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Objectives: To investigate possible persistent performance deficits after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in elite athletes., Methods: A prospective cohort study in three Belgian professional male football teams was performed during the 2020 - 2021 season. Participants were submitted to strength, jump, and sprint tests and an aerobic performance test (the Yo-Yo Intermittent Recovery test (YYIR)). These tests were repeated at fixed time intervals throughout the season. Assessment of SARS-CoV-2 infection was performed by a polymerase chain reaction (PCR) test before each official game., Results: Of the 84 included participants, 22 were infected with SARS-CoV-2 during follow-up. At the first testing after infection (52.0 ± 11.2 days after positive PCR testing) significantly higher percentages of maximal heart rate (%HRmax) were seen - within the isolated group of infected players- during ( p  = .006) and after the YYIR (2 min after, p  = .013), compared to pre-infection data. This increase in %HRmax was resolved at the second YYIR testing after infection (127.6 ± 33.1 days after positive PCR testing). Additionally, when comparing the first test after infection in formerly infected to non-infected athletes, significantly higher %HRmax were found during ( p  < .001) and after the YYIR test ( p  < .001),No significant deficits were found for the jump, muscular strength or sprint tests., Aerobic performance seems compromised even weeks after infection. Simultaneously, anaerobic performance seemed to be spared. Because of the potential detrimental effects on the immune system, caution might be advised with high-intensity exposure until aerobic performance is restored.KEY MESSAGESElite football players' aerobic performance seems to be affected for weeks after they return to sports after a SARS-CoV-2 infection.Similarly, anaerobic performance tests showed no discernible changes between both before and after SARS-CoV-2 infections.Regular YYIR testing is recommended to monitor aerobic performance after SARS-CoV-2 infection.

Objectives: The aim of this study was to investigate the association between SARS-CoV-2 infection and muscle strain injury in elite athletes., Methods: A prospective cohort study in three Belgian professional male football teams was performed during the first half of the 2020-2021 season (June 2020-January 2021). Injury data were collected using established surveillance methods. Assessment of SARS-CoV-2 infection was performed by a PCR test before each official game., Results: Of the 84 included participants, 22 were infected with SARS-CoV-2 and 14 players developed a muscle strain during the follow-up period. Cox's proportional hazards regression analyses demonstrated a significant association between SARS-CoV-2 infection and the development of muscle strain (HR 5.1; 95% CI 1.1 to 23.1; p=0.037), indicating an increased risk of developing muscle strains following SARS-CoV-2 infection. All athletes who sustained a muscle strain after infection were injured within the first month (15.71±11.74 days) after sports resumption and completed a longer time in quarantine (14.57±6.50 days) compared with the infected players who did not develop a muscle strain (11.18±5.25 days)., Conclusion: This study reported a five times higher risk of developing a muscle strain after a SARS-CoV-2 infection in elite male football players. Although this association should be examined further, it is possible that short-term detraining effects due to quarantine, and potentially pathological effects of the SARS-CoV-2 infection are associated with a higher risk of muscle strain injury., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Motor coordination and physical fitness are multidimensional concepts which cannot be reduced to a single variable. This study evaluated multivariate relationships among morphology, physical fitness and motor coordination in 74 pre-pubertal girls 8.0-8.9 years of age. Data included body dimensions, eight fitness items and four motor coordination tasks (KTK battery). Maturity status was estimated as percentage of predicted mature stature attained at the time of observation. Canonical correlation analysis was used to examine the relationships between multivariate domains. Significant pairs of linear functions between indicators of morphology and fitness (r c = 0.778, Wilks' Lambda = 0.175), and between fitness and motor coordination (r c = 0.765, Wilks' Lambda = 0.289) were identified. Girls who were lighter and had a lower waist-to-stature ratio and % fat mass attained better scores in the endurance run, sit-ups and standing long jump tests, but poorer performances in hand grip strength and 2-kg ball throw. Better fitness test scores were also associated with better motor coordination scores. Relationships between body size and estimated fatness with motor fitness suggested an inverse relationship that was particularly evident in performance items that required the displacement of the body through space, while motor coordination was more closely related with fitness than with somatic variables.

Background: The Tanner-Whitehouse radius-ulna-short bone protocol (TW2 RUS) for the assessment of skeletal age (SA) is widely used to estimate the biological (skeletal) maturity status of children and adolescents. The scale for converting TW RUS ratings to an SA has been revised (TW3 RUS) and has implications for studies of youth athletes in age-group sports., Objectives: The aim of this study was to compare TW2 and TW3 RUS SAs in an international sample of male youth soccer players and to compare distributions of players by maturity status defined by each SA protocol., Methods: SA assessments with the TW RUS method were collated for 1831 male soccer players aged 11-17 years from eight countries. RUS scores were converted to TW2 and TW3 SAs using the appropriate tables. SAs were related to chronological age (CA) in individual athletes and compared by CA groups. The difference of SA minus CA with TW2 SA and with TW3 SA was used to classify players as late, average, or early maturing with each method. Concordance of maturity classifications was evaluated with Cohen's Kappa coefficients., Results: For the same RUS score, TW3 SAs were systematically and substantially reduced compared with TW2 SAs; mean differences by CA group ranged from - 0.97 to - 1.16 years. Kappa coefficients indicated at best fair concordance of TW2 and TW3 maturity classifications. Across the age range, 42% of players classified as average with TW2 SA were classified as late with TW3 SA, and 64% of players classified as early with TW2 SA were classified as average with TW3 SA., Conclusion: TW3 SAs were systematically lower than corresponding TW2 SAs in male youth soccer players. The differences between scales have major implications for the classification of players by maturity status, which is central to some talent development programs.

An Online First version of this article was made available online at https://link.springer.com/article/10.1007%2Fs40279-017-0799-7 on 29 October 2017. Errors were subsequently identified in the article, and the following corrections should be noted.

The goal of this article was twofold, and a 2-study approach was conducted. The first study aimed to expose the anthropometrical, physical performance, and motor coordination characteristics that influence dropout from a high-level soccer training program in players aged 8-16 years. The mixed-longitudinal sample included 388 Belgian youth soccer players who were assigned to either a "club group" or a "dropout group." In the second study, cross-sectional data of anthropometry, physical performance, and motor coordination were retrospectively explored to investigate which characteristics influence future contract status (contract vs. no contract group) and first-team playing time for 72 high-level youth soccer players (mean age = 16.2 years). Generally, club players outperformed their dropout peers for motor coordination, soccer-specific aerobic endurance, and speed. Anthropometry and estimated maturity status did not discriminate between club and dropout players. Contract players jumped further (p = 0.011) and had faster times for a 5-m sprint (p = 0.041) than no contract players. The following prediction equation explains 16.7% of the variance in future playing minutes in adolescent youth male soccer players: -2,869.3 + 14.6 × standing broad jump. Practitioners should include the evaluation of motor coordination, aerobic endurance, and speed performances to distinguish high-level soccer players further succeeding a talent development program and future dropout players, between 8 and 16 years. From the age of 16 years, measures of explosivity are supportive when selecting players into a future professional soccer career.

It was hypothesized that differences in anthropometry, physical performance, and motor coordination would be found between Belgian elite and sub-elite level female volleyball players using a retrospective analysis of test results gathered over a 5-year period. The test sample in this study consisted of 21 young female volleyball players (15.3 ± 1.5 years) who were selected to train at the Flemish Top Sports Academy for Volleyball in 2008. All players (elite, n = 13; sub-elite, n = 8) were included in the same talent development program, and the elite-level athletes were of a high to very high performance levels according to European competition level in 2013. Five multivariate analyses of variance were used. There was no significant effect of playing level on measures of anthropometry (F = 0.455, p = 0.718, (Equation is included in full-text article.)= 0.07), flexibility (F = 1.861, p = 0.188, (Equation is included in full-text article.)= 0.19), strength (F = 1.218, p = 0.355, (Equation is included in full-text article.)= 0.32); and speed and agility (F = 1.176, p = 0.350, (Equation is included in full-text article.)= 0.18). Multivariate analyses of variance revealed significant multivariate effects between playing levels for motor coordination (F = 3.470, p = 0.036, (Equation is included in full-text article.)= 0.59). A Mann-Whitney U test and a sequential discriminant analysis confirmed these results. Previous research revealed that stature and jump height are prerequisites for talent identification in female volleyball. In addition, the results show that motor coordination is an important factor in determining inclusion into the elite level in female volleyball.

We investigated the evolution and stability of anthropometric and soccer-specific endurance characteristics of 42 high-level, pubertal soccer players with high, average and low yo-yo intermittent recovery test level 1 (YYIR1) baseline performances over two and four years. The rates of improvement were calculated for each performance group, and intra-class correlations were used to verify short- and long-term stability. The main finding was that after two and four years, the magnitudes of the differences at baseline were reduced, although players with high YYIR1 baseline performance still covered the largest distance (e.g., low from 703 m to 2126 m; high from 1503 m to 2434 m over four years). Furthermore, the YYIR1 showed a high stability over two years (ICC = 0.76) and a moderate stability over four years (ICC = 0.59), due to large intra-individual differences in YYIR1 performances over time. Anthropometric measures showed very high stability (ICCs between 0.94 to 0.97) over a two-year period, in comparison with a moderate stability (ICCs between 0.57 and 0.75) over four years. These results confirm the moderate-to-high stability of high-intensity running performance in young soccer players, and suggest that the longer the follow-up, the lower the ability to predict player's future potential in running performance. They also show that with growth and maturation, poor performers might only partially catch up their fitter counterparts between 12 and 16 years. Key pointsYoung, high-level soccer players with a relatively low intermittent-endurance capacity are capable to catch up with their better performing peers after four years.Individual development and improvements of anthropometric and physical characteristics should be considered when evaluating young soccer players.

The aim of the study was to investigate test reliability of the Yo-Yo intermittent recovery test level 1 (YYIR1) in 36 high-level youth soccer players, aged between 13 and 18 years. Players were divided into three age groups (U15, U17 and U19) and completed three YYIR1 in three consecutive weeks. Pairwise comparisons were used to investigate test reliability (for distances and heart rate responses) using technical error (TE), coefficient of variation (CV), intra-class correlation (ICC) and limits of agreement (LOA) with Bland-Altman plots. The mean YYIR1 distances for the U15, U17 and U19 groups were 2024 ± 470 m, 2404 ± 347 m and 2547 ± 337 m, respectively. The results revealed that the TEs varied between 74 and 172 m, CVs between 3.0 and 7.5%, and ICCs between 0.87 and 0.95 across all age groups for the YYIR1 distance. For heart rate responses, the TEs varied between 1 and 6 bpm, CVs between 0.7 and 4.8%, and ICCs between 0.73 and 0.97. The small ratio LOA revealed that any two YYIR1 performances in one week will not differ by more than 9 to 28% due to measurement error. In summary, the YYIR1 performance and the physiological responses have proven to be highly reliable in a sample of Belgian high-level youth soccer players, aged between 13 and 18 years. The demonstrated high level of intermittent endurance capacity in all age groups may be used for comparison of other prospective young soccer players.

Purpose: To model the development of soccer-specific aerobic performance, assessed by the Yo-Yo Intermittent Recovery Test Level 1 in 162 elite pubertal soccer players, age 11-14 y at baseline., Methods: Longitudinal multilevel modeling analyses comprised predictors related to growth (chronological age, body size [height and weight] and composition [fat mass, fat-free mass]), and motor coordination [3 KÖrperkoordination Test für Kinder subtests: jumping sideways, moving sideways, backward balancing] and estimated biological-maturation groups (earliest [percentile 66])., Results: The best-fitting model on soccer-specific aerobic performance could be expressed as -3639.76 + 369.86 × age + 21.38 × age² + 9.12 × height - 29.04 × fat mass + 0.06 × backward balance. Maturity groups had a negligible effect on soccer-specific aerobic performance (-45.32 ± 66.28; P > .05)., Conclusion: The current study showed that the development of aerobic performance in elite youth soccer is related to growth and muscularity and emphasized the importance of motor coordination in the talent-identification and -development process. Note that biological maturation was excluded from the model, which might endorse the homogeneity in estimated biological-maturation status in the current elite pubertal soccer sample.

This study investigated convergent and discriminant validity between two motor competence assessment instruments in 2485 Flemish children: the Bruininks-Oseretsky Test of Motor Proficiency 2 Short Form (BOT-2 Short Form) and the KörperKoördinationsTest für Kinder (KTK). A Pearson correlation assessed the relationship between BOT-2 Short Form total, gross and fine motor composite scores and KTK Motor Quotient in three age cohorts (6-7, 8-9, 10-11 years). Crosstabs were used to measure agreement in classification in children scoring below percentile 5 and 15 and above percentile 85 and 95. Moderately strong positive (r=0.44-0.64) associations between BOT-2 total and gross motor composite scores and KTK Motor Quotient and weak positive correlations between BOT-2 Short Form fine motor composite and KTK Motor Quotient scores (r=0.25-0.37) were found. Levels of agreement were fair to moderate. Therefore, some proof of convergent and discriminant validity between BOT-2 Short Form and KTK was established in this study, underlining the notion that the evaluation of motor competence should not be based upon a single assessment instrument., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The goal of this study was to investigate differences in physical fitness and sports participation over 2 years in children with relatively high, average, and low motor competence. Physical fitness and gross motor coordination of 501 children between 6-10 years were measured at baseline and baseline+2 years. The sample compromised 2 age cohorts: 6.00-7.99 and 8.00-9.99 years. An age and sex-specific motor quotient at baseline testing was used to subdivide these children into low (MQ < P33), average (P33 ≤ MQ < P66) and high (MQ ≥ P66) motor competence groups. Measures of sports participation were obtained through a physical activity questionnaire in 278 of the same children. Repeated Measures MANCOVA and two separate ANOVAs were used to analyze differences in changes in physical fitness and measures of sports participation respectively. Children with high motor competence scored better on physical fitness tests and participated in sports more often. Since physical fitness levels between groups changed similarly over time, low motor competent children might be at risk for being less physically fit throughout their life. Furthermore, since low motor competent children participate less in sports, they have fewer opportunities of developing motor abilities and physical fitness and this may further prevent them from catching up with their peers with an average or high motor competence.

The purpose of the study was to evaluate the developmental changes in performance in a repeated-sprint ability (RSA) test in young soccer players of contrasting maturity status. A total of 83 regional level Portuguese youth soccer players, aged 11-13 years at baseline was assessed annually. Stature, body mass, 7x34.2-m sprint protocol (25-s active recovery), 20-m multi-stage continuous shuttle endurance run and counter-movement jump (CMJ) without the use of the arms were measured. Fat-free mass (FFM) was determined by age and gender-specific formulas. Developmental changes in total sprint time across ages were predicted using multilevel modeling. Corresponding measurements were performed on an independent cross-sectional subsample of 52 youth soccer players 11-17 years to evaluate the predictive model. CA, CA(2), maturational status (SA-CA), body size (mass and stature), FFM, aerobic endurance, lower limb explosive strength and annual volume training significantly improved the statistical fit of the RSA multilevel model. In 'late' maturing athletes, the best model for predicting change in RSA was expressed by the following equation: 86.54 - 2.87 x CA + 0.05 x CA(2) - 0.25 x FFM + 0.15 x body mass + 0.05 x stature - 0.05 x aerobic endurance - 0.09 x lower limb explosive strength - 0.01 x annual volume training. The best fitting models for players who were 'on time' and 'early' maturing were identical to the best model for late maturing players, less 0.64 seconds and 1.74 seconds, respectively. Multilevel modeling provided performance curves that permitted the prediction of individual RSA performance across adolescent years in regional level soccer players. Key pointsRepeated-sprint ability tests are a valuable sport-specific field test of sprint performance in youth soccer players. Here, the test had reasonable reliability and can be useful to trainers and coaches in the assessment of young athletes and in monitoring changes over time.The total sprint time of youth soccer players advanced in biological maturation improves more, on average, than that of players who are on time (average) and late in maturation. The performance difference between early and late maturing players is consistent after about 13 years of age.Multilevel modeling is a promising statistical technique for analyzing the development of functional capacity in a sport. It has the potential to provide useful information to assist trainers and coaches in evaluating and facilitating the development of individual players.

Socioeconomic status (SES) is often indicated as a factor that influences physical activity and associated health outcomes. This study examined the relationship between SES and sport participation, morphology, fitness and motor coordination in a sample of 1955 Flemish children 6-11 years of age. Gender, age and SES-specific values for morphologic dimensions, amount and type of sport participation and fitness and motor coordination tests were compared. SES was positively and significantly associated with sport participation and sports club membership in both sexes. Although differences were not consistently significant, morphologic dimensions and tests of fitness and motor coordination showed a trend in favor of children from higher SES. The results suggest that public and local authorities should consider providing equal opportunities for children in all social strata and especially those in the lower SES to experience the beneficial effects of sport participation through which they can enhance levels of physical fitness and motor coordination.

The Developmental Model of Sports Participation proposes two pathways towards expertise in sports between 6 and 12 years of age: early specialization and early diversification. This study investigated the effect of sampling various sports and of spending many or few hours in sports on fitness and gross motor coordination. Altogether, 735 boys in three age groups (6-8, 8-10, and 10-12 years) were profiled using a fitness test battery. A computerized physical activity questionnaire was used to obtain data on sports participation. In the eldest group, (M)ANCOVA showed a positive effect of sampling various sports on strength, speed, endurance, and gross motor coordination (P < 0.05). A positive effect of many hours per week spent in sports was apparent in every age group. These data suggest an acute positive effect of many hours in sports and a latent positive effect of early sampling on fitness and gross motor coordination. Multiple comparisons revealed that boys aged 10-12 years, who spent many hours in various sports, performed better on standing broad jump (P < 0.05) and gross motor coordination (P < 0.05) than boys specializing in a single sport. Therefore, our results highlight the importance of spending many hours in sports and sampling various sports in the development of fitness and gross motor coordination.

Gymnastics talent identification focuses on the identification of young gymnasts who display characteristics for potential success in the future. The aim of this study was to identify which current performance characteristics are related to performance in competition 2 years later. Twenty-three female gymnasts aged 7-8 years completed a multidimensional test battery measuring anthropometric, physical, and coordinative characteristics and were technically evaluated by expert coaches. Two years later, the all-around competition results of those gymnasts now participating in elite (n = 12) and sub-elite (n = 11) competition were obtained. None of the initial measurements significantly correlated with the results of the sub-elite gymnasts 2 years later. For the elite gymnasts, a non-sport-specific motor test battery correlated strongly with the competition result, with more than 40% of the variation in competition performance being explained by the result on that test 2 years earlier. Neither the coaches' judgement nor the anthropometric and physical characteristics were sensitive enough to predict performance. A motor coordination test might be valuable in the early identification of gymnasts, as its discriminative and predictive qualities might be sufficiently powerful for selection within a relatively homogeneous population of gymnasts exhibiting similar anthropometric and physical profiles.

We report the morphology (height, weight, body fat, body mass index), fitness (strength, speed, agility, flexibility), and soccer-specific (dribbling) and non-specific motor coordination skills (Körper KoordinationsTest für Kinder; KTK) of 78 Belgian international youth soccer players aged 15-16 years with varying biological maturity status. The more mature players (U16 and U17) possessed higher morphological measures and outperformed their later maturing peers (U16 Futures and U17 Futures) on almost all fitness tests. However, soccer-specific and non-specific motor coordination tests did not distinguish the more mature players from the later maturing players in both age groups. When adjusted for the confounder (age at peak height velocity), multivariate analysis of covariance revealed that several morphology- and fitness-related parameters did not differ between selection groups, again in both age groups. These findings indicate that biological maturation affects morphology and fitness more so than motor coordination skills. In conclusion, to prevent the dropout of promising late maturing players, we suggest avoiding one-dimensional approaches and to include measures of biological maturity status as well as maturity independent performance tests during the talent identification and selection process.

Background: Adolescence is characterized by increments in body size and physical performance. Short bursts of maximal intensity, requiring anaerobic metabolism, are important in many team sports including basketball., Aim: Variation of anaerobic power of adolescent basketball players (n = 93, 14-16 years) in relation to years before and after estimated age at peak height velocity (PHV) and variation in body size was considered., Methods: The cross-sectional study included chronological age, estimated age at PHV, training experience; stature, body mass (BM), free-fat mass (FFM) and estimated lower-limb volume (LLV) by anthropometry; and short-term power outputs derived from the Wingate Anaerobic Test (WAnT). Based on proportional allometric modeling, power outputs were partitioned for biological maturity status and size variables. Pearson correlations were used to estimate the associations between distance to PHV (maturity offset) and training experience with absolute and scaled estimates of short-term power., Results: Absolute WAnT increased linearly (PP, r = 0.72; MP, r = 0.74) through the interval of rapid growth of the adolescent spurt. Increments were related mainly to BM and muscle mass. Nevertheless, a residual significant positive influence of chronological age per se on maximal short-term power outputs remained independent of body size., Conclusion: Allometric modelling to partition size may reveal other potentially meaningful factors in the development of short-term performance in adolescent athletes.

Discussions of growth and motor performance of children are often set in the context of physical fitness. Although there is a clear theoretical concept or definition of fitness comprising motor coordination, the latter is not systematically considered. This study determined to what extent the variance in motor coordination might be explained by morphological and fitness characteristics. To postulate understanding of this association during childhood, 613 boys aged 7-11 years completed the morphological measurements, the Körperkoordinationstest für Kinder (KTK) and different fitness tests. The results demonstrated a substantial interrelationship among morphology, fitness and motor coordination in elementary school boys. The magnitude of explained variance and the loadings of the canonical correlation between the several constructs are strongly pronounced during childhood indicating that these constructs should be well considered given their contribution to a child's general development.

Relationships between growth, maturation and maximal short-term power outputs were investigated in 94 youth basketball players aged 14-16 years. Data included chronological age (CA), skeletal age (SA), years of training; body dimensions, estimated thigh volume, a running based short-term exercise assessed by the line drill test (LDT), the Bangsbo sprint test (BST) and short-term muscle power outputs with the Wingate anaerobic test (WAnT). Multiple linear regression analyses were used to estimate the effects of CA, skeletal maturity (SA/CA), years of training experience, body size and lower-limb volume on short-term performance in the LDT, BST and WAnT, respectively. Explained variances differed between cycle-ergometry outputs (52-54%) and running test performances (23-46%). The independent effects of predictors were small in the fatigue scores of the WAnT (4%) and the BST (11%). Skeletal maturity, body mass and leg length were primary predictors for all maximal short-term power output measures. Leg length was more relevant as a predictor than stature in the WAnT outputs, while stature and body mass appeared in the model with the running tests as dependent variable. Maximal short-term running abilities were also sensitive to years of training. In summary, skeletal maturation, body size and thigh muscle mass explained moderate to large proportions of the variance on maximal short-term performances of adolescent basketball players. The results highlight the importance of considering maturity status in evaluating the maximal short-term power outputs of adolescent athletes.

This study evaluates the validity and reliability of the line-drill (LD) test of anaerobic performance in 76 male basketball players 14.0-16.0 years of age. The Wingate Anaerobic Test (WAnT) was used as the reference for anaerobic performance. Wingate Anaerobic Test and LD test were moderately correlated (0.39 and 0.43, p < 0.01). Estimated age at peak height velocity (APHV) was moderately, negatively, and significantly (p < 0.01) correlated with WAnT peak (r = -0.69) and mean power (r = -0.71); earlier-maturing players had greater anaerobic power. Training experience was not associated with anaerobic performance, but chronological age (CA) and estimated APHV were significant covariates of the LD test (p < 0.05). National players were better than local players on the LD test (p < 0.01) after controlling for CA and body size. Short-term reliability of the LD test (n = 12, 1-week interval) was good: technical error of measurement = 0.44 seconds (95% confidence interval [CI] 0.31-0.75 seconds), intraclass correlation coefficient = 0.91 (95% CI 0.68-0.97), and coefficient of variation = 1.4% (95% CI 1.0-2.3%). Although the relationship between the LD test and WAnT was moderate, the LD test effectively distinguished local- and national-level adolescent basketball players. In contrast to WAnT, the LD test was not influenced by estimated biological maturity status. Thus, the LD test may be suitable for field assessment of anaerobic performance of youth basketball players.

Former research demonstrated that depression is associated with dysfunctional attentional processing of emotional information. Most studies examined this bias by registration of response latencies. The present study employed an ecologically valid measurement of attentive processing, using eye-movement registration. Dysphoric and non-dysphoric participants viewed slides presenting sad, angry, happy and neutral facial expressions. For each type of expression, three components of visual attention were analysed: the relative fixation frequency, fixation time and glance duration. Attentional biases were also investigated for inverted facial expressions to ensure that they were not related to eye-catching facial features. Results indicated that non-dysphoric individuals were characterised by longer fixating and dwelling on happy faces. Dysphoric individuals demonstrated a longer dwelling on sad and neutral faces. These results were not found for inverted facial expressions. The present findings are in line with the assumption that depression is associated with a prolonged attentional elaboration on negative information., (© 2010 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business)

Background: The reproducibility of day-to-day testing of isokinetic concentric and eccentric muscular actions among adolescent basketball players aged 14 to 16 years and relationships of mean within-subject variation in two isokinetic testing sessions with chronological age, biological maturation (estimated age at peak height velocity), training experience, body size, lower-body morphology, and initial strength performance were evaluated., Material and Methods: The sample included 27 basketball players who completed replicate test sessions of 5 repetitions of reciprocal concentric and eccentric knee extensions and flexions at 60º s(-1). A randomly selected subsample of 8 players completed a third testing session to confirm reliability estimates., Results: Coefficients of variation (CV) between sessions 1 and 2 ranged from 8.1% to 17.4%, and intraclass coefficients (ICCs) ranged from 0.72 to 0.89. For sessions 1 and 3, CVs ranged from 3.9% to 6.0%, and ICCs ranged from 0.95 to 0.99. The initial level of strength of eccentric knee flexion (r=-0.43) and eccentric knee extension (r=-0.42) were correlated (P<0.05) with eccentric knee extension within-variation between two sessions. Training experience (r=-0.37, P<0.05) and initial values of concentric knee flexion (r=-0.62, P<0.01) were correlated with concentric knee flexion within-subject differences. Within-subject variation of eccentric knee extension was correlated (P<0.05) with chronologic age (r=0.41), estimated age at peak height velocity (r=-0.38), body size (r=0.41 to 0.47), and leg volume (r=0.39)., Conclusions: Familiarization sessions may improve the reliability of concentric and eccentric knee isokinetic strength testing at 60º s(-1) in adolescent basketball players. Age, maturity status, and training experience of young athletes should be considered when testing knee isokinetic strength at 60º s(-1).

Aim: The influence of maturity status on body size, functional capacities and basketball-specific skills was evaluated and multivariate relationships between domains of variables were examined in 80 male basketball players 12.0-13.9 years., Methods: Height, body mass and two skinfolds were measured. Stage of pubic hair (PH) was assessed clinically. Functional capacity was assessed with the vertical jump (squat jump, countermovement jump), 2-kg medicine ball throw, hand grip strength, 60-second sit-ups and endurance shuttle run. Performances on four basketball skills were tested: shooting, passing, dribbling and defensive movements. Analysis of covariance with age as the covariate was used to test differences among players by stage of puberty. Associations among body size, adiposity, functional capacities and skills were evaluated with canonical correlation analysis., Results: Maturity status explained a significant portion of variance in body size (F=50.13, P<0.01, h2=057, for height; F=13.47, P<0.01, h2=0.26, for weight). The effect of pubertal status was significant for the jumps and upper limb strength, but not for sit-ups or aerobic endurance. Canonical correlations showed an inverse relationship of height and adiposity with skill tests, and a positive relationship between skills and a combination of abdominal muscular strength (sit-ups) and aerobic endurance., Conclusion: Skill appeared to be independent of pubertal status and the tallest group of basketball players did not attain better scores in basketball-specific skill tests.

Aim: The main aim of the current study was to compare the anthropometrical and fitness profile of female soccer players by level and by playing positions. The second purpose was to explore correlations between kicking speed on the one hand and anthropometric features and explosive strength on the other., Methods: Female soccer players (N.=190) were tested divided in two groups: elite group (N.=100) and non-elite group (N.=90). Body mass, height, leg length, body composition, counter movement jump, drop jump and kicking speed with both legs were measured., Results: After controlling for experience with multivariate analysis of covariance (MANCOVA), body mass, body fat and muscle mass differed significantly by level. MANCOVA also revealed that all the anthropometrical variables differed by playing position. However, MANCOVA did not show significant differences by level of play, neither for explosive strength nor for kicking speed but revealed significant differences among playing positions. There were significant positive correlations between body mass, height, leg length, muscle mass, counter movement jump height, drop jump height and experience on the one hand and kicking speed with dominant and non-dominant leg on the other for the elite and non-elite players., Conclusions: Elite players differ from their non-elite counterparts in terms of anthropometrical features, while explosive strength and kicking speed are not sensitive enough to distinguish between levels. On the other hand, the findings indicate few positional variations, and only goalkeepers, tend to have a specific anthropometric and fitness profile. Anthropometric variables, explosive strength and experience have an influence on kicking speed.

The aim of the present study was to examine how explosive strength, kicking speed, and body composition are affected by a 12-week plyometric training program in elite female soccer players. The hypothesis was that this program would increase the jumping ability and kicking speed and that these gains could be maintained by means of regular soccer training only. Twenty adult female players were divided into 2 groups: control group (CG, n = 10, age 23.0 +/- 3.2 yr) and plyometric group (PG, n = 10; age 22.8 +/- 2.1 yr). The intervention was carried out during the second part of the competitive season. Both groups performed technical and tactical training exercises and matches together. However, the CG followed the regular soccer physical conditioning program, which was replaced by a plyometric program for PG. Neither CG nor PG performed weight training. Plyometric training took place 3 days a week for 12 weeks including jumps over hurdles, drop jumps (DJ) in stands, or horizontal jumps. Body mass, body composition, countermovement jump height, DJ height, and kicking speed were measured on 4 separate occasions. The PG demonstrated significant increases (p < 0.05) in jumping ability after 6 weeks of training and in kicking speed after 12 weeks. There were no significant time x group interaction effects for body composition. It could be concluded that a 12-week plyometric program can improve explosive strength in female soccer players and that these improvements can be transferred to soccer kick performance in terms of ball speed. However, players need time to transfer these improvements in strength to the specific task. Regular soccer training can maintain the improvements from a plyometric training program for several weeks.

Objective: The association of sedentary behaviour and leisure time physical activity with a validated continuous metabolic syndrome risk score was investigated in adults., Subjects/methods: A number of 992 adults (559 men) without cardiovascular disease or diabetes. Subjects reported time spent in leisure time physical activity and television watching/computer activities. A validated metabolic syndrome risk score, based on waist circumference, triglycerides, blood pressure, fasting plasma glucose and high-density lipoprotein cholesterol, was used. The metabolic syndrome risk score and time spent in sedentary behaviour and physical activity were analysed as continuous variables using multiple linear regression., Results: Metabolic syndrome risk was positively associated with time spent watching television/computer activities, irrespective of physical activity level, and after adjustment for age, education level, smoking status and dietary intake in women aged > or =45 years (beta=0.184, P<0.05). Independent of the time being sedentary, moderate to vigorous leisure time physical activity was inversely associated with metabolic syndrome risk in men (<45 years: beta=-0.183, P<0.01; > or =45 years: beta=-0.192, P<0.01) and women aged > or =45 years (beta=-0.203, P<0.01)., Conclusions: Although cross-sectional, the present results support inclusion of efforts to decrease sedentary behaviour in metabolic syndrome prevention strategies for women aged > or =45 years, besides promotion of moderate to vigorous physical activity, since both behavioural changes might show additional effects.

Many children strive to attain excellence in sport. However, although talent identification and development programmes have gained popularity in recent decades, there remains a lack of consensus in relation to how talent should be defined or identified and there is no uniformly accepted theoretical framework to guide current practice. The success rates of talent identification and development programmes have rarely been assessed and the validity of the models applied remains highly debated. This article provides an overview of current knowledge in this area with special focus on problems associated with the identification of gifted adolescents. There is a growing agreement that traditional cross-sectional talent identification models are likely to exclude many, especially late maturing, 'promising' children from development programmes due to the dynamic and multidimensional nature of sport talent. A conceptual framework that acknowledges both genetic and environmental influences and considers the dynamic and multidimensional nature of sport talent is presented. The relevance of this model is highlighted and recommendations for future work provided. It is advocated that talent identification and development programmes should be dynamic and interconnected taking into consideration maturity status and the potential to develop rather than to exclude children at an early age. Finally, more representative real-world tasks should be developed and employed in a multidimensional design to increase the efficacy of talent identification and development programmes.

The authors examined the complex interactions between perception, cognition, and expertise by using a film-based decision-making test. They stratified 40 youth soccer players (aged 13.0-15.8 years) into groups by using a within-task criterion. They assigned the players to successful or less successful groups on the basis of their performance on a laboratory-based test of tactical skill. Using soccer-specific film simulations, movement-based response measures, and eye movement registration techniques, the authors determined the players' decision-making processes and skill level. The results showed that investigators can use film-based tests to discriminate soccer players of comparable experience and playing level on the basis of their decision-making skills. When compared with their less successful counterparts, successful decision-makers used more goal-oriented search strategies, which resulted in superior performance, as characterized by faster decision times and greater response accuracy. Successful decision-makers (a) spent more time fixating the player in possession of the ball and (b) alternated gaze more frequently between that player and other areas of the display. An earlier study in which researchers (R. Vaeyens, M. Lenoir, A. M. Williams, L. Mazyn, & R. M. Philippaerts, 2007) stratified participants into groups on the basis of playing level had not revealed those differences. The implication of the present findings is that a within-task criterion provides investigators with a more sensitive approach when they try to identify the mechanisms underlying decision-making skill. Implications for research and practice are discussed.

We examined differences in visual search behaviors and decision-making skill across different microstates of offensive play in soccer using youth participants (13.0-15.8 years) varying in skill and experience. We used realistic film simulations of offensive play, movement-based response measures, and an eye movement registration technique. Playing experience, skill level, and the unique constraints of the task, expressed by the number of players and relative proportion of offensive and defensive players, determined both the observed search behavior and processing requirements imposed on players in dynamic offensive team simulations. Significant differences in performance were observed between players and nonplayers and across three groups of soccer players who differed in skill level. Implications for talent identification and development are considered.

Purpose: To investigate the association of muscular strength and aerobic fitness with a continuous metabolic syndrome risk score in male and female adults., Methods: This cross-sectional study included 1019 (571 men) Flemish adults, aged 18-75. Muscular strength was evaluated by measuring isometric knee extension and flexion peak torque, using a Biodex System Pro 3 dynamometer. Aerobic fitness was quantified as VO2peak and was determined during a maximal cycle ergometer exercise test. Both strength and aerobic fitness were scaled for differences in FFM, using allometric analyses. A validated metabolic syndrome risk score that was based on waist circumference, triglycerides, blood pressure, fasting plasma glucose, and HDL cholesterol was used. Metabolic syndrome risk score, strength, and aerobic fitness were analyzed as continuous variables using multiple linear regression., Results: Metabolic syndrome risk was inversely associated with strength, independently of aerobic fitness, and after adjustment for age, height, education level, smoking status, and dietary intake in women (beta = -0.172, P < 0.001). In men, however, adjustment for aerobic fitness attenuated the inverse association between strength and metabolic syndrome risk (beta = -0.044, P > 0.05). Independently of strength, aerobic fitness was inversely associated with metabolic syndrome risk (men: beta = -0.309, P < 0.001; women: beta = -0.208, P < 0.001). Furthermore, independent associations were found for strength and aerobic fitness with several individual metabolic syndrome risk factors in women, and most of these associations were only partially mediated by central and general adiposity indicators., Conclusion: Although cross-sectional, the present results support inclusion of strength training in addition to aerobic exercise in physical activity recommendations for women, because both types of activity might show additional effects in reducing the risk of the metabolic syndrome.

Objectives: To determine the relationships between physical and performance characteristics and level of skill in youth soccer players aged 12-16 years., Methods: Anthropometry, maturity status, functional and sport-specific parameters were assessed in elite, sub-elite, and non-elite youth players in four age groups: U13 (n = 117), U14 (n = 136), U15 (n = 138) and U16 (n = 99)., Results: Multivariate analyses of covariance by age group with maturity status as the covariate showed that elite players scored better than the non-elite players on strength, flexibility, speed, aerobic endurance, anaerobic capacity and several technical skills (p<0.05). Stepwise discriminant analyses showed that running speed and technical skills were the most important characteristics in U13 and U14 players, while cardiorespiratory endurance was more important in U15 and U16 players. The results suggest that discriminating characteristics change with competitive age levels., Conclusions: Characteristics that discriminate youth soccer players vary by age group. Talent identification models should thus be dynamic and provide opportunities for changing parameters in a long-term developmental context.

Longitudinal changes in height, weight and physical performance were studied in 33 Flemish male youth soccer players from the Ghent Youth Soccer Project. The players' ages at the start of the study ranged from 10.4 to 13.7 years, with a mean age of 12.2 +/- 0.7 years. Longitudinal changes were studied over a 5 year period. Peak height velocity and peak weight velocity were determined using non-smoothed polynomials. The estimations of peak height velocity, peak weight velocity and age at peak height velocity were 9.7 +/- 1.5 cm x year-1, 8.4 +/- 3.0 kg x year-1 and 13.8 +/- 0.8 years, respectively. Peak weight velocity occurred, on average, at the same age as peak height velocity. Balance, speed of limb movement, trunk strength, upper-body muscular endurance, explosive strength, running speed and agility, cardiorespiratory endurance and anaerobic capacity showed peak development at peak height velocity. A plateau in the velocity curves was observed after peak height velocity for upper-body muscular endurance, explosive strength and running speed. Flexibility exhibited peak development during the tear after peak height velocity. Trainers and coaches should be aware of the individual characteristics of the adolescent growth spurt and the training load should also be individualized at this time.

The reliability and validity of a physical activity computer questionnaire of a usual week were studied in 33 adolescents between 12 and 18 years of age. Intraclass correlation coefficients and Kappa values were calculated to verify test-retest reliability. Validity was investigated by calculating Pearson correlation coefficients between the questionnaire and the Computer Science and Applications uniaxial accelerometer (CSA). Accelerometer data were obtained during seven successive days (sum and mean counts, estimated MET). Intraclass coefficients generally exceeded 0.70 and all Kappa values but one varied between 0.44 and 1.00. Transport variables (active transport from and to school, and during leisure time) showed no relationship with CSA. Sport participation during leisure time, sport participation summed with total transport, and the frequencies of moderate and hard activity were significantly correlated with CSA (r between 0.48 and 0.78). These data indicate that the physical activity computer variables provide reliable information. Moreover, sport participation (and summed with total transport) and the frequencies of moderate and hard activity provide valid data about adolescents' usual week physical activity, based on CSA comparison.

Young adult soccer players often encounter difficulty progressing from youth competition to being regularly selected for high-level, open-age competition. In an attempt to increase the playing opportunities of semi-professional and amateur under-21 players in first teams, the Royal Belgian Football Association required national division teams to include at least two players younger than 21 in their match selection (under-21 rule). Over four seasons, the following variables were analysed across 2138 semi-professional and amateur soccer players aged 16-39 years: (1) the number of times a player was selected to be in the first team squad; (2) the number of times a player was selected to play in the starting line-up; and (3) the number of minutes played. Chi-square analysis demonstrated that second and third division teams had complied with the new selection regulations. However, two-way analysis of variance of individual player data revealed no increase in the number of playing minutes in the under-21 group. It would appear that many teams had complied with the new regulations by selecting young players as substitutes. The results highlight the difficulties that talented young soccer players experience progressing from youth to senior competition. We conclude that the rule imposed by the Royal Belgian Football Association has failed to improve the playing opportunities of young adult soccer players. Alternative strategies for increasing playing opportunities for young talented players are required.

Asymmetries in the distributions of birth dates in senior professional and youth soccer players have been interpreted as evidence for systematic discrimination against individuals born shortly before the cut-off date in assigning youth to specific age groups. This concept is known as the "relative age effect". The results of a longitudinal study of birth date distritubions of 2757 semi-professional and amateur senior soccer players in Belgium are presented. Records for competitive games were available in official statistics provided by the Royal Belgian Football Association. The chi-square statistic was used to examine differences between observed and expected birth date distributions. Regression analyses indicated a shift of bias when two different start dates were compared. Players born in the early part of the new age band (January to March) were over-represented compared with players born late in the new selection period (October to December). However, players with birthdays at the start of the old selection year (August) were still represented. In a retrospective analysis of 2138 players, variables indicative of match involvement, number of selections for matches, and time played were examined in relation to the relative age effect. The group of semi-professional and amateur senior soccer players born in the first quarter of the selected age band received more playing opportunities. Comparisons of birth date distributions (traditional approach to relative age effect) with match-related variables gave similar, though not entirely consistent, results. However, there were no differences for the mean number of selections and for playing minutes between players born at the start or the end of the selection year. Our findings suggest that match-based variables may provide a more reliable indication of the relative age effect in soccer.

Limited information is available about the associations between adolescent fitness levels and adult physical activity. In the present study, these associations are investigated using different indicators of physical activity. It is hypothesized that both health- and performance-related fitness characteristics, observed during the adolescent period, contribute equally to the explained variance in adult physical activity levels. Subjects were 109 Flemish males followed over a period of 27 years from 13 to 40 years of age in the Leuven Longitudinal Study on Lifestyle Fitness and Health. Performance and health-related fitness characteristics were observed during the growth period and at 40 years of age. The Work Index, Leisure Time Index, and Sport Index of the Baecke questionnaire were used as indicators of physical activity together with triaxial accelerometry. Multiple regression and discriminant analyses contrasting extreme quintiles of activity groupings were used to analyse the associations. Only the Baecke Sport Index showed consistent significant associations (R2 = 0.03 to R2 = 0.23) with adolescent fitness levels observed at 13, 15, and 18 years. When upper and lower quintiles were contrasted, fitness characteristics observed at the three age levels during adolescence were significantly different for each of the three indices of the Baecke questionnaire at 40 years of age. Lowest associations (R2 = 0.09 to R2 = 0.17) were found for the Work Index, followed by the Leisure Time Index (R2 = 0.12 to R2 = 0.28) and Sport Index (R2 = 0.25 to R2 = 0.43). Highest associations were evident for the 18- to 40-year interval. Performance- and health-related fitness characteristics explain equally well the variance in physical activity indicators.

Two physical activity questionnaires were evaluated against cardiorespiratory fitness (VO2 peak), and a tri-axial accelerometer for movement registration (Tracmor) in 166 men, aged 40 years, within the framework of the Leuven Longitudinal Study on Lifestyle, Fitness, and Health. Tracmor data were obtained during four successive days. Besides the work index, the sport index, and the total activity index from the Baecke questionnaire, the subjective activity score, calculated energy expenditure during work, work index, and the total activity index from the Tecumseh Community questionnaire showed significant correlation coefficients with the mean Tracmor output (r = 0.26-0.47, p < 0.01). The questionnaire submeasures and the Tracmor output as generated in the same physical activity dimension showed the same relationships (r = 0.22-0.50, p < 0.01). Multiple stepwise regression and stepwise discriminant analyses showed the Baecke questionnaire as the best indicator of the subject's physical activity level. Extra information about the physical activity level was given by two Tecumseh submeasures, e.g. energy expenditure during work and sleeping time. The results indicated that the Baecke questionnaire is superior in large-scale studies because of simplicity. However, the Tecumseh questionnaire can give detailed information about physical activity patterns and energy expenditure.

The stability of physical fitness and physical activity in Flemish males from 18 to 40 years of age was investigated. In addition, effects of a consistently low-activity or high-activity level during the same age period on physical fitness were studied. The sample consisted of males who were followed longitudinally from age 13 to age 18 years, and were remeasured at the ages of 30, 35, and 40 years. Complete data about physical fitness and physical activity between 13 and 40 years were available for 130 subjects. Stability was measured using Pearson autocorrelations and simplex models. Multivariate analysis of variance (MANOVA) for repeated measurements was used to look for the effects of activity level on physical fitness. Simplex models showed higher stability coefficients than Pearson correlations, and stability of physical fitness was higher than stability of physical activity. Physical fitness showed the highest stability in flexibility (r = 0.91 between 18 and 30 years, r = 0.96 for both the 30-35 and 35-40 ages intervals), while physical activity showed the highest stability during work (r between 0.70 and 0.98 for the 5-year intervals). Results from MANOVA indicated that for some fitness characteristics the high-active subjects were more fit than their low-active peers. Stability of physical activity was higher than assumed and, therefore, it is a useful and independent indicator for further research. Although possible confounding factors are present (e.g., heredity), a higher level of physical activity during work and leisure time on a regular basis benefits physical fitness considerably. Am. J. Hum. Biol. 12:487-497, 2000. Copyright 2000 Wiley-Liss, Inc.