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Purpose: The study of load and recovery gained significant interest in the last decades, given its important value in decreasing the likelihood of injuries and improving performance. So far, findings are typically reported on the group level, whereas practitioners are most often interested in applications at the individual level. Hence, the aim of the present research is to examine to what extent group-level statistics can be generalized to individual athletes, which is referred to as the “ergodicity issue.” Nonergodicity may have serious consequences for the way we should analyze, and work with, load and recovery measures in the sports field. Methods: The authors collected load, that is, rating of perceived exertion × training duration, and total quality of recovery data among youth male players of a professional football club. This data were collected daily across 2 seasons and analyzed on both the group and the individual level. Results: Group- and individual-level analysis resulted in different statistical outcomes, particularly with regard to load. Specifically, SDs within individuals were up to 7.63 times larger than SDs between individuals. In addition, at either level, the authors observed different correlations between load and recovery. Conclusions: The results suggest that the process of load and recovery in athletes is nonergodic, which has important implications for the sports field. Recommendations for training programs of individual athletes may be suboptimal, or even erroneous, when guided by group-level outcomes. The utilization of individual-level analysis is key to ensure the optimal balance of individual load and recovery.

Purpose: To determine the test–retest reliability of the recently developed Hip Load metric, evaluate its construct validity, and assess the differences with Playerload during football-specific short-distance shuttle runs. Methods: Eleven amateur football players participated in 2 identical experimental sessions. Each session included 3 different shuttle runs that were performed at 2 pace-controlled running intensities. The runs consisted of only running, running combined with kicks, and running combined with jumps. Cumulative Playerload and Hip Loads of the preferred and nonpreferred kicking leg were collected for each shuttle run. Test–retest reliability was determined using intraclass correlations, coefficients of variation, and Bland–Altman analyses. To compare the load metrics with each other, they were normalized to their respective values obtained during a 54-m run at 9 km/h. Sensitivity of each load metric to running intensity, kicks, and jumps was assessed using separate linear mixed models. Results: Intraclass correlations were high for the Hip Loads of the preferred kicking leg (.91) and the nonpreferred kicking leg (.96) and moderate for the Playerload (.87). The effects (95% CIs) of intensity and kicks on the normalized Hip Load of the kicking leg (intensity: 0.95 to 1.50, kicks: 0.36 to 1.59) and nonkicking leg (intensity: 0.96 to 1.53, kicks: 0.06 to 1.34) were larger than on the normalized Playerload (intensity: 0.12 to 0.25, kicks: 0.22 to 0.53). Conclusions: The inclusion of Hip Load in training load quantification may help sport practitioners to better balance load and recovery.

Introduction: Performance assessment in professional soccer often focusses on notational assessment like assists or pass accuracy. However, rather than statistics, performance is more about making the best possible tactical decision, in the context of aplayer's positional role and the available options at the time. With the current paper, we aim to construct an improved model for the assessment of pass risk and reward across different positional roles, and validate that model by studying differences in decision-making between players with different positional roles. Methods: To achieve our aim, we collected position tracking data from an entire season of Dutch Eredivisie matches, containing 286.151 passes of 336 players. From that data, we derived several features on risk and reward, both for the pass that has been played, as well as for the pass options that were available at the time of passing. Results: Our findings indicate that we could adequately model risk and reward, outperforming previously published models, and that there were large differences in decision-making between players with different positional roles. Discussion: Our model can be used to assess player performance based on what could have happened, rather than solely based on what did happen in amatch.

In professional soccer, increasing amounts of data are collected that harness great potential when it comes to analysing tactical behaviour. Unlocking this potential is difficult as big data challenges the data management and analytics methods commonly employed in sports. By joining forces with computer science, solutions to these challenges could be achieved, helping sports science to find new insights, as is happening in other scientific domains. We aim to bring multiple domains together in the context of analysing tactical behaviour in soccer using position tracking data. A systematic literature search for studies employing position tracking data to study tactical behaviour in soccer was conducted in seven electronic databases, resulting in 2338 identified studies and finally the inclusion of 73 papers. Each domain clearly contributes to the analysis of tactical behaviour, albeit in - sometimes radically - different ways. Accordingly, we present a multidisciplinary framework where each domain's contributions to feature construction, modelling and interpretation can be situated. We discuss a set of key challenges concerning the data analytics process, specifically feature construction, spatial and temporal aggregation. Moreover, we discuss how these challenges could be resolved through multidisciplinary collaboration, which is pivotal in unlocking the potential of position tracking data in sports analytics.Highlights Over the recent years, there has been a considerable growth in studies on tactical behaviour using position tracking data, especially in the domains of sports science and computer science. Yet both domains have contributed distinctly different studies, with the first being more focused on developing theories and practical implications, and the latter more on developing techniques.Considerable opportunities exist for collaboration between sports science and computer science in the study of tactics in soccer, especially when using position tracking data.Collaborations between the domains of sports science and computer science benefit from a stronger dialogue yielding a cyclical collaboration.We have proposed a framework that could serve as the foundation for the combination of sports science and computer science expertise in tactical analysis in soccer.

In elite basketball, players are exposed to intensified competition periods when participating in both national and international competitions. How coaches manage training between matches and in reference to match scheduling for a full season is not yet known. Purpose: First, to compare load during short-term match congestion (ie, ≥2-match weeks) with regular competition (ie, 1-match weeks) in elite male professional basketball players. Second, to determine changes in well-being, recovery, neuromuscular performance, and injuries and illnesses between short-term match congestion and regular competition. Methods: Sixteen basketball players (age 24.8 [2.0] y, height 195.8 [7.5] cm, weight 94.8 [14.0] kg, body fat 11.9% [5.0%], VO2max 51.9 [5.3] mL·kg−1·min−1) were monitored during a full season. Session rating of perceived exertion (s-RPE) was obtained, and load was calculated (s-RPE × duration) for each training session or match. Perceived well-being (fatigue, sleep quality, general muscle soreness, stress levels, and mood) and total quality of recovery were assessed each training day. Countermovement jump height was measured, and a list of injuries and illnesses was collected weekly using the adapted Oslo Sports Trauma Research Center Questionnaire on Health Problems. Results: Total load (training sessions and matches; P P P = .01) and less fatigue (P = .001) were found during ≥2-match weeks compared with 1-match weeks. Conclusion: Total load and training load were lower during short-term match congestion compared with regular competition. Furthermore, better well-being and less fatigue were demonstrated within short-term match congestion. This might indicate that coaches tend to overcompensate training load in intensified competition.

To assess the real-life magnitude of the heading incidence in children's and youth’ football in eight European countries with different “football cultures,” a cross-sectional observational design, in which one match per team in 480 different teams from eight European countries (2017/18-2018/19), was recorded by video. One training session was recorded in 312 teams. Clubs with Under-10, Under-12 (female/male/mixed), and Under-16 female and male teams were eligible to participate. Heading frequencies and types were analyzed. Results are presented as headers per match/training and per team. Incidence rates (IR) per 1000 match/training hours were calculated. Under-10 teams carried out the lowest average number of headers per match (8.8), followed by Under-16 female (17.7), Under-12 (18.4), and Under-16 male (35.5). Total number of headers per match and team varied between countries. 80% of the total number of headers were single intentional headers, 12% heading duels, 3% unintentional headers by getting hit, and 5% others (trends apparent in all age groups). Three head injuries occurred during match play corresponding to an IR of 0.70 (95% CI, 0.23-2.16). The lowest number of headers per training and team was found in Under-10 (21.3), followed by Under-16 females (34.1), Under-12 (35.8), and Under-16 males (45.0). In conclusion, this large-scale study presents novel data about the number and type of headers in youth’ football throughout Europe. A more precise understanding of the heading incidence, specifically in young players, is mandatory for the debate of restrictions on heading in youth football.

Background: A limited number of patients return to sport (RTS) after an anterior cruciate ligament reconstruction (ACLR) and patients who RTS have a relatively high risk for second ACL injury. The purpose of the current study was to compare the results of a test battery between patients who returned to the pre-injury level of sport (RTS group) and patients who did not (NO-RTS group).It was hypothesized that the RTS group showed better test results.Methods: Sixty-four patients (age 27.8 +/- 8.8 years) were included. The results of a multicomponent test battery (jump-landing task assessed with the Landing Error Scoring System (LESS), three hop tests, isokinetic strength test for quadriceps and hamstring) were compared between groups with a 2 x 2 ANOVA.Results: The RTS group showed a significantly lower LESS score (p = 0.010), significantly higher absolute scores on hop tests with both legs (injured leg: single leg hop test p = 0.013, triple leg hop test p = 0.024, side hop test p = 0.021: non-injured leg: single leg hop test p 0.011, triple leg hop test p = 0.023, side hop test p = 0.032) and significantly greater hamstring strength in the injured leg (p = 0.009 at 60 degrees/s, p = 0.012 at 180 degrees/s and p - 0.013 at 300 degrees/s). No differences in test results were identified between patients who sustained a second ACL injury and patients who did not.Conclusion: Patients after ACLR with better jump-landing patterns, hop performance and greater hamstring strength have greater likelihood for RTS. However, our findings show that RTS criteria fail to identify patients who are at risk for a second ACL injury. (C) 2020 The Author(s). Published by Elsevier B.V.

Current athlete monitoring practice in team sports is mainly based on positional data measured by global positioning or local positioning systems. The disadvantage of these measurement systems is that they do not register lower extremity kinematics, which could be a useful measure for identifying injury-risk factors. Rapid development in sensor technology may overcome the limitations of the current measurement systems. With inertial measurement units (IMUs) securely fixed to body segments, sensor fusion algorithms and a biomechanical model, joint kinematics could be estimated. The main purpose of this article is to demonstrate a sensor setup for estimating hip and knee joint kinematics of team sport athletes in the field. Five male subjects (age 22.5 +/- 2.1 years; body mass 77.0 +/- 3.8 kg; height 184.3 +/- 5.2 cm; training experience 15.3 +/- 4.8 years) performed a maximal 30-meter linear sprint. Hip and knee joint angles and angular velocities were obtained by five IMUs placed on the pelvis, both thighs and both shanks. Hip angles ranged from 195 degrees (+/- 8 degrees) extension to 100.5 degrees (+/- 8 degrees) flexion and knee angles ranged from 168.6 degrees (+/- 12 degrees) minimal flexion and 62.8 degrees (+/- 12 degrees) maximal flexion. Furthermore, hip angular velocity ranged between 802.6 degrees.s(-1) (+/- 192 degrees.s(-1)) and -674.9 degrees.s(-1) (+/- 130 degrees.s(-1)). Knee angular velocity ranged between 1155.9 degrees.s(-1) (+/- 200 degrees.s(-1)) and -1208.2 degrees.s(-1) (+/- 264 degrees.s(-1)). The sensor setup has been validated and could provide additional information with regard to athlete monitoring in the field. This may help professionals in a daily sports setting to evaluate their training programs, aiming to reduce injury and optimize performance.

Training load monitoring systems in football do not focus on lower extremities and therefore potentially neglect important information to optimise performance or reduce injury risk. The current study aims to present joint and segment angular accelerations as novel indicators to quantify lower extremity biomechanical load measured by a new inertial sensor setup. Relationships were explored with commonly used whole-body training load indicators using principal component analysis (PCA). Sixteen male amateur football players performed a linear sprint and an agility T-test. An inertial sensor setup, and local position measurement system were used to collect training load data. Hip Load, Knee Load, Thigh Load and Shank Load were introduced to quantify lower extremity biomechanical load. Three principal components were identified for both tests, explaining 91% and 86% of the variance. The indicators for the lower extremities contributed to the second principal component for both tests and provide distinct information compared to whole-body load indicators. The results show the potential to use an inertial sensor setup combined with common monitoring systems to evaluate training load, which may help optimise future performance and reduce injury risk. These relationships should be further examined during other football specific activities such as shooting or jumping.

Background It is crucial to balance load and recovery during short-term match congestion in basketball. Currently, it is unknown if higher total load during short-term match congestion lead to higher injury and illness rates. Objective Aim of this study was to compare injuries and illnesses and total weekly load during 1-match weeks compared to ≥2-match weeks in basketball. Design During this prospective observational study, players were monitored during a full season. Setting Two basketball teams participating in the domestic-league championship, CUP matches and Euro league were followed. Patients (or Participants) Sixteen elite male professional basketball players participated in this study. Characteristics of the players were (mean±SD): age 24.8±2.0 years, height 195.8±7.5 cm, weight 94.8±14.0 kg, body fat 11.9±5.0% and VO2max 51.9±5.3 mL·kg−1·min−1. Interventions (or Assessment of Risk Factors) In total 47 matches by basketball team A (9 players) and 41 matches by team B (7 players) were performed throughout the season. All training sessions and matches were executed as prescribed by the training and coaching staff without interference or manipulation. Main Outcome Measurements The Oslo Sports Trauma Research Center (OSTRC) Questionnaire on Health Problems was used to collect data on injuries and illnesses on a weekly base. Furthermore, players filled in s-RPE and duration for each training and match. Prevalence’s, severity scores, time-loss and total weekly load were compared for 1-match weeks and ≥2-match weeks. The data were analyzed using multi-level modeling. Results Prevalence of injuries and illnesses were 18.1% and 4.6% for 1-match weeks and 17.2% and 3.3% for ≥2-match weeks. Severity scores and time-loss were not significantly different for 1-match weeks compared to ≥2-match weeks. Total weekly load was lower during ≥2-match weeks compared to 1-match weeks. Conclusions No significant differences for injuries and illnesses were observed between 1-match weeks and ≥2-match weeks. Coaches appeared to reduce training load to compensate for multiple matches during short-term match congestion.

Decision-makers in soccer routinely assess the tactical behaviour of a team and its opponents both during and after the game to optimize performance. Currently, this assessment is typically driven by notational analysis and observation. Therefore, potential high-impact decisions are often made based on limited or even biased information. With the current study, we aimed to quantitatively assess tactical performance by abstracting a set of spatiotemporal features from the general offensive principles of play in soccer using position tracking data, and to train a machine learning classifier to predict match outcome based on these features computed over the full game as well as only parts of the game. Based on the results of these analyses, we describe a proof of concept of a decision support system for coaches and managers. In an analysis of 302 professional Dutch Eredivisie matches, we were able to train a Linear Discriminant Analysis model to predict match outcome with fair to good (74.1%) accuracy with features computed over the full match, and 67.9% accuracy with features computed over only 1/4th of the match. We therefore conclude that using only position tracking data, we can provide valuable feedback to coaches about how their team is executing the various principles of play, and how these principles are contributing to overall performance.

Substitution is an essential tool for a coach to influence the match. Factors like the injury of a player, required tactical changes, or underperformance of a player initiates substitutions. This study aims to predict the physical performance of individual players in an early phase of the match to provide additional information to the coach for his decision on substitutions. Tracking data ofindividual players, except for goalkeepers, from 302 elite soccer matches of the Dutch ‘Eredivisie’ 2018–2019 season were used to enable the prediction of the individual physical performance. The players’ physical performance is expressed in the variables distance covered, distance in speed category, and energy expenditure in power category. The individualized normalized variables wereused to build machine learning models that predict whether players will achieve 100%, 95%, or 90% of their average physical performance in a match. The tree-based algorithms Random Forest and Decision Tree were applied to build the models. A simple Naïve Bayes algorithm was used as the baseline model to support the superiority of the tree-based algorithms. The machine learningtechnique Random Forest combined with the variable energy expenditure in the power category was the most precise. The combination of Random Forest and energy expenditure in the power category resulted in precision in predicting performance and underperformance after 15 min in a match, andthe values were 0.91, 0.88, and 0.92 for the thresholds 100%, 95%, and 90%, respectively. To conclude, it is possible to predict the physical performance of individual players in an early phase of the match. These findings offer opportunities to support coaches in making more informed decisions on playersubstitutions in elite soccer.

During rugby sevens tournaments, it is crucial to balance match load and recovery to strive for optimal performance. Purpose: To determine changes in well-being, recovery, and neuromuscular performance during and after an elite women’s rugby sevens tournament and assess the influence of match-load indicators. Methods: Twelve elite women rugby sevens players (age = 25.3 [4.1]y, height = 169.0 [4.0] cm, weight = 63.9 [4.9] kg, and body fat = 18.6% [2.7%]) performed 5 matches during a 2-d tournament of the Women’s Rugby Sevens World Series. Perceived well-being (fatigue, sleep quality, general muscle soreness, stress levels, and mood), total quality of recovery, and countermovement-jump flight time were measured on match days 1 and 2, 1 d posttournament, and 2 d posttournament. Total distance; low-, moderate-, and high-intensity running; and physical contacts during matches were derived from global positioning system–based time–motion analysis and video-based notational analysis, respectively. Internal match load was calculated by session rating of perceived exertion and playing time (rating of perceived exertion × duration). Results: Well-being (P P P P P = .005), and total quality of recovery (P r = −.60, P = .049) and a larger number of physical contacts with more general muscle soreness (r = −.69, P = .013). Conclusion: Perceived well-being and total quality of recovery were already impaired after match day 1, although performance was maintained. High-intensity running and physical contacts were predominantly related to fatigue and general muscle soreness, respectively.

Association football teams can be considered complex dynamical systems of individuals grouped in subgroups (defenders, midfielders and attackers), coordinating their behaviour to achieve a shared goal. As research often focusses on collective behaviour, or on static subgroups, the current study aims to analyse spatiotemporal behaviour of dynamic subgroups in relation to successful attacks. We collected position tracking data of 118 Dutch Eredivisie matches, containing 12424 attacks. Attacks were classified as successful (N = 1237) or non-successful (N = 11187) based on the potential of creating a scoring opportunity. Using unsupervised machine learning, we automatically identified dynamic formations based on position tracking data, and identified dynamic subgroups for every timeframe in a match. We then compared the subgroup centroids to assess the intra- and inter-team spatiotemporal synchronisation during successful and non-successful attacks, using circular statistics. Our results indicated subgroup-level variables provided more information, and were more sensitive to disruption, in comparison to team-level variables. When comparing successful and non-successful attacks, we found decreases (p < .01) in longitudinal inter- and intra-team synchrony of interactions involving the defenders of the attacking team during successful attacks. This study provides the first large-scale dynamic subgroup analysis and reveals additional insights to team-level analyses.

It has been claimed that increased reliance on context, or allocentric information, develops when aiming movements are more consciously monitored and/or controlled. Since verbalizing target features requires strong conscious monitoring, we expected an increased reliance on allocentric information when verbalizing a target label (i.e. target number) during movement execution. We examined swiping actions towards a global array of targets embedded in different local array configurations on a tablet under no-verbalization and verbalization conditions. The global and local array configurations allowed separation of contextual-effects from any possible numerical magnitude biases triggered from calling out specific target numbers. The patterns of constant errors in the target direction were used to assess differences between conditions. Variation in the target context configuration systematically biased movement endpoints in both the no-verbalization and verbalization conditions. Ultimately, our results do not support the assertion that calling out target numbers during movement execution increases the context-dependency of targeted actions.

Injuries of runners reduce the ability to train and hinder competing. Literature shows that the relation between potential risk factors and injuries are not definitive, limited, and inconsistent. In team sports, workload derivatives were identified as risk factors. However, there is an absence of literature in running on workload derivatives. This study used the workload derivatives acute workload, chronic workload, and acute: chronic workload ratios to investigate the relation between workload and injury risk in running. Twenty-three competitive runners kept a daily training log for 24 months. The runners reported training duration, training intensity and injuries. One-week (acute) and 4-week (chronic) workloads were calculated as the average of training duration multiplied by training intensity. The acute:chronic workload ratio was determined dividing the acute and chronic workloads. Results show that a fortnightly low increase of the acute:chronic workload ratio (0.10–0.78) led to an increased risk of sustaining an injury (p

By assessing the precision of gestural interactions with touchscreen targets, the authors investigate how the type of gesture, target location, and scene visibility impact movement endpoints. Participants made visually and memory-guided pointing and swiping gestures with a stylus to targets located in a semicircle. Specific differences in aiming errors were identified between swiping and pointing. In particular, participants overshot the target more when swiping than when pointing and swiping endpoints showed a stronger bias toward the oblique than pointing gestures. As expected, the authors also found specific differences between conditions with and without delays. Overall, the authors observed an influence on movement execution from each of the three parameters studied and uncovered that the information used to guide movement appears to be gesture specific.

Inertial sensor-based measurements of lower body kinematics in football players may improve physical load estimates during training sessions and matches. However, the validity of inertial-based motion analysis systems is specific to both the type of movement and the intensity at which movements are executed. Importantly, such a system should be relatively simple, so it can easily be used in daily practice. This paper introduces an easy-to-use inertial-based motion analysis system and evaluates its validity using an optoelectronic motion analysis system as a gold standard. The system was validated in 11 football players for six different football specific movements that were executed at low, medium, and maximal intensity. Across all movements and intensities, the root mean square differences (means &plusmn, SD) for knee and hip flexion/extension angles were 5.3&deg, &plusmn, 3.4&deg, and 8.0&deg, 3.5&deg, respectively, illustrating good validity with the gold standard. In addition, mean absolute flexion/extension angular velocities significantly differed between the three movement intensities. These results show the potential to use the inertial based motion analysis system in football practice to obtain lower body kinematics and to quantify movement intensity, which both may improve currently used physical load estimates of the players.

Olthof, SBH, Frencken, WGP, and Lemmink, KAPM. A match-derived relative pitch area facilitates the tactical representativeness of small-sided games for the official soccer match. J Strength Cond Res 33(2): 523–530, 2019—Small-sided games (SSGs) are a promising training format in soccer to replicate (situations of) the official match across all age groups. Typically, SSGs are played on a smaller relative pitch area (RPA; i.e.

In crew rowing, crew members need to mutually synchronize their movements to achieve optimal crew performance. Intuitively, poor crew coordination is often deemed to involve additional boat movements such as surge velocity fluctuations, heave, pitch, and roll, which would imply lower efficiency (eg, due to increased hydrodynamic drag). The aim of this study was to investigate this alleged relation between crew coordination and boat movements at different stroke rates. Fifteen crews of two rowers rowed in a double scull (ie, a two-person boat) at 18, 22, 26, 30, and 34 strokes per minute. Oar angles (using potentiometers) and movements of the boat (using a three-axial accelerometer-gyroscope sensor) were measured (200Hz). Results indicated that crew synchronization became more consistent with stroke rate, while surge, heave, and pitch fluctuations increased. Further, within each stroke rate condition, better crew synchronization was related to less roll of the boat, but increased fluctuations regarding surge, heave, and pitch. Together this demonstrates that while better crew synchronization relates to enhanced lateral stability of the boat, it inevitably involves more detrimental boat movements and hence involves lower biomechanical efficiency.

Background: Hop tests are frequently used to determine return to sports (RTS) after anterior cruciateligament reconstruction (ACLR). Given that bilateral deficits are present after ACLR, this may result in afalsely high limb symmetry index (LSI), since LSI is calculated as a ratio between the values of the limbs.Hypothesis: Athletes after ACLR would achieve LSI > 90% for the hop test. Secondly, athletes after ACLRdemonstrate decreased jump distance on the single hop for distance (SLH) and triple leg hop for dis-tance (TLH) and decreased number of hops for the side hop (SH) for both involved and uninvolved limbscompared to normative data of sex, age and type of sports matched healthy athletes.Materials and methods: Fifty-two patients (38 males mean age 23.9 ± 3.5 years; 14 females mean age21.7 ± 3.5 years) who had undergone an ACLR participated in this study. Patients performed the 3 hoptests at a mean time of 7 months after ACLR. Hop distance, number of side hops and LSI were comparedwith normative data of 188 healthy athletes.Results: The differences between the involved limb and the uninvolved limb were significant in all hoptests (SLH P = 0.003, TLH P = 0.003, SH P = 0.018). For females, only significant between limb differenceswere found in the SLH (P = 0.049). For both the SLH and the TLH, significant differences were foundbetween the involved limb and the normative data (males; SLH P < 0.001, TLH P < 0.001; females; SLHP < 0.001, TLH P = 0.006) and between the uninvolved limb and the normative data for both males andfemales (males; SLH P < 0.001, TLH P < 0.001; females; SLH P = 0.003, TLH P = 0.038). For the SH, only sig-nificant differences were found between the involved limb and the normative values in males (P = 0.033).Conclusion: Athletes who have undergone an ACLR demonstrate bilateral deficits on hop tests in com-parison to age and sex matched normative data of healthy controls. Using the LSI may underestimateperformance deficits and should therefore be analyzed with caution when used as a criterion for RTSafter ACLR

OBJECTIVE: The aim of this study is to investigate if changes in perceived stress and recovery over the course of a season are risk factors for acute and overuse injuries. DESIGN: A prospective nonexperimental cohort design. SETTING: Data were gathered at the SportsFieldLab Groningen and at the facilities of the participating teams. PARTICIPANTS: Eighty-six male and female basketball, volleyball, and korfball players aged 21.9 ± 3.5 years. INTERVENTIONS: In this 10-month observational study, the independent variables are the changes in perceived stress and recovery. MAIN OUTCOME MEASURES: The Recovery-Stress Questionnaire for Athletes (RESTQ-Sport) was filled out every 3 weeks throughout the season to assess changes in perceived stress and recovery. Acute and overuse injuries were registered by the teams' physical therapists. Odds ratios and 95% confidence intervals were calculated. RESULTS: During one season, 66 acute and 62 overuse injuries were registered. Multinomial regression analysis showed that perceived General Recovery, shown in the scales Social Recovery and General Well-Being, decreased in the 6-week period before an acute injury (OR 0.59 and 0.61, respectively, P ≤ 0.05) compared with healthy periods. Risk of overuse injuries increased when perceived Sport Recovery, shown in the Personal Accomplishment scale, decreased in the 3-week period before the injury (OR 0.59, P ≤ 0.05) compared with healthy periods. CONCLUSIONS: Therefore, decreased perceived recovery can indicate an increased injury risk. General Recovery affects acute injury risk and Sport Recovery affects the risk of an overuse injury. Monitoring perceived recovery over the course of a season could give guidance for recovery enhancing practices to prevent injuries. Language: en

Objectives:The purpose of the current study was to compare the results of a progressive strengthtraining protocol for soccer players after anterior cruciate ligament reconstruction (ACLR) with healthycontrols, and to investigate the effects of the strength training protocol on peak quadriceps andhamstring muscle strength.Design:Between subjects design.Setting:Outpatient physical therapy facility.Participants:Thirty-eight amateur male soccer players after ACLR were included. Thirty age-matchedamateur male soccer players served as control group.Main outcome measures:Quadriceps and hamstring muscle strength was measured at three time pointsduring the rehabilitation. Limb symmetry index (LSI)>90% was used as cut-off criteria.Results:Soccer players after ACLR had no significant differences in peak quadriceps and hamstringmuscle strength in the injured leg at 7 months after ACLR compared to the dominant leg of the controlgroup. Furthermore, 65.8% of soccer players after ACLR passed LSI>90% at 10 months for quadricepsmuscle strength.Conclusion:Amateur male soccer players after ACLR can achieve similar quadriceps and hamstringmuscle strength at 7 months compared to healthy controls. Thesefindings highlight the potential ofprogressive strength training in rehabilitation after ACLR that may mitigate commonly reported strengthdeficits Non declared The authors would like to acknowledge T.P.C. Franke (PT, MSc)and D. Peeters (PT, BSc) for their contribution in describing therehabilitation protocol

Quality as well as quantity of tracking data have rapidly increased over the recent years, and multiple leagues have programs for league-wide collection of tracking data. Tracking data enables in-depth performance analysis, especially with regard to tactics. This already resulted in the development of several Key Performance Indicators (KPI’s) related to scoring opportunities, outplaying defenders, numerical balance and territorial advantage. Although some of these KPI’s have gained popularity in the analytics community, little research has been conducted to support the link with performance. Therefore, we aim to study the relationship between match outcome and tactical KPI’s derived from tracking data. Our dataset contains tracking data of all players and the ball, and match outcome, for 118 Dutch premier league matches. Using tracking data, we identified 72.989 passes. For every pass-reception window we computed KPI’s related to numerical superiority, outplayed defenders, territorial gains and scoring opportunities using position data. This individual data was then aggregated over a full match. We then split the dataset in a train and test set, and predicted match outcome using different combinations of features in a logistic regression model. KPI’s related to a combination of off-the-ball features seemed to be the best predictor of match outcome (accuracy of 64.0% and a log loss of 0.67), followed by KPI’s related to the creation of scoring opportunities (accuracy of 58% and a log loss of 0.69). This indicates that although most (commercially) available KPI’s are based on ball-events, the most important information seems to be in off-the-ball activity. We have demonstrated that tactical KPI’s computed from tracking data are relatively good predictors of match outcome. As off-the-ball activity seems to be the main predictor of match outcome, tracking data seems to provide much more insight than notational analysis.

Aim. To explore (1) general practitioners’ (GPs’) motivations to refer to lifestyle interventions and to investigate the association between GPs’ own lifestyle behaviors and their referral behavior and (2) patient indicators in the decision-making process of the GPs’ referral to lifestyle interventions. Method. A cross-sectional study was conducted among 99 Dutch primary care GPs. Their motivation to refer was assessed by beliefs regarding lifestyle interventions. GPs’ referral behaviors were assessed—considering referral and self-reported actual referral—as well as their own lifestyle behaviors (physical activity, dieting, being overweight). Decision making regarding referring patients to lifestyle interventions was assessed by imposed patient indicators, spontaneously suggested decisive patient indicators, and case-based referring (vignettes). Results. A substantial group of GPs was not motivated for referral to lifestyle interventions. GPs’ referral behavior was significantly associated with their perceived subjective norm, behavioral control, and their own physical activity and diet. Most important, patient indicators in referral to lifestyle interventions were somatic indicators and patients’ motivation for lifestyle interventions. Conclusions. GPs’ motivation and referral behavior might be improved by providing them with tailored resources about evidence-based lifestyle interventions, with support from allied health professionals and with official guidelines for a more objective and systematic screening of patients.

Olthof, SBH, Frencken, WGP, and Lemmink, KAPM. When something is at stake: Differences in soccer performance in 11 vs. 11 during official matches and training games. J Strength Cond Res 33(1): 167-173, 2019-11 vs. 11 training games are used to mimic the official match, but differ in playing duration and a consequence of winning or losing. Anxiety levels, crowd pressure, and the intention to win are examples of constraints present in the match, but absent or less prevalent in training. The aim is, therefore, to compare soccer performance in official matches with 11 vs. 11 training games. Six elite youth soccer teams played 5 official matches and 15 training games. Soccer performance, defined as a combination of game characteristics (game duration, transitions, and ball possession duration) and physical (distance covered, high-intensity distance, and sprints), technical (passing), and team tactical performance (inter-team and intra-team distances) and corresponding interaction patterns, was determined with video footage and positional data (local position measurement system). Soccer performance in official matches differed from similar training games, in a way that players covered more distance, sprinted more often, but game pace was lower and players made more mistakes. In addition, team width was smaller and length-per-width ratio larger and teams were tighter coupled in official matches. 11 vs. 11 training games can be used to mimic the match, in particular the team tactical performance. Coaches could increase physical and technical representativeness of training games by raising the stakes and increasing the consequence of winning or losing.

Video feedback may be a powerful tool to change biomechanical landing patterns associated with anterior cruciate ligament (ACL) injury risk. This study investigated the effect of video feedback on drop vertical jump (DVJ) landing strategies in team sport athletes. 59 athletes were assigned to a video feedback (VI) or control (CTRL) group. A pretest, 2 training sessions and a posttest were conducted. In both training sessions, video feedback, consisting of a video of the athlete's contour superimposed onto an expert's contour performing the DVJ landing task, was provided to the VI group; the CTRL group did not receive feedback. Outcomes included: kinematics and kinetics at peak knee valgus/varus moment during pre- and posttest and percentage overlap of expert and athlete during the training sessions. At posttest, males in the VI group showed greater hip flexion angles (p = 0.001) and range of motion (p

The aim of this study is to investigate the predictive value of landing stability and technique to gain insight into risk factors for ankle and knee injuries in indoor team sport players. Seventyfive male and female basketball, volleyball or korfball players were screened by measuring landing stability after a single-leg jump landing and landing technique during a repeated counter movement jump by detailed 3-dimensional kinematics and kinetics. During the season 11 acute ankle injuries were reported along with 6 acute and 7 overuse knee injuries by the teams’ physical therapist. Logistic regression analysis showed less landing stability in the forward and diagonal jump direction (OR 1.01–1.10, p ≤ 0.05) in players who sustained an acute ankle injury. Furthermore landing technique with a greater ankle dorsiflexion moment increased the risk for acute ankle injury (OR 2.16, p ≤ 0.05). A smaller knee flexion moment and greater vertical ground reaction force increased the risk of an overuse knee injury (OR 0.29 and 1.13 respectively, p ≤ 0.05). Less one-legged landing stability and suboptimal landing technique were shown in players sustaining an acute ankle and overuse knee injury compared to healthy players. Determining both landing stability and technique may further guide injury prevention programs.

Objectives: To evaluate dynamic stability index (DSI) differences between males and females for different jump directions. To examine both preseason DSI differences between players with and without a history of ankle sprain, and between players with and without an ankle sprain during the subsequent season.Design: Prospective cohort design.Setting: Laboratory.Participants: 47 male (22.9 +/- 3.9 y) and 19 female (21.5 +/- 2.9 y) sub-elite and elite team sport players. Main outcome measures: Ankle sprain history was collected using an injury history questionnaire. DSI of a single-leg hop-stabilization task measured preseason was collected using force plates and calculated using a Matlab program. Ankle sprains were reported during the subsequent season.Results: Male players demonstrated larger DSI than female players on forward medial/lateral stability index (MLSI) and vertical stability index (VSI), diagonal VSI, and lateral anterior/posterior stability index (APSI) and VSI. Forward, diagonal and lateral dynamic postural stability indices (DPSI) were larger for males (p Conclusion: Male players showed larger DSI scores than female players, indicating lower dynamic stability. Sex-specific training sessions or prevention programs should be developed. (C) 2015 Elsevier Ltd. All rights reserved.

Sports analytics in general and soccer analytics, in particular, have evolved in recent years due to the increased availability of large data amounts of (tracking) data. Especially in terms of evaluating tactical behavior, data science could change the way we think about soccer. In this study, we evaluate passing performance in soccer to prove the hypothesis that tactical behavior in team sports can be analyzed based exclusively on tracking data. To prove this point, we explore the relationship between changes in spatiotemporal variables in relation to passing and key performance indicators. Based on our results that demonstrate the ability of spatiotemporal variables to predict pass accuracy and key performances indicators on an individual level, we confirmed our hypothesis. Furthermore, we calculated a simple composite performance indicator to evaluate passes and players based on tracking data. In conclusion, our results can be used as an approach for real-time evaluation of tactical behavior and as a new method to scout and evaluate players in soccer and team sports in general.

OBJECTIVE: Intervening on barrier beliefs (BBs) may inhibit the role of barriers as mediating factors in lifestyle behavior. The aim of this study was to analyze the effects of a barrier-belief counseling intervention (BBCI) on physical activity (PA) and healthy food intake.METHODS: An RCT was conducted in a primary care setting among adults (aged 18-70), with two interventions: a BBCI (n = 123) and a standardized lifestyle group intervention (SLI) (n = 122). A non-treated hanging control group (n = 36) received no intervention. Outcomes on PA (accelerometer and SQUASH) and fruit and vegetable intake (self-report) were measured with follow-ups at 6, 12 and 18 months, and analyzed using multiple regression.RESULTS: The BBCI was more effective on PA compared with the SLI (p CONCLUSIONS: BBCI in primary care improves PA compared with SLI.PRACTICE IMPLICATIONS: The customized BB approach seems promising for implementation in healthcare practice to stimulate PA.

In professional soccer, nowadays almost every team employs tracking technology to monitor performance during trainings and matches. Over the recent years, there has been a rapid increase in both the quality and quantity of data collected in soccer resulting in large amounts of data collected by teams every single day. The sheer amount of available data provides opportunities as well as challenges to both science and practice. Traditional experimental and statistical methods used in sport science do not seem fully capable to exploit the possibilities of the large amounts of data in modern soccer. As a result, tracking data are mainly used to monitor player loading and physical performance. However, an interesting opportunity exists at the intersection of data science and sport science. By means of tracking data, we could gain valuable insights in the how and why of tactical performance during a soccer match. One of the most interesting and most frequently occurring elements of tactical performance is the pass. Every team has around 500 passing interactions during a single game. Yet, we mainly judge the quality and effectiveness of a pass by means of observational analysis, and whether the pass reaches a teammate. In this article, we present a new approach to quantify pass effectiveness by means of tracking data. We introduce two new measures that quantify the effectiveness of a pass by means of how well a pass disrupts the opposing defense. We demonstrate that our measures are sensitive and valid in the differentiation between effective and less effective passes, as well as between the effective and less effective players. Furthermore, we use this method to study the characteristics of the most effective passes in our data set. The presented approach is the first quantitative model to measure pass effectiveness based on tracking data that are not linked directly to goal-scoring opportunities. As a result, this is the first model that does not overvalue forward passes. Therefore, our model can be used to study the complex dynamics of build-up and space creation in soccer.

Purpose There is a lack of objective factors which can be used in guiding the return to sport (RTS) decision after an anterior cruciate ligament reconstruction (ACLR). The purpose of the current study was to conduct qualitative analysis of the single leg hop (SLH) in patients after ACLR with a simple and clinical friendly method and to compare the possible difference in movement pattern between male and female patients. Methods Sixty-five patients performed the single leg hop (SLH) test at 6.8 ± 1.0 months following isolated ACLR. Digital video camcorders recorded frontal and sagittal plane views of the patient performing the SLH. Knee flexion at initial contact (IC), peak knee flexion, knee flexion range of motion (RoM), and knee valgus RoM were calculated. In addition, limb symmetry index (LSI) scores were calculated. Results No differences were found in movement pattern between males and females. Movement analysis revealed that males had a decrease in knee flexion at IC (p = 0.018), peak knee flexion (p = 0.002), and knee flexion RoM (p = 0.017) in the injured leg compared to the non-injured leg. Females demonstrated a decrease in peak knee flexion (p = 0.011) and knee flexion RoM (p = 0.023) in the injured leg compared to the non-injured leg. Average LSI scores were 92.4% for males and 94.5% for females. Conclusions Although LSI scores were > 90%, clinical relevant altered movement patterns were detected in the injured leg compared to the non-injured leg. Caution is warranted to solely rely on LSI scores to determine RTS readiness. Clinical trial registry name and registration The University of Groningen, ID 2012.362. Level of evidence III.

How do outfielders control their locomotor behavior in running to catch fly balls? This question has been the topic of many empirical studies. It is interesting that a little addressed but highly relevant issue in this regard is that of the influence of perceived catchability on locomotor control. We examined what factors determine catchability and whether catchability can be reliably perceived. We had participants run to catch fly balls that could either be catchable or uncatchable. Participants performed two tasks. In the catching task, they were instructed to attempt to catch the ball and to keep running even when they felt that a ball was uncatchable. In the judging task, they were instructed to call "no" as soon as they perceived a ball to be uncatchable. Using Generalized Linear Mixed Effects Regression (GLMER) on data from the catching task, we modeled catchability, identifying five behaviorally relevant agent-environment variables that together explained 84.4% of the variance in catching performance. Next, we examined whether judgments of catchability were accurate. Using the GLMER-model, the catchability of every fly ball in the judging task was predicted and subsequently compared with participants' judgments. Participants were able to correctly judge the catchability of a fly ball on 85.4% of the trials. It is interesting that participants' judgments of fly balls to be uncatchable most often were given only after they had started running. Present findings provide a valuable step toward the formalization of an affordance-based control strategy for running to catch fly balls. (PsycINFO Database Record

Purpose: The purpose of the current prospective study was to assess the changes over time in patients tested at 6 months and 9 months after anterior cruciate ligament reconstruction (ACLR) with a return to sport (RTS) test battery. It was hypothesized that more patients passed RTS criteria at 9 months compared to 6 months. Methods: Sixty-two ACLR patients performed a test battery at an average of 6.5 ± 0.7 and 9.5 ± 0.9 months after ACLR. All patients underwent a standardized rehabilitation protocol. The test battery consisted of the following tests: a jump-landing task assessed with the Landing Error Scoring System (LESS), three single-leg hop tasks (single-leg hop test, triple-leg hop test, side hop test), isokinetic quadriceps and hamstring strength at 60, 180 and 300°/s and two questionnaires (IKDC and ACL–RSI). Cut off criteria were set as Limb Symmetry Index (LSI) > 90% (for isokinetic strength and for single-leg hop tasks), LESS < 5, IKDC score within 15th percentage of healthy subjects and ACL–RSI > 56 respectively. Results: At 6 months, two patients (3.2%) passed all criteria. At 9 months, seven patients (11.3%) passed all criteria. Patients improved in all RTS criteria over time except for the IKDC score. Twenty-nine patients (46.8%) did not pass the strength criterion at 60°/s at 9 months after ACLR. Conclusions: The percentages of patients passing all RTS criteria were low at both 6 and 9 months after ACLR. Quadriceps strength revealed persistent deficits and the lack of improvement in the IKDC score questionnaires shows insufficient self-reported knee function for RTS. Level of evidence: III.

The purpose was to investigate perceived stress and recovery related to cycling performance of female athletes over one full year. 20 female athletes ( age, 27 +/- 8 years; VO2max, 50.3 +/- 4.6 mL center dot kg(-1) center dot min(-1)) were measured 8 times in one year to determine perceived stress and recovery ( RESTQ-Sport) in relation to cycling performance ( Lamberts and Lambert Submaximal Cycle Test ( LSCT)). All 19 RESTQ-Sport scales were calculated and scores of the 4 main categories were determined ( i. e., general stress, general recovery, sport- specific stress and sport- specific recovery). A balance score of total stress and recovery was calculated by recovery- stress. Power at the second stage ( P80), third stage ( P90) and heart rate recovery ( HRR60 s) of the LSCT were determined as performance parameters. 110 RESTQ- Sports and LSCTs were analysed using a multilevel approach ( random intercepts model). Higher self- efficacy was related to improvement of all performance parameters. Higher total recovery stress, and lower emotional stress were related to improvement of P90 and HRR60 s. Higher sportspecific recovery was related to P80, higher general stress, fatigue and physical complaints were related to decreased P90 and higher social stress and injury were related to decreased HRR60 s. Improved perceived recovery and stress contributed to an improved performance. Relevant information could be provided by monitoring changes in perceived stress and recovery of female athletes.

Otter, RTA, Brink, MS, Lamberts, RP, and Lemmink, KAPM. A new submaximal rowing test to predict 2,000-m rowing ergometer performance. J Strength Cond Res 29(9): 2426-2433, 2015-The purpose of this study was to assess predictive value of a new submaximal rowing test (SmRT) on 2,000-m ergometer rowing time-trial performance in competitive rowers. In addition, the reliability of the SmRT was investigated. Twenty-four competitive male rowers participated in this study. After determining individual HRmax, all rowers performed an SmRT followed by a 2,000-m rowing ergometer time trial. In addition, the SmRT was performed 4 times (2 days in between) to determine the reliability. The SmRT consists of two 6-minute stages of rowing at 70 and 80% HRmax, followed by a 3-minute stage at 90% HRmax. Power was captured during the 3 stages, and 60 seconds of heart rate recovery (HRR60s) was measured directly after the third stage. Results showed that predictive value of power during the SmRT on 2,000-m rowing time also increased with stages. CVTEE% is 2.4, 1.9, and 1.3%. Pearson correlations (95% confidence interval [95% CI]) were -0.73 (-0.88 to -0.45), -0.80 (-0.94 to -0.67), and -0.93 (-0.97 to -0.84). 2,000-m rowing time and HRR60s showed no relationship. Reliability of power during the SmRT improved with the increasing intensity of the stages. The coefficient of variation (CVTEM%) was 9.2, 5.6, and 0.4%. Intraclass correlation coefficients (ICC) and 95% CI were 0.91 (0.78-0.97), 0.92 (0.81-0.97), and 0.99 (0.97-1.00). The CVTEM% and ICC of HRR60s were 8.1% and 0.93 (0.82-0.98). In conclusion, the data of this study shows that the SmRT is a reliable test that it is able to accurately predict 2,000-m rowing time on an ergometer. The SmRT is a practical and valuable submaximal test for rowers, which can potentially assist with monitoring, fine-tuning and optimizing training prescription in rowers.

Purpose Adding external focus of attention (EF, focus on the movement effect) may optimize current anterior cruciate ligament (ACL) injury prevention programmes. The purpose of the current study was to investigate the effects of an EF, by a visual stimulus and an internal focus, by a verbal stimulus during unexpected sidestep cutting in female and male athletes and how these effects remained over time. Methods Ninety experienced basketball athletes performed sidestep cutting manoeuvres in three sessions (S1, S2 and S3). In this randomized controlled trial, athletes were allocated to three groups: visual (VIS), verbal (VER) and control (CTRL). Kinematics and kinetics were collected at the time of peak knee frontal plane moment. Results Males in the VIS group showed a larger ver- tical ground reaction force (S1: 25.4 ± 3.1 N/kg, S2: 25.8 ± 2.9 N/kg, S3: 25.2 ± 3.2 N/kg) and knee flexion moments (S1: −3.8 ± 0.9 Nm/kg, S2: −4.0 ± 1.2 Nm/ kg, S3: −3.9 ± 1.3 Nm/kg) compared to the males in the VER and CTRL groups and to the females in the VIS group (p < 0.05). Additionally, the males in the VIS group reduced knee valgus moment and the females in the VER group reduced knee varus moment over time (n.s.). Conclusion Male subjects clearly benefit from visual feedback. Females may need different feedback modes to learn a correct movement pattern. Sex-specific learning preferences may have to be acknowledged in day by day practice. Adding video instruction or feedback to regular training regimens when teaching athletes safe movement patterns and providing individual feedback might target suboptimal long-term results and optimize ACL injury prevention programmes. Level of evidence I.

Physical and psychosocial stress and recovery are important performance determinants. A holistic approach that monitors these performance determinants over a longer period of time is lacking. Therefore this study aims to investigate the effect of a player’s physical and psychosocial stress and recovery on field-test performance. In a prospective non-experimental cohort design 10 female Dutch floorball players were monitored over 6 months. To monitor physical and psychosocial stress and recovery, daily training-logs and three-weekly the Recovery-Stress Questionnaire for Athletes (RESTQ-Sport) were filled out respectively. To determine field-test performance 6 Heart rate Interval Monitoring System (HIMS) and 4 Repeated Modified Agility T-test (RMAT) measurements were performed. Multilevel prediction models were applied to account for within-players and between-players field-test performance changes. The results show that more psychosocial stress and less psychosocial recovery over 3 to 6 weeks before testing decrease HIMS performance (p≤0.05). More physical stress over 6 weeks before testing improves RMAT performance (p≤0.05). In conclusion, physical and psychosocial stress and recovery affect submaximal interval-based running performance and agility up to 6 weeks before testing. Therefore both physical and psychosocial stress and recovery should be monitored in daily routines to optimize performance.

Purpose: Young soccer players need excellent tactical skills to reach the top. Tactical behavior emerges through interactions between opposing teams. However, few studies have focused on on-field tactical behavior of teams with talented soccer players. Therefore, this study aimed to determine teams' tactical behavior during small-sided games in two age categories, Under-17 and Under-19.Methods: Positional data of thirty-nine elite-standard soccer players were collected during twenty-four small-sided games to calculate longitudinal and lateral inter-team distances, stretch indices and length per width ratios. Corresponding interaction patterns and game-to-game variability were also determined.Results: Under-19 showed a significantly larger lateral stretch index and a significantly lower length per width ratio compared with Under-17. Furthermore, teams of both age groups showed similar large proportions of in-phase behavior. Variability of tactical performance measures within and between games was similar for Under-17 and Under-19.Conclusions: Variability within games seems to be functional for attacking teams for creating goal-scoring opportunities. In conclusion, the main difference was that Under-19 adopted a wider pitch dispersion than Under-17, represented by a larger lateral stretch index and smaller length per width ratio. Coach instructions and training exercises should be directed at exploiting pitch width to increase the pursuit of goal-scoring. (C) 2015 Elsevier B.V. All rights reserved.

BackgroundInsufficient postmatch recovery in elite players may cause an increased risk of injuries, illnesses and non-functional over-reaching.ObjectiveTo evaluate postmatch recovery time courses of physical performance and biochemical markers in team ball sport players.Study designSystematic review.Data sourcesPubMed and Web of Science.Eligibility criteria for selecting studiesThis systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The Critical Review Form for Quantitative Studies was used to evaluate quality. Studies were included if they met the following criteria: (1) original research evaluated players’ physical recovery postmatch; (2) team/intermittent sports; and (3) at least two postmeasurements were compared with baseline values.ResultsTwenty-eight studies were eligible. Mean methodological quality was 11.2±1.11. Most used performance tests and biochemical markers were the countermovement jump test, sprint tests and creatine kinase (CK), cortisol (C) and testosterone (T), respectively.Summary/conclusionsThe current evidence demonstrates that underlying mechanisms of muscle recovery are still in progress while performance recovery is already reached. CK recovery time courses are up to ≥72 hours. Soccer and rugby players need more time to recover for sprint performance, CK and C in comparison to other team ball sports. There are more high-quality studies needed regarding recovery in various team sports and recovery strategies on an individual level should be evaluated.Clinical relevanceOngoing insufficient recovery can be prevented by the use of the presented recovery time courses as specific practical recovery guidelines.

Applying an established theory of cognitive development―Skill Theory―the current study compares the game-reading skills of youth players selected for a soccer school of a professional soccer club (n = 49) and their non-selected peers (n = 38). Participants described the actions taking place in videos of soccer game plays, and their verbalisations were coded using Skill Theory. Compared to the non-selected players, the selected players generally demonstrated higher levels of complexity in their game-reading, and structured the information of game elements―primarily the player, teammate and field―at higher complexity levels. These results demonstrate how Skill Theory can be used to assess, and distinguish game-reading of youth players with different expertise, a skill important for soccer, but also for other sports.

Introduction: Cutting is an important skill in team-sports, but unfortunately is also related to non-contact ACL injuries. The purpose was to examine knee kinetics and kinematics at different cutting angles.Material and methods: 13 males and 16 females performed cuts at different angles (45°, 90°, 135° and 180°) at maximum speed. 3D kinematics and kinetics were collected. To determine differences across cutting angles (45°, 90°, 135° and 180°) and sex (female, male), a 4 × 2 repeated measures ANOVA was conducted followed by post hoc comparisons (Bonferroni) with alpha level set at α ≤ 0.05 a priori.Results: At all cutting angles, males showed greater knee flexion angles than females (p Conclusion: It can be concluded that different cutting angles demand different knee kinematics and kinetics. Sharper cutting angles place the knee more at risk. However, females and males handle this differently, which has implications for injury prevention.

Background: Hop tests are frequently used to determine return to sports (RTS) after anterior cruciate ligament reconstruction (ACLR). Given that bilateral deficits are present after ACLR, this may result in a falsely high limb symmetry index (LSI), since LSI is calculated as a ratio between the values of the limbs. Hypothesis: Athletes after ACLR would achieve LSI. >. 90% for the hop test. Secondly, athletes after ACLR demonstrate decreased jump distance on the single hop for distance (SLH) and triple leg hop for distance (TLH) and decreased number of hops for the side hop (SH) for both involved and uninvolved limbs compared to normative data of sex, age and type of sports matched healthy athletes. Materials and methods: Fifty-two patients (38 males mean age 23.9. ±. 3.5. years; 14 females mean age 21.7. ±. 3.5 years) who had undergone an ACLR participated in this study. Patients performed the 3 hop tests at a mean time of 7 months after ACLR. Hop distance, number of side hops and LSI were compared with normative data of 188 healthy athletes. Results: The differences between the involved limb and the uninvolved limb were significant in all hop tests (SLH P = 0.003, TLH P = 0.003, SH P = 0.018). For females, only significant between limb differences were found in the SLH (P = 0.049). For both the SLH and the TLH, significant differences were found between the involved limb and the normative data (males; SLH P

During intensified phases of competition, attunement of exertion and recovery is crucial to maintain performance. Although a mismatch between coach and player perceptions of training load is demonstrated, it is unknown if these discrepancies also exist for match exertion and recovery. Purpose:To determine match exertion and subsequent recovery and to investigate the extent to which the coach is able to estimate players’ match exertion and recovery. Methods:Rating of perceived exertion (RPE) and total quality of recovery (TQR) of 14 professional basketball players (age 26.7 ± 3.8 y, height 197.2 ± 9.1 cm, weight 100.3 ± 15.2 kg, body fat 10.3% ± 3.6%) were compared with observations of the coach. During an in-season phase of 15 matches within 6 wk, players gave RPEs after each match. TQR scores were filled out before the first training session after the match. The coach rated observed exertion (ROE) and recovery (TQ-OR) of the players. Results:RPE was lower than ROE (15.6 ± 2.3 and 16.1 ± 1.4; P = .029). Furthermore, TQR was lower than TQ-OR (12.7 ± 3.0 and 15.3 ± 1.3; P < .001). Correlations between coach- and player-perceived exertion and recovery were r = .25 and r = .21, respectively. For recovery within 1 d the correlation was r = .68, but for recovery after 1–2 d no association existed. Conclusion:Players perceive match exertion as hard to very hard and subsequent recovery reasonable. The coach overestimates match exertion and underestimates degree of recovery. Correspondence between coach and players is thus not optimal. This mismatch potentially leads to inadequate planning of training sessions and decreases in performance during fixture congestion in basketball.

Tactical match performance depends on the quality of actions of individual players or teams in space and time during match-play in order to be successful. Technological innovations have led to new possibilities to capture accurate spatio-temporal information of all players and unravel the dynamics and complexity of soccer matches. The main aim of this article is to give an overview of the current state of development of the analysis of position data in soccer. Based on the same single set of position data of a high-level 11 versus 11 match (Bayern Munich against FC Barcelona) three different promising approaches from the perspective of dynamic systems and neural networks will be presented: Tactical performance analysis revealed inter-player coordination, inter-team and inter-line coordination before critical events, as well as team-team interaction and compactness coefficients. This could lead to a multi-disciplinary discussion on match analyses in sport science and new avenues for theoretical and practical implications in soccer.

The present study examined whether performance characteristics discriminated between selected and deselected players in talent development programmes. This examination was carried out in talented soccer players, aged 16-18 years using objective measurement instruments. Four domains of multidimensional performance characteristics (physiological, technical, tactical and psychological) were assessed by using a test battery consisting of soccer-specific field tests and questionnaires. Multivariate analyses of covariance revealed that the physiological characteristics peak and repeated shuttle sprint, the technical characteristics of peak and repeated shuttle dribble and the tactical characteristic of 'positioning and deciding', significantly differed between the selected (n=76) and deselected players (n=37), with selected players performing better (P

The beauty of football is hidden in its complexity. To be able to perform on an elite level, excellent physical, technical, and tactical skills are required (Impellizzeri and Marcora 2009). These s...

Purpose:The aim of the current study was to investigate and compare coaches’ and players’ perceptions of training dose for a full competitive season.Methods:Session rating of perceived exertion (RPE), duration, and training load (session RPE × duration) of 33 professional soccer players (height 178.2 ± 6.6 cm, weight 70.5 ± 6.4 kg, percentage body fat 12.2 ± 1.6) from an under-19 and under-17 (U17) squad were compared with the planned periodization of their professional coaches. Before training, coaches filled in the session rating of intended exertion (RIE) and duration (min) for each player. Players rated session RPE and training duration after each training session.Results:Players perceived their intensity and training load (2446 sessions in total) as significantly harder than what was intended by their coaches (P < .0001). The correlations between coaches’ and players’ intensity (r = .24), duration (r = .49), and load (r = .41) were weak (P < .0001). Furthermore, for coach-intended easy and intermediate training days, players reported higher intensity and training load (P < .0001). For hard days as intended by the coach, players reported lower intensity, duration, and training load (P < .0001). Finally, first-year players from the U17 squad perceived training sessions as harder than second-year players (P < .0001).Conclusion:The results indicate that young elite soccer players perceive training as harder than what was intended by the coach. These differences could lead to maladaptation to training. Monitoring of the planned and perceived training load of coaches and players may optimize performance and prevent players from overtraining.