Examining the reliability and predictive validity of performance assessments by soccer coaches and scouts:The influence of structured collection and mechanical combination of information

Soccer coaches and scouts typically assess in-game soccer performance to predict players’ future performance. However, there is hardly any research on the reliability and predictive validity of coaches’ and scouts’ performance assessments, or on strategies they can use to optimize their predictions. In the current study, we examined whether robust principles from psychological research on selection – namely structured information collection and mechanical combination of predictor information through a decision-rule – improve soccer coaches’ and scouts’ performance assessments. A total of n = 96 soccer coaches and scouts participated in an elaborate within-subjects experiment. Participants watched soccer players’ performance on video, rated their performance in both a structured and unstructured manner, and combined their ratings in a holistic and mechanical way. We examined the inter-rater reliability of the ratings and assessed the predictive validity by relating the ratings to players’ future market values. Contrary to our expectations, we did not find that ratings based on structured assessment paired with mechanical combination of the ratings showed higher inter-rater reliability and predictive validity. In contrast, unstructured-holistic ratings yielded the highest reliability and predictive validity, although differences were marginal. Overall, reliability was poor and predictive validities small-to-moderate, regardless of the approach used to rate players’ performance. The findings provide insights into the difficulty of predicting future performance in soccer

Sensorimotor and neuromuscular performance capabilities in elite young soccer players

Following a review of the literature and using a prospective observational design delivered in an ecologically valid setting, this thesis enhances knowledge of sensorimotor (SM) and neuromuscular (NM) performance capabilities in elite young soccer players, culminating with a controlled cohort study to further investigate the influence of high intensity exercise stress on performance capabilities. Alterations in player perceived capabilities using the Borg Category-Ratio Scale (CR-10) and Perceived percentage of completed task duration (PTD), were also investigated. Impaired NM performance as a symptom of fatigue has previously been demonstrated in elite soccer players. However, the results from outcome measures offering such detailed and granular biological insights have not been documented previously. In addition, this research project aimed to observe (Chapter 6) and then provoke (Chapter 7) turbulence, physiologically, to examine whether the SM system is similarly affected, thereby verifying this mechanism as operational for soccer players. To objectify the conditioning dosage to which elite young soccer players are typically exposed to, Chapter 3 offered a season-long patterning of training and match-workload. To further contextualise the backdrop of this research project, NM performance capabilities were benchmarked by comparison with senior professional players in Chapter 4. Performance capabilities of sixteen elite male soccer players (age: 19.2 ± 1.1 years; height: 183.3 ± 6.1 cm; body mass: 76.1 ± 7.8 kg) were evaluated at weekly intervals over a 6-week in-season mesocycle (Chapter 5), and daily during a weekly competitive microcycle (Chapter 6). Assessments of peak twitch force (PTFe) and electromechanical delay (EMD) demonstrated significant changes in NM performance capability (p 0.05). Congruence amongst fluctuating patterns of intra-mesocycle training workloads and concomitant neuromuscular performance responses was noted over time for Acute Training Load (ATL) with PF (r = -0.59; p 0.05). Additionally, although both CR-10 and PTD ultimately demonstrated efficacy in predicting exercise cessation, a significant interaction effect (p < 0.01) was observed indicating a divergence between candidate explanatory paradigms of self-perception of capabilities for players within the task. This thesis has increased current knowledge and understanding by providing a novel exploratory evaluation of sensorimotor and neuromuscular performance capabilities in early career professional soccer players. The findings presented in this thesis will better inform future studies on conditioning soccer players and allow more targeted prophylactic strategies to be implemented by performance support staff. Key words: Sensorimotor, neuromuscular, socce

Prognostic Validity of Professional Soccer Status by Anthropometrics and Repeated Jump Testing

ABSTRACT Soccer is characterized by intermittent high-intensity actions interspersed with lower intensity ones. Soccer clubs invest time and money to early identify and nurture potential professional players in the premise to maximize the return of their investment. Multidimensional talent identification models are proposed as best practice but are difficult to be implemented in the field. Explosive lower limbs strength assessment by vertical jumping (VJ) is used as a single predictor for future player status. Alternative to VJ, the repeated vertical jump test (RVJ) has been proposed, but its prognostic ability is still unexplored. PURPOSE: To analyze the prognostic validity of the RVJ obtained variables within professional (PRO) and under 19 years old (U19) male soccer players. It was hypothesized that anthropometric and performance related variables modeled on U19 will fail to predict the PRO status. METHODS: Forty-four participants (PRO=24, U19=20), after the end of the preseason, performed 15 RVJ aiming for highest jump (hJUMP) with the minimum possible ground contact time. Group differences examined by t-test, binomial logistic regression (BLR) calculated the likelihood of each individual to be categorized as PRO or U19 and receiver operating characteristic (ROC) for prognostic validity of anthropometric and performance derivative values in predicting PRO status were used at p \u3c0.05. Statistical analyses were performed using the R-based software Jamovi version 2.3.3.0. RESULTS: PRO and U19 significantly differed in body height, mass, body mass index (BMI), hJUMP, average jump height, and relative jump power. The prediction model was significant (x2(2) = 17.12, p \u3c0.001). From the examined variables, only height and BMI were positive predictors of the PRO status (b = 21.66, SE = 8.20, p = 0.008 and b = 0.94, SE = 0.38, p = 0.014, respectively). The model was 73% accurate, 75% specific, and 71% sensitive, with acceptable area under the curve (AUC = 0.82). CONCLUSION: The RVJ test demonstrated acceptable discriminating prognostic validity between PRO and U19 soccer players. Until the applicability of the multidimensional models in predicting future player status is further established, field practitioners may use the simplistic and single dimensional RVJ testing to predict future status among male soccer players

High-intensity endurance capacity assessment as a tool for talent identification in elite youth female soccer.

Talent identification and development programmes have received broad attention in the last decades, yet evidence regarding the predictive utility of physical performance in female soccer players is limited. Using a retrospective design, we appraised the predictive value of performance-related measures in a sample of 228 youth female soccer players previously involved in residential Elite Performance Camps (age range: 12.7-15.3 years). With 10-m sprinting, 30-m sprinting, counter-movement jump height, and Yo-Yo Intermittent Recovery Test Level 1 (IR1) distance as primary predictor variables, the Akaike Information Criterion (AIC) assessed the relative quality of four penalised logistic regression models for determining future competitive international squads U17-U20 level selection. The model including Yo-Yo IR1 was the best for predicting career outcome. Predicted probabilities of future selection to the international squad increased with higher Yo-Yo IR1 distances, from 4.5% (95% confidence interval, 0.8 to 8.2%) for a distance lower than 440 m to 64.7% (95% confidence interval, 47.3 to 82.1%) for a score of 2040 m. The present study highlights the predictive utility of high-intensity endurance capacity for informing career progression in elite youth female soccer and provides reference values for staff involved in the talent development of elite youth female soccer players

Deceptive body movements reverse spatial cueing in soccer

This article has been made available through the Brunel Open Access Publishing Fund.The purpose of the experiments was to analyse the spatial cueing effects of the movements of soccer players executing normal and deceptive (step-over) turns with the ball. Stimuli comprised normal resolution or point-light video clips of soccer players dribbling a football towards the observer then turning right or left with the ball. Clips were curtailed before or on the turn (-160, -80, 0 or +80 ms) to examine the time course of direction prediction and spatial cueing effects. Participants were divided into higher-skilled (HS) and lower-skilled (LS) groups according to soccer experience. In experiment 1, accuracy on full video clips was higher than on point-light but results followed the same overall pattern. Both HS and LS groups correctly identified direction on normal moves at all occlusion levels. For deceptive moves, LS participants were significantly worse than chance and HS participants were somewhat more accurate but nevertheless substantially impaired. In experiment 2, point-light clips were used to cue a lateral target. HS and LS groups showed faster reaction times to targets that were congruent with the direction of normal turns, and to targets incongruent with the direction of deceptive turns. The reversed cueing by deceptive moves coincided with earlier kinematic events than cueing by normal moves. It is concluded that the body kinematics of soccer players generate spatial cueing effects when viewed from an opponent's perspective. This could create a reaction time advantage when anticipating the direction of a normal move. A deceptive move is designed to turn this cueing advantage into a disadvantage. Acting on the basis of advance information, the presence of deceptive moves primes responses in the wrong direction, which may be only partly mitigated by delaying a response until veridical cues emerge

Achievement Goals, Competition Appraisals, and the Well- and Ill-Being of Elite Youth Soccer Players Over Two Competitive Seasons

Grounded in the 2 × 2 achievement goal framework (Elliot & McGregor, 2001),the purpose of this study was to investigate the temporal relationships between achievement goals, competition appraisals and indices of psychological and emotional welfare among elite adolescent soccer players. A subsidiary aim was to ascertain the mediational role of competition appraisals in explaining the potential achievement goal and well-/ill-being relationships. Ninety-one boys (mean age = 13.82 years) involved in an elite soccer program completed multisection questionnaires capturing the targeted variables. Measures were obtained on five occasions across two competitive seasons. Multilevel regression analyses revealed that MAp goals positively, and MAv goals negatively, predicted within-person changes in well-being over two seasons. PAp goal adoption was positively associated to within-person changes in negative affect. PAv goals corresponded negatively to between-person mean differences in positive affect. The results of the indirect effects showed challenge appraisals accounted for within-person associations between a MAp goal focus and well- and ill-being over time. The present findings provide only partial support for the utility of the 2 × 2 achievement goal framework in predicting young athletes’ psychological and emotional functioning in an elite youth sport setting

Actions Speak Louder Than Goals: Valuing Player Actions in Soccer

Assessing the impact of the individual actions performed by soccer players during games is a crucial aspect of the player recruitment process. Unfortunately, most traditional metrics fall short in addressing this task as they either focus on rare actions like shots and goals alone or fail to account for the context in which the actions occurred. This paper introduces (1) a new language for describing individual player actions on the pitch and (2) a framework for valuing any type of player action based on its impact on the game outcome while accounting for the context in which the action happened. By aggregating soccer players' action values, their total offensive and defensive contributions to their team can be quantified. We show how our approach considers relevant contextual information that traditional player evaluation metrics ignore and present a number of use cases related to scouting and playing style characterization in the 2016/2017 and 2017/2018 seasons in Europe's top competitions.Comment: Significant update of the paper. The same core idea, but with a clearer methodology, applied on a different data set, and more extensive experiments. 9 pages + 2 pages appendix. To be published at SIGKDD 201

Stochastic Prediction of Multi-Agent Interactions from Partial Observations

We present a method that learns to integrate temporal information, from a learned dynamics model, with ambiguous visual information, from a learned vision model, in the context of interacting agents. Our method is based on a graph-structured variational recurrent neural network (Graph-VRNN), which is trained end-to-end to infer the current state of the (partially observed) world, as well as to forecast future states. We show that our method outperforms various baselines on two sports datasets, one based on real basketball trajectories, and one generated by a soccer game engine.Comment: ICLR 2019 camera read

The impact of long-term soccer-specific training on the physical development of elite junior soccer players

The goal of any soccer talent development programme is to guide players towards professional characteristics. In order to maximise this process it is essential to gain an insight into their individual characteristics. Within this specific population there are many factors from maturation, hormonal, anatomical and musculoskeletal changes that accompany paediatric development and consequently have a direct impact upon their development. The aim of this thesis was to determine the relative influence of changes in maturation and long-term systematic training on the physical development of elite junior soccer players. The aim of the first study (Chapter 4) was to assess the reliability of a range of anthropometric and performance measures in aged matched academy and non-academy soccer players (U14-18). The results demonstrated that all anthropometric (%CV values of 0.1 – 1.3%) and performance measures (%CV values of 1.8-6.2%) were highly reproducible in both the academy and non-academy soccer players. These assessments would be subsequently used to determine the impact of long-term training on changes in physical development of junior soccer players. The aim of study two (Chapter 5) was to determine the validity of a non-invasive approach (maturity offset) for predicting end height stature in academy soccer players (U14-18). Overall, agreement between estimates of end height stature in elite youth soccer players’ using skeletal x-ray and the maturity-offset method were poor with a SEM and 95 % LOA of 4 cm and +11cm being observed respectively. These findings indicate that care must be taken when predicating end height stature in academy soccer players when using maturity offset method. The aim of the third study (Chapter 6) was to examine the typical weekly training load experienced by academy and non-academy soccer players (U12-U16) during the in-season competitive period. Physiological loading associated with training sessions and match-play were monitored using heart rate (HR) and ratings of perceived exertion (RPE). Training and match loads were calculated by multiplying global session RPE and duration (RPE-TL). Weekly training load in the academy players (U12, 737±51; U14, 646±106; U16, 750±81) was higher than the non-academy players (U12, 157±28; U14, 161±19; U16, 193±26) across the three age groups. Similarly, match load and % time spent >90%HRmax was higher in the academy players compared to the non-academy players. The present findings indicate that the overall load and intensity of training is greater in academy players compared to aged match non-academy players. The aim of the fourth study (Chapter 7) was to determine the relative influence of changes in maturation and long-term systematic training on changes in physical performance in age matched academy and non-academy junior soccer player. The three-year change in the physical performance of twenty-seven academy and eighteen non-academy soccer players (U12-U16) were monitored. When corrected for differences in both baseline performance and change in maturity status (maturity offset), greater changes in countermovement jump (7.3 + 2.6 cm, 5.4 + 2.5 cm), 10 m (-0.15 + 0.05 s, -0.10 + 0.04 s) and 20 m sprint (-0.30 + 0.16 s, -0.15 + 0.13 s), agility (-0.19 + 0.01 s, -0.08 + 0.08 s), repeated sprint (-0.60 + 0.26 s, -0.41 + 2.1 s) and intermittent endurance capacity (1128 + 406 m, 315 + 370 m) were observed in the Academy players compared with non-academy players (p0.7). These findings indicate that long-term player development programs accelerate the rate physical development of academy soccer players relative to age and maturity matched non-academy players. In summary, the present thesis highlights that academy soccer players experience greater rates of improvement in physical performance indicators compared to non-academy players, independently from the initial performance level of the child and change in maturation over the same time period. These difference are likely to reflect the increased volume and intensity of soccer-specific training experienced by the young soccer players as part of the academy’s approach to long-term athlete development. Future research is warranted in order to determine training loads in elite youth soccer players at different stages of biological maturity which serve to enhance performance whilst minimising the risk of injury