-group application in females

Inter-individual differences in maturation-associated development can lead to variations in physical performance, resulting in performance (dis)advantages and maturation selection bias within youth sport systems. To address such bias and account for maturational differences, Maturation-based Corrective Adjustment Procedures (Mat-CAPs) could be beneficial. The present study aimed to: (1) determine maturity timing distributions in youth female swimming; (2) quantify the relationship between maturation status and 100-m front-crawl (FC) performance; (3) implement Mat-CAPs to remove maturational influences upon swimming performance. For Aim 1 and 2, participants were 663 female (10–15 years) swimmers who participated in 100-m FC events at Australian regional, state, and national-level competitions between 2016–2020 and underwent anthropometric assessment (mass, height and sitting height) to estimate maturity timing and offset. For Aim 3, participants aged 10–13 years were categorised into maturity timing categories. Maturity timing distributions for Raw (‘All’, ‘Top 50%’ and ‘Top 25%’) and Correctively Adjusted swim times were examined. Chi-square, Cramer’s V and Odds Ratios determined the presence of maturation biases, while Mat-CAPs identified whether such biases were removed in targeted age and selection-groups. Results identified that between 10–13 years, a significantly higher frequency of ‘early’ maturers was apparent, although tapered toward higher frequencies of ‘Late-normative’ maturers by 14–15 years. A curvilinear relationship between maturity-offset and swim performance was identified (R²= 0.51, p<0.001) and utilised for Mat-CAPs. Following Mat-CAPs application, maturity timing biases evident in affected age-groups (10–13 years), and which were magnified at higher selection levels (‘Top 50%’ & ‘25%’ of swim performances) were predominantly removed. Findings highlight how maturation advantages in females occurred until approximately 13 years old, warranting restricted Mat-CAPs application. Mat-CAPS has the potential to improve female swimmer participation experiences and evaluation.

A Mixed-Longitudinal Study of Height Velocity of Greek Schoolchildren and the Milestones of the Adolescent Growth Spurt

Height velocity (HV) growth charts constructed from longitudinal studies are scarce as they have inherent difficulties, e.g., time, and costs. These difficulties can be partly overcome by a mixed-longitudinal study that covers the entire age range within 3–6 years. To construct HV charts of Greek children and to estimate the milestones of the adolescent growth spurt (AGS), i.e., the onset of AGS (take-off), peak HV, and total pubertal growth (TPG), we performed a mixed longitudinal study in 1514 Greek schoolchildren (6–18 years) with height measurements every 6 months during three schoolyears. We constructed HV charts for boys and girls. Take-off occurs earlier in girls, and, in both sexes, it precedes by 1–1.5 years the appearance of physical signs of puberty. PHV in boys occurs at 12.61 years and in girls at 10.93 years. At take-off, boys are 5 cm taller than girls and TPG for boys is 35.8 cm and for girls 27.3 cm. We constructed HV charts plotted by age, irrespective of pubertal status, and presented data on the milestones of AGS. Furthermore, we suggest that the gradual increase in IGF-1 and E2 that occurs after 5 to 6 years of age triggers the onset of AGS, which precedes physical signs of puberty.

Musculoskeletal pain and its association with health status, maturity, and sports performance in adolescent sport school students: a 2-year follow-up

Background

Musculoskeletal pain and its risk factors are rarely assessed in studies on adolescent athletes. The aim was to identify risk factors at baseline that were associated with the persistence or development of musculoskeletal pain at a two-year follow-up in adolescent sport school students, and to study cross-sectional associations at follow-up between musculoskeletal pain and sports performance.

Methods

Sport school students (79 boys and 52 girls, aged 14 years at baseline) were divided into infrequent (never–monthly) or frequent (weekly–almost daily) pain groups, based on frequency of pain using a pain mannequin. Logistic regression analyses were performed to study longitudinal associations between frequent pain at follow-up and baseline variables: pain group, number of regions with frequent pain, health status by EQ-5D, maturity offset (pre, average, or post peak height velocity), and sports (contact or non-contact). Linear regression analyses were used to study cross-sectional associations between pain groups and 20-m sprint, agility T-test, counter-movement jump, and grip strength at follow-up. Results were stratified by sex.

Results

A higher percentage of girls than boys reported frequent pain at follow-up (62% vs. 37%; p = 0.005). In boys, frequent pain at follow-up was associated with being pre peak height velocity at baseline (OR 3.884, CI 1.146–13.171; p = 0.029) and participating in non-contact sports (OR 3.429, CI 1.001–11.748; p = 0.050). In girls, frequent pain at follow-up was associated with having frequent pain in two or more body regions at baseline (OR 3.600, CI 1.033–12.542; p = 0.044), having a worse health status at baseline (OR 3.571, CI 1.026–12.434; p = 0.045), and participating in non-contact sports (OR 8.282, CI 2.011–34.116; p = 0.003). In boys, frequent pain was associated with worse performances in 20-m sprint and counter-movement jump, but not in agility T-test and grip strength.

Conclusions

Baseline risk factors for having frequent pain at follow-up were late maturation in boys, frequent pain and worse health status in girls, and participation in non-contact sports in both sexes. Boys with pain performed worse in sports tests. Coaches and school health-care services should pay attention to the risk factors and work towards preventing pain from becoming persistent.

The association between academic achievement in physical education and timing of biological maturity in adolescents

Individual differences in tempo and timing of biological maturity, especially in adolescents, has been argued as a potential underlying cause of relative age effects observed in Physical education (PE). Indeed, differences in maturation could influence pupils`achievement in PE where motor behavior and physical activity are central tenets. However, the timing of biological maturity has not previously been investigated in the context of academic achievement in PE. Therefore, the current study`s aim was to investigate the association between timing of biological maturity and relative age on adolescents`academic achievement in PE. The data material consists of two samples from lower secondary schools (13–16 years old). Sample 1 (45 boys and 31 girls) was used to compare differences in anthropometrics and indicators of biological maturity between pupils with different grades (i.e., 3/4, 5, 6), while in sample 2 (114 boys and 127 girls) differences in mean grade were compared between birth quartiles. Pupils`final grade in PE were collected for both samples as a proxy for academic achievement. A one-way analysis of variance indicated a moderate-to-large association between timing of biological maturity, through age at peak height velocity, and academic achievement in PE, where later maturing pupils received a higher grade compared to earlier maturing pupils. Results from a factorial analysis of variance indicated an interaction effect between gender and birth quartile on academic achievement in PE. Post hoc analysis revealed that relatively younger boys received significantly lower grades as opposed to their relatively older peers. This effect was not present for girls. Collectively, these results indicate that developmental differences are associated with academic achievement in PE. Hence, PE teachers should be aware of these individual constraints in their teaching and assessment practice to accommodate fair and equal opportunities for achievement in the subject.

Deadbug Bridging Performance in 6- to 15-Year-Old Competitive Alpine Skiers—A Cross-Sectional Study

Simple Summary

In competitive alpine skiing, a stable trunk plays an important role in increasing performance and preventing injuries. The aim of the present study was to investigate the ability to stabilize the trunk during so-called deadbug bridging (DBB) exercises, a stabilizing, dynamic movement task in the supine position with the pelvis lifted and unilateral leg raising, in 6- to 15-year-old skiers. Trunk stabilization performance was better in female skiers of the under 15-year (U15) category than in their male counterparts, whereas there was no sex difference at ages under 10 years (U10). The only potential confounder when testing youth skiers revealed being body height, but only in female U10 skiers. In summary, this study provided sport-specific normative reference data that may be of equal interest to both researchers and sport practitioners.

Abstract

In competitive alpine skiing, a superior antirotation and rear-chain stabilization capacity is essential to constantly remain in dynamic equilibrium while skiing and to counteract the ski-specific adverse loading patterns of the back. As such, skiers’ trunk stabilization performance during deadbug bridging (DBB) exercises has been shown to be associated with both skiing performance and overuse complaints of the lower back in skiers under 16 years of age (U16). However, to date, little is known about the corresponding stabilization abilities in younger skiers, i.e., 6- to 15-year-old skiers. As part of a biomechanical field experiment during a national off-snow fitness competition, a total of 101 youth competitive alpine skiers were tested with respect to their trunk stabilization performance during DDB exercise. The maximum contralateral displacement of the pelvic drop during leg lift (DBB_displacement) was quantified using reflective markers and a motion capture system (Vicon, Oxford, UK). Potential age group and sex differences in DBB_displacement were assessed using analysis of variance (ANOVA) at p < 0.05. Within each subgroup, the associations of DBB_displacement with age, anthropometrics and maturity offset were analysed using Pearson’s correlation (p < 0.05). Female skiers under 15 years of age (U15) showed better DBB performance than male U15 skiers, while there was no sex difference at the under 10-year (U10) level. In female U10 skiers, DBB_displacement was moderately associated with body height, while in all other subgroups, no confounding associations with anthropometrics or biological maturation were found. Biomechanically quantifying DBB performance may be considered a feasible and nonconfounded screening test approach in young skiers older than 6 years. Body height may represent a confounding bias in exclusively the U10 female skier cohort and, therefore, should be considered when interpreting the test results. In summary, this study provided sport-specific normative reference data that may be of equal interest to both researchers and sport practitioners.

Equations predicting maturity status: Validation in a cross-sectional sample to assess physical growth and body adiposity in Chilean children and adolescents

OBJECTIVE

To validate regression equations that predict the state of maturity (MS) to evaluate the physical growth and body fatness of Chilean children and adolescents.

MATERIAL AND METHODS

A transversal study was carried out in 8094 school children between 6.0 and 18.9 years old. Weight, standing height, sitting height, and waist circumference (WC) were evaluated. Peak growth rate (PVC) was estimated by the mathematical model 1 of Preece-Baines (MPB). Mirwald's equations (based on age, weight, standing height, sitting height, and leg length) and Moore's equations (based on age, weight, and standing height) were used to estimate MS. The body mass index (BMI) was calculated.

RESULTS

The BMP showed that the PVC in men was 10.33 ± 0.29 years and in women was 12.81 ± 0.27 years. Using Mirwald's equation, men reached MS at 14.09 ± 0.8 APVC and women at 11.6 ± 0.9 APVC, while using Moore's equation, men reached 13.7 ± 0.6 APVC and women at 12.1 ± 0.6 APVC. There were significant differences between MPB with Mirwald, MPB with Morre, and between Mirwald and Moore (p < 0.001). Explanation values by MS category were Mirwald's equation [men (early R² = 0.81, mean R² = 0.69 and late R² = 0.09) and women (early R² = 0.83, mean R² = 0.83 and late R² = 0.77)], Moore's equation [men (early R² = 0.93, mean R² = 0.70 and late R² = 0.79) and women (early R² = 0.89, mean R² = 0.89 and late R² = 0.83)]. Percentiles were created for weight, height, CC and BMI.

CONCLUSION

It was verified that Moore's and Mirwald's equations differ with the mathematical model MPB in both sexes. However, Moore's equation could be useful for the evaluation of MS in Chilean children and adolescents.

A Cross-Sectional Observation on Maximal Eccentric Hamstring Strength in 7- to 15-Year-Old Competitive Alpine Skiers

Simple Summary

Competitive alpine skiing is a sport with frequent occurrence of severe knee injuries, and it is well known that the hamstring muscles play an important role in preventing these injuries. The aim of this study was to assess the maximal strength capacity for braking, the downward movement during Nordic Hamstring Exercises, the so called maximal eccentric hamstring strength, in 7- to 15-year-old skiers. Absolute strength values were greater in skiers under 15 years old (U15) skiers than in those under 10 years old (U10), as well as in U15 males compared to their female counterparts. There were no sex differences in U10 skiers. Absolute strength values were generally dependent on age and biological developmental stage, but this dependence was considerably attenuated when body weight was considered. This should be kept in mind when testing athletes around the growth spurt.

Abstract

Severe knee injuries are common in alpine skiing and the hamstring muscles are known to counteract the anterior tibial displacement that typically accompanies major injury mechanisms. This study aimed to assess the Maximal Eccentric Hamstring Strength (MEHS) of youth competitive alpine skiers during Nordic Hamstring Exercise (NHE) in terms of dependence of sex, age and biological maturation. A total of 246 7- to 15-year-old skiers were tested with respect to their MEHS using an NHE-based measurement device (Vald Performance, Newstead, Australia). Significantly greater absolute MEHS was observed in skiers of the under 15 years (U15) category compared to skiers under 10 years old (U10) (227.9 ± 61.1 N vs. 142.6 ± 28.9 N; p < 0.001), also when grouped by sex. Absolute MEHS was revealed to be lower in U15 females compared to males (213.5 ± 49.0 N vs. 241.9 ± 68.4 N; p = 0.001); in U10 skiers there was no sex difference. For all age groups and sexes, absolute MEHS values were significantly correlated with age and biological maturation (p < 0.001). However, when normalized to body weight such associations disappeared, which is why this is strongly recommended when testing around their growth spurt. Overall, this study established sport-specific normative reference data that may be of interest to researchers and sport practitioners alike.

The Assessment of Functional Movement in Children and Adolescents: A Systematic Review and Meta-Analysis

Background

The Functional Movement Screen™ (FMS™) is an assessment of human movement that may signal potential deficits that could predispose an otherwise healthy person to injury risk. FMS™ scores are well reported in both athletic and adult samples. However, to date, there has been no comprehensive systematic review and meta-analysis of FMS™ data among school-aged children and adolescents.

Objective

We aimed to systematically review and analyse functional movement proficiency of children and adolescents, specifically when assessed using the FMS™, and to establish initial normative values for the FMS™ in this population group and to further estimate differences in functional movement proficiency between the sexes, by school level (i.e., between primary and secondary school-level children and adolescents), and based on differences in child and adolescent body mass index (BMI).

Methods

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, prospective studies were identified from searches across eight databases (MEDLINE, SPORTDiscus, CINAHL, Web of Science, EMBASE, ERIC, PsychINFO and PubMed), without any date restrictions, up to December 2020. The primary meta-analysis estimated the overall FMS™ score for school-aged children and adolescents across published studies. An additional three subgroup meta-analyses estimated comparisons for FMS™ data with school level, sex, and BMI across published studies. FMS™ data were meta-analysed using a number of different meta packages (Schwarzer et al. in Meta-Analysis with R, 1st ed, Springer International Publishing, Berlin, 2015), available in R Studio.

Results

A total of 19 articles were included in the systematic review. Meta-analysis revealed a weighted FMS™ mean score of 14.06, with a standardised Tau value of 0.56, signalling a moderate-to-large degree of variability in FMS™ means between studies. The difference in FMS™ means between samples of males (weighted FMS™ mean 13.91) and females (weighted FMS™ mean 14.56) was compatible with a possible small effect size (standardised mean difference − 0.27). The variability in FMS™ means between studies was approximately five times greater in samples of secondary school children (factor difference in Tau values 5.16). The final meta-regression identified a negative association between BMI and FMS™ scores (r =  − 0.42), which signalled a moderate-to-large difference in FMS™ scores between healthy weight and overweight children/adolescents.

Conclusion

This systematic review and meta-analysis represents a novel and important synthesis of published FMS™ data from groups of children and adolescents. The study signals possible sex- and age-related differences in FMS™ scores, as well as a clear negative relationship between BMI and functional movement proficiency. More longitudinal research is needed to better understand the developmental trajectory and the effects of maturation milestones on FMS™ proficiency. Additional research is also needed to identify the types of interventions that could improve functional movement proficiency among ‘at risk’ groups, who are susceptible to functional movement deficiency, and whether changes in body composition mediate the relationship between these interventions and the improvement of FMS™ scores.

Observed and predicted ages at peak height velocity in soccer players

The purpose of the study was to evaluate predicted maturity offset (time before age at PHV) and age at PHV (chronological age [CA] minus maturity offset) in a longitudinal sample of 58 under-13 club level soccer players in central Portugal for whom ages at PHV were estimated with the SITAR model. Two maturity offset prediction equations were applied: the original equation which requires CA sitting height, estimated leg length, height and weight, and a modified equation which requires CA and height. Predicted maturity offset increased, on average, with CA at prediction throughout the age range considered, while variation in predicted maturity offset and ages at PHV within CA groups was considerably reduced compared to variation in observed ages at offset and at PHV. Predicted maturity offset and ages at PHV were consistently later than observed maturity offset and age at PHV among early maturing players, and earlier than observed in late maturing players. Both predicted offset and ages at PHV with the two equations were, on average, later than observed among players maturing on time. Intra-individual variation in predicted ages at PHV with each equation was considerable. The results for soccer players were consistent with similar studies in the general population and two recent longitudinal studies of soccer players. The results question the utility of predicted maturity offset and age at PHV as valid indicators of maturity timing and status.

Maturity-associated considerations for training load, injury risk, and physical performance in youth soccer: One size does not fit all

Biological maturation can be defined as the timing and tempo of progress to achieving a mature state. The estimation of age of peak height velocity (PHV) or percentage of final estimated adult stature attainment (%EASA) is typically used to inform the training process in young athletes. In youth soccer, maturity-related changes in anthropometric and physical fitness characteristics are diverse among individuals, particularly around PHV. During this time, players are also at an increased risk of sustaining an overuse or growth-related injury. As a result, the implementation of training interventions can be challenging. The purpose of this review was to (1) highlight and discuss many of the methods that can be used to estimate maturation in the applied setting and (2) discuss the implications of manipulating training load around PHV on physical development and injury risk. We have provided key stakeholders with a practical online tool for estimating player maturation status (Supplementary Maturity Estimation Tools). Whilst estimating maturity using predictive equations is useful in guiding the training process, practitioners should be aware of its limitations. To increase the accuracy and usefulness of data, it is also vital that sports scientists implement reliable testing protocols at predetermined time-points.

Chronological Age, Somatic Maturation and Anthropometric Measures: Association with Physical Performance of Young Male Judo Athletes

Sport for children and adolescents must consider growth and maturation to ensure suitable training and competition, and anthropometric variables could be used as bio-banding strategies in youth sport. This investigation aimed to analyze the association between chronological age, biologic maturation, and anthropometric characteristics to explain physical performance of young judo athletes. Sixty-seven judokas (11.0–14.7 years) were assessed for anthropometric and physical performance. Predicted adult stature was used as a somatic maturation indicator. A Pearson’s bivariate correlation was performed to define which anthropometric variables were associated with each physical test. A multiple linear hierarchical regression was conducted to verify the effects of age, maturity, and anthropometry on physical performance. The regression models were built with age, predicted adult stature, and the three most significantly correlated anthropometric variables for each physical test. Older judokas performed better in most of the physical tests. However, maturation attenuated the age effect in most variables and significantly affected upper body and handgrip strength. Anthropometric variables attenuated age and maturity and those associated with body composition significantly affected the performance in most tests, suggesting a potential as bio-banding strategies. Future studies should investigate the role of anthropometric variables on the maturity effect in young judokas.

Equations predicting maturity status: Validation in a cross-sectional sample to assess physical growth and body adiposity in Chilean children and adolescents

OBJECTIVE

To validate regression equations that predict the state of maturity (MS) to evaluate the physical growth and body fatness of Chilean children and adolescents.

MATERIAL AND METHODS

A transversal study was carried out in 8,094 school children between 6.0 and 18.9 years old. Weight, standing height, sitting height, and waist circumference (WC) were evaluated. Peak growth rate (PVC) was estimated by the mathematical model 1 of Preece-Baines (MPB). Mirwald's equations (based on age, weight, standing height, sitting height, and leg length) and Moore's equations (based on age, weight, and standing height) were used to estimate MS. The body mass index (BMI) was calculated.

RESULTS

The BMP showed that the PVC in men was 10.33±0.29 years and in women was 12.81±0.27 years. Using Mirwald's equation, men reached MS at 14.09±0.8APVC and women at 11.6±0.9APVC, while using Moore's equation, men reached 13.7±0.6APVC and women at 12.1±0.6APVC. There were significant differences between MPB with Mirwald, MPB with Morre, and between Mirwald and Moore (p<0.001). Explanation values by MS category were Mirwald's equation [men (early R2=0.81, mean R2=0.69 and late R2=0.09) and women (early R2=0.83, mean R2=0.83 and late R2=0.77)], Moore's equation [men (early R2=0.93, mean R2=0.70 and late R2=0.79) and women (early R2=0.89, mean R2=0.89 and late R2=0.83)]. Percentiles were created for weight, height, CC and BMI.

CONCLUSION

It was verified that Moore's and Mirwald's equations differ with the mathematical model MPB in both sexes. However, Moore's equation could be useful for the evaluation of MS in Chilean children and adolescents.

Morphological and Fitness Attributes of Young Male Portuguese Basketball Players: Normative Values According to Chronological Age and Years From Peak Height Velocity

The aims of the present study were: (i) to describe the structural and functional attributes of young male Portuguese basketball players aged 12-16 years and (ii) to generate normative data according to chronological age and years from peak height velocity. A total of 281 male Portuguese young basketball players between the ages of 12 and 16 years were assessed in this study. Chronological age, maturity parameters (maturity offset and predicted age at peak height velocity), morphological (body mass, height, and skinfolds and length), and fitness (sprint, change of direction ability, jump, and upper body strength) attributes were measured. Descriptive statistics were determined for the age and maturity status, and the 10th, 25th, 50th, 75th, and 90th percentiles were chosen as reference values. Descriptive and normative values of the players' morphological and fitness attributes, stratified by age and maturity status, are provided. The normative values of age at peak height velocity (category YAPHV = 0) showed that regional basketball players presented average values (50th percentile) of 169.8 cm for height, 173.3 cm for arm span, 55.6 kg for body mass, 3.34 s for the 20-m speed test, 10.31 s for the T-test, 4.75 m for the 2-kg medicine ball throw, 66.9 kg for the combined right and left handgrip strength, and 30.1 and 35.9 cm for jump height in the countermovement jump (CMJ) and CMJ with arm swing, respectively. In conclusion, these results may be helpful to quantify and control an athlete's performance over time and to adjust strength and conditioning programs to biological demands.

Specific physical performances among male elite youth soccer players: effect of maturity status

BACKGROUND

There is a lack of studies that investigated the relationship between anthropometric profile, biological maturity and specific soccer performances. Therefore, the aims of the present study were to establish normative data of anthropometric and specific physical performances and to determine the impact age and somatic maturation on young soccer players (U13-U19, n=487).

METHODS

Measurements include anthropometric variables to determine the age of peak height velocity (PHV), leg muscle volume (LMV) and soccer specific test (SST); Squat jump (SJ), Counter Movement jump (CMJ), sprint 10 meter (T<inf>10m</inf>), sprint 20 meter (T<inf>20m</inf>), sprint 30 meter (T<inf>30m</inf>) and intermittent-endurance tests.

RESULTS

Reference values showed a significant difference between anthropometric variables, LMV and SST according to PHV categories. (M)ANOVA analysis showed a significant age using maturity interaction effect of all anthropometric variables. A significant result was reported in the majority of SST performances for the age, the T<inf>10m</inf> and for T<inf>20m</inf> performances. The full model of multiple regressions and the multiple equations was used to determine the best predictors of physical performances according to anthropometric variables.

CONCLUSIONS

This study provides normative data for anthropometric characteristics and physical performances according to chronological age (U13-U19) and maturity groups of young soccer players.

A Multi-Block Multivariate Analysis to Explore the Influence of the Somatic Maturation in Youth Basketball

The aim of this study was to examine the influence of somatic maturation in anthropometric, physical, and game-related variables in youth basketball age groups under-13 (U-13) and under-15 (U-15). One-hundred and eighty-five basketball players performed anthropometrical and physical tests during a non-official youth basketball tournament. Predicted maturity offset (MO) and game-related variables were also analyzed. Cluster analysis was used to analyze the between-maturation status differences in all parameters in each age group. Also, regularized generalized canonical correlation analysis (RGCCA) was used to assess relative contributions of maturational, physical, and game-related variables within each age group. Based on MO, two different clusters were identified within each age category. Greater differences in MO were identified among U-13 clusters than among U-15 clusters. No significant differences were observed between clusters in terms of physical and game-related variables. High correlations between maturational, physical, and game-related variables (i.e., points scored, field goals attempted, and rebounds) were found for boys. In girls, different trends in terms of correlations were observed. The strongest association between blocks was observed between physical tests and game-related variables in all age categories, except for U-15 girls. Knowing and identifying performance profiles according to biological age is of upmost importance since it allows the coach to create challenging situations adjusted to the individual's needs.

Physical Characteristics of Elite Youth Female Soccer Players Characterized by Maturity Status

Emmonds, S, Scantlebury, S, Murray, E, Turner, L, Robsinon, C, and Jones, B. Physical characteristics of elite youth female soccer players characterized by maturity status. J Strength Cond Res 34(8): 2321-2328, 2020-The purpose of this study was to investigate the influence of maturity status on the physical characteristics of youth female soccer players. One hundred fifty-seven players from 3 elite soccer academies in England completed assessments of anthropometry, strength (isometric midthigh pull), lower-body power (countermovement jump [CMJ]), aerobic capacity (Yo-Yo intermittent recovery test level 1), change of direction (CoD: 505-left/right), and speed (10 and 30 m). Each player was classified into 1 of 6 maturity groups based on their estimated years from peak height velocity (YPHV). Magnitude-based inferences were used to assess for the practical significance between consecutive groups. Speed, CoD time, CMJ, and aerobic capacity were all possibly most likely better in more mature players. However, there was a likely difference in relative peak force between maturity groups -0.5 YPHV (27.13 ± 4.24 N·Kg) and 0.5 YPHV (24.62 ± 3.70 N·Kg), which was associated with a likely difference in 10-m sprint time (-0.5 YPHV: 2.00 ± 0.12 vs. 0.5 YPHV 2.08 ± 0.16 seconds) and unclear changes in CMJ and CoD time. Findings provide novel comparative data for this cohort relative to maturity status and can be used by strength and conditioning coaches to inform the design of training programs for youth female soccer players. Strength and conditioning coaches should be aware that youth female soccer players may experience a decrease in relative strength around peak height velocity, which may impact upon the speed, CoD time, and CMJ of players.

Genome-Wide Association Analysis of Longitudinal Bone Mineral Content Data From the Iowa Bone Development Study

The foundation for osteoporosis risk is, in part, established during childhood, adolescence, and young adulthood, all periods of development when bone mass is acquired rapidly. The relative quantity of bone mass accrued is influenced by both lifestyle and genetic factors, although the genetic component is not yet well understood. The purpose of this study was to use a genome-wide association (GWA) analysis to discover single nucleotide polymorphisms (SNPs) associated with: (1) the sex-specific hip bone mineral content at approximately the age of 19 when the amount of bone accrued is near its peak; and (2) the sex-specific rate of hip bone mineral content accrual during the adolescent growth spurt. The Iowa Bone Development Study, a longitudinal cohort study exploring bone health in children, adolescents, and young adults was the source of data. From this cohort, n = 364 (190 females, 174 males) participants were included in GWA analyses to address (1) and n = 258 participants (125 females and 133 males) were included in GWA analyses to address (2). Twenty SNPS were detected having p < 1.0 × 10-5. Of most biologic relevance were 2 suggestive SNPs (rs2051756 and rs2866908) detected in an intron of the DKK2 gene through the GWA analysis that explored peak bone mass in females.

Accuracy of maturity prediction equations in individual elite male football players

BACKGROUND

Equations predicting age at peak height velocity (APHV) are often used to assess somatic maturity and to adjust training load accordingly. However, information on the intra-individual accuracy of APHV in youth athletes is not available.

AIM

The purpose of this study is to assess the accuracy of predication equations for the estimation of APHV in individual youth male football players.

SUBJECTS AND METHODS

Body dimensions were measured at least every three months in 17 elite youth male football players (11.9 ± 0.8 years at baseline) from the 2008-2009 through the 2011-2012 seasons. APHV was predicted at each observation with four suggested equations. Predicted APHV was compared to the player's observed APHV using one-sample-t-tests and equivalence-tests. Longitudinal stability was assessed by comparing the linear coefficient of the deviation to zero.

RESULTS

Predicted APHV was equivalent to the observed APHV in none of the players. A difference with a large effect size (Cohen's d > 0.8) was noted in 87% of the predictions. Moreover, predictions were not stable over time in 71% of the cases.

CONCLUSIONS

None of the evaluated prediction equations is accurate for estimating APHV in individual players nor are predictions stable over time, which limits their utility for adjusting training programmes.

Biological Maturity Status in Elite Youth Soccer Players: A Comparison of Pragmatic Diagnostics With Magnetic Resonance Imaging

The influence of biological maturity status (BMS) on talent identification and development within elite youth soccer is critically debated. During adolescence, maturity-related performance differences within the same age group may cause greater chances of being selected for early maturing players. Therefore, coaches need to consider players' BMS. While standard methods for assessing BMS in adolescents are expensive and time-consuming imaging techniques (i.e., X-ray and MRI), there also exist more pragmatic procedures. This study aimed to evaluate commonly used methods to assess BMS within a highly selected sample of youth soccer players. A total of N = 63 elite male soccer players (U12 and U14) within the German Soccer Association's talent promotion program completed a test battery assessing BMS outcomes. Utilizing MRI diagnostics, players' skeletal age (SA_MRI) was determined by radiologists and served as the reference method. Further commonly used methods included skeletal age measured by an ultrasound device (SA_US), the maturity offset (MO_MIR), and the percentage of adult height (PAH_KR). The relation of these alternative BMS outcomes to SA_MRI was examined using different perspectives: performing bivariate correlation analyses (1), modeling BMS as a latent variable (BMS_lat) based on the multiple alternative diagnostics (2), and investigating individual differences in agreement (3). (1) Correlations of SA_MRI and the further BMS variables ranked from r = 0.80 to r = 0.84 for the total sample and were lower for U12 (0.56 ≤ r ≤ 0.66), and U14 (0.61 ≤ r ≤ 0.74) (2). The latent structural equation modeling (SEM) (R² = 51%) revealed a significant influence on BMS_lat for MO_MIR (β = 0.51, p <0.05). The additional contribution of PAH_KR (β = 0.27, p = 0.06) and SA_US (β = −0.03, p = 0.90) was rather small (3). The investigation of individual differences between the reference method and alternative diagnostics indicated a significant bias for MO_MIR (p <0.01). The results support the use of economical and time-efficient methods for assessing BMS within elite youth soccer. Bivariate correlation analyses as well as the multivariate latent variable approach highlight the measures' usefulness. However, the observed individual level differences for some of the utilized procedures led to the recommendation for practitioners to use at least two alternative assessment methods in order to receive more reliable information about players' BMS within the talent promotion process.

Prediction of maturity offset and age at peak height velocity in a longitudinal series of boys and girls

BACKGROUND

Predicted maturity offset, defined as time before peak height velocity (PHV) is increasingly used as an indicator of maturity status in studies of physical activity, fitness, and sport.

OBJECTIVE

To validate maturity offset prediction equations in longitudinal samples of boys and girls.

METHODS

The original and modified maturity offset prediction equations were applied to serial data for 266 boys (8-17 years) and 147 girls (8-16 years) from the Cracow Growth Study. Actual age at PHV for each youngster was estimated with the SITAR protocol. In addition to maturity offset, the difference between CA at prediction and maturity offset provided an estimate of predicted age at PHV.

RESULTS

Predicted maturity offset and age at PHV increased, on average, with CA at prediction. Variation in predictions was reduced compared to that in observed ages at offset and at PHV, and was more apparent with the modified equations. Relatively few predicted ages at PHV approximated observed age at PHV in early and late maturing youth of both sexes; predictions were later than observed among the former, and earlier than observed among the latter.

CONCLUSION

Predicted maturity offset and ages at PHV with the original and modified equations increase with CA at prediction, have reduced variation, and have major limitations with early and late maturing boys and girls.

Maturational timing, physical self-perceptions and physical activity in UK adolescent females: investigation of a mediated effects model

BACKGROUND

Advanced (early) biological maturation may be a risk factor for inactivity among adolescent girls.

AIM

To test the mediational effects of body attractiveness and physical self-worth on the relationship between biological maturity and accelerometer assessed moderate-to-vigorous physical activity (MVPA) in a large multi-ethnic sample of girls from the Midlands area in the UK (11-14 years).

SUBJECTS AND METHODS

Biological maturity (predicting age at peak height velocity (APHV)); self-perceptions of body attractiveness, physical self-worth, and minutes spent in MVPA were assessed in 1062 females aged 11-14 years.

RESULTS

Structural equation modelling using maximum likelihood estimation and boot- strapping procedures supported the hypothesised model. Later maturation predicted higher perceptions of body attractiveness (β = 0.25, p < .001) which, in turn, predicted higher perceptions of physical self-worth (β = 0.91, p < .001) and, significantly higher MVPA (β = 0.22, p < .001). Examination of the bootstrap-generated bias-corrected confidence intervals suggested that perceptions of body attractiveness and physical self-worth partially mediated a positive association between predicted APHV and MVPA (β = 0.05, p < .001).

CONCLUSIONS

Greater biological maturity (i.e. early maturity) in adolescent girls is associated with less involvement in MVPA and appears to be partly explained by lower perceptions of body attractiveness and physical self-worth. Physical activity interventions should consider girls' perceptions of their pubertal related physiological changes during adolescence, particularly among early maturing girls.

Differences in Maturity, Morphological, and Fitness Attributes Between the Better- and Lower-Ranked Male and Female U-14 Portuguese Elite Regional Basketball Teams

Ramos, S, Volossovitch, A, Ferreira, AP, Barrigas, C, Fragoso, I, and Massuça, L. Differences in maturity, morphological and fitness attributes between the better- and lower-ranked male and female U-14 Portuguese elite regional basketball teams. J Strength Cond Res 34(3): 878-887, 2020-During a national championship, the anthropometric, physiological, and maturation attributes of 13-14-year-old players of regional selection basketball teams and their association with team's final classification were analyzed. Body parameters (body mass, height, skinfolds, and lengths) were measured and physiological capacities assessed by sprint (20 m), agility, jump, and upper-body strength tests. Chronological age, maturity offset (years from age at peak height velocity; YAPHV), and predicted age at peak height velocity were calculated. In both sexes, no significant differences were found for maturity. Anthropometric and physiological analysis indicated that male players from finalist's teams were significantly faster, were more agile, threw the medicine ball longer, and showed lower percentages of body fat than players from lower-ranked teams. Further, semifinalists were faster than lower-ranked players. In the same sense, female players from semifinalist teams demonstrated to be significantly faster, more agile, and threw the medicine ball longer than female players from lower-ranked teams. In addition, discriminant analysis showed that speed (in boys) and the combination of speed and upper limb strength (in girls) could successfully discriminate players with different performances in a championship. In conclusion, speed and upper limb strength appear to be the physical attributes associated with better team performance in youth basketball. Coaches should be aware of the relationship between the improvement of these physical attributes and the teaching-learning process of the basketball game.

Longitudinal development of 5m sprint performance in young female tennis players

Sprint performance over short distances is a central component in young tennis players' development. This study aimed to examine the longitudinal development of sprint performance in young female tennis players, and to investigate differences between performance levels. Also potentially explanatory variables were investigated. Female tennis players aged 10-15 (N = 167) participated in a, mixed-longitudinal study (n = 48 elite; n = 119 sub-elite). Players were measured annually on the 5 m sprint as well as for possible explaining variables for 5 m sprint performance development (age, height, body mass, maturity status, lower limb explosive strength). Multilevel analysis was used to obtain a developmental model. Moreover, it was possible to predict sprint performance (5 m) based on chronological age, body size given by height, and lower limb strength performance (p < .05). Significant different developmental patterns were found for elite and sub-elite players, with elite players aged 10-14 being faster. After age 14, no significant differences were found in sprint performance between elite and sub-elite players (p > . 05). Sprint performance is an important characteristic of young female tennis players and seemed to depend on growth and maturation in parallel to physical fitness.

Bio-Banding in Youth Sports: Background, Concept, and Application

Inter-individual differences in size, maturity status, function, and behavior among youth of the same chronological age (CA) have long been a concern in grouping for sport. Bio-banding is a recent attempt to accommodate maturity-associated variation among youth in sport. The historical basis of the concept of maturity-matching and its relevance to youth sport, and bio-banding as currently applied are reviewed. Maturity matching in sport has often been noted but has not been systematically applied. Bio-banding is a recent iteration of maturity matching for grouping youth athletes into 'bands' or groups based on characteristic(s) other than CA. The percentage of predicted young adult height at the time of observation is the estimate of maturity status of choice. Several applications of bio-banding in youth soccer have indicated positive responses from players and coaches. Bio-banding reduces, but does not eliminate, maturity-associated variation. The potential utility of bio-banding for appropriate training loads, injury prevention, and fitness assessment merits closer attention, specifically during the interval of pubertal growth. The currently used height prediction equation requires further evaluation.

Scaling left ventricular mass in adolescent female soccer players

BACKGROUND

The aim of the study was to examine the contribution of chronological age (CA), skeletal maturation, training experience and concurrent body size descriptors, to inter-individual variance in left ventricular mass (LVM) among female adolescent soccer players.

METHODS

The sample included 228 female soccer players 11.8-17.1 years. Training experience defined as years of participation in competitive soccer (range 2-9 years), was obtained by interview. Stature, body mass and skinfolds (triceps, medial calf) were measured. Fat mass was estimated; Fat-free mass was derived. LVM was assessed by echocardiography. Skeletal maturity status was as the difference of skeletal age (SA, Fels method) minus CA.

RESULTS

Fat-free mass was the most prominent single predictor of LVM (R2 = 36.6%). It was associated with an allometric coefficient close to linearity (k = 0.924, 95%CI: 0.737 to 1.112). A significant multiplicative allometric model including body mass, fat-free mass, CA, training experience and skeletal maturity status was also obtained (R = 0.684; R2 = 46.2%).

CONCLUSION

Stature has limitations as a valid size descriptor of LVM. Body mass, fat-free mass, training experience, CA, body mass and skeletal maturity status were relevant factors contributing to inter-individual variability in LVM.

FUNCTIONAL MOVEMENT SCREEN™ in YOUTH SPORT PARTICIPANTS: EVALUATING the PROFICIENCY BARRIER for INJURY

Background & Purpose

The number of youth participating in sport increases yearly; however, the evaluation of youths' movement ability and preparedness for sport remains inadequate or neglected. The Functional Movement Screen (FMS™) is an assessment of an individual's movement quality that has been utilized to evaluate risk of injury in collegiate and professional sport; however, there is minimal support regarding the predictive value of the screen in youth sport. The purpose of this study was to evaluate the mean and distribution of FMS™ performance in sport participants age 11-18, and to evaluate the existence of a composite FMS™ score proficiency barrier to predict injury risk.

Study Design

Prospective cohort study.

Methods

One hundred, thirty-six participants (63 male, 73 female) age 11 to 18 years (16.01 + 1.35) were recruited from local schools and sport organizations. The FMS™ was administered prior to each participant's competitive season and scored by researchers who demonstrated reliability in assessments derived from the screen (κ_w = 0.70 to 1). Injury data were collected by the participants' Athletic Trainer over one season. An injury was defined as any physical insult or harm resulting from sports participation that required an evaluation from a health professional with time modified or time lost from sport participation.

Results

Females scored significantly higher than males for mean FMS™ composite score (t = 14.40; m = 12.62; p < 0.001), and on individual measures including: the hurdle step (t = 1.91; m = 1.65; p < 0.001), shoulder mobility (t = 2.68; m = 2.02; p < 0.001), active straight leg raise (t = 2.32; m = 1.87; p < 0.001), and the rotary stability components (t = 1.91; m = 1.65; p < 0.05). Two FMS™ composite scores (score < 14 and <15) significantly increased the odds of injury (OR = 2.955). When adjusting for sport, there was no score relating to increased odds of injury.

Conclusion

Dysfunctional movement as identified by the FMS™ may be related to increased odds of injury during the competitive season in youth athletes. Consideration of an individual's movement within the context of their sport is necessary, as each sport and individual have unique characteristics. Addressing movement dysfunction may aid in injury reduction and potentially improve sport performance.

Level of Evidence

1b.

A cross-sectional study on the deprivation and sex differences in health-related fitness measures in school children

This study aimed to investigate deprivation and sex differences in selected health-relatedfitness measures in 9-12-year-old children. Data were captured on 3,407 children (49.3% boys; aged 10.5 ± 0.6 years). Cardiorespiratory fitness(20 m multistage shuttle run test; 20 m MSRT), muscular strength (handgrip strength) and body mass index (BMI) were measured. Welsh Index of Multiple Deprivation (WIMD) scores were used to make quintile groups. A two-way Analysis of Variance examined differences in BMI z-score by sex and WIMD quintiles. Two-wayAnalysis of Covariances investigated the effect of sex and WIMD quintiles on grip strength and shuttles achieved in 20 m MSRT, adjusting for BMI z-score and maturation, repectively. Independent of sex, children in the middle quintile had a significantly higher mean BMI z-score (p = 0.029) than their least deprived counterparts. There was a significant increase in grip strength (p = 0.005) and20 m MSRT (boys p < 0.001; girls p = 0.028) between most and least deprived quintiles. Significant differences in 20 m MSRT score were more apparent with decreases in deprivation in boys.Overall, inequalities exist in health-related fitness by sex and deprivation. These results can be used to inform focused services to improve current and future health.

Cross-Sectional Analysis Investigating the Concordance of Maturity Status Classifications in Elite Caucasian Youth Tennis Players

BACKGROUND

To evaluate the concordance of skeletal age (SA) with two predicted estimates of biological maturity status in elite British youth tennis players.

METHOD

Participants were 71 male and female elite youth tennis players aged 8 to 16 years. Weight, height, and sitting height were measured. SA (Fels method) was the criterion indicator of maturity status. Maturity status was predicted with two methods: predicted age at peak height velocity and percentage of predicted adult height at the time of observation. Players were classified as late, average (on time), or early maturing with each method. Concordance of classifications was evaluated with kappa coefficients and Spearman's rank order correlations.

RESULTS

Kappa coefficients between maturity status classifications were low in both sexes, - 0.11 to 0.22, while Spearman's rank order correlations between maturity status classifications based on SA and the percentage of predicted mature height were moderate in males (0.35) and females (0.25), but the corresponding correlations based on predicted age at peak height velocity (PHV) varied, moderate and negative in boys (- 0.37) and low and positive in girls (0.11). Concordance of maturity status classifications based on the prediction methods and SA among tennis players was thus limited.

CONCLUSIONS

Maturity status based on the percentage of predicted mature height at the time of observation correlated better with maturity status based on SA in contrast to status based on predicted age at PHV in this sample of elite youth tennis players.

Jump higher, run faster: effects of diversified sport participation on talent identification and selection in youth basketball

The aims of this study were to examine the medium-term effects of previous experiences during early stages of sport development on physical capacities of under-13 (U-13) talented basketball players and, to identify variables that discriminated under-14 (U-14) national team training camp selection. Anthropometrical and physical measurements were collected during a basketball training camp. Previous sport experiences (6-10 years), maturity offset, power outputs for jumping and sprinting were determined. A cluster analysis was used to allocate the subjects according to their different levels of sport experiences (more specialized vs. less specialized) to allow creating a dummy variable for the subsequent analysis of the physical variables. A stepwise discriminant analysis was computed to identify the construct that best classifies selected and non-selected players for U-14 national team training camp. The less specialized group outscored more specialized in all physical parameters, irrespectively of gender. The Abalakov Jump Peak Power and Predicted Adult Height (PAH) could successfully discriminate selected from non-selected players for U-14 national team training camp in boys and PAHin girls. The diversified and non-specific sport stimulus during early ages seem to be determinant to the acquisition and development of fundamental movement skills of talented basketball players.

Fundamental Motor Skills Mediate the Relationship Between Physical Fitness and Soccer-Specific Motor Skills in Young Soccer Players

Fundamental motor skills (FMS) are the basic elements of more complex sport-specific skills and should be mastered at the end of early childhood; however, the relationship between FMS and sport-specific skills has not yet been verified in prepubertal soccer players. Therefore, the aim of this study was to determine the role of FMS in the process of acquiring soccer-specific motor skills (measured using speed dribbling) with regard to physical fitness and biological maturation. Forty male soccer players (11.5 ± 0.3 years of age) at the highest performance level participated in the study. The test of Gross Motor Development - second edition and Unifittest 6-60 were used to assess FMS and physical fitness, respectively. The role of FMS in a complex theoretical model with the relationships between physical fitness, biological maturation and speed dribbling was analyzed by multiple regression path analyses (MRPA). Moderate to strong correlations were found between FMS, physical fitness, and speed dribbling (r = 0.56-0.66). Biological maturation did not appear to be a significant predictor of physical fitness or speed dribbling. The MRPA model using FMS as mediator variable between physical fitness and speed dribbling showed a significant indirect effect (standard estimation = -0.31, p = 0.001; R 2 = 0.25). However, the direct correlation between physical fitness and speed dribbling was non-significant. Our results showed that FMS significantly strengthened the influence of physical fitness on the performance of speed dribbling, a soccer-specific motor skill, and thus play an important role in the process of acquiring sport-specific motor skills in prepubertal soccer players. When considering the long-term training process, especially during childhood and before puberty, a wide range of FMS activities should be applied for better and possibly faster acquisition of soccer-specific motor skills.

Relative age effect: Characteristics of youth soccer players by birth quarter and subsequent playing status

PURPOSE

To compare characteristics of club level male soccer players 11 and 13 years of age, and to evaluate playing status in soccer two and 10 years after baseline by birth quarter (BQ).

METHODS

Youth players 11 (n = 62, born 1992, observed December 2003) and 13 (n = 50, born 1990, observed April 2004) years were grouped by BQ. Baseline data included stature, weight, maturity status, functional capacities, soccer skills, goal orientation, and coach evaluation of potential. Playing status in soccer in 2006 and 2014 was also available. Baseline characteristics and subsequent playing status were compared by BQ.

RESULTS

Baseline characteristics did not differ by BQ except for age and percentage of predicted adult height. Though not significant, coaches tended to rate players in BQ1as higher in potential. For those competing in soccer as adults, BQ2 (4), BQ3 (5) and BQ4 (2) were represented among players11 years, and BQ1 (3), BQ2 (2), BQ3 (1) and BQ4 (4) among players 13 years.

CONCLUSION

Although limited to small numbers, differences among players by BQ were inconsistent. The results indicate a need to extend potential explanations of the RAE to include behavioral variables, coaches, training environment, and perhaps the culture of the sport.

Musculoskeletal pain and its association with maturity and sports performance in 14-year-old sport school students

OBJECTIVES

In youth sports, musculoskeletal pain is often studied from the standpoint of sports injuries, but little is known about pain conditions in which athletes still participate. The aim was to study the frequency of pain and associations with maturity offset, health status and sports performance in 14-year-old sport school students.

METHODS

Cross-sectional design. One hundred and seventy-eight students (108 boys and 70 girls) completed anthropometric measures for maturity offset (height, weight and sitting height), questionnaires (pain mannequin and EQ-5D for health status) and sports performance tests (sprint, agility, counter-movement jump and grip strength). Differences between groups were analysed with Student's t-test and analysis of covariance.

RESULTS

Thirty-one students (18.6%) reported infrequent pain, 85 (50.9%) frequent pain and 51 (30.5%) constant pain. Students in the constant pain group had worse health status than those in the infrequent pain group. Boys with constant pain (n=27) had a lower mean maturity offset (-0.38 vs 0.07 years; p=0.03) than boys with infrequent pain (n=22), and pain was associated with worse sports performance. There was no difference in maturity or sports performance between girls with constant pain (n=24) and girls with infrequent pain (n=9).

CONCLUSION

Musculoskeletal pain is common in sport school students and coincides with worse health status and with a younger biological age in boys. The high prevalence of pain should be acknowledged by coaches and student healthcare workers in order to promote a healthy and sustainable development in young athletes.

Modified Maturity Offset Prediction Equations: Validation in Independent Longitudinal Samples of Boys and Girls

BACKGROUND

Predicted maturity offset and age at peak height velocity are increasingly used with youth athletes, although validation studies of the equations indicated major limitations. The equations have since been modified and simplified.

OBJECTIVE

The objective of this study was to validate the new maturity offset prediction equations in independent longitudinal samples of boys and girls.

METHODS

Two new equations for boys with chronological age and sitting height and chronological age and stature as predictors, and one equation for girls with chronological age and stature as predictors were evaluated in serial data from the Wrocław Growth Study, 193 boys (aged 8-18 years) and 198 girls (aged 8-16 years). Observed age at peak height velocity for each youth was estimated with the Preece-Baines Model 1. The original prediction equations were included for comparison. Predicted age at peak height velocity was the difference between chronological age at prediction and maturity offset.

RESULTS

Predicted ages at peak height velocity with the new equations approximated observed ages at peak height velocity in average maturing boys near the time of peak height velocity; a corresponding window for average maturing girls was not apparent. Compared with observed age at peak height velocity, predicted ages at peak height velocity with the new and original equations were consistently later in early maturing youth and earlier in late maturing youth of both sexes. Predicted ages at peak height velocity with the new equations had reduced variation compared with the original equations and especially observed ages at peak height velocity. Intra-individual variation in predicted ages at peak height velocity with all equations was considerable.

CONCLUSION

The new equations are useful for average maturing boys close to the time of peak height velocity; there does not appear to be a clear window for average maturing girls. The new and original equations have major limitations with early and late maturing boys and girls.

Impact of Martial Arts (Judo, Karate, and Kung Fu) on Bone Mineral Density Gains in Adolescents of Both Genders: 9-Month Follow-Up

PURPOSE

To compare bone mineral density (BMD) gains in adolescents of both genders stratified according to different martial art styles in a 9-month follow-up study.

METHODS

The longitudinal study consisted of 29 adolescents of both genders and age between 11 and 17 years stratified into a control group (not engaged in any sport) and 50 fighters (kung fu/karate, n = 29; judo, n = 21). All 79 subjects underwent anthropometric measures (weight, height, leg length, and height set) and dual-energy X-ray absorptiometry (BMD, in g/cm²) at 2 moments, baseline and 9 months later. Maturity offset (age at peak height velocity), lean soft tissue, chronological age, and resistance training were treated as covariates.

RESULTS

Male judoists presented higher gains in BMD-spine [0.098 g/cm² (95% confidence interval, 0.068-0.128)] than control group [0.040 g/cm² (95% confidence interval, 0.011-0.069)] (post hoc test with P = .030). There was no effect of martial art on BMD gains among girls. Independently of gender, in all multivariate models, lean soft tissue constituted the most relevant covariate.

CONCLUSIONS

Judo practice in adolescents affected the bone accrual significantly after 9-month follow-up compared with controls, mainly in boys.

What is the most accurate and reliable methodological approach for predicting peak height velocity in adolescents? A systematic review

OBJECTIVES

To identify the most accurate method of predicting peak height velocity in adolescents.

DESIGN

Systematic review.

METHODS

A comprehensive literature search of six electronic databases and reference lists was conducted. Studies that met selection criteria of (1) observational longitudinal cohort study (2) reproducible method/s of predicting peak height velocity (3) minimum six-month follow-up (4) healthy male and/or female adolescent subjects, with the exception of participants with adolescent idiopathic scoliosis, were considered for review. Studies were screened using a modified quality assessment checklist, with only those scoring >50% included. The type of surrogate measure of peak height velocity, its reliability and ability to predict peak height velocity were extracted from the year or stage immediately preceding peak height velocity. We defined "predict" as when both the estimates of effect and 95% confidence intervals of the surrogate occurred prior to the actual age of PHV.

RESULTS

The nine included studies examined three anthropometric, three equation and four radiographic-based surrogates for PHV. Of these, the radiographic measures were reported to exhibit moderate to high intra- and inter-rater reliability. Three of the four radiographic surrogates predicted PHV. Two anthropometric measures also predicted PHV but reliability of the measures is unknown. All equation-based methods predicted the timing of PHV to occur later than it actually happened when applied in the year prior to expected PHV.

CONCLUSIONS

In the year/stage immediately preceding peak height velocity, radiograph-based methods appear to be accurate and reliable surrogates.

Biological Maturation, Central Adiposity, and Metabolic Risk in Adolescents: A Mediation Analysis

BACKGROUND

Earlier biological maturation has been related to increased metabolic risk. In this study, we verified mediating effects by central adiposity of the relationship between somatic maturity and metabolic risk factors in adolescents.

METHODS

In a cross-sectional study, 1034 adolescents aged 10-16 years from Londrina/PR/Brazil were evaluated. The age of peak height velocity (PHV) method was used to evaluate somatic maturity. Central adiposity was estimated through waist circumference measurements. Fasting glucose, triglycerides, high-density lipoprotein cholesterol (HDL-C), and blood pressure were measured as metabolic risk indicators. Physical activity (Baecke questionnaire) and cardiorespiratory fitness (20-m shuttle run test) were used as covariates.

RESULTS

Except for fasting glucose, waist circumference showed partial or full mediation of the relationship between maturity and the following metabolic risk factors with their respective z-score values: triglycerides (boys = -3.554 vs. girls = -5.031), HDL-C (boys = +5.300 vs. girls = +5.905), systolic blood pressure (boys = -3.540 vs. girls = -3.763), diastolic blood pressure (boys = -2.967 vs. girls = -3.264), and metabolic risk score (boys = -5.339 vs. girls = -6.362).

CONCLUSIONS

The results suggest that central obesity plays a mediating role in the relationship between somatic maturation and metabolic risk during adolescence.