Improving the Prediction of Maturity From Anthropometric Variables Using a Maturity Ratio

Skeletal age prediction models by maturity status in male soccer players

This study focus is to develop a new model to estimate skeletal age (SA) as a function of the state of biological maturation in male soccer players, and to propose cut-off points to classify the state of biological maturation based on the percentage of adult height (PAH). SA was determined in 747 Portuguese male soccer players, using the Tanner-Whitehouse (TW) 3 method, and PAH was predicted by TW3 (P-TW3) and Khamis-Roche (P-KR) methods. Subsequently, the sensitivity and specificity of the P-TW3 were estimated to classify late, on-time and early maturers to obtain cut-off points, by age; and to develop specific equations for each maturation stage. Both the model using P-TW3 and the model using P-KR showed a SA predictive capacity of 93%. The average differences were similar to zero. P-TW3 cutoff points were established by ROC curve analysis to identify late and early maturers according to their SA. Following, predictive models were developed to estimate SA according to maturity status. The predictive capacity of the models was 87.3% in late maturers, 92.3% in on-time maturers and 93.5% in early maturers. The prediction models are a reliable and cost-effective method to estimate SA in male soccer players.

Comparative Analysis of Maturation Prediction Methods (Moore, Mirwald, BAUSportTM): Croatian Female Volleyball Youth Team Example

Objectives: The study aims to compare three distinct protocols-Moore, Mirwald, and the new BAUSportTM SonicBone system-for predicting somatic maturation in youth athletes. Methods: The participants were female members of the Croatian national volleyball youth team (U-17) (n = 16). The study involved comprehensive measurements, including height, weight, sitting height, leg length, wrist diameter, hand joint diameter, hand grip strength, and ultrasound measurements for skeletal age assessment. Results: Correlation analysis showed moderate to strong correlations between the Moore and Mirwald skeletal age estimates, but both showed weaker correlations with the BAUSportTM skeletal age. Repeated-measures ANOVA showed no significant difference between the Moore and Mirwald methods (p > 0.05); significant differences between both the Moore and Mirwald methods and the BAUSportTM method (p < 0.05). Regression analysis revealed that height, weight, sitting height, leg length, wrist diameter, and hand joint diameter explained 69% of BAUSportTM, with wrist diameter being the only significant predictor. While the Moore and Mirwald methods remain useful tools for estimating the timing of an athlete's growth spurt, BAUSportTM represents a potential advancement in skeletal age assessment. Further research is needed to validate BAUSportTM across diverse populations and optimize its calibration to accommodate anatomical variations. Conclusions: The findings suggest that with further refinement, BAUSportTM could become a new standard for monitoring skeletal development in youth athletes. Additionally, studies should explore comparative analyses with other emerging technologies, such as genetic markers, hormonal assessments, and MRI, for further understanding of biological maturation in talent identification.

Effects of maximal power and the force-velocity profile on sprint acceleration performance according to maturity status and sex

This study aimed to determine whether maturational and sex-related differences in sprint times were accompanied by changes in relative maximal power (Pmax), force-velocity profiles (SFV) and optimal sprint distances (xopt). Sprint times and continuous velocity-time data were collected using a radar. Inverse dynamics applied to the centre of mass provided accurate estimations of force-velocity relationship parameters (Pmax, F0, v0, SFV, xopt) and technical variables (RFmax, DRF). Somatic maturity was determined from peak height velocity (PHV). Performance increased with maturation in girls and boys (p < 0.001, d = 0.86‒2.78) accompanied by increases in relative Pmax from pre to post-PHV (p < 0.011‒0.001, d = 0.98‒5.20). Increases in relative Pmax were predominantly due to more velocity-oriented profiles (p < 0.007‒0.001, d = 0.76‒1.41). xopt, RFmax and DRF also increased with maturation (p < 0.030‒0.001, d = 0.87‒3.40). Pmax increases in girls and boys throughout maturation enabling them to reduce sprint times. Both girls and boys increased Pmax through a shift to more velocity-oriented profiles. However, plateaus in F0 and RFmax were present from pre-PHV in girls, while boys had slower development from mid-PHV. Improving Pmax through increases in F0 and RFmax, while maintaining a velocity-oriented profile, will likely benefit youth sprint performance. A specific focus on these parameters is necessary from pre-PHV onwards in girls and from mid-PHV in boys.

The relative age effect and the relationship between biological maturity and athletic performance in Austrian elite youth soccer players

Purpose

Publications from recent years suggest that the biological developmental stage of underage athletes has a significant impact on their athletic performance. This scientific study is the first quantitative attempt in Austria to investigate the impact of the relative age effect and biological maturity on the physical performance of young elite soccer players.

Methods

Birth data from a total of 98 male players in the U13 to U18 age groups of a first-division Austrian soccer club were collected. By measuring height, sitting height and body mass, the individual biological age was calculated using the Mirwald equation. The athletes underwent a standardized battery of tests, which included assessments of speed, strength and endurance.

Results

The results indicate a significant effect of the relative age effect on player selection in the U14 and U15 teams (p < .05), which diminishes with increasing player age. Compared to typical Austrian adolescents of similar age, U13, U14 and U15 players demonstrate a higher level of biological maturity (p < .05). Correlational analyses revealed that the maturity offset, reflecting the time before or after the greatest individual growth spurt, was positively related to eccentric hamstring strength (r = 0.82) and vertical jumping ability (r = 0.61) and positively related to sprint performance over 5, 10 and 20 m (0.62 < r < 0.69; all p ≤ .001).

Conclusion

Biological maturity and the associated anthropometric adaptations are decisive for athletic performance. The study supports the notion that biologically more mature players achieve better athletic performance than less mature players, especially before the onset of puberty.

Does team size affect Scottish male academy soccer player technical, locomotor and psychosocial outcomes during age and maturity bio-banded small-sided games?

The timing of the adolescent growth spurt (i.e. peak height velocity [PHV]) varies greatly, causing significant differences in maturity-related anthropometric and physical development among chronologically age-categorised youth soccer players. These differences can lead to a maturity-selection bias favouring early maturing players. Using fifty-three players from two professional Scottish soccer academies, this study examined the effects of team size (4v4, 5v5, and 6v6) and bio-banding (i.e. grouping players by maturity status) on players technical (i.e. touches, releases, possessions), physical (i.e. distance covered, accelerations/decelerations), and psychological (i.e. confidence, competitiveness, positive attitude) performance during small-sided games, using foot-mounted inertial measurement units (F-IMU) and coach observations. Data were analysed using multivariate ANOVA. During maturity-matched games, technical actions decreased as team size increased. More mature players displayed greater technical actions in 4v4 compared to 6v6. Maturity-mismatched games revealed significant technical action differences for less mature players, particularly in 4v4 formats. More mature players covered greater high-intensity distances in maturity-matched and mismatched 6v6 games. Psychological scores were higher for more mature players in smaller team sizes (4v4), whereas less mature players showed consistent psychological scores across all formats. Smaller team sizes and maturity-matched bio-banding formats enhanced technical actions and psychological characteristics, particularly for more mature players.

Is Biobanding the Future of Youth Sport Participation?

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

Quadriceps Muscle Geometry and Strength Throughout Maturation in National-Level Male Soccer Players: A Cross-Sectional Study

Purpose

Adolescent soccer players experience distinct physiological changes due to chronological and biological maturation, impacting their soccer performance. Here, we explored age-related variations and associations between quadriceps geometry and strength in male national-level adolescent soccer players.

Patients and Methods

We used ultrasonography to examine the regional architecture and morphology of the rectus femoris (RF) and vastus lateralis (VL) muscles, and we assessed knee extension strength by isometric and isokinetic dynamometry. Players were categorized into four age groups: under (U) 15 (n=18, age=13.7±0.5 years), U16 (n=15, age=14.7±0.5), U17 (n=19, age=15.7±0.5), U18 (n=18, age=16.7±0.5) and U21 (n=25, age=18.5±0.5).

Results

The absolute and relative strengths were higher in the U16 compared to U15 by 12-15% and 6-8%, 11-12% and 6-7% in the U17 compared to U16, 5-7% and -1-2% in the U18 compared to U17 and 0-15% and -1-11% in the U21 compared to U18 age groups, respectively. VL architecture did not change relevantly between the age groups. The muscle anatomical cross-sectional area (ACSA) of the VL and RF differed non-uniformly and muscle region-specific by 10-36%, with highest values in the U21 age group. Moderate correlations between the VL architecture and knee extension strength in both legs were observed only in the U16 age group. The quadriceps ACSA showed age-specific correlations with knee extension strength.

Conclusion

Our findings highlight non-uniform differences in quadriceps muscle morphology and absolute and relative strength among male national-level adolescent soccer players in different age groups. The correlations observed between muscle morphology or architecture and strength were muscle, muscle region, leg and age dependent.

Injury Risk in Elite Young Male Soccer Players: A Review on the Impact of Growth, Maturation, and Workload

ABSTRACT

Ribeiro, N, Martinho, DV, Pereira, JR, Rebelo, A, Monasterio, X, Gonzalo-Skok, O, Valente-dos-Santos, J, and Tavares, F. Injury risk in elite young male soccer players: a review on the impact of growth, maturation, and workload. J Strength Cond Res 38(10): 1834-1848, 2024-The long-term development of young male soccer players involves a prolonged period of significant adjustments, highlighting the importance of studying the complex interaction between dynamic variables, including workload, and inherent elements like growth and maturity. This analysis examines the intricate connections involving the development, maturity, workload, and susceptibility to injuries among adolescent male soccer players. Significantly, these connections become prominent at the peak height velocity (PHV) period, a crucial moment in maturation. Growth rates vary among individuals, and higher rates have been associated with an increased risk of injury in young soccer players, particularly during periods of rapid growth. Identifying possible risk factors and understanding the complex connections between them is crucial to developing specific methods for reducing the risk of injury. Sharing this valuable information with essential stakeholders is crucial for guaranteeing young athletes' comprehensive growth and maturation process. Furthermore, this review emphasizes the immediate need for long-term studies and thorough injury analyses to comprehend better the dynamic interactions that influence injury patterns in young male soccer players. This review will allow practitioners to better understand the main modifiable and nonmodifiable risk factors for injury and provide essential information focusing on practical strategies, facilitating more informed decision making by all stakeholders. The review aims to clarify these complexities and offer crucial insights that can assist in designing and implementing efficient strategies to reduce the risk of injury, specifically for the challenges faced during PHV and within the broader framework of long-term athletic development in young soccer.

Variations in External and Internal Intensities and Impact of Maturational Age on Soccer Training Tasks

During peak height velocity, adjusting training intensity is crucial for optimizing performance and minimizing injury risk. This cross-sectional study compares external and internal intensities in different training tasks (analytical tasks, small-sided games, and training matches) and analyzes their effect on the maturation age of young players. Fifty-five U-15 and U-16 boys from two soccer clubs in southwestern Spain were monitored using inertial movement units and heart rate monitors to report training intensities. Anthropometric data and birthdates were collected to estimate maturation age. The Friedman test and Durbin-Conover post hoc test identified specific differences between groups, and Spearman's rank correlation coefficients assessed variable impacts. Training matches showed significantly higher distance covered, maximum and average speed, and average heart rate compared to small-sided games and analytical tasks. High-intensity actions and sprints were significantly higher (p < 0.0001) during training matches compared to analytical tasks and during small-sided games compared to analytical tasks. Player load per minute was significantly highest (p < 0.05) during training matches, followed by small-sided games, and lowest in analytical tasks. Positive correlations between maturational age and high-intensity actions, accelerations, and decelerations indicated higher intensity (p < 0.05) in more mature players. A negative correlation between player load per minute and maturational age suggested more efficient intensity management in mature players. These findings highlight the importance of considering biological maturation and training task variability in youth athletes' development.

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.

Self-management including exercise, education and activity modification compared to usual care for adolescents with Osgood-Schlatter (the SOGOOD trial): protocol of a randomized controlled superiority trial

BACKGROUND

Osgood-Schlatter is the most frequent growth-related injury affecting about 10% of physically active adolescents. It can cause long-term pain and limitations in sports and physical activity, with potential sequela well into adulthood. The management of Osgood-Schlatter is very heterogeneous. Recent systematic reviews have found low level evidence for surgical intervention and injection therapies, and an absence of studies on conservative management. Recently, a novel self-management approach with exercise, education, and activity modification, demonstrated favorable outcomes for adolescents with patellofemoral pain and Osgood-Schlatter in prospective cohort studies.

AIM

The aim of this trial is to assess the effectiveness of the novel self-management approach compared to usual care in improving self-reported knee-related function in sport (measured using the KOOS-child 'Sport/play' subscale) after a 5-month period.

METHODS

This trial is a pragmatic, assessor-blinded, randomized controlled trial with a two-group parallel arm design, including participants aged 10-16 years diagnosed with Osgood-Schlatter. Participants will receive 3 months of treatment, consisting of either usual care or the self-management approach including exercise, education, and activity modification, followed by 2 months of self-management. Primary endpoint is the KOOS-child 'Sport/play' score at 5 months. This protocol details the planned methods and procedures.

DISCUSSION

The novel approach has already shown promise in previous cohort studies. This trial will potentially provide much-needed level 1 evidence for the effectiveness of the self-management approach, representing a crucial step towards addressing the long-term pain and limitations associated with Osgood-Schlatter.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT05174182. Prospectively registered December 30th 2021. Date of first recruitment: January 3rd 2022. Target sample size: 130 participants.

Relationship Between Cognitive Functions and Agility Performance in Elite Young Male Soccer Players

ABSTRACT

Matlák, J, Fridvalszki, M, Kóródi, V, Szamosszegi, G, Pólyán, E, Kovács, B, Kolozs, B, Langmár, G, and Rácz, L. Relationship between cognitive functions and agility performance in elite, young, male soccer players. J Strength Cond Res 38(1): 116-122, 2024-The aim of this study was to assess the relationship between agility performance and cognitive functions measured under laboratory conditions among elite young soccer players. Twenty-five, elite, young, male soccer players (12.3 ± 0.4 years, 155.4 ± 7.6 cm, 42.6 ± 6.9 kg) completed a battery of field tests, including 5-, 10-, 20-m sprints, change of direction speed (CODS), standing long jump, and an agility test based on a human stimulus. Subjects also completed choice reaction (RT, S3) and reactive stress tolerance (DT, S1) tests on the Vienna Test System. There was a moderate significant relationship (p < 0.05) found between mean reaction time and mean motor time during the choice reaction task and decision time in the agility test. Decision time also showed a large significant correlation (p < 0.05) with total time in the agility test. No significant correlation was found between total time in the agility test and variables measured during RT and DT tests. No significant correlations were found between agility test results and results from straight line sprints, CODS, and standing long jump tests. The results of this study suggest that choice reaction time is related to decision-making speed during the agility task used in this study and can have an indirect effect on agility performance in elite young soccer players. Further studies assessing the relationship between different cognitive functions and agility performance in different sports and age categories could help in the identification of determinant cognitive functions in perceptual and decision-making factors of agility.

Methods to predict the timing and status of biological maturation in male adolescent soccer players: A narrative systematic review

The aim of this review was to summarise the methods used to predict and assess maturity status and timing in adolescent, male, academy soccer players. A systematic search was conducted on PubMed, Scopus, Web of Science, CINAHL, Medline and SPORTDiscus. Only experimental studies including male, academy players aged U9-U18 years registered with a professional soccer club were included. The methodological quality of the included studies was assessed using guidelines from the Framework of Potential Biases. Fifteen studies fulfilled our inclusion criteria. Studies were mainly conducted in European countries (n = 12). In total, 4,707 players were recruited across all 15 studies, with an age range of 8-18 years. Five studies were longitudinal, two studies were mixed-method designs and eight studies were cross-sectional. Due to high heterogeneity within the studies, a meta-analysis was not performed. Our findings provided no equivalent estimations of adult height, skeletal age, or age at PHV. Discrepancies were evident between actual and predicted adult height and age at PHV. The Bayley-Pinneau [1952], Tanner-Whitehouse 2 [1983] and Khamis-Roche [1994] methods produced estimates of adult height within 1cm of actual adult height. For age at PHV, both Moore [2015] equations produced the closest estimates to actual age at PHV, and the Fransen [2018] equation correlated highly with actual age at PHV (>90%), even when the period between chronological age and age at PHV was large. Medical imaging techniques (e.g., Magnetic Resonance Imaging, X-Ray, Dual energy X-ray Absorptiometry) demonstrated high intra/inter-rater reliability (ICC = 0.83-0.98) for skeletal maturity assessments. The poor concordance between invasive and non-invasive methods, is a warning to practitioners to not use these methods interchangeably for assessing maturational status and timing in academy soccer players. Further research with improved study designs is required to validate these results and improve our understanding of these methods when applied in this target population.

Age and Maturation Matter in Youth Elite Soccer, but Depending on Competitive Level and Gender

This study aimed to explore the relevance of the relative age effect (RAE), maturity status and anthropometry, and their influence on coaches' assessment of players' performance, analyzing both genders and different types of academies (elite vs. non-elite). The sample included 603 soccer players (385 male), from the under 12 (U12), under 14 (U14) and under 16 (U16) categories, belonging to elite and nonelite teams. Coaches' assessment of players' performance, chronological age, anthropometric characteristics, maturity offset (MO) and peak height velocity (PHV) were registered. Our results showed that RAE was present in both genders within the elite, but not in the nonelite academies. Early maturity players were overrepresented in the male elite, but not in the female academies. No relationship was found between RAE and anthropometry in male elite academies. Male elite players showed better anthropometric characteristics than nonelite players, while this pattern of results was not found for female players. The coaches' assessment on players' current performance was not influenced by the chronological age nor anthropometry, but it was linked to the PHV. Coaches from nonelite academies rated better in current assessment of performance the taller players. Our findings suggest that maturity status and RAE play an independent and important role in the talent selection process.

Soccer academy practitioners' perceptions and application of bio-banding

The primary aims of this study were to examine the application of maturity status bio-banding within professional soccer academy programmes and understand the methods employed, the intended objectives, and the potential barriers to bio-banding. Using a mixed method design, twenty-five professional soccer academy practitioners completed an online survey designed to examine their perceptions of the influence of maturation on practice, their perceptions and application of bio-banding, and the perceived barriers to the implementation of this method. Frequency and percentages of responses for individual items were calculated. In the next phase of the study, seven participants who had experience with, or knowledge of, the bio-banding process within an academy youth soccer setting were recruited to complete a semi-structured interview. Interview data was transcribed and analysed using a combination of deductive and inductive approaches to identify key themes. The main findings across the two phases of the study were that [1] there is consensus among the practitioners that the individual effect of maturation impacts their ability to accurately assess the soccer competencies, [2] the majority (80%) of the sample had implemented bio-banding, with practitioners showing a clear preference for using the Khamis and Roche method to bio-band players, with the greatest perceived benefit being during maturity-matched formats, specifically for late or post-PHV players, [3] Practitioners perceived that bio-banding enhances their ability to assess academy soccer players, and [4] practitioners who have used bio-banding believe that the method is an effective way of enhancing the perception of challenge thereby providing a number of psycho-social benefits. Findings suggest that a collaborative and multi-disciplinary approach is required to enhance the likelihood of bio-banding being successfully implemented within the typical training schedules across the adolescent phase of the player development pathway.

Ultrasound Imaging-Based Methods for Assessing Biological Maturity during Adolescence and Possible Application in Youth Sport: A Scoping Review

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.

Maturity-based correction mechanism for talent identification: When is it needed, does it work, and does it help to better predict who will make it to the pros?

When identifying talent, the confounding influence of maturity status on motor performances is an acknowledged problem. To solve this problem, correction mechanisms have been proposed to transform maturity-biased test scores into maturity-unbiased ones. Whether or not such corrections also improve predictive validity remains unclear. To address this question, we calculated correlations between maturity indicators and motor performance variables among a sample of 121 fifteen-year-old elite youth football players in Switzerland. We corrected motor performance scores identified as maturity-biased, and we assessed correction procedure efficacy. Subsequently, we examined whether corrected scores better predicted levels of performance achievement 6 years after data collection (47 professionals vs. 74 non-professional players) compared with raw scores using point biserial correlations, binary logistic regression models, and DeLong tests. Expectedly, maturity indicators correlated with raw scores (0.16 ≤ | r | ≤ 0.72; ps < 0.05), yet not with corrected scores. Contrary to expectations, corrected scores were not associated with an additional predictive benefit (univariate: no significant r-change; multivariate: 0.02 ≤ ΔAUC ≤ 0.03, ps > 0.05). We do not interpret raw and corrected score equivalent predictions as a sign of correction mechanism futility (more work for the same output); rather we view them as an invitation to take corrected scores seriously into account (same output, one fewer problem) and to revise correction-related expectations according to initial predictive validity of motor variables, validity of maturity indicators, initial maturity-bias, and selection systems. Recommending maturity-based corrections is legitimate, yet currently based on theoretical rather than empirical (predictive) arguments.

Examination of differential ratings of perceived exertion (dRPE) during bio-banded small-sided games

The aims of the current study were to investigate the use of dRPE with academy soccer players to: 1) examine the effect of bio-banded and non-bio-banded maturity groups within SSG on players dRPE; 2) describe the multivariate relationships between dRPE measures investigating the sources of intra and inter-individual variation, and the effects of maturation and bio-banding. Using 32 highly trained under (U) 12 to U14 soccer players (mean (SD) age 12.9 (0.9) years, body mass 46.4 (8.5) kg and stature 158.2 (14.9) cm) academy soccer players from two English professional male soccer academies. Players were categorised according to somatic maturity status using estimated percentage of adult stature attainment, with players randomly assigned into teams to play 4v4 SSG. The study used a repeated measures design, whereby the selected players participated within 6 bio-banded (maturity matched [pre-PHV Vs pre-PHV and post-PHV vs post PHV] and miss-matched [pre-PHV vs post-PHV] and 6 mixed maturity SSG at their respective clubs. Using mixed and fixed effect regression models, it was established hat pre-PHV players exhibited higher dRPE compared with their post-PHV counterparts. Mixed bio-banded games reported higher dRPE outputs overall. Variation in dRPE measures across a series of bio-banded games are caused by both between and within sources of variation in relatively equal amounts. Across a series of bio-banded games, the four dRPE measures do not provide unique information, and between variation is best expressed by one or two highly correlated components, with within variation best explained by a single equally loaded component. Using a bio-banding SSG design study, we have shown that pre-PHV players report higher subjective measures of exertion than post-PHV players during. Additionally, when evenly mixing players based on measures of maturation, higher measures of perceived exertion were generally reported.

Is Motor Coordination the Key to Success in Youth Cycling?

PURPOSE

To evaluate the predictive value of a (non-)sport-specific test battery on the future success of young cyclists, test scores were compared with competition performances 2-3 years later.

METHODS

Three motor coordination, 5 physical performance, and 2 cycling-specific measurements were collected in 111 U15 (13.0-14.9 y) and 67 U17 (15.0-16.9 y) male road cyclists. In addition, maturity status, relative age, and competition history were assessed. National and provincial competition results 2-3 years later, in the U17year2 and U19year2 categories, were submitted to 2 separate 4-stage hierarchical regressions.

RESULTS

The results of the model of the U15 group revealed that maturity, relative age, competition history, motor coordination, physical performance, and cycling-specific performance accounted for 22.6% of the variance in competitive success. For the U15 category, only maturity and motor coordination were significant predictors of competitive success in the U17year2 category. Maturity and motor coordination each uniquely explained ±5% of the variance. However, for the U17 group-neither motor coordination, physical performance, nor cycling-specific performance could predict competitive success in the U19year2 category.

CONCLUSIONS

The current study underlines the importance of general motor coordination as a building block necessary for optimal development in youth cycling. However, considering the lack of predictive value from the U17 category onward, other features may determine further development of youth athletes. Nevertheless, it is questioned why athletes need to possess a minimum level of all physical, motor coordination, and cycling-specific characteristics to experience success and enjoyment in their sport.

Leveling the Playing Field: A New Proposed Method to Address Relative Age- and Maturity-Related Bias in UK Male Academy Soccer Players

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

The confounding effect of biological maturity on talent identification and selection within youth Australian football

This study measured the influence of biological maturity across numerous performance parameters for talent identification in Australian football. Anthropometry, estimated maturity status using a maturity ratio from anthropometric measurements and chronological age, motor competence, physical fitness and small-sided match involvements of 227 U13-U15 high-level academy athletes were assessed. Multivariate analysis of variance revealed significant moderate effects of maturity status on physical fitness (p = 0.008, ES = 0.07) and significant large effects on anthropometry (p = 0.001, ES = 0.20), but not on motor competence or match involvements. Univariate analyses of variance demonstrated significant large effects of maturity on anthropometry, but only one subset of physical fitness (i.e. lower-body power). U15 players selected into a U16 development programme were biologically older thandeselected players, despite selection being independent of maturity when a categorical descriptor was used. This study confirms that maturation affects anthropometry and certain measures of physical fitness in youth Australian football players, but not match involvements and motor competence. Furthermore, a player's maturity could affect selection and progression into advanced academy programmes. Involvements and motor competence should be included in multidimensional assessment batteries for Australian Football as they appear less confounded by maturity than fitness and anthropometry.

The effect of bio-banding on physical and psychological indicators of talent identification in academy soccer players

The aim of this study was to examine the effect of bio-banding on indicators of talent identification in academy soccer players. Seventy-two 11 to 14-year-old soccer players were bio-banded using percentage of estimated adult stature attainment (week 1), maturity-offset (week 2) or a mixed-maturity method (week 3). Players contested five maturity (mis)matched small-sided games with physical and psychological determinants measured. Data were analysed using a series of Bayesian hierarchical models, fitted with different response distributions and different random and fixed effect structures. Few between-maturity differences existed for physical measures. Pre-peak height velocity (PHV) and post-PHV players differed in PlayerLoad^TM (anterior-posterior and medial-lateral) having effect sizes above our criterion value. Estimated adult stature attainment explained more of the variance in eight of the physical variables and showed the greatest individual differences between maturity groups across all psychological variables. Pre-PHV and post-PHV players differed in positive attitude, confidence, competitiveness, total psychological score (effect sizes = 0.43-0.69), and session rating of perceived exertion. The maturity-offset method outperformed the estimated adult stature attainment method in all psychological variables. Maturity-matched bio-banding had limited effect on physical variables across all players while enhancing a number of psychological variables considered key for talent identification in pre-PHV players.

The effect of bio-banding on academy soccer player passing networks: Implications of relative pitch size

The primary aims of this study were to examine the effects of bio-banding players on passing networks created during 4v4 small-sided games (SSGs), while also examining the interaction of pitch size using passing network analysis compared to a coach-based scoring system of player performance. Using a repeated measures design, 32 players from two English Championship soccer clubs contested mixed maturity and bio-banded SSGs. Each week, a different pitch size was used: Week 1) small (36.1 m2 per player); week 2) medium (72.0 m2 per player); week 3) large (108.8 m2 per player); and week 4) expansive (144.50 m2 per player). All players contested 12 maturity (mis)matched and 12 mixed maturity SSGs. Technical-tactical outcome measures were collected automatically using a foot-mounted device containing an inertial measurement unit (IMU) and the Game Technical Scoring Chart (GTSC) was used to subjectively quantify the technical performance of players. Passing data collected from the IMUs were used to construct passing networks. Mixed effect models were used with statistical inferences made using generalized likelihood ratio tests, accompanied by Cohen's local f2 to quantify the effect magnitude of each independent variable (game type, pitch size and maturation). Consistent trends were identified with mean values for all passing network and coach-based scoring metrics indicating better performance and more effective collective behaviours for early compared with late maturation players. Network metrics established differences (f2 = 0.00 to 0.05) primarily for early maturation players indicating that they became more integral to passing and team dynamics when playing in a mixed-maturation team. However, coach-based scoring was unable to identify differences across bio-banding game types (f2 = 0.00 to 0.02). Pitch size had the largest effect on metrics captured at the team level (f2 = 0.24 to 0.27) with smaller pitch areas leading to increased technical actions. The results of this study suggest that the use of passing networks may provide additional insight into the effects of interventions such as bio-banding and that the number of early-maturing players should be considered when using mixed-maturity playing formats to help to minimize late-maturing players over-relying on their early-maturing counterparts during match-play.

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.

The effect of bio-banding on the anthropometric, physical fitness and functional movement characteristics of academy soccer players

The study examined if maturity status bio-banding reduces within-group variance in anthropometric, physical fitness and functional movement characteristics of 319, under-14 and under-15 players from 19 UK professional soccer academies. Bio-banding reduced the within-bio-banded group variance for anthropometric values, when compared to an aggregated chronological banded group (chronological: 5.1-16.7%CV; bio-banded: 3.0-17.3%CV). Differences between these bio-banded groups ranged from moderate to very large (ES = 0.97 to 2.88). Physical performance variance (chronological: 4.8-24.9%CV; bio-banded: 3.8-26.5%CV) was also reduced with bio-banding compared to chronological aged grouping. However, not to the same extent as anthropometric values with only 68.3% of values reduced across banding methods compared to 92.6% for anthropometric data. Differences between the bio-banded groups physical qualities ranged from trivial to very large (ES = 0.00 to 3.00). The number of functional movement metrics and %CV reduced by bio-banding was lowest within the 'circa-PHV' groups (11.1-44.4%). The proportion of players achieving the threshold value score of ≥ 14 for the FMS™ was highest within the 'post-PHV' group (50.0-53.7%). The use of maturity status bio-banding can create more homogenous groups which may encourage greater competitive equity. However, findings here support a bio-banding maturity effect hypothesis, whereby maturity status bio-banding has a heightened effect on controlling for characteristics which have a stronger association to biological growth.

Maturity-Associated Differences in Match Running Performance in Elite Male Youth Soccer Players

PURPOSE

To investigate the influence of maturation on match running performance in elite male youth soccer players.

METHODS

A total of 37 elite male youth soccer participants from an English professional soccer academy from the U14s, U15s, and U16s age groups were assessed over the course of 1 competitive playing season (2018-2019). Relative biological maturity was assessed using percentage of predicted adult height. A global positioning system device was used between 2 and 30 (mean = 8 [5]) times on each outfield player. The position of each player in each game was defined as defender, midfielder, or attacker and spine or lateral. A total of 5 match-running metrics were collected total distance covered, high-speed running distance, very high-speed running distance, maximum speed attained, and number of accelerations.

RESULTS

Relative biological maturity was positively associated with all global positioning system running metrics for U14s. The U15/16s showed variation in the associations among the global positioning system running metrics against maturity status. A multilevel model which allowed slopes to vary was the best model for all parameters for both age groups. In the U14 age group, advanced maturation was associated with greater high-speed running distance. However, maturation did not contribute toward variance in any of the indices of running performance in the U15/16s. In the U15/16 age group, significance was observed in the spine/lateral playing positions when undertaking actions that required covering distance at high speeds.

CONCLUSIONS

Maturation appeared to have an impact on match-running metrics within the U14s cohort. However, within the U15/16s, the influence of maturation on match-running metrics appeared to have less of an impact.

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.

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.

M. Biceps Femoris Long Head Architecture and Sprint Ability in Youth Soccer Players

PURPOSE

Hamstring muscle architecture may be associated with sprint performance and the risk of sustaining a muscle injury, both of which increase during puberty. In this study, we investigated the m. biceps femoris long head (BFlh) cross-sectional area (ACSA), fascicle length (FL) and pennation angle (PA), and sprint performance as well as their relationship in under 13 to 15 youth soccer players.

METHODS

We measured 85 players in under-13 (n = 29, age = 12.5 [0.1] y, height = 155.3 [6.2] cm, weight = 43.9 [7.6] kg), under-14 (n = 25, age = 13.5 [0.3] y, height = 160.6 [7.7] cm, weight = 47.0 [6.8] kg), and under-15 (n = 31, age = 14.4 [0.3] y, height = 170.0 [7.7] cm, weight = 58.1 [8.8] kg) teams. We used ultrasound to measure BFlh ACSA, FL and PA, and sprint tests to assess 10- and 30-m sprint time, maximal velocity  (vmax), and maximal acceleration (αmax). We calculated Pearson r to assess the relationship between sprint ability and architectural parameters.

RESULTS

All muscle architectural parameters increased from the under-13 to the under-15 age group (BFlh ACSA = 37%, BFlh FL = 11%, BFlh PA = 8%). All sprint performance parameters improved from the under-13 to under-15 age categories (30-m time = 7%, 10-m time = 4%, vmax = 9%, αmax = 7%). The BFlh ACSA was correlated with 30-m sprint time (r = -.61 (95% compatibility interval [CI] [-.73, -.45]) and vmax (r = .61, 95% CI [.45, .72]). A combination of BFlh ACSA and age best predicted 30-m time (R² = .47 [.33, .62]) and 10-m time (R² = .23 [.08, .38]).

CONCLUSIONS

Muscle architectural as well as sprint performance parameters increase from the under-13 to under-15 age groups. Even though we found correlations for all assessed architectural parameters, BFlh ACSA was best related to the assessed sprint parameters.

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.

Italian Physical Fitness Decline: A True Fact or a Mindset? A 10-Year Observational Perspective Study

Evidence regarding a putative physical fitness decline remains less well documented for Italian children and adolescents. An update review of data collection articles was undertaken concerning motor performances (power, strength, speed-agility and indirect cardiorespiratory fitness) of children and adolescents worldwide and compared with 2859 11-12-year-old Italian students of both sexes, throughout a ten-year observational period. Lower limb explosive strength (standing broad jump), flexibility (sit-and-reach), endurance (Cooper) and speed (SP-30) performances of sixth grade Italian students showed nearly stable trends, with no differences during the observed decade, in both sexes. This 10-year perspective study confirmed that Italian physical fitness levels flatlined rather than actually declined. According to these study data, the decline in physical fitness of the Italian youth is ostensible and needs a further in-depth analysis.

Skeletal age prediction model from percentage of adult height in children and adolescents

Skeletal age (SA) is considered the gold standard to assess the degree of maturation and has been widely used in sports, education and public health areas; however, it requires sophisticated equipment and well-trained technicians. Therefore, it is important to develop non-invasive methods for its evaluation. The aim was to develop an equation to predict SA using the percentage of adult height. SA was measured by Tanner-Whitehouse-3 method, and the percentage of adult height was estimated by two methodologies: Tanner-Whitehouse-3 method (P-TW3) and Khamis-Roche method (P-KR) using 839 schoolchildren of both sexes. Linear regression was used for predicting SA from P-TW3; then P-TW3 was replaced in the equation for P-KR value. Bland-Altman graphs, interclass correlation coefficient and Kappa index were used as validation tests. Model showed a SA predictive capacity of 93.2% in boys and 96.8% in girls. The average differences between SA measured and SA predicted by P-TW3 was 0.0504 (± 0.664) in boys and 0.0144 (± 0.435) in girls (P = 0.229 and 0.667, respectively). When P-TW3 was replaced for P-KR value in the equation, the average differences were - 0.0532 in boys and 0.0850 in girls (P = 0.509 and 0.167 respectively). The present model, based on the percentage of adult height, showed an adequate estimation of SA in children and adolescents and it can be used in the absence of bone X-ray equipment, in healthy boys aged 9 to 15 and girls 8 to 13.

Importance of dimensional changes on glycolytic metabolism during growth

PURPOSE

The aim of the present study was to investigate (i) how glycolytic metabolism assessed by accumulated oxygen deficit (AOD_gly) and blood metabolic responses (lactate and pH) resulting from high-intensity exercise change during growth, and (ii) how lean body mass (LBM) influences AOD_gly and its relationship with blood markers.

METHODS

Thirty-six 11- to 17-year olds performed a 60-s all-out test on a rowing ergometer. Allometric modelling was used to investigate the influence of LBM and LBM + maturity offset (MO) on AOD_gly and its relationship with the extreme post-exercise blood values of lactate ([La]_max) and pH (pH_min) obtained during the recovery period.

RESULTS

AOD_gly and [La]_max increased while pH_min decreased linearly with LBM and MO (r² = 0.46 to 0.72, p < 0.001). Moreover, AOD_gly was positively correlated with [La]_max (r² = 0.75, p < 0.001) and negatively correlated with pH_min (r² = 0.77, p < 0.001). When AOD_gly was scaled for LBM, the coefficients of the relationships with blood markers drastically decreased by three to four times ([La]_max: r² = 0.24, p = 0.002; pH_min: r² = 0.30, p < 0.001). Furthermore, by scaling AOD_gly for LBM + MO, the correlation coefficients with blood markers became even lower ([La]_max: r² = 0.12, p = 0.037; pH_min: r² = 0.18, p = 0.009). However, MO-related additional changes accounted much less than LBM for the relationships between AOD_gly and blood markers.

CONCLUSION

The results challenge previous reports of maturation-related differences in glycolytic energy turnover and suggest that changes in lean body mass are a more powerful influence than maturity status on glycolytic metabolism during growth.

Role of physique and physical fitness in the balance of Korean national snowboard athletes

Background

The objective of this study is to understand the relationship between physique, physical fitness, and balance performance for snowboard athletes.

Methods

We considered all Korean national snowboard athletes (n = 9 with 6 males and 3 females, age = 17.44 ± 4.42), who have an experience of competition at continental cup level, to measure their physique, physical fitness, and (both static and dynamic) balance. Static balance was evaluated based on one-legged standing, while dynamic balance was estimated using a stability platform.

Results

Static balance is strongly correlated (p < 0.05) with circumference of the left lower leg (34.49 ± 2.42 cm; ρ = 0.68), sit-up (57.56 ± 8.8; ρ = 0.72), sargent jump (50.22 ± 11.78 cm; ρ = 0.67), strength of bench press (39.11 ± 17.73 kg; ρ = 0.67), angle of left ankle dorsiflexion (73.78 ± 7.86°; ρ = 0.77), average extension strength at 180° for left knee (321 ± 63.95 %BW; ρ = 0.77) and right knee (337 ± 60.32 %BW; ρ = 0.77), and right knee peak flexion strength at 60° (148 ± 25.61 %BW; ρ = 0.73). Center dynamic balance is negatively correlated with circumference of the right lower leg (34.63 ± 2.38 cm; ρ = −0.67, p < 0.05), while right dynamic balance is positively correlated with left ankle flexion (148.44 ± 5.20°; ρ = 0.78, p < 0.05).

Conclusion

Static balance is related to core muscle endurance and power, ankle flexibility, and knee stability, while dynamic balance is negatively correlated with circumference of the most frequently used lower leg (i.e., the leg dominating the snowboarding stance). The relationship between physique, physical fitness, and balance provides an insight into improving the balance performance of elite snowboard athletes through a training program that can affect the physique and physical fitness factors related to balance.

Decline of physical activity in early adolescence: A 3-year cohort study

This study analyses the changes of moderate-to-vigorous physical activity (MVPA) in a cohort of boys and girls aged 11 (n = 50) and 14 (n = 50). Physical activity was assessed with Bodymedia SenseWear Pro Armband monitor for 6 days in October 2013 and October 2016, considering 90% of daily wear time (21h and 40min). The initial sample (n = 160) included the children who wore the monitors at age 11 but the final analyzed sample included only those children from the initial sample (n = 50), whose data fulfilled the inclusion criteria at age 11 and 14. Physical fitness and somatic characteristics of the final sample (n = 50) were compared to a representative sample of Slovenian schoolchildren at ages 11 (n = 385) and 14 (n = 236) to detect possible bias. Changes in MVPA were controlled for maturity using the timing of adolescent growth spurt as its indicator. The average MVPA decreased more than one quarter (34.96 min) from age 11 to age 14. Children were significantly more active at age 11 than at age 14 (p < 0.01, d = 0.39). The timing of puberty onset in girls was significantly earlier (12.01 ± 1.0 years) (p < 0.01) than in boys (13.2 ± 0.75 years) (p < 0.01, d = 1.35). There was a significant gender difference in moderate-to vigorous physical activity at age 14 (p < 0.05, η2 = 0.12) and between moderate-to vigorous physical activity at age 11 and 14 (η2 = 0.11). After controlling for the timing of adolescent growth spurt the girls at age 11 showed significantly higher level of physical activity than at age 14 (p < 0.01, η2 = 0.17). Early adolescence is crucial for the development of physical activity behaviours, which is especially pronounced in girls. The significant decline of MVPA between ages 11 and 14 in Slovenia are likely influenced by environmental changes since the timing of adolescent growth spurt did not prove as a factor underlying the decline of MVPA.

Biological maturation and match running performance: A national football (soccer) federation perspective

OBJECTIVES

To examine the influence of maturation and its interaction with playing position upon physical match performances in U15 footballers from a national federation.

DESIGN

Observational study.

METHODS

278 male outfield players competing in a national tournament were assessed for somatic maturity and match physical performances according to playing position. Stature, sitting height, and body mass were measured and entered into an algorithm to estimate the age at peak height velocity (APHV). Players match movements were recorded by Global Positioning System devices (10 Hz), to determine peak speed, and total- (TD), low-speed running (LSR; ≤13.0 km h^-1), high-speed running (HSR; 13.1-16.0 km h^-1), very high-speed running (VHSR; 16.1-20.0 km h^-1) and sprint distances (SPR; >20.0 km h^-1) expressed relative to match exposure (m min^-1).

RESULTS

Linear-mixed models using log transformed response variables revealed a significant contribution of estimated APHV upon TD (1.01; 95% CI: 0.99-1.02 m·min^-1; p < 0.001), HSR (1.05; 95% CI: 0.98-1.13 m min^-1; p < 0.001) and VHSR (1.07; 95% CI: 1.00-1.14 m min^-1; p = 0.047). An increase by one year in APHV was associated with an increase of 0.6, 5.4 and 6.9% in TD, HSR and VHSR respectively. No effects of APHV were observed for LSR, SPR, and peak speed. Further, no APHV effects were observed relative to players' field position.

CONCLUSIONS

Later maturing players covered substantially more higher-intensity (HSR and VHSR) running in matches, irrespective of playing position. The greater match intensity of later maturing players may inform talent identification and athletic development processes within a national federation.

A multidimensional approach to talent identification and selection in high-level youth Australian Football players

There is limited research in talent identification in youth Australian Football (AF), especially the factors that underpin selection into higher-level development programs. Therefore, this study explored age-related differences in high-level youth AF players and investigated characteristics influencing selection into a high-level development program. Anthropometry (stature, sitting height, body mass), maturity (estimated age at peak height velocity), motor competence (Körperkoordinationstest für Kinder), fitness (change of direction speed, lower body power and upper body muscular endurance) and coach skill ratings (kicking, marking and handballing) of 277 state academy players (U13-U15) were assessed. MANOVAs identified significant age-related differences for anthropometry, fitness, and coach skill ratings. Furthermore, 90.9 and 90.0% of U15 selected and deselected players were classified correctly. Selected players were more mature, taller, heavier, more explosive, faster at changing directions, and had superior kick technique and marking results. These results demonstrate considerable age-group performance outcome differences, highlighting that high-level academies should aim to select or deselect after 15 years of age. Additionally, it appears earlier maturing players are favoured for selection into a high-level academy. While practitioners must consider the confounding effect of maturation, early maturing players may be favoured for their ability to withstand increasing demands in higher-level youth AF.