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

Proposed complementary osteological indicators: Advancing the estimation of puberty stages in Bioarcheology

OBJECTIVES

The study of puberty is a well-established area of bioarcheological research, which greatly enhances our understanding of adolescence and growth in the past. Since the publications of Shapland and Lewis' works, which have become "standards" for estimating puberty in skeletal material, no additional osteological indicators of puberty have been proposed. Nevertheless, clinical practice constantly develops skeletal maturation markers that could be useful in bioarcheology. This study aims to assess the applicability and reliability of novel puberty indicators as a complementary tool to estimate puberty in skeletal remains.

MATERIALS AND METHODS

Four new maturation markers including spheno-occipital synchondrosis, humeral head ossification, calcaneal apophysis ossification, and mandibular premolar mineralization were selected and applied to a sample of 85 adolescents from pre-Roman southern Italy (Pontecagnano, 7th-4th BCE).

RESULTS

Despite some limits in adapting the original clinical methods to osteoarcheological material, the use of these novel skeletal indicators had moderate to excellent scoring repeatability and an overall high agreement with the puberty and menarche status previously estimated with standard methods. These results encourage us to apply these markers in bioarcheology. In some cases, minor adaptations of the original scoring systems are suggested to enhance reliability.

DISCUSSION

Including the proposed indicators in routine puberty data collection allows us to refine puberty estimation and improve the ability to identify key growth milestones in poorly preserved skeletons. Further application to osteological collections with diverse chronology and geographical differences is needed to assess how and to what extent the newly proposed maturation markers perform.

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.

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.

Correlations Between Hamstring Muscle Architecture, Maturation, and Anthropometric Measures in Academy Soccer Players

PURPOSE

Muscle architecture is associated with motor performance and muscle injury. While muscle architecture and knee-flexor eccentric strength change with growth, the influence of anthropometric measures on these properties is rarely considered. This study aimed to investigate the relationship between hamstring muscle architecture and knee-flexor eccentric strength with anthropometric measurements.

METHODS

Sixty male footballers (16.6 [1.05] y) from the U16, U17, and U19 teams of an elite soccer club were included in this study. Fascicle length, pennation angle, and muscle thickness of the biceps femoris long head (BFlh) and semimembranosus muscles were measured in both legs using ultrasound. Knee-flexor eccentric strength, height, body mass, leg length, femur length, and peak height velocity (PHV) were measured within 1 week of the ultrasound images. A stepwise regression and 1-way analysis of variance tests were used to evaluate the effects of age, maturity, and anthropometric measurements on muscle properties.

RESULTS

Variance within BFlh and semimembranosus muscle thickness (r < .61), semimembranosus pennation angle (r < .58), and knee-flexor eccentric strength (r = .50) were highly related to body mass. We observed no significant correlations between muscle architecture and age (P > .29). However, moderately greater BFlh muscle thickness was shown for the post-PHV compared with the PHV group (effect size ± 90% CI: 0.72 ± 0.49).

CONCLUSIONS

In conclusion, weak correlations between muscle architecture and anthropometric measurements suggest that other factors (ie, genetics, training regimen) influence muscle architecture. The moderate effect of maturity on BFlh muscle thickness strongly suggests post-PHV hypertrophy of the BFlh muscle. Our results confirmed previous findings that eccentric knee-flexor strength is influenced by body mass.

Tensiomyographic Assessment of Contractile Properties in Elite Youth Soccer Players According to Maturity Status

Little is known about how muscle contractile properties are affected by biological maturation in elite youth soccer players. This study aimed to determine the effects of maturation on contractile properties of rectus femoris (RF) and biceps femoris (BF) muscles assessed by tensiomyography (TMG) and provide reference values for elite youth soccer players. One hundred twenty-one elite youth soccer players (14.98 ± 1.83 years; 167.38 ± 10.37 cm; 60.65 ± 11.69 kg) took part in the study. The predicted peak height velocity (PHV) was used in order to establish players' maturity status (Pre-PHV, n = 18; Mid-PHV, n = 37; Post-PHV = 66). Maximal radial displacement of the muscle belly, contraction time, delay time, and contraction velocity for RF and BF muscles were recorded. One-way ANOVA showed no significant differences between PHV groups for any tensiomyography variables in RF and BF muscles (p > 0.05). Our results established that maturity status did not show a significant effect in mechanical and contractile properties on RF and BF muscles evaluated by TMG in elite youth soccer players. These findings and reference values can be useful for strength and conditioning coaches of elite soccer academies in order to optimize the evaluation of neuromuscular profiles.

Gender- and Sport-specific Normative Anthropometric and Physical Values in Talent-Identified High School Athletes

ABSTRACT

Larkin, P, Sortino, B, Carlon, T, Saunders, T, and Pane, C. Gender- and sport-specific normative anthropometric and physical values in talent-identified high school athletes. J Strength Cond Res 37(3): 606-615, 2023-Youth sport is associated with the identification and promotion of athletes within talent development pathways, with anthropometric and physical performance measures being key assessment and monitoring tools. To adequately evaluate performance within a population, normative reference data are needed; however, currently, there is limited normative values of talent-identified youth athletes. The aim of the current study is to present normative values of talent-identified youth sport academy athletes in relation to gender, age, and sport. Over a 5-year period, a total of 794 talent-identified youth athletes who attended a specialized school sports academy were assessed using anthropometric (i.e., heigh,; body mass) and physical performance (i.e., vertical jump, 20-m sprint, Yo-Yo intermittent recovery test 1) measures. In total, 451 male and 343 female athletes (grade 7: 12-13 years; grade 8: 13-14 years; grade 9: 14-15 years; grade 10: 15-16 years) were tested annually. The result demonstrates that for each gender, as age increases, there is a general increase in anthropometric measures (i.e., height and body mass). Furthermore, with increasing age, athletes generally have a higher vertical jump, faster sprint performance, and improved physical endurance. The results highlight sport-specific differences for each measure. Overall, the results of the study provides age-, gender-, and sport-specific normative data of talent-identified youth athletes. These findings provide representative performance profiles of talent-identified high school athletes, with the values potentially being used by coaching staff (i.e., head coaches, strength and conditioning coaches, rehabilitation staff) for comparison purposes.

Effects of Taekwondo Training on Growth Factors in Normal Korean Children and Adolescents: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The growth of children and adolescents is both an important health indicator and a major public health issue. Many recent studies have investigated the effects of taekwondo on growth factors, but no consensus has yet been reached. This meta-analysis aimed to determine the effects of taekwondo on the growth factors in children and adolescents (aged 8 to 16 years). Randomized controlled trials from PubMed, Web of Science, Cochrane Library, the Research Information Sharing Service, the Korea Citation Index, and the Korean-studies Information Service System were analyzed. The effect sizes (standardized mean differences, SMD) were calculated, the risk of bias and publication bias were assessed, and the effect size and subgroup analyses were pooled. We found that the taekwondo group had significantly higher levels of growth hormones (SMD 1.78, 95% confidence interval [CI] 0.98-2.58, and p < 0.001) and insulin-like growth factors (SMD 1.76, 95% CI 0.60-2.92, and p < 0.001) than the control group. For height, a medium effect size was observed (SMD 0.62, 95% CI -0.56-1.80, and p = 0.300), but the between-group difference was not significant. Thus, taekwondo had significant positive effects on the secretion of growth hormones and insulin-like growth factors in Korean children and adolescents. A longitudinal follow-up is necessary to determine the effect on height. This suggests that taekwondo can be recommended as an appropriate physical exercise for maintaining normal growth in children and adolescents.

Anthropometry and Physical Performance in 13-Year-Old Australian Talent-Identified Male and Female Athletes Compared to an Age-Matched General Population Cohort

Talent-identified male and female athletes are assumed to have greater speed and power than the general population at a given age. However, a comparison of the jump and sprint performance of an Australian cohort of male and female youth athletes from various sports to age-matched controls has not occurred. Therefore, the aim of this study was to compare anthropometric and physical performance markers between ~13-year-old talent-identified youth athletes and general population Australian youth. The anthropometry and physical performance in talent-identified youth athletes (n = 136, 83 males) and general population youth (n = 250, 135 males) were tested during the first month of the school year in an Australian high school within a specialized sports academy. Talent-identified females were taller (p < 0.001; d = 0.60), sprinted faster (20 m: p < 0.001; d = -1.16), and jumped higher (p < 0.001; d = 0.88) than general population youth females. Similarly, talent-identified males sprinted faster (20 m: p < 0.001; d = -0.78) and jumped higher (p < 0.001; d = 0.87) than general population youth males, but were not taller (p = 0.13; d = 0.21). Body mass was not different between groups for males (p = 0.310) or females (p = 0.723). Overall, youth, particularly females, who are trained in a variety of sports, exhibit greater speed and power during early adolescence compared to their age-matched peers, with anthropometric differences only occurring in females at 13 years of age. Whether talented athletes are selected because they exhibit these traits or whether speed and power are developed through sport participation requires further investigation.

Reliability of biological maturation analyses performed by equations predicting skeletal age and peak height velocity with hand and wrist X-ray results

BACKGROUND

Hand-wrist radiography is the gold standard for the assessment of skeletal age (SA) and the assignment of biological maturation (BM) status. However, its practical use in the field is questioned, prompting the development of anthropometric equations to estimate BM. However, there is no consensus on the reliability of these equations in relation to hand-wrist X-rays.

OBJECTIVE

To test the reliability of the BM estimated from predictive equations with the results of hand-wrist X-rays.

METHODS

One-hundred forty-four young athletes (38%-males, 62%-females; 12.3 ± 1.4 years) were recruited. SA was assessed by analyzing X-rays of the hand-wrist using the Greulich-Pyle protocol. SA was predicted using the anthropometric equations of Cabral and Macêdo. By subtracting chronological age from SA, a measure of BM or biological age (BA) was computed. In addition, a BA of years from peak height velocity (PHV) was predicted using the anthropometric equations of Mirwald and Moore.

RESULTS

Relative to X-ray, Cabral's equations showed high reliability in estimating BM in both sexes (p < .0001) while Macêdo's equations showed substantial reliability or males (p < .0001) only. Mirwald and Moore's equations showed weak reliability (p < .05 and p = .043, respectively).

CONCLUSION

The prediction of SA using anthropometric equations was found to be reliable in categorizing individuals as late, synchronized, and/or early maturers in both sexes. However, the predictive equations of years from PHV only reliably categorized late and synchronized maturation stages in males and the synchronized maturers in females.

Longitudinal association of biological maturation with physical activity behaviors in girls transitioning from 5th to 7th grade

Introduction

This longitudinal study determined if social cognitive variables influence physical activity in girls stratified on the basis of maturity status.

Methods

Participants attended South Carolina public schools (Mage in 5th grade = 11.1 years) and included a cohort of 529 girls who provided physical activity data in the 5th grade and in 6th and/or 7th grade. The measure of maturity status was age at peak height velocity (APHV) estimated from maturity offset when the children were in the 5th grade. The Earlier Maturity (EM) group included girls whose APHV was one standard deviation or more below the mean APHV for the full sample. All other girls were placed in the Later Maturity (LM) group. Physical activity was assessed at each time point via accelerometry. Social‐cognitive variables were assessed at each time point by a questionnaire measuring self‐efficacy, enjoyment, competence, appearance, fitness, and social motives for physical activity. Growth curves for the total, Earlier Maturing, and Later Maturing groups assessed relationships between physical activity over time and time‐varying social cognitive variables.

Results

Physical activity was lower in the Earlier Maturing group and was positively associated with self‐efficacy and enjoyment motivation in the total group. These relationships were observed in the 5th grade and maintained through 7th grade. In the Later Maturing group, we observed positive relationships between physical activity and self‐efficacy, enjoyment and competence motivation.

Conclusions

Strategies to increase confidence, skills, and enjoyment of physical activity may only be effective for promoting activity among later maturing girls.

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.

A Simplified Skeletal Maturity Scale and Thumb Ossification Composite Index to Assess Skeletal Maturity and Predict Height Velocity in Japanese Females with Adolescent Idiopathic Scoliosis

INTRODUCTION

Since Little et al. first reported that peak height velocity (PHV) could be described as a reliable clinical marker for the prediction of remaining growth and curve progression of adolescent idiopathic scoliosis (AIS) in clinical practice, much attention has been paid to PHV as a possible predictor of curve progression in patients with AIS. However, PHV itself is only identified retrospectively, so its value is not available at the first outpatient clinic visit. Using the simplified skeletal maturity scale (SSMS) and the thumb ossification composite index (TOCI) staging systems, this study aims to assess skeletal maturity and predict height velocity (HV) in Japanese female patients with AIS.

METHODS

This study involved 95 female patients with AIS, ranging from 9 to 17 years old. A standing AP radiograph of the entire spine and a hand radiograph were retrospectively obtained to establish the skeletal maturity stage in accordance with the SSMS and TOCI systems. Height measurements were recorded at each visit; HV was calculated as the height change (cm) divided by the time interval (years).

RESULTS

The TOCI stage rating increased identically to the SSMS stage rating increase. The chi-square test showed that there was a significant correlation between the two scoring systems (χ2=720.4). The Cramer V correlation also demonstrated a very strong correlation (Cramer V=0.62). Regarding the relationship between HV and each SSMS and TOCI stage, HV decreased as SSMS and TOCI stages increased. η 2 equaled to 0.67 in both groups and displayed a strong correlation between HV and SSMS and TOCI stages.

CONCLUSIONS

These findings suggest that evaluation of the rate of HV using these radiological assessments is of supreme importance for determining the status of pubertal maturity and predicting the remaining amount of adolescent growth at the outpatient clinic visit.

Relationship between Biological Maturation, Physical Fitness, and Kinanthropometric Variables of Young Athletes: A Systematic Review and Meta-Analysis

There is a growing interest in knowing the relationship between biological maturation and sport performance-related variables of young athletes. The objective of this study is to analyze the relationship between biological maturation, physical fitness, and kinanthropometric variables of athletes during their growing period, according to their sex. The systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement and the search protocol was registered in PROSPERO, code: CRD42020208397. A search through the PubMed, Web of Sciences, and EBSCO databases was performed. A total of 423 studies were screened and 13 were included in the meta-analysis. The meta-analysis was completed by using the mean and standard deviation of each variable according to each maturation status (early, on time, or late). Differences depending on maturation were found on physical fitness, with better results in the advanced maturational groups in the male population (standard mean difference (SMD) = 0.17-2.31; p < 0.001-0.05). Differences depending on maturation were found for kinanthropometric variables in males (SMD = 0.37-2.31; p < 0.001-0.002) and height and body mass in females (SMD = 0.96-1.19; p < 0.001). In conclusion, the early maturation group showed higher values in kinanthropometric variables and better results in physical fitness, highlighting the importance of the maturational process in the talent selection programs. Despite that, more research is needed to clarify the relationship of maturation with the other variables on female populations and the changes in the muscle and bone variables during the maturation processes of both sexes.

Assessing the Evidence of Micronutrients on Depression among Children and Adolescents: An Evidence Gap Map

There is some evidence indicating that nutrition may have the ability to prevent, treat, and/or influence the severity of depression. The aims of this evidence gap map (EGM) are to provide an overview and to determine evidence gaps in the existing research on micronutrients and their impact on depression among children and adolescents. We conducted a comprehensive search in multiple databases of primary and secondary literature assessing the impact of micronutrients on depression-related outcomes such as unipolar depression, major depressive disorders, dysthymia, acute depression, and mood disorders. Abstracts and full-text articles were dual-screened based on predefined eligibility criteria. A total of 30 primary research publications were included in the EGM. About 47% of included studies focused on late adolescents (15-19 y), ∼40% on early adolescents (10-14 y), and ∼13% on children aged 6-9 y. Among the included studies, 8 studies examined a single micronutrient intervention and 22 studies examined micronutrient concentrations (either intake or serum), and their impact on depression. The most frequently studied micronutrients were vitamin D (n = 8), zinc (n = 8), iron (n = 6), folate (n = 7), and vitamin B-12 (n = 5). More longitudinal studies and trials are needed to determine the role of micronutrients in the etiology and treatment of depression among children and adolescents.

The effect of biological maturity status on ground reaction force production during sprinting

Sprint ability develops nonlinearly across childhood and adolescence. However, the underpinning ground reaction force (GRF) production is not fully understood. This study aimed to uncover the kinetic factors that explain these maturation-related sprint performance differences in Japanese boys and girls. A total of 153 untrained schoolchildren (80 boys, 73 girls) performed two 50-m maximal effort sprints over a 52-force-platform system embedded in an indoor track. Maturity offset (years from peak height velocity; PHV) was estimated using anthropometric data and used to categorise the children into six-year-long maturation groups (from group 1 [5.5-4.5 years before PHV] to group 6 [0.5 years before to 0.5 years after PHV). Maximum and mean step-averaged velocities across 26 steps were compared across consecutive maturation groups, with further GRF analysis (means and waveforms [statistical parametric mapping]) performed when velocity differences were observed. For boys, higher maximum velocities (effect size ± 90% CI = 1.63 ± 0.69) were observed in maturation group 2 (4.5-3.5 years before PHV) compared to group 1 (5.5-4.5 years before PHV), primarily attributable to higher antero-posterior GRFs across shorter ground contacts. Maximum velocities increased from maturation group 4 (2.5-1.5 years before PHV) to group 5 (1.5-0.5 years before PHV) in the girls (effect size ± 90% CI = 1.00 ± 0.78), due to longer ground contacts rather than higher GRFs per se. Waveform analyses revealed more effective reversal of braking forces and higher propulsive forces (e.g. 14%-77% of stance 4), particularly for comparisons involving boys, which suggested potentially enhanced stretch-shortening ability. Youth sport practitioners should consider these maturation-specific alterations when evaluating young athletes' sprint abilities.

BMI and inverted BMI as predictors of fat mass in young people: a comparison across the ages

Background: The use of body mass index (BMI) could lead to over/under estimation of fat mass percentage (FM%). An alternative index (inverted BMI, iBMI) has been proposed as a better estimator of FM% in adults, while its practical feasibility in children and adolescents has not been fully investigated.Aim: To examine if iBMI can better estimate FM% than BMI in children/adolescents.Subjects and methods: Height, weight, and triceps and subscapularis skinfolds were measured in 6686 schoolchildren aged 11-14-years-old. BMI and iBMI (squared height/weight) were calculated; FM% was estimated by skinfold thicknesses. The Pearson correlation coefficient and the coefficient of determination were obtained to test the best regression model between the indexes and FM%.Results: FM% was linearly related to both indexes with R2 values that were overall > 0.7. No significant differences among the R2 values were found (p value = .2, ANOVA).Conclusion: BMI persists as a robust index for health surveillance screening in children/adolescents, being very intuitive and ready-to-use. Inverted BMI may be more accurate within a cohort of adults who experience only ponderal modifications, directly implicated in the variation of FM. In conclusion, the BMI remains a quick, handy and intuitive predictor of FM%.

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.

Relationship Between Sever Disease and Skeletal Maturity

BACKGROUND

Sever disease is a common condition in active, growing children. This condition presents as pain in the heel and is thought to be an overuse condition of the calcaneal apophysis. There are currently no defined radiographic diagnostic criteria for evaluation of Sever disease, with radiographs generally showing normal appearance of the calcaneal apophysis. A better understanding of the relationship of Sever disease and skeletal maturity may allow for improved interpretation of radiographs when trying to diagnose this condition.

METHODS

ICD-9 code 732.5 was used to search for patients diagnosed with Sever disease from 2007 to 2015 at a single hospital. For every patient with Sever disease with available calcaneal imaging within 40 days of diagnosis, heel x-rays were staged for calcaneal maturity score using a previously described calcaneal skeletal maturity assessment system. Controls matched by age, race, and sex were evaluated for calcaneal stage to compare with the Sever patients.

RESULTS

The chart review yielded 78 patients diagnosed with Sever disease by the orthopaedic attending, 39 of which have x-rays around the time of diagnosis. Calcaneal scores averaged 2.2±0.8 for all patients, 2.1±0.9 for male individuals, and 2.3±0.8 for female individuals. The average age for male individuals was 10.4±1.9 years and for female individuals, 9.2±2.2 years. The ages of diagnosis were similar for patients with and without x-rays. Twenty-two of 39 patients with Sever disease were calcaneal stage 2, and 37 of 39 were stages 1, 2, or 3. We calculated the absolute difference from stage 2 for the Sever and control groups. Mean difference from stage 2 was 0.51±0.68 for the Sever patients and 0.95±0.79 for control patients (P=0.01).

CONCLUSION

Sever disease occurs in a very narrow range of skeletal maturity, as measured by the calcaneal skeletal maturity assessment system and our observations with chronological age. When compared with age-matched and race-matched controls, stage 2 was seen more frequently in the Sever patients. If a child is not within calcaneal stages 1, 2, or 3, then a different diagnosis should be considered.

LEVEL OF EVIDENCE

Level III-retrospective case-control study.

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.

Age and maturity related differences in motor coordination among male elite youth soccer players

This study investigated differences in generic and soccer specific motor coordination, as well as speed and agility depending on age and maturity in elite youth soccer players (U10-U15, N = 619). Measurements included body height, body weight and sitting height to estimate age at peak height velocity (APHV); three Körperkoordinationstest für Kinder subtests (i.e. jumping sideways (JS), moving sideways (MS), balancing backwards (BB)) to assess generic motor coordination; the UGent dribbling test for soccer specific motor coordination; a 5m/30m sprint and T-test for speed and agility, respectively. Age specific z-scores of the predicted APHV identified players as earlier, on time or later maturing. (M)ANOVA analyses showed significant age by maturity interaction effects for the speed and agility test cluster, revealing maturity related differences in U14 and U15 players. Next to an overall higher performance with age for all test clusters (η² 0.080-0.468), earlier maturing players outperformed their later maturing peers in 5m/30m sprinting. The opposite was seen for JS and BB. So, players' maturity status should be taken into account to adequately value performance in talent identification. Also, the focus on characteristics that appear to be minimally biased by an earlier maturational timing (i.e. motor coordination) should be increased.

When does the influence of maturation on anthropometric and physical fitness characteristics increase and subside?

The relationships between maturation and anthropometric and physical performance characteristics are dynamic and often asynchronous; confounding the capability to accurately evaluate performance during adolescence. This study aimed to (i) examine the influence of chronological age (CA) and somatic maturation (YPHV) upon anthropometric and physical performance parameters, and (ii) identify the transition/change time points in these relationships using segmental regression. N = 969 soccer players (8-18 years of age) completed anthropometric and physical test assessments, including a countermovement jump (CMJ), agility T test, 10 and 20 m sprints, and multistage fitness test (MSFT). When modeled against CA and YPHV, results identified time point phases with increased rates of stature (CA-7.5, YPHV-8.6 cm/y at 10.7-15.2 years or -3.2 to +0.8 YPHV) and body mass gain (CA-7.1, YPHV-7.5 kg/y at 11.9-16.1 years or -1.6 to +4.0 YPHV), followed by gain reductions. Increased rates of sprint performance development (31%-43% gains) occurred at 11.8-15.8 CA or -1.8 to +1.2 YPHV, with gains subsiding thereafter. CMJ, T test, and MSFT gains appeared relatively linear with no change in developmental rate apparent. Developmental tempos did again, however, subside at circa (CMJ and T test) to post-PHV (MSFT). Based on our sample and analysis, periods of increased developmental rates (stature, mass, sprint) were apparent alongside progressive gains for other physical measures, before all subsided at particular age and maturation time points. Findings highlight dynamic asynchronous development of players, physical attributes, and the need to account for the influence of maturation on athletic performance until post-PHV.

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

PURPOSE

This study aimed to improve the prediction accuracy of age at peak height velocity (APHV) from anthropometric assessment using nonlinear models and a maturity ratio rather than a maturity offset.

METHODS

The dataset used to develop the original prediction equations was used to test a new prediction model, utilizing the maturity ratio and a polynomial prediction equation. This model was then applied to a sample of male youth academy soccer players (n = 1330) to validate the new model in youth athletes.

RESULTS

A new equation was developed to estimate APHV more accurately than the original model (new model: Akaike information criterion: -6062.1, R² = 90.82%; original model: Akaike information criterion = 3048.7, R² = 88.88%) within a general population of boys, particularly with relatively high/low APHVs. This study has also highlighted the successful application of the new model to estimate APHV using anthropometric variables in youth athletes, thereby supporting the use of this model in sports talent identification and development.

CONCLUSION

This study argues that this newly developed equation should become standard practice for the estimation of maturity from anthropometric variables in boys from both a general and an athletic population.

South Asian Children Have Increased Body Fat in Comparison to White Children at the Same Body Mass Index

The ability of body mass index (BMI) to predict excess fat in South Asian children is unknown. This cross-sectional study examines the influence of ethnicity on body fatness in children. Weight status and body fat were determined using BMI, waist circumference (WC), two skinfold sites (SF; triceps and subscapula) and leg-to-leg bioelectrical impedance analysis (BIA; Tanita BF350, Tanita, Tokyo, Japan) in 194 children aged 8.47 ± 0.50 years from Coventry, United Kingdom. Biological maturity was also determined. Analysis of covariance (ANCOVA) identified significant differences between ethnic (p < 0.001) and gender groups’ BMI (p = 0.026), with a significant covariate for skinfold (p < 0.001) and bioelectrical impedance (p < 0.001). For a given body fat value, South Asian children and females had a lower BMI value (−1.12 kg/m², p < 0.001 and −0.50 kg/m², p = 0.026, respectively, when adjusted for SF; −1.56 kg/m², p < 0.001 and −0.31 kg/m², p = 0.16, respectively, when adjusted for BIA) compared with white children and boys. The prediction model including ethnicity, gender and BIA explained 80.4% of the variance in BMI. Maturation was not found to be a significant covariate (p > 0.05). To conclude, the findings suggest that BMI cut-points may need to be lowered in South Asian children, and thus age-by-sex-by-ethnicity specific BMI cut-points are needed in children. Further research examining body composition with health parameters in this population is needed.