The maturity related physical phenotypes of English, elite youth soccer players : exploring the elite player performance plan

The aims of this thesis were to examine the relationships between relative age, maturity status, and physical phenotypes on the selection, playing position allocation, and development tempo of a broad sample of elite youth soccer players’ that best represents UK development programs governed by the Elite Player Performance Plan (EPPP).The first research study (Chapter 4) aimed to establish the short-term reliability (STR) and smallest worthwhile changes (SWC) for a battery of field tests commonly used to assess elite youth soccer players’ physical and somatic phenotypes. On two occasions, the within-practitioner STR of three anthropometric measures (stature, seated height and body-mass) were assessed to estimate age at peak height velocity (APHV). In addition, within-player STR of the Multi-Stage Fitness Test (MSFT), 10 and 20 m sprints were assessed using 45 elite youth soccer players (age: 13.5 ± 1.5 years; body-mass: 49.2 ± 10.3 kg; stature: 177.7 ± 6.4 cm). In addition, within-player STR was established for T-Test and counter-movement jump (CMJ) performance using 21 senior amateur soccer players (age: 24 ± 5.3 years; body-mass: 84.3 ± 7.1 kg; stature: 177.7 ± 6.4 cm). The within-practitioner STR (coefficient of variance [CV], (95% confidence interval [CI])) and SWC were established for anthropometric measures (stature: CV = 0.4 % [CI = 0.3 to 0.5 %], SWC = 2.3 cm; seated height: CV = 1.1 % [0.9 to 1.4 %], SWC = 1.1 cm; body-mass: CV = 0.7 % [0.6 to 0.9 %], SWC = 2.3 kg) and APHV (CV = 0.8 % [0.7 to 1.0 %], SWC 0.1 year) respectively. Within-player physical fitness reliability and SWC were also established for CMJ (CV = 5.9 % [4.6 to 9.0 %], SWC = 0.6 cm), T-Test (CV = 1.7 % [1.3 to 2.4 %], SWC = 0.08 s), 10 m sprint (CV = 2.7 % [2.2 to 3.4 %], SWC = 0.03 s) and 20 m sprint (CV = 4.9 % [4.1 to 6.4 %], SWC = 0.06 s) performances. This battery of anthropometric and physical fitness field tests observed a high level STR and produced SWC values that will permit talent development (TD) practitioners to implement SWC % to assess changes in player growth, maturity and physical fitness.Research study 2 (Chapter 5) aimed to quantify the relative-age effect (RAE) and examine differences in physical phenotypes owing to the RAE of 731 (U11 to 18) elite youth soccer players sampled from 17 UK soccer development centres. Chi-squared analysis identified a clear un-even birth distribution across all age groups, demonstrating an over-representation of players born in the first quartile (Q1) (U11 to 12: 39%; U13 to 14: 46%; U15 to 16: 57%; U17 to 18: 42%) in comparison to Q4 (U11 to 12: 13%; U13 to 14: 8%; U15 to 16: 8%; U17 to 18: 14%) of the selection year that significantly differed to the distribution expected from National census data (all ≤ 0.001). Small to moderate differences in player stature and body-mass were identified for U11 to 14 players, whereby players born in Q1 were both heavier (ES = 0.48 to 0.57) and taller (ES = 0.62 to 1.06) than players born in Q4. U11 to U12 and U17 to 18 players born in Q1 were generally (ES = 0.37 to 0.70) more mature than their relatively younger (Q4) counterparts. There were no significant differences in agility (P = 0.108 to 0.643), 10 m (P = 0.122 to 0.886) and 20 m (0.090 to 0.911) sprint times between Q1 and Q4 players. However, relatively younger (Q4) U15 to U16 players showed small to moderate (ES = 0.34 to 0.49) inferiority in MSFT performance that continued for Q2 (Q2 vs. Q4: P = 0.041, ES = 0.91). The obvious birth distribution bias identified within this chapter favours the selection of players who are born earlier in the selection year, who possess enhanced maturity related anthropometric and aerobic performance characteristics.Study 3 (Chapter 6) assessed the contribution of relative age, maturity and physical phenotypes upon soccer playing position allocation (goalkeeper [GK], central-defender [CD], lateral-defender [LD], central-midfield [CM], lateral-midfielder [LM], and forward [FWD]) in 465 elite-youth soccer players (U13 to U18`s). U13 to 14 CD were identified as being relatively older than LD (ES = 0.72). CD and GK were generally taller (U13 to 14: ES = 0.49 to 1.19; U15 to 16: ES = 0.72 to 1.48; U17 to 18: ES = 0.96 to 1.58) and heavier (U13 to 14: ES = 0.64 to 1.40; U15 to 16: ES = 0.24 to 1.57; U17 to 18: ES = 0.51 to 1.32) than other players at each developmental stage and were advanced maturers at U13 to 14 (ES = 0.63 to 1.22). Position specific fitness characteristics were distinguished at U17 to 18, where LD and LM were faster than their central counterparts (10m: ES = 0.72 to 0.83; 20m: ES = 0.94 to 1.07). In summary, relative age, maturity and anthropometric characteristics appear to bias the allocation of players into key defensive roles from an early development stage, whereas position-specific physical attributes do not become apparent until the latter stages (U17 to 18) of talent development in outfield players.Study 4 (Chapter 7) assessed the development tempo of anthropometric and physical fitness characteristics according to players decimal age and maturity offset (YPHV) of 969 (U9 to U18) UK elite youth soccer players using battery of 7 field tests. Segmented regression analysis established that estimated stature increases were highest between 10.7 (CI = 10.2 to 11.2) to 15.2 (CI = 14.8 to 11.2) years, and between -3.2 (-3.5 to -2.9) to 0.8 (0.5 to 1.1) YPHV, with estimated annual growth rates of 7.5 (CI = 7.0 to 7.9) and 8.6 (CI = 8.3 to 9.0) cm·year-1 identified for decimal age and YPHV, respectively. Estimated rate of body-mass developmet was also increased (7.1 [CI = 6.6 to 7.6] kg·year-1) between 11.9 (CI = 11.5 to 12.3) to 16.1 (CI = 15.5 to 16.7) years of age, whereas when modelled against somatic maturity, body-mass increases continued at 7.5 (CI = 7.2 to 7.7) kg·year-1 from -1.6 (CI = -2.1 to -1.1) to ~4.0 YPHV, without plataeu. Estimated CMJ development tempo decreased from 2.5 (CI = 2.2 to 2.8) to 1.3 (CI = 0.7 to 1.9) cm·year-1 circa- PHV (0.6 [-0.4 to 1.6] YPHV). Estimated T-Test performance gains ceased from 15.8 (CI = 15.2 to 16.4) years of age onwards, but when modelled against somatic maturity status, improvements slowed by ~43% at 0.4 (CI = -0.1 to 0.9) YPHV. Players estimated endurance capacity increased by 169 (CI = 158 to 179) and 185 (CI = 173 to 198) m·year-1, until 16.4 (CI = 15.9 to 17.0) years and 2.1 (CI = 1.6 to 2.5) years post PHV, respectively. Estimated 10 and 20m sprint performance increased until 11.8 (CI = 11.2 to 12.5) years of age, or -1.8 (CI = -2.5 to -1.0) YPHV, before development tempo increased (31-43%) until 15.8 (CI = 15.3 to 16.3) years, or 1.2 (CI = 0.1 to 2.3) to 1.3 (CI = 0.8 to 1.8)YPHV. Findings identified that model strength for stature and body-mass was slightly higher in YPHV (r2 = 0.89) versus decimal age (r2 = 0.81). However these trends were not apparent for the development of physical fitness attributes. In addition, Chapter 7 revealed that players estimated sprint performance development markedly increased (31 to 43%) between 11.8 years and 15.8 years, or 1.2 to 1.3 YPHV. This data will provide practitioners with a guide to help forecast players’ rate of anthropometric and physical fitness characteristics development at an early stage of their development. Findings here’s suggest that TD practitioners should systematically use estimates of maturity offset to reduce the premature deselection of equally talented but slower players who may reach the same sprint capacity in adulthood, but are slightly later maturers versus there team-mates.In summary, the standardised battery of field-tests used within this thesis observed high levels of STR. There was a clear birth distribution bias that favours the selection of players’ for UK elite soccer development centres, who are born earlier in the selection year. It is likely that transient anthropometric advantages afforded to relatively older players within younger age categories act as a major contributory factor that bias the premature selection and role allocation of these players in to key defensive (GK and CD) roles, before the development of position-specific physical attributes become apparent during the latter stages (U17 to 18) of the EPPP in outfield players. Likely to be of particular importance to TD practitioners, players’ estimated sprint performance development increased across decimal ages (11.8 to 15.8 years) spanning PHV (-1.8 to 1.3 YPHV), justifying research to further examine the intricacies between training prescription and maturity on sprint speed development.Monitoring player maturity will enable a better understanding of maturity related anthropometric and performance gains, and is likely to improve sensitivity of training prescription and physical phenotype development forecasting. Emphasising the necessity for systematic and consistent monitoring of player growth and maturity that will likely inform talent identification and development processes, and reduce the biases associated with relative age and anthropometric advantages upon talent selection and positional role allocation

Mechanisms of Luteinising Hormone Regulation in Female Steroidogenesis

Abstract Understanding the mechanisms of steroidogenic regulation in female fertility is fundamental to determining dysfunction. Research has revealed a strong relationship between fertility and metabolic disturbances. With many endocrine signals involved in activation of steroidogenic cascades, it has become necessary to map the complex cross-talk between these regulatory systems and this review looks to establish this based on current understanding. Luteininsing hormone is a vital endocrine hormone that is already known to signal via these pathways, although its involvement in metabolic disturbance is less understood. Studies investigating activation of the LH receptor in key steroidogenic cells, ovarian theca and granulosa, have highlighted overlaps in important signaling cascades including PKC/MAPK/PKA and PI3K. Here, we review LH and its signaling cross-talk in key steroidogenic pathways

A survey on the English FA heading guidelines for youth soccer: Evidence of compliance, but with limited knowledge of safety

Soccer heading may be problematic for neurocognitive function. The English Football Association (FA) recently introduced guidelines in order to limit the number of headers within training for youth soccer. However, it remains to be seen what the influence of these guidelines has been on the leaders of soccer teams that are primarily responsible for implementing the guidelines. Thus, we aimed to explore grassroot youth coaches’ knowledge of, views on, and adherence to the heading guidelines. An online survey was distributed to team representatives across Local County FAs. The survey comprised of three sections: (1) background information, (2) heading practices including details on heading activities and views on heading safety, and (3) heading guidelines including levels of awareness, knowledge, and compliance. 240 coaches responded by stating they rarely (21%) or never (73%) practiced heading, although they mostly perceived heading as being somewhat safe (36%). While respondents indicated being only somewhat aware of the guidelines (43%), they scored very high on their perceived (92%) and actual (based on retrospective accounts of heading) (87%) compliance with the guidelines. There was a mixed perceived change within practice following the introduction of the guidelines (disagree = 26% vs. agree = 22%), and they were perceived as safe (86%) and appropriate (81%). Factors that were identified as being potential barriers were only marginally agreed upon (<30%) and tended to be related to in-game rules. While there is scope to successfully implement heading guidelines, there is some discrepancy between the requirements for heading safety and coaches’ knowledge

Effectiveness of short-term heat acclimation on intermittent exercise in thermoneutral and hot environments

It is well-established that repetition of heat stress exposure has been shown to facilitate adaptations to the heat but these protocols have tended to be of a fixed work intensity, continuous exercise, long-term in duration (>7 days) and use hydration. Secondly, there is limited information on the potential use of heat acclimation as a training method for human performance in thermoneutral conditions. Therefore, the aims of this study were to investigate the effectiveness of short-term heat acclimation (STHA) for 5 days, using the controlled hyperthermia technique with dehydration, on intermittent exercise in thermoneutral and hot environments

Practitioners’ multi-disciplinary perspectives of soccer talent according to phase of development and playing position

The study aimed to establish the perceived importance that academy soccer practitioners placed on technical/tactical, physical, psycho-social player attributes during player selection and explore whether perceptions change according to Elite Player Performance Plan phase. Seventy academy practitioners working within Elite Player Performance Plan programs (Category 1: n = 29; Category 2: n = 13 and Category 3: n = 28) completed an online survey. Psychological factors were rated significantly (p ≤ 0.01) higher than sociological, technical/tactical, and physical factors, with recruitment staff specifically valuing psychological factors significantly (p ≤ 0.01) more than medical staff. Youth Development phase practitioners valued sociological factors significantly (p < 0.05) more than in the Foundation phase, which was also true for physical factors. Practitioners indicated significant positional differences for most physical and technical/tactical attributes. There was no playing position effect for relative age effect or maturity. Between playing position variance of outfield players for most technical and physical attributes increased according to advancing Elite Player Performance Plan phase. Attitudes to holistic talent identification criteria likely change according to practitioner role. Therefore, this study provides evidence to suggest that Elite Player Performance Plan practitioners place less perceived importance on enhanced maturity status and relative age of players but does indicate an enhancing and significant positional preference for physical and technical/tactical attributes. Suggesting that practitioners are less likely to (de)select players based on transient, maturity-related attributes and instead place greater emphasis on specialist physical/technical position-specific attributes as players navigate the Elite Player Performance Plan pathway towards professional status

Quantifying high-speed running in rugby league: An insight into practitioner applications and perceptions

High-speed running has previously been documented as a popular metric among rugby league researchers. Researchers place importance on high-speed running due to its inclusion in assessing the demands of training and match-play to help prescribe accurate training loads and recovery methods. However, there is currently no information available as to how important rugby league practitioners perceive high-speed running to be and what methods are currently used by practitioners to quantify high-speed running. Furthermore, practitioners’ perceptions of specific benefits, barriers and motivations when selecting high-speed running methods are also currently limited. Therefore, the aim of this study was to provide a current insight into the practice and perceptions of rugby league practitioners when quantifying high-speed running. This study surveyed practitioners working in the European Super League (n = 12) and the Australasian National Rugby League (n = 11). Ranking analysis established high-speed running to be the most important metric for both training practice and match-play. Absolute high-speed running thresholds were applied by 52% of respondents (n = 12) with the most common being 5.5 m·s−1 (n = 9). Individualised high-speed running thresholds were applied by 48% of respondents (n = 11) with the most common approach implementing peak sprint speed methods (n = 9). Absolute high-speed running thresholds are perceived to permit better group data comparison, whereas individualised methods are perceived to permit better interpretation of high-speed running data. Ultimately, practitioners are motivated to implement their chosen methods with the possibility of more accurately prescribed high-speed running thresholds, although the impracticality of specific testing procedures may act as a barrier

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

Talent identification in soccer: The influence of technical, physical and maturity-related characteristics on a national selection process

The present study examines the influence of technical, physical, and relative age characteristics on players selection success within the Scottish Performance School trials. Ninety adolescent players (81 males, 9 females; mean ± standard deviation: age = 11.3 ± 0.4 years, height = 149.6 ± 6.9 cm, mass 38.1 ± 4.7 kg) performed a battery of physical fitness (20m Sprint, CMJ, 5-0-5 agility test), anthropometric, and 8 small-sided games (SSG; 9v9) as part of a talent identification (TID) programme. Players technical (ball touches, time on the ball, high-speed releases) and locomotor activities (high-speed running distance, sprint distance, accelerations, and decelerations) were monitored using foot-mounted inertial measurements units during SSG’s. The data was analysed using independent sample T-tests. Mann-Whitney U analyses were conducted to examine the differences between groups whose data was determined as being (non)parametric, with Cohen effect sizes applied. Successful players performed significantly better during physical tests (Effect size ± confidence limits: Left 5-0-5 = -0.89±0.13, Right 5-0-5 = -0.51±0.11), had significantly higher locomotor activities during SSG (high-intensity distance = 0.4±26.6, horizontal accelerations = 0.59±1.19) and significantly higher technical outputs during SSG (touches = 0.71±6.1, releases = 0.49±2.5, high-speed releases = 0.59±2.7, time on the ball = 0.52±3.4) compared to unsuccessful players. Successful players had significantly higher locomotor activities and technical outputs during SSG than their unsuccessful counterparts. Monitoring technical and locomotor activities during SSG may compliment or replace physical testing batteries for assessing TID processes in soccer

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 coaches perceived influence of maturation on practice, perceptions of bio-banding, their application of bio-banding and their perceived barriers to bio-banding implementation. 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-structure interview and the interview schedule was informed by common themes within the survey data. Frequency and percentages of responses for individual items were calculated. Interview data was transcribed and were analysed using a directed approach to content analysis with combination of inductive and deductive approaches being used to identify meaning units which were subsequently grouped together to form emergent categories (lower-order themes) based on their similarity to each other and distinction from other categories. The main findings 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, and provides psycho-social benefits. For the implementation of bio-banding to succeed, a collaborative approach to its implementation should be taken to permit the successful embedment of bio-banding within the typical training schedules across the adolescent phase of the player development pathway