Latest research in football - week 50 - 2020

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Regulatory Fit: Impact on Anxiety, Arousal, and Performance in College-Level Soccer Players
Reference:  Int J Exerc Sci. 2020 Sep 1;13(5):1430-1447. eCollection 2020.
Authors: Brianna N Leitzelar, Lindsey C Blom, Justin Guilkey, Jocelyn Bolin, Anthony Mahon
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Summary: Sport performance may be facilitated using regulatory fit, which is a match between individuals' situational strategy and their chronic self-regulatory strategy. However, researchers have not examined the impact of regulatory fit on psychological and physiological components of sport performance, such as anxiety and arousal. Therefore, the purpose of this study was to evaluate the psychophysiological reactions to regulatory fit by examining anxiety, arousal, and sport performance. Female college-level soccer players (n = 25) were randomly assigned to the regulatory match or regulatory mismatch conditions and completed anxiety (Competitive Sport Anxiety Inventory-2R, CSAI-2R) and underwent arousal (heart rate variability, HRV; pre-ejection period, PEP) measures pre- and post-regulatory focus manipulation. Subsequently, participants completed a sport performance task (10 penalty kicks). The impact of regulatory fit on the dependent variables was explored through repeated measures ANOVAs. Results revealed a significant time effect for cognitive anxiety and self-confidence subscales of the CSAI-2R, suggesting the penalty kicking task increased cognitive anxiety and reduced self-confidence in all participants. In addition, there was a significant interaction effect of condition on pre-ejection period (PEP), with a greater increase in PEP for those experiencing regulatory fit compared to those who were not. There were non-significant interaction and main effects for all other variables. Since PEP is an inverse measure of sympathetic (SNS) modulation, experiencing regulatory fit may reduce SNS involvement in the heartbeat. Thus, the current results indicate experiencing regulatory fit may influence arousal prior to athletic competition.

#2 Video analysis of concussion mechanisms and immediate management in French men's professional football (soccer) from 2015 to 2019
Reference: Scand J Med Sci Sports. 2020 Oct 10. doi: 10.1111/sms.13852. Online ahead of print.
Authors: Hélène Cassoudesalle, Bertrand Laborde, Emmanuel Orhant, Patrick Dehail
Summary: In this study, the concussion mechanisms were analysed in male professional competition football, with the main objective to specify the frequency of head-to-head impact, and immediate management of the concussed players was described in order to check its compliance with the recommendations of football's governing bodies. Based on continuously recorded data from the French Football Federation (FFF), a retrospective database of all reported concussions during matches in the 1st and 2nd French Male leagues was generated comprising seasons 2015/16-2018/19. Injury mechanisms, playing action, immediate medical assessment and management of concussed players, foul play-referee's decision were analysed from video recordings. In total, 41 concussions were reported (incidence rate of 0.44/1000 hours of match exposure [95% CI: 0.40 to 0.49]) of which 36 were identified and analysed on video sequences. The commonest playing action leading to concussion was aerial challenge (61%) and the main mechanism was head-to-head impact (47%). Following the head impact, 28% of concussed players were not medically assessed on-pitch and 53% returned to play the same match. Head-to-head impact was not associated with systematic medical assessment, nor with foul play. In conclusion, the main cause of concussions involved head-to-head impact occurring when two players challenge for heading the ball in the air. The detection of potential concussive head impacts and the immediate management of players possibly concussed during matches remain insufficient according to the international recommendations. Some rules changes, with particular vigilance in case of head-to-head impact, should be discussed.

#3 Behind the mask: demedicalising race and mental health in professional football
Reference: Lancet Psychiatry. 2020 Oct 9;S2215-0366(20)30418-1. doi: 10.1016/S2215-0366(20)30418-1. Online ahead of print.
Authors: Michael Bennett
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#4 Evaluation of a Reactive Agility Assessment Device in Youth Football Players
Reference: J Strength Cond Res. 2020 Oct 9. doi: 10.1519/JSC.0000000000003867. Online ahead of print.
Authors: Jay R Hoffman
Summary: The purpose of this study was to examine the reliability and validity of the Blazepod reactive agility device on sport-specific movements in competitive youth football players. Thirty-one male athletes (16.7 ± 1.5 years; 179.4 ± 7.0 cm; 75.0 ± 21.0 kg), all members of a youth tackle football team, volunteered to participate in this study. Subjects performed 3 reactive agility drills (side shuffle reactive agility, 1-m reactive agility, and 3-m reactive agility) at least 72 hours apart. In addition, all subjects also performed 3 traditional agility exercises: proagility, T drill, and L drill. These sessions were part of the offseason conditioning program for the football team that involved sport-specific drills. All assessments occurred following a warm-up and conducted in the same order on each occasion. To assess the validity of the reactive agility drills, the head coach was asked to rank the football playing and agility ability of the players participating in the study. The intraclass correlation coefficient values indicated that all 3 reactive agility drills displayed excellent reliability (r's ranging from 0.833 to 0.884). The measurement error was smaller than the individual variability, indicating that measurement error had a very limited effect on the results. Subjective rankings for agility significantly correlated with each of the agility and reactive agility measurements. Results of this study indicate that the Blazepod reactive agility device is a reliable measure of reactive agility performance and are consistent with the coach's perception of the athlete's agility performance, thus demonstrating construct validity.

#5 Explicit and implicit activation of gender stereotypes additively impair soccer performance and learning in women
Reference: Eur J Sport Sci. 2020 Oct 13;1-21. doi: 10.1080/17461391.2020.1833087. Online ahead of print.
Authors: Priscila Lopes Cardozo, Leon Flôres Cibeira, Luiz Carlos Rigo, Suzete Chiviacowsky
Summary: Studies involving the manipulation of instructions regarding the negative characteristics of a group or comparisons with members of another group (explicit activation of stereotypes) have shown that age, weight, and gender stereotypes can be harmful to motor performance and learning. To date, however, no study has observed whether implicit stereotype threats, such as the sex of the coach or experimenter, can also influence the acquisition of motor skills. In the present study, the individual and combined impact of implicit and explicit influences of gender stereotype on women's soccer performance and learning was examined. In a 2 × 2 design, 60 women were divided into four groups according to the presence or absence of explicit (ES) and implicit (IS) stereotypes: ES/IS, ES, IS, and control. The groups with implicit activation practiced in the presence of a male experimenter. The groups with explicit activation received instructions activating the gender negative stereotype. The control group practiced without stereotype activations. The results showed that both explicit and implicit activation additively impaired soccer performance and learning, with both main effects being significant for practice and retention. The ES/IS group showed lower scores on the task relative to the other groups, while the ES and IS groups showed worse scores compared with the control group. The findings suggest that stigmatized populations may be forced to cope with more than one social identity threat while learning sport motor skills and indicate the importance of further studies testing strategies to minimize the deleterious effects of negative stereotypes.

#6 PassVizor: Toward Better Understanding of the Dynamics of Soccer Passes
References: IEEE Trans Vis Comput Graph. 2020 Oct 13;PP. doi: 10.1109/TVCG.2020.3030359.
Authors: Xiao Xie, Jiachen Wang, Hongye Liang, Dazhen Deng, Shoubin Cheng, Hui Zhang, Wei Chen, Yingcai Wu
Summary: In soccer, passing is the most frequent interaction between players and plays a significant role in creating scoring chances. Experts are interested in analyzing players' passing behavior to learn passing tactics, i.e., how players build up an attack with passing. Various approaches have been proposed to facilitate the analysis of passing tactics. However, the dynamic changes of a team's employed tactics over a match have not been comprehensively investigated. To address the problem, we closely collaborate with domain experts and characterize requirements to analyze the dynamic changes of a team's passing tactics. To characterize the passing tactic employed for each attack, we propose a topic-based approach that provides a high-level abstraction of complex passing behaviors. Based on the model, we propose a glyph-based design to reveal the multi-variate information of passing tactics within different phases of attacks, including player identity, spatial context, and formation. We further design and develop PassVizor, a visual analytics system, to support the comprehensive analysis of passing dynamics. With the system, users can detect the changing patterns of passing tactics and examine the detailed passing process for evaluating passing tactics. We invite experts to conduct analysis with PassVizor and demonstrate the usability of the system through an expert interview.

#7 Does acute soccer heading cause an increase in plasma S100B? A randomized controlled trial
Reference: PLoS One. 2020 Oct 23;15(10):e0239507. doi: 10.1371/journal.pone.0239507. eCollection 2020.
Authors: Megan E Huibregtse, Madeleine K Nowak, Joseph E Kim, Rachel M Kalbfell, Alekhya Koppineni, Keisuke Ejima, Keisuke Kawata
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Summary: The purpose of this study was to test the effect of subconcussive head impacts on acute changes in plasma S100B. In this randomized controlled trial, 79 healthy adult soccer players were randomly assigned to either the heading (n = 41) or kicking-control groups (n = 38). The heading group executed 10 headers with soccer balls projected at a speed of 25 mph, whereas the kicking-control group performed 10 kicks. Plasma samples were obtained at pre-, 0h post-, 2h post- and 24h post-intervention and measured for S100B. The primary hypothesis was that there would be a significant group difference (group-by-time interaction) in plasma S100B at 2h post-intervention. Secondary hypotheses included (1) no significant group differences in plasma S100B concentrations at 0h post- and 24h post-intervention; (2) a significant within-group increase in S100B concentrations in the heading group at 2h post-intervention compared to pre-intervention; and (3) no significant within-group changes in plasma S100B in the kicking-control group. Data from 68 subjects were available for analysis (heading n = 37, kicking n = 31). There were no differences in S100B concentrations between heading and kicking groups over time, as evidenced by nonsignificant group-by-time interaction at 2h post-intervention (B = 2.20, 95%CI [-22.22, 26.63], p = 0.86) and at all the other time points (0h post: B = -11.05, 95%CI [-35.37, 13.28], p = 0.38; 24h post: B = 16.11, 95%CI [-8.29, 40.51], p = 0.20). Part of the secondary outcome, the heading group showed elevation in plasma S100B concentrations at 24h post-intervention compared to pre-heading baseline (B = 19.57, 95%CI [3.13, 36.02], p = 0.02), whereas all other within-group comparisons in both remained nonsignificant. The data suggest that 10 bouts of acute controlled soccer headings do not elevate S100B concentrations up to 24-hour post-heading. Further dose-response studies with longer follow-up time points may help determine thresholds of acute soccer heading exposure that are related to astrocyte activation.

#8 The impact of team preferences on soccer offside judgments in laypersons: a quasi-experimental study
Reference: Cogn Res Princ Implic. 2020 Oct 23;5(1):50. doi: 10.1186/s41235-020-00253-2.
Authors: Peter Wühr, Frowin Fasold, Daniel Memmert
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Summary: The present study uses a quasi-experimental design to investigate the impact of team preferences on the accuracy of offside judgments. In Experiments 1 and 2, supporters of two German soccer clubs (i.e., Borussia Dortmund and FC Schalke 04) judged offsides in artificial scenes from a match between the clubs. We expected that supporters of both clubs would less frequently report the offside position of a forward from the preferred team. The results of Experiment 1 partly confirmed the predictions. Both groups reported the offside position of a yellow forward less frequently than that of a blue forward, and this effect was much larger for supporters of Borussia Dortmund than for supporters of Schalke 04. The difference between groups could be attributed to team preferences. The weaker effect of team preference in supporters of Schalke 04 was attributed to an unexpected perceptual effect that increased the accuracy of offside judgments for blue forwards in both groups. Experiments 2 and 3 showed the presumed effect of team preferences and the perceptual effect, respectively, in isolation. In summary, the results of our experiments provide evidence for (a) an effect of team preferences and (b) an effect of shirt-background contrast on offside judgments in soccer.

#9 Neural correlates of cognitive processing capacity in elite soccer players
Reference: Biol Psychol. 2020 Oct 19;107971. doi: 10.1016/j.biopsycho.2020.107971. Online ahead of print.
Authors: Chun-Hao Wang, Chih-Chun Lin, David Moreau, Cheng-Ta Yang, Wei-Kuang Liang
Summary: Although great progress has been made in our understanding of perceptual-cognitive expertise in team sports, the neurocognitive mechanisms underlying such cognitive advantage in the face of multiple, sometimes conflicting, channels of information are not well understood. Two electroencephalographic indices associated with perceptual decisions, the P3 component of event-related potential and alpha inter-trial phase coherence (ITPC), were measured and compared across elite soccer players and non-athletic controls while performing a redundant-target task. Specifically, we adopted an effective diagnostic tool, Systems Factorial Technology, to assess participants' workload capacity. Soccer players exhibited larger workload capacity while making faster decisions compared with controls. Moreover, this larger workload capacity was associated with modulations of P3 and alpha ITPC when processing two targets relative to one target and one distractor, an effect that was not observed in controls. Together, the present findings offer a possible mechanistic explanation of perceptual-cognitive expertise in the context of team sports.

#10 Technical determinants of success in professional women's soccer: A wider range of variables reveals new insights
Reference: PLoS One. 2020 Oct 22;15(10):e0240992. doi: 10.1371/journal.pone.0240992. eCollection 2020.
Authors: Laura M S de Jong, Paul B Gastin, Maia Angelova, Lyndell Bruce, Dan B Dwyer
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Summary: Knowledge of optimal technical performance is used to determine match strategy and the design of training programs. Previous studies in men's soccer have identified certain technical characteristics that are related to success. These studies however, have relative limited sample sizes or limited ranges of performance indicators, which may have limited the analytical approaches that were used. Research in women's soccer and our understanding of optimal technical performance, is even more limited (n = 3). Therefore, the aim of this study was to identify technical determinants of match outcome in the women's game and to compare analytical approaches using a large sample size (n = 1390 team performances) and range of variables (n = 450). Three different analytical approaches (i.e. combinations of technical performance variables) were used, a data-driven approach, a rational approach and an approach based on the literature in men's soccer. Match outcome was modelled using variables from each analytical approach, using generalised linear modelling and decision trees. It was found that the rational and data-driven approaches outperformed the literature-driven approach in predicting match outcome. The strongest determinants of match outcome were; scoring first, intentional assists relative to the opponent, the percentage of shots on goal saved by the goalkeeper relative to the opponent, shots on goal relative to the opponent and the percentage of duels that are successful. Moreover the rational and data-driven approach achieved higher prediction accuracies than comparable studies about men's soccer.

#11 Changes in resting-state functional brain connectivity associated with head impacts over one men's semi-professional soccer season
Reference: J Neurosci Res. 2020 Oct 21. doi: 10.1002/jnr.24742. Online ahead of print.
Authors: Hélène Cassoudesalle, Adrien Petit, Sandra Chanraud, Hervé Petit, Jérôme Badaut, Igor Sibon, Patrick Dehail
Summary: Soccer, as a contact sport, exposes players to repetitive head impacts, especially through heading the ball. The question of a long-term brain cumulative effect remains. Our objective was to determine whether exposure to head impacts over one soccer season was associated with changes in functional brain connectivity at rest, using magnetic resonance imaging (MRI). In this prospective cohort study, 10 semi-professional men soccer players, aged 18-25 years, and 20 age-matched men athletes without a concussion history and who do not practice any contact sport were recruited in Bordeaux (France). Exposure to head impacts per soccer player during competitive games over one season was measured using video analysis. Resting-state functional magnetic resonance imaging data were acquired for both groups at two times, before and after the season. With a seed-based analysis, resting-state networks that have been intimately associated with aspects of cognitive functioning were investigated. The results showed a mean head impacts of 42 (±33) per soccer player over the season, mainly intentional head-to-ball impacts and no concussion. No head impact was found among the other athletes. The number of head impacts between the two MRI acquisitions before and after the season was associated with increased connectivity within the default mode network and the cortico-cerebellar network. In conclusion, our findings suggest that the brain functioning changes over one soccer season in association with exposure to repetitive head impacts.

#12 Sleep Restriction in Elite Soccer Players: Effects on Explosive Power, Wellbeing, and Cognitive Function
Reference: Res Q Exerc Sport. 2020 Oct 21;1-8. doi: 10.1080/02701367.2020.1834071. Online ahead of print.
Authors: W Abbott, A Brett, A W Watson, H Brooker, T Clifford
Summary: The aim was to investigate the cognitive, physical, and perceptual effects of sleep restriction (SR) in soccer players following a night match. In a crossover design, nine male soccer players from the English Premier League 2 (age, 21 ± 5 years; height, 1.80 ± 0.75 m; body mass, 74.2 ± 6.8 kg) recorded their sleep quality and quantity with sleep logs and a subjective survey after two night matches (19:00); one where sleep duration was not altered (CON) and one where sleep was restricted by a later bed-time (SR). Countermovement jump height (CMJ), subjective wellbeing (1-5 likert scale for mood, stress, fatigue, sleep, and soreness), and cognitive function were measured at baseline and the morning following the match (+12 h; M + 1). Bed-time was later in SR than CON (02:36 ± 0.17 vs. 22:43 ± 29; P = .0001; ηp2 = 0.999) and sleep duration was shorter in SR than CON (5.37 ± 0.16 vs. 8.59 h ± 0.36; P = .0001; ηp2 = 0.926). CMJ decreased by ~8% after the match in both SR and CON (P = .0001; ηp2 = 0.915) but there were no differences between the conditions (P > .05; ηp2 = 0.041-0.139). Wellbeing was rated worse after both matches (P = .0001; ηp2 = 0.949) but there were no differences between the trials (P > .05; ηp2 = 0.172-257). SR did not influence cognitive function (P > .05; interaction effects, ηp2 = 0.172-257). SR following a nighttime soccer match does not impair CMJ performance, subjective wellbeing, or cognitive function the following morning.

#13 Reliability of Change-of-Direction Economy in Soccer Players
Reference: Int J Sports Physiol Perform. 2020 Oct 28;1-7. doi: 10.1123/ijspp.2019-0877. Online ahead of print.
Authors: Filippo Dolci, Andrew E Kilding, Tania Spiteri, Paola Chivers, Ben Piggott, Andrew Maiorana, Nicolas H Hart
Summary: The purpose was to evaluate the reliability of new change-of-direction-economy tests (assessing energetic efficiency when performing continuous shuttle runs) compared with common running-economy tests in soccer players Methods: Sixteen subelite, male soccer players were recruited to perform a testing battery involving running economy (RE), 10-m shuttle-running economy (SRE10), and 20-m shuttle-running economy (SRE20) at 8.4 km·h-1 mean speed on 2 different days within 48 hours. SRE10 and SRE20 consisted of continuous shuttle runs interspersed with 180° directional changes. During the RE, SRE20, and SRE10 tests, respiratory exchange ratio and oxygen uptake were collected and used to calculate the movement-economy values over any running condition as oxygen cost and energetic cost. The secondary variables (carbon dioxide production, heart rate, minute ventilation, and blood lactate) were also monitored during all tests. Depending on expression (oxygen cost or energetic cost), reliability was established for RE (CV: 5.5%-5.8%; ICC = .77-.88), SRE10 (CV: 3.5%-3.8%; ICC = .78-.96), and SRE20 (CV: 3.5%-3.8%; ICC = .66-.94). All secondary physiological variables reported good reliability (CV < 10%), except for blood lactate (CV < 35.8). The RE, SRE10, and SRE20 tests show good reliability in soccer players, whereas blood lactate has the highest variability among physiological variables during the economy tests. The assessment of change-of-direction economy through performing 20- and 10-m shuttle runs is reliable and can be applied to evaluate soccer players' energetic movement efficiency under more soccer-specific running conditions.

#14 Male and female soccer players exhibit different knee joint mechanics during pre-planned change of direction
Reference: Sports Biomech. 2020 Oct 29;1-14. doi: 10.1080/14763141.2020.1830160. Online ahead of print.
Authors: Christopher Thomas, Thomas Dos'Santos, Paul Comfort, Paul A Jones
Summary: Change of direction manoeuvres is important in soccer and associated with non-contact anterior cruciate ligament injury, yet it is not known how the mechanics differentiate between males and females during 180° turns. Twenty-eight soccer players (14 males and 14 females) performed 180° turns with ground reaction forces collected over penultimate and final contacts. A two-way (contact × limb) multivariate analysis of variance (MANOVA) were run to examine differences between contact (penultimate and final) or limb (dominant and non-dominant) for sagittal plane hip, knee and ankle peak angles and moments, and frontal plane knee abduction moments and angles between sexes. Average horizontal GRF was increased on the dominant limb, compared to non-dominant and for the final contact compared to the penultimate contact. Knee abduction angles were increased in females compared to males, while the opposite was true for knee abduction moments. Statistically significant differences were evident, with increases in peak vertical GRF, peak hip flexion angle, peak knee flexion angle, peak knee extensor moment, and peak ankle dorsiflexion angle observed in the penultimate contact compared to final contact. The results indicate the penultimate contact during turns helps reduce loading on the final contact, yet male and female soccer players exhibit different knee joint mechanics during pre-planned change of direction.

#15 Short-Term Detraining Does Not Impair Strength, Speed, and Power Performance in Elite Young Soccer Players
Reference: Sports (Basel). 2020 Oct 25;8(11):E141. doi: 10.3390/sports8110141.
Authors: Lucas A Pereira, Tomás T Freitas, Bruno Pivetti, Pedro E Alcaraz, Ian Jeffreys, Irineu Loturco
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Summary: This study aimed to examine the effects of short-term detraining on the strength, speed, and jump capacities of under-20 soccer players. Twenty-four elite under-20 soccer players from the same professional club were assessed pre and post 26 days of detraining. The measurements were performed in the following order: countermovement jump (CMJ); 10 m linear sprint velocity; and one-repetition maximum test (1RM) in the horizontal leg-press exercise. To analyze the differences between pre- and post-tests, a paired T-test was applied. The significance level was set as p < 0.05. Soccer players exhibited a significant increase in CMJ performance (p = 0.02) and no significant differences in 10 m sprint velocity and 1RM leg-press were found after the short-term training cessation (p = 0.61; p = 0.55, respectively). We demonstrated that a short-term detraining period was capable of promoting a significant increase in the vertical jump height without inducing negative effects on the strength and speed capabilities of elite under-20 soccer players. Practitioners and sport scientists should be aware of these findings to program more effective training strategies at the beginning of the subsequent training cycle.

#16 Reproducibility and inter-observer agreement of Greulich-Pyle protocol to estimate skeletal age among female adolescent soccer players
Reference: BMC Pediatr. 2020 Oct 26;20(1):494. doi: 10.1186/s12887-020-02383-4.
Authors: Yuri V Faustino-da-Silva, Diogo V Martinho, Manuel J Coelho-E-Silva, João Valente-Dos-Santos, Jorge Conde, Tomás G Oliveira, Enio R V Ronque, Ricardo R Agostinete, Rômulo A Fernandes, Lauren B Sherar
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Summary: Skeletal age (SA) is considered the best method of assessing biological maturation. The aim of this study was to determine intra-observer (reproducibility) and inter-observer agreement of SA values obtained via the Greulich-Pyle (GP) method. In addition, the variation in calculated SAs by alternative GP protocols was examined. The sample was composed of 100 Portuguese female soccer players aged 12.0-16.7 years. SAs were determined using the GP method by two observers (OB1: experience < 100 exams using GP; OB2: experience > 2000 exams using several methods). The radiographs were examined using alternative GP protocols: (wholeGP) the plate was matched to the atlas as an overall approach; (30-boneGP) bone-by-bone inspections of 30-bones; (GPpmb) bone-by-bone inspections of the pre-mature bones only. For the 30-boneGP and GPpmb approaches, SA was calculated via the mean (M) and the median (Md). Reproducibility ranged 82-100% and 88-100% for OB1 and OB2, respectively. Inter-observer agreement (100 participants multiplied by 30 bones) was 92.1%. For specific bones, agreement rates less than 90% were found for scaphoid (81%), medial phalange V (83%), trapezium (84%) and metacarpal V (87%). Differences in wholeGP SAs obtained by the two observers were moderate (d-cohen was 0.79). Mean differences between observers when using bone-by bone SAs were trivial (30-boneGP: d-cohen less than 0.05; GPpmb: d-cohen less than 0.10). The impact of using the mean or the median was negligible, particularly when analyses did not include bones scored as mature. The GP appeared to be a reasonably reproducible method to assess SA and inter-observer agreement was acceptable. There is evidence to support a recommendation of only scoring pre-mature bones during later adolescence. Further research is required to examine whether these findings are consistent in younger girls and in boys.

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