Impact of (long) COVID on athletes' performance: a prospective study in elite football players.

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.

Longitudinal Development of Explosive Leg Power from Childhood to Adulthood in Soccer Players.

The aim of the this study was to investigate the development of explosive leg power by using 2 similar jumping protocols (countermovement jump and standing broad jump) in 555 Belgian, high-level young soccer players, aged between 7 and 20 years. The total sample was divided into 3 longitudinal samples related to growth and maturation (pre-teenchildhood: (6-10 years;), early adolescence: (11-16 years;) and late adolescence: (17-20 years)), and 6 multilevel regression models were obtained. Generally, both jumping protocols emphasized that chronological age, body size dimensions (by means of fat mass in the late childhood and early adolescence groups, fat-free mass in the late adolescence group and stature--(not for CMJ in late childhood group) and fat mass in the late childhood and early adolescence groups, and fat-free mass in the late adolescence group) and motor coordination (one item of a 3-component test battery) are longitudinal predictors of explosive leg power from childhood to young adulthood. The contribution of maturational status was not investigated in this study. The present findings highlight the importance of including non-specific motor coordination in soccer talent development programs.

Cue usage in volleyball: a time course comparison of elite, intermediate and novice female players.

This study compared visual search strategies in adult female volleyball players of three levels. Video clips of the attack of the opponent team were presented on a large screen and participants reacted to the final pass before the spike. Reaction time, response accuracy and eye movement patterns were measured. Elite players had the highest response accuracy (97.50 ± 3.5%) compared to the intermediate (91.50 ± 4.7%) and novice players (83.50 ± 17.6%; p<0.05). Novices had a remarkably high range of reaction time but no significant differences were found in comparison to the reaction time of elite and intermediate players. In general, the three groups showed similar gaze behaviour with the apparent use of visual pivots at moments of reception and final pass. This confirms the holistic model of image perception for volleyball and suggests that expert players extract more information from parafoveal regions.

Relative age, biological maturation and anaerobic characteristics in elite youth soccer players.

Being relatively older and having an advanced biological maturation status have been associated with increased likelihood of selection in young elite soccer players. The aims of the study were to investigate the presence of a relative age effect (RAE) and the influence of birth quarter on anthropometry, biological maturity and anaerobic parameters in 374 elite Belgian youth soccer players. The sample was divided into 3 age groups, each subdivided into 4 birth quarters (BQ). Players had their APHV estimated and height, weight, SBJ, CMJ, sprint 5 and 30 m were assessed. Overall, more players were born in BQ1 (42.3%) compared with players born in BQ4 (13.7%). Further, MANCOVA revealed no differences in all parameters between the 4 BQ's, controlled for age and APHV. These results suggest that relatively youngest players can offset the RAE if they enter puberty earlier. Furthermore, the results demonstrated possible differences between BQ1 and BQ4, suggesting that caution is necessary when estimating differences between players because of large discrepancies between statistical and practical significance. These findings also show that coaches should develop realistic expectations of the physical abilities of younger players and these expectations should be made in the context of biological characteristics rather than chronological age-based standards.

A longitudinal analysis of gross motor coordination in overweight and obese children versus normal-weight peers.

BACKGROUND: The relationship of childhood overweight (OW) and obesity (OB) with motor skill and coordination is gaining due attention; however, longitudinal evidence is currently lacking. OBJECTIVE: The dual purpose of this study was (1) to investigate the short-term evolution in the level of gross motor coordination according to children's weight status, and (2) to identify those factors predicting their gross motor coordination performance over a 2-year interval. SUBJECTS: Participants were 50 children with OW, including 8 with OB (aged 6-10 years at baseline, with 52% boys), and 50 with normal-weight (NW) matched for gender and age. MEASUREMENTS: Anthropometrics (body height, body weight, body mass index (BMI), %body fat) and level of gross motor coordination (Körperkoordinationstest für Kinder, KTK) were assessed in 2007 (baseline) and 2 years later in 2009 (follow-up). At baseline, participants completed a survey based on the Flemish Physical Activity Questionnaire (FPAQ) to obtain socio-demographic information and to determine physical activity levels in diverse domains. RESULTS: The evolution in the level of gross motor coordination over time was strongly related to children's weight status. Participants in the NW group showed more progress than their OW/OB peers, who demonstrated significantly poorer performances. Accordingly, between-group differences in KTK outcomes (that is, raw item scores and total motor quotient) became more evident over time. Multiple linear regression analysis further indicated that, in addition to BMI per se (negative predictor), participation in organized sports within a sports club (positive predictor) determines gross motor coordination performance(s) 2 years later. CONCLUSION: Our results provide conclusive evidence for an increasingly widening gap of OW/OB children's gross motor coordination relative to NW peers across developmental time in the absence of targeted initiatives. Special attention is thus needed for OW/OB children, especially for those not practicing sports in a club environment, in terms of motor skill improvement to promote regular participation in physical activity.

Relative age effect and Yo-Yo IR1 in youth soccer.

The aims of the study were to investigate the presence of a relative age effect and the influence of birth quarter on anthropometric characteristics, an estimation of biological maturity and performance in the Yo-Yo Intermittent Recovery Test level 1 in 606 elite, Flemish youth soccer players. The sample was divided into 5 chronological age groups (U10-U19), each subdivided into 4 birth quarters. Players had their APHV estimated and height, weight and Yo-Yo IR1 performance were assessed. Differences between quarters were investigated using uni- and multivariate analyses. Overall, significantly (P<0.001) more players were born in the first quarter (37.6%) compared to the last (13.2%). Further, no significant differences in anthropometric variables and Yo-Yo IR1 performance were found between the 4 birth quarters. However, there was a trend for players born in the first quarter being taller and heavier than players born in the fourth quarter. Players born in the last quarter tended to experience their peak in growth earlier, this may have enabled them to compete physically with their relatively older peers. Our results indicated selection procedures which are focused on the formation of strong physical and physiological homogeneous groups. Relative age and individual biological maturation should be considered when selecting adolescent soccer players.

The contribution of growth and maturation in the functional capacity and skill performance of male adolescent handball players.

The present study determined to what extent the variance in performance might be explained by chronological age, biological maturation, training load and anthropometry in 168 Belgian male handball players aged 14 years: anthropometric, strength, speed and sport-specific skills were assessed. MANOVA tested the effect of chronological age and biological maturity, whereas MANCOVA was used to compare maturity groups controlling for chronological age and training load. In addition, canonical correlation analysis was used between age, maturity-offset and anthropometry, on one side, and performance and sport-specific skills, on the other side. Results revealed significant differences between early, on-time and late maturity groups for anthropometry (p<0.001), strength (p<0.001) and sprint 20-m (p<0.05) in favour of the early maturing players. The difference between the mean values of the extreme groups for height was 24.8 cm, for weight 33.2 kg and, for body fat 6.5%; for handgrip 20.2 kg, for 5-jump test 1.1 m and for 20-m sprint 0.20 s. Maturity status had no effect on sport-specific skills. Canonical correlations indicated that poorer scores in sport-specific skills were related to fatness and lack of training. In parallel, a substantial relationship was found between early maturity-offset, body size, strength and 20-m sprint.

Factors discriminating gymnasts by competitive level.

This study examined the relationship between the performance level as evaluated by expert coaches and the results on a multidimensional test battery in female gymnastics. 4 coaches assigned 168 female gymnasts aged 6-8 years into 2 groups (Elite-level potential, n=103 and Sub-elite-level potential, n=65) based upon their technical evaluation of the gymnastics abilities on the 4 apparatus. Moreover, anthropometric, physical and coordinative characteristics were assessed. ANOVA with age as fixed factor revealed that results on all aforementioned characteristics, except body fat%, sit-and-reach, rope climbing and a motor coordination test, significantly improved with increasing age. MANCOVA with competitive level as fixed factor and age and maturity as covariates indicated that all gymnasts portrayed a similar athletic built (Wilks' lambda=0.95, F=2.20, p=0.071), but the elite-level potential gymnasts outperformed the less gifted gymnasts on all physical (Wilks' lambda=0.65, F=8.00, p<0.001) and coordinative variables (Wilks' lambda=0.79, F=22.10, p<0.001). Discriminant analysis revealed motor coordination to be the most important factor in discriminating between young female elite and sub-elite gymnasts. A test battery measuring multidimensional performance characteristics is valuable in addition to the coaches' technical judgment in the search of young gifted female gymnasts.

The KörperkoordinationsTest für Kinder: reference values and suitability for 6-12-year-old children in Flanders.

An adequate coordination level in children is important for their general development, but also for health, psychosocial, academic and well-being-related reasons. In this study, the suitability of the KörperkoordinationsTest für Kinder (KTK) as an assessment instrument for the gross motor coordination was evaluated in 2470 children from 26 elementary schools for general education spread over the Flemish and Brussels-capital region. All children performed four subtests: walking backwards (WB), moving sideways (MS), hopping for height (HH) and jumping sideways (JS). Age and gender-specific values were established for the Flemish children anno 2008. Overall, the current sample scored significantly worse than their 1974 German counterparts (P<0.001). Score distribution showed 21% of the children being placed in the problematic range of gross motor coordination level. A decline in coordination was observed especially in those tasks relying primarily on coordinative capacities (WB and MS), while improvements or status quo in those tasks relying on strength and speed (JS and HH) were explained by secular trends. We suggest that the KTK is a valuable instrument for the assessment of the gross motor coordination of Flemish children and efforts should be made in order to face the decline in coordination.

Discrimination of u-14 soccer players by level and position.

Adolescence is often viewed as a critical period for selection in youth soccer. The present study compared the characteristics of regionally selected and non-selected under-14 players (U-14) as a group and by position. Players were classified as local (n=69) and regional (n=45). Weight, height, skinfolds, functional capacities, soccer skills and goal orientation were measured and skeletal age was assessed with the Fels method. Factorial ANOVA was used to test the effect of selection, position and respective interaction terms, while discriminant analysis was used to identify the variables that contributed to selection. Selected players had an advanced maturity status (F=24.97, p<0.01), were heavier (F=30.67, p<0.01) and taller (F=35.07, p<0.01); performed better in explosive power (F=21.25, p<0.01), repeated sprints (F=20.04, p<0.01) and ball control (F=3.69, p<0.05); and were more ego oriented (F=13.29, p<0.01). The 2 competitive groups did not differ in agility, aerobic endurance, dribbling, shooting, passing, and task orientation. Position-related variation was negligible. The percentage of players who were correctly classified in the original groups was slightly lower when the analysis was performed for the total sample (86%) than by position (86-90%). Future research on talent identification and selection should adopt a multidimensional approach including variables related to the physiological, perceptual, cognitive and tactical demands.

Growth, maturation, functional capacities and sport-specific skills in 12-13 year-old- basketball players.

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.

Anthropometric and anaerobic fitness profile of elite and non-elite female soccer players.

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.

Sedentary behaviour, physical activity and a continuous metabolic syndrome risk score in adults.

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.

Relationship of obesity with physical activity, aerobic fitness and muscle strength in Flemish adults.

AIM: The aim of this study was to analyse differences in physical activity, cardiorespiratory fitness (CRF) and muscle strength between normal weight, overweight and obese adults and to investigate the role of physical activity variables in the analyses of differences in CRF and muscle strength between these groups. METHODS: A total of 807 men and 633 women (age: 18-75 years) were included in this cross-sectional study. Weight, height, waist circumference (WC) and bioelectrical impedance were measured. Different dimensions of physical activity were assessed using a validated questionnaire. CRF (VO(2peak)) was evaluated by a maximal test on a cycle ergometer. Knee strength was measured with a calibrated Biodex System Pro 3 dynamometer. Three methods were used for classification in obesity groups: body mass index (BMI), WC and combined BMI-WC classification. RESULTS: Health-related sports and physical activity level are negatively associated with obesity in men, but not in women. Television viewing is positively associated with obesity, while VO(2peak)/fat free mass (FFM) and knee strength/FFM show a negative association with obesity in both genders. Overall, subjects with normal WC seem to be more physically active and to have somewhat better values for CRF compared to those with high WC within the same BMI category. Lower values for relative CRF and knee strength in obese subjects compared to their lean counterparts remain after adjustment for physical activity. CONCLUSION: This study confirms the lower level of physical activity and the impaired CRF and knee strength in obese adults compared to their lean counterparts. This study also sustains the importance of measuring WC and CRF during clinical examinations.

Running economy in early and late maturing youth soccer players does not differ.

PURPOSE: The aim of this study was to investigate the influence of maturity on running economy in a population of young soccer players. METHODS: 13 boys (mean age 14.3 years) active in soccer were divided into two groups: 6 early and 7 late maturers. Anthropometrical characteristics, respiratory exchange ratio, heart rate and maximal oxygen uptake were measured. Running economy was assessed at three submaximal running speeds (8, 9.5 and 11 km/h). Allometric coefficients were calculated and used to diminish the effect of body mass. In addition, running style was analysed biomechanically (stride length and meaningful kinematic values). RESULTS: There was no significant difference in the running economy of early and late maturing soccer players, nor any significant differences in mass adjusted physiological values. Therefore physiological differences cannot explain why late maturers succeed in keeping up with early maturers. Late maturing boys take longer relative strides, and have more anteversion of the thigh at heel contact, a smaller knee-angle during swing-phase and a lower mass moment of inertia. CONCLUSION: Running style seems to be an important determinant in running economy of children.

A multidisciplinary selection model for youth soccer: the Ghent Youth Soccer Project.

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.

Validity of a physical activity computer questionnaire in 12- to 18-year-old boys and girls.

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.

Intrinsic risk factors for inversion ankle sprains in females--a prospective study.

Ankle sprains are extremely common. However, very little is known about the variables that predispose individuals to these injuries. The purpose of this study was to examine prospectively intrinsic risk factors for inversion sprains in a young physically active female population. One hundred and fifty-nine female physical education students were evaluated for several possible intrinsic risk factors for inversion sprains at the beginning of their academic study. The evaluated intrinsic risk factors included anthropometrical and physical characteristics, ankle joint position sense, isokinetic ankle muscle strength, lower leg alignment characteristics, postural control and muscle reaction time during a sudden inversion perturbation. All sports injuries were registered during 1-3 years and exposure to sport was recorded (mean: 15.33+/-4.33 h a week). Thirty-two (20%) of the 159 females sprained their ankle. The number of ankle sprains per 1000 h of sports exposure was 0.75. The Cox regression analysis revealed that females with less accurate passive joint inversion position sense [hazard ratio (HR): 1.08, 95% confidence interval (CI): 1.02-1.14 for absolute error at 15 degrees inversion], a higher extension range of motion at the first metatarsophalangeal joint (HR: 1.03, 95% CI: 1.00-1.06) and less coordination of postural control (HR: 0.96, 95% CI: 0.93-1.00 for endpoint excursion; HR: 0.94, 95% CI: 0.89-0.99 for maximal endpoint excursion) are at greater risk of an ankle sprain. The findings of this study suggest that effective prevention and conservative rehabilitation of ankle inversion sprains should include attention to these variables.

Age at menarche in relation to anthropometric characteristics, competition level and boat category in elite junior rowers.

BACKGROUND: Within the context of the effects of training for sports on growth and maturation, there is very little menarcheal data for elite rowing athletes. Knowledge of the relationship of the maturational status with training level, different boat categories, and somatic features of the athletes will clarify the assumed impact of rowing training on the growth and maturational process of youngsters. AIM: The aim of this study was to determine the age at menarche in world top junior rowing athletes and to investigate its relationship with anthropometric characteristics, and competition level, rowing style and boat category. SUBJECTS AND METHODS: The sample consisted of 212 female junior rowers, with a mean chronological age of 17.6 +/- 0.8 years, all participants at the 1997 FISA World Junior Rowing Championships. Anthropometric dimensions, somatotype and body composition characteristics were measured, and age at menarche and training data were retrospectively obtained by questionnaires. RESULTS: Results revealed that the mean age at menarche of the total group of rowers was 12.8 +/- 1.2 years and did not differ from a non-athletic reference population. Rowers who started their rowing training before menarche (n = 78) showed a significant (p

Relation between cardiovascular risk factors at adult age, and physical activity during youth and adulthood: the Leuven Longitudinal Study on Lifestyle, Fitness and Health.

This study investigated the relationship between sports participation/physical activity during youth (13 - 18 years of age) and adulthood (30 - 40 years of age), and cardiovascular risk factors (body fat and fat distribution, blood pressure, lipoprotein levels and cardiorespiratory fitness) at 40 years of age. Subjects were 166 Flemish males from "The Leuven Longitudinal Study on Lifestyle, Fitness and Health". Physical activity was assessed by means of a sports participation inventory and the Tecumseh community Health Study Questionnaire. In addition to correlation and multiple stepwise regression analyses, different groups (at risk, not at risk) were contrasted on sports participation/physical activity parameters using ANOVA. Long-term exposure during adulthood to daily physical activity was slightly related to a low/high risk profile for waist circumference, percent body fatness, triglycerides and peak VO(2). Sports participation during adolescence was not related to levels of cardiovascular risk factors at 40 years of age.