Bio-banding in male under-15 and -16 ice hockey teams: A pilot study on players’ and coaches’ experiences

Maturity-related developmental inequalities in age-group swimming: The testing of ‘Mat-CAPs’ for their removal

This study explored academy football coaches’ perceptions and experiences of managing individual differences in the maturity timing of male adolescent football players in an English Premier League academy. Using a longitudinal mixed method design, 98 under 12–16 players were assessed for maturity status, growth velocities, and match performance grade. Interviews with nine respective coaches were conducted in parallel. The qualitative and quantitative data were combined to generate a contextualised richer understanding and four archetypal case studies. Findings showed coaches perceive various advantages and disadvantages to players maturing either ahead or in the delay of their peers and had different expectations of performance based upon a players maturity status; biological maturity status and timing had large implications for selection and release decisions. This study highlights the challenges of developing, managing and selecting adolescent players in elite male youth football. Biological maturation confounds talent identification and development, and academy environments need to monitor maturity status and educate coaches and selectors on the complexities and intricacies of individual differences in maturity timing.

Injuries have a negative impact on the development of football players. Maturation is a potential risk factor for football injuries but available data on this topic provide limited evidence due to methodological shortcomings. The aim of this study was to describe the injury burden of male academy football players according to growth curve-derived maturity status and timing. Injury and growth data were collected from 2000 to 2020. Longitudinal height records for 110 individual players were fitted with the Super-Imposition by Translation and Rotation model to estimate age at peak height velocity (PHV). Players were clustered according to maturity status (pre-, circa-, post-PHV, or adults) and timing (early, on-time, late maturers). Overall and specific injury burdens (days lost/player-season) and rate ratios for comparisons between groups were calculated. Overall injury burden increased with advanced maturity status; pre-PHV players had 3.2-, 3.7-, and 5.5-times lower burden compared with circa-PHV, post-PHV, and adult players, respectively. Growth-related injuries were more burdensome circa-PHV, while muscle and joint/ligament injuries had a higher impact post-PHV and in adults. Further, in the pre-PHV period, late maturers showed lower burden of overall, growth-related, anterior inferior iliac spine osteochondrosis, and knee joint/ligament injuries compared with on-time maturers. In adult players, however, injuries were less burdensome for early maturers than on-time and late maturers. In addition, joint/ligament injuries of adult late maturers were 4.5-times more burdensome than those of early maturers. Therefore, monitoring maturity seems crucial to define each player’s maturation profile and facilitate design of targeted injury prevention programmes. Highlights Injury burden is significantly lower in football players at pre-peak height velocity (PHV). Growth-related injuries are most burdensome circa-PHV, while muscle and joint/ligament injuries are more burdensome post-PHV and especially in adults. Before PHV, growth-related and knee joint/ligament injuries have lower burden in players who mature late than those who mature on-time. Adult late maturers have greater burden of overall and joint/ligament injuries than early maturers. Football academies should regularly assess the maturity status and timing of young football players, as the impact of injuries varies with maturation status and timing. Management of the maturity-related injury risk profile, in combination with other relevant factors (training load, neuromuscular and biomechanical factors, physiotherapy, coaching, communication, psychosocial factors …), might help improve the success of player development programmes and protect the health of young football players.

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

The purpose of this study was to examine the effects of detraining on fitness performance in 7-year-old children after 8 weeks of muscular fitness training, which took place during the first 15 minutes of regularly scheduled physical education (PE) class. Children from 2 PE classes were cluster randomized into either an exercise group (n = 20) or a standard PE control group (n = 19). Performance on the long jump, single-leg hop, curl-up, and balance test was assessed at baseline, after training, and after an 8-week detraining period. A significant interaction of group by time after training was observed in the exercise group with improvements noted in abdominal curl-up and single-leg hop performance (p < 0.05). After detraining, the exercise group maintained training-induced gains on the curl-up (group mean [95% confidence interval] posttraining of 27.9 [21.2-34.5] to detraining 27.3 [21.1-33.6] repetitions; p < 0.05) and single-leg hop (posttraining 79.8 [73.2-86.4] to detraining 79.7 [73.0-86.5] cm; p < 0.05). Conversely, long jump (posttraining 113.8 [108.2-119.5] to detraining 110 [102.6-117.5] cm; p < 0.05) regressed toward baseline values in both groups. After detraining, balance performance (1.5 [1.3-1.7] seconds) regressed relative to baseline (2.0 [1.7-2.4] seconds) and posttraining (2.0 [1.8-2.4] seconds; p < 0.05). These findings indicate that the phenomenon of detraining in children is complex and characterized by different adaptations and regressions in strength, power, and balance. Regular participation in fitness activities during PE may be needed to enhance and maintain performance in all measures of muscular fitness in 7-year-old children.

The aims of this study were 1) to analyze the influence of chronological age, relative age, and biological maturation on accumulated training load and perceived exertion in young sub-elite football players and 2) to understand the interaction effects amongst age grouping, maturation status, and birth quartiles on accumulated training load and perceived exertion in this target population. A 6-week period (18 training sessions and 324 observation cases) concerning 60 young male sub-elite football players grouped into relative age (Q1 to Q4), age group (U15, U17, and U19), and maturation status (Pre-peak height velocity (PHV), Mid-PHV, and Post-PHV) was established. External training load data were collected using 18 Hz global positioning system technology (GPS), heart-rate measures by a 1 Hz short-range telemetry system, and perceived exertion with total quality recovery (TQR) and rating of perceived exertion (RPE). U17 players and U15 players were 2.35 (95% CI: 1.25–4.51) and 1.60 (95% CI: 0.19–4.33) times more likely to pertain to Q1 and Q3, respectively. A negative magnitude for odds ratio was found in all four quartile comparisons within maturation status (95% CI: 6.72–0.64), except for Mid-PHV on Q2 (95% CI: 0.19–4.33). Between- and within-subject analysis reported significant differences in all variables on age group comparison measures (F = 0.439 to 26.636, p = 0.000 to 0.019, η2 = 0.003–0.037), except for dynamic stress load (DSL). Between-subject analysis on maturity status comparison demonstrated significant differences for all training load measures (F = 6.593 to 14.424, p = 0.000 to 0.037, η2 = 0.020–0.092). Interaction effects were found for age group x maturity band x relative age (Λ Pillai’s = 0.391, Λ Wilk’s = 0.609, F = 11.385, p = 0.000, η2 = 0.391) and maturity band x relative age (Λ Pillai’s = 0.252, Λ Wilk’s = 0.769, F = 0.955, p = 0.004, η2 = 0.112). Current research has confirmed the effects of chronological age, relative age, and biological maturation on accumulated training load. Perceived exertion does not seem to show any differences concerning age group or maturity status. Evidence should be helpful for professionals to optimize the training process and young football players’ performance.

Reducing injuries to youth players is of primary importance to academies, as injuries can result in a significant loss in both training and match time, as well as, negatively affecting player development. In total, 76 talented young football players were analysed over two full competitive seasons. The injury incidence and burden for all non-contact and overuse injuries were recorded. Exposure was calculated as the total number of competitive matches hours played. Somatic maturation was estimated by expressing the current height of each player as a percentage of their predicted adult height [Roche, A. F., Tyleshevski, F., & Rogers, E. (1983). Non-invasive measurements of physical maturity in children. Research Quarterly for Exercise and Sport, 54(4), 364–371.]. The period of circa-peak height velocity (PHV) (24.5 injuries per 1000 h) was associated with a significantly higher injury incidence rate and burden compared to pre-PHV (11.5 injuries per 1000 h; RR:2.15, 95%CI:1.37–3.38, P < .001). No significant differences in injury risk between maturity timing groups were observed. The interaction effect between maturity status and maturity timing confirmed there is a risk period circa-PHV, but this was not dependent on maturity timing. The main practical application of this study is that football academies should regularly assess the maturity status of young footballers to identify those players with increased susceptibility to injury. Moreover, academies should individualise training and injury prevention strategies based on maturation.

ABSTRACTThis 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.

Large interindividual differences can exist in the timing and tempo of growth and maturation of youth athletes. This can provide significant physical performance advantages to young athletes who mature in advance of their peers. The aim of this systematic review was to determine the magnitude of differences in sprinting and jumping performance in youth of different maturity status (classified as pre-, circa- or post-peak height velocity [PHV]) (aged < 18years) to enhance the evaluation of performance. Eligibility criteria for inclusion were as follows: (1) the study had cross-sectional data available; (2) participants were male and/or female ≤ 18years of age; (3) a somatic measure of maturity was used to identify maturity status (e.g. Mirwald or Khamis-Roche methods) with at least two maturity status classifications present; (4) the study included a measurement of sprinting speed (e.g. 10-100-m sprint data) and/or jump tests commonly used to assess power (e.g. countermovement jump [CMJ]). Searches were conducted up to November 2024 in PubMed, Embase, SPORTDiscus and preprint servers SportRxiv and medRxiv to identify any unpublished trials. Risk of bias and study quality was assessed using the Appraisal tool for Cross-Sectional Studies (AXIS). Meta-analysis was computed using a random-effects model. The search identified 1578 studies. From those, 40 studies were identified for qualitative assessment and quantitative synthesis. In the primary analysis, 21 studies provided data for measures of speed, and 19 studies provided data for measures of power using jump tests. Sprinting and jumping performance increased with advancing maturity status and overall effect sizes were predominantly moderate to large between maturity groups. Pre-PHV versus post-PHV comparisons found moderate to large overall effect sizes (ES) for sprinting performance (10-m ES 1.34 [95% CI 0.87-1.80]; 20-m ES 1.40 [95% CI 0.85-1.96]; and 30-m ES 0.93 [95% CI 0.15-1.76] sprint times) and large to very large ES for the jump tests (CMJ ES 1.53 [95% CI 1.14-1.92]; squat jump ES 1.32 [95% CI 0.70-1.94]; and standing long jump ES 2.18 [95% CI 1.32-3.04]). When comparing consecutive maturity groups (i.e. pre- to circa-PHV and circa- to post-PHV), ES were predominantly moderate across the sprinting and jumping measures, with only a trivial difference found in 30-m sprint time (ES 0.45 [95% CI 0.21-0.69]) for the circa- to post-PHV comparisons. Large differences exist in sprinting and jumping performance between the least and most mature male athletes (pre- and post-PHV), with trivial to moderate ES indicated between consecutive groups (e.g. pre- and circa-PHV). Practitioners working with youth athletes should consider how these differences may impact performance in the athlete's sport, and regularly assess individual maturity to accurately evaluate performance against age and maturity group benchmarks to account for large differences in maturity that exist within chronological age groups. It should be noted we observed inconsistencies in maturity thresholds and test methods; thus, standardization is required for future research.

The purpose of this study was to measure health-related fitness of children based on different implementation levels of the physical education program. Another was to determine the effect of anthropometric and social factors on students’ health-related fitness. A total of 918 students’ age 13, 14, and 16 years old were selected from three different implementation levels program. The total score of the checklist questions was used as criteria in classifying implementation levels in Selangor schools. Heights and weights were measured, from which the BMI was calculated. Data concerning students’ family income were collected from school files. Data on student involvement in a variety of PA during and outside of school hours were gathered from information given by students (SKAF questionnaire). Tanner, self-reported assessment was used to estimate students’ stage of maturation. Length was considered as indicator of adolescent growth. While, students’ health-fitness was measured by a battery of health fitness tests. Effectiveness of these factors on students’ health-related fitness was determined by comparing the pre-post-health-fitness tests scores of students. Results indicated that children in the high-implementation-level have better-health fitness performance on both pre-test and post-test measurements than children in the low-implementation level. However, health- fitness performances that reflect significant differences were different among age groups. The older age groups generally performed better on overall fitness tests than did the younger age groups. Several covariates had strong relationships with pre and post-test fitness scores for different age groups such as; height, weight, BMI, maturity status, time spent in PA, race, and family income. Variations of health-related fitness performance between students involved in this study are most likely contributing to the different implementation levels. Thus, a well-programmed and supervised PE program can develop the health status of students at all levels of education

Introduction: Reaction time is important in various situations, as it influences quick decision-making and the performance of daily activities. Objective: To correlate upper limb reaction time [TRES (expressed in hits and execution time)] with chronological age and maturity in young non-athletes. FITLIGHT® technology and system were used for this purpose. Methods: A correlational study was conducted on 73 young people aged 12 to 20 (40 males and 33 females). The sample selection was non-probabilistic. Weight and height were assessed. Body mass index (BMI) was calculated. Maturity status was determined using a regression equation that takes into account sex, chronological age, and height. The FITLIGHT® system was used for assessment (number of hits and 10 repetitions with both hands in seconds). Results: Chronological age showed low positive correlations with the number of hits in both sexes (men r=0.13 and women r=0.29). By maturity status, the correlations increased significantly in both sexes (males r=0.16 and females r=0.36). The correlations between maturity status and number of correct answers were negative and low (r = -0.11 in males and -0.25 in females), and between maturity status and time taken for 10 repetitions were low to moderate in both sexes (in males r = -0.13 and in females r = -0.28). Conclusion: TRES in adolescents and young adults showed a stronger association with maturity than with chronological age. In addition, a similar number of correct responses was observed in both sexes, but males were faster, suggesting that maturity influences motor efficiency, especially in females.

Experiments were carried out to evaluate the effect of incubation time on nuclear maturation (Experiment 1) and determine the cleavage rate of alpaca oocytes after of IVF time (Experiment 2) In Experiment 1, CCOs were collected from slaughterhouse ovaries and transported to the laboratory in a thermos flask containing a saline solution 0.9% with antibiotic antimycotic at 35°C. CCOs were aspirated from follicles &gt;2 mm and pooled in a conical tube to sedimentation previous to evaluation under stereomicroscope and CCOs with a cytoplasm homogeneous and 2 or more layers of cumulus cells were transferred to plates with a 40-μL drop of maturation medium TCM-199 supplemented with 10% FCS (v : v) plus 0.5 μg mL-1 FSH, 10 μg mL-1 hCG, 0.2 mM sodium pyruvate, 50 μg mL-1 gentamicine, and 1 μg mL-1 Estradiol under mineral oil with 10-12 oocytes/drop. Oocytes were incubated under the following maturation times: 30, 34, and 38 h at 39°C in an atmosphere of 5% CO2 and high humidity. After each maturation time, CCOs were removed from maturation medium and washed with PBS supplemented with 10% FCS and 1 mgmL-1 of hyaluronidase and fixed in ethanol: acetic acid (3 : 1). Oocytes were placed on the slide with minimum medium and stained with 1% orcein for 5 min The slides were examined under a phase contrast microscope at × 400 to evaluate status of nuclear maturation and classified as germinal vesicle (GV); metaphase I (M-I), anaphase-telophase; metaphase II (M-II) and degenerated. Experiment 2: The same maturation method as Experiment 1 was used. Testes were collected of mature males from slaughterhouse and transported to the laboratory. Caudal epididymide was isolated. A prick was made on the convoluted tubules with a sterile hypodermic needle and the fluid, rich in spermatozoa, was aspirated in syringes containing 2 mL of Tris-fructose egg yolk extender. Motile spermatozoa were obtained by centrifugation: 700 g on a Percoll discontinuous gradient (22.5 :45.0%) for 25 min. The supernatant was removed by aspiration and pellet (containing viable spermatozoa) was resuspended in TL stock. Spermatozoa and oocytes were co-incubated for 18-20 h at 39°C with 5% CO2 and then cultivated in TCM-199 supplemented with 10% FCS (v: v), 0.2 mM sodium pyruvate, and 50 μg mL-1 gentamicine and evaluated at 48 h. Data were subjected to ANOVA. For Experiment 1, the proportions of oocytes reaching M-II stage was 18.9 ± 15.7, 42.9 ± 16.2, and 65.8 ± 8.1% for the 30, 34, and 38 h of culture, respectively, with difference to maturation time (P &lt; 0.05). For Experiment 2, the cleavage rate was 9.5, 7.7, and 15.4% to 30, 34, and 38 h after of fertilization time 48 h culture. These results indicate that 38 or more h is required for the maturation and fertilization of alpaca oocytes. Grant 064 FINCyT-PIBAP 2008.

1. With 3-year-old fruiting Delaware grapes, the effect of night temperature during the ripening process on the maturity and quality of berries was observed. Plants grown in pots were kept in the respective controlled temperature chambers of 15°, 22°, 28° and 35°C at night (6p.m. to 8a.m.), and placed outdoors in the daytime from August 6 to Sept. 10 in 1962.2. The time of maturity when the berries got full varietal specific color was as follows; August 27 at 28°C, Sept. 3 at 22°C, and Sept. 10 at 15°C, and berries never colored well at 35°C. The pigment content of the skin on Sept. 10 was in the order of 28°≥22°>15°>35°C.3. The soluble solids content of the juice(refractometer method) increased as the berries matured. The order of the content among the different temperature treatments was 28°>22°>15°>35°C on August 27, 28°=22°>15°>35°C on Sept. 3, and 22°>15° >28°>35°C on Sept. 10. The main kinds of sugars (paper chromatographic method) were glucose and fructose. They were of nearly equal amount at the time of maturity, though glucose was surpassed by fructose with a further advance of maturity.4. The free organic acid content of the juice (titration method) decreased rapidly with the progress of maturity, the trend being more marked in the treatments of the higher temperature. However, the content became nearly the same in all the treatments when the berries overripened. The main kinds of the free organic acids were tartaric acid and malic acid. The malic acid content decreased more rapidly than the tartaric acid with an advanced maturity and with an increased temperature of treatment.5. Fully matured berries of Delaware grapes sent from the chief producing districts of Japan were compared concerning their quality in relation to the average air temperature of nearly one month before harvest. As a result, the lower the temperature within a range of 22° and 28°C, the more delayed the maturity, while the more increased the pigment content of the skin, and the more abundant both the soluble solids and the free organic acids in the juice. Furthermore, berries produced in the region of the lower temperature such as Nagano contained less glucose than fructose, and berries which matured in Kagawa under the highest temperature had the least malic acid.

Player performance in an intense sport such as basketball is known to be related to attributes such as speed, agility, and power. This study presents a comparative analysis of associations between anthropometric assessment and physical performance in different age groups of elite youth basketball players, while simultaneously identifying the predictors for speed and agility in these players. U14 (n = 44), U15 (n = 45), and U16 (n = 51) players were tested for anthropometry, lower-body power, speed, and agility. U16 players were found to be taller, heavier, more muscular than U14 and U15 players. In addition, the U16 group showed better performance in all performance tests. Age had a significant positive correlation with countermovement (CMJ) and drop jump (DJ) performance in U14 players, and a significant negative correlation with 15m and 20m sprint times in the U15 group. CMJ and DJ emerged as the most significant predictors for sprint and agility variables, respectively. Body fat percentage was found to be a significant predictor for the speed and agility tests in all age groups, but a negative lower-body power predictor. Therefore, besides all sport-specific and fitness tests, it is essential to place emphasis on the percentage of body fat when designing players’ individualized training programs, and during team selection.

To investigate the effect of adjusting for differences in timing of maturation when assessing overweight prevalence among adolescents in different populations by using an international reference recommended by the WHO. Cross-sectional, comparative study in three large samples from China, Russia and the United States. A total of 2014 American, 1316 Chinese and 744 Russian non-pregnant adolescent girls aged 10-18 y. Data on body weight, height, menarcheal status and age at menarche (AAM) were collected. Overweight was defined as age-sex-specific body mass index (BMI) greater than the 85th percentiles from the US NHANES I data (collected in 1971-1974), which is recommended by the WHO for international use. Maturity adjustments were made using population differences in median age at menarche (MAM), calculated using the status quo method. MAM was 12.8 in the WHO reference population, 13.7 in China, 13.2 in Russia, and 12.6 in the US (NHANES III data). Maturation age-matched BMI cut-offs were used to compute the adjusted prevalence. We also compared population-adjusted results with individually adjusted results in post-menarcheal American girls (based on each girl's AAM) and in pre-menarcheal girls (based on breast stage). Maturity adjustment increased the estimated prevalence of overweight in China and Russia where girls mature later than the reference population, and decreased it in the NHANES III sample. The unadjusted and adjusted prevalence was 3.5 vs 4.9% in the China sample, 8.3 vs 9.7% in Russia, and 29.2 vs 28.0% in the US. The adjustment had a greater effect in younger adolescent girls (10-13 y) than in older girls (14-18 y). In general, we found a good agreement between the population and individual adjustments. Viewing the individual adjustment as a 'gold standard', the population method has a high sensitivity and specificity. This is the first study to assess WHO recommendations for maturation adjustment when estimating overweight prevalence in different countries. While the overall effects of adjustment are small, maturation status should be considered, particularly when assessing young adolescents, and populations with markedly different timing of maturation relative to the international reference. Population-based adjustment is useful and practical in situations where individual maturity data are not available.