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.

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.

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.

Adolescent physical performance and adult physical activity in Flemish males.

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.

Comparison of two questionnaires with a tri-axial accelerometer to assess physical activity patterns.

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.

Doubly labelled water validation of three physical activity questionnaires.

This study investigated the validity of the Baecke Questionnaire, the Five City Project Questionnaire, and the Tecumseh Community Health Study Questionnaire in 19 Flemish males, using correlation and multiple stepwise regression analyses. The three questionnaires are commonly used physical activity questionnaires in epidemiological studies. The physical activity level (PAL) as measured with the doubly labelled water method was used as the criterion. The Baecke total activity index showed the highest correlation coefficient with PAL (r = 0.69, p < 0.001). Also the sweat index from the Five City Project Questionnaire, and total daily energy expenditure from the Tecumseh Community Health Study Questionnaire showed significant associations with PAL, respectively 0.57 (p < 0.05) and 0.64 (p < 0.01). Multiple stepwise regression analyses supported the findings from the correlation study. The largest individual contribution in PAL was from the activity index (45%) for the Baecke Questionnaire, the sweat index (29%) for the Five City Project Questionnaire, and total daily energy expenditure (38%) for the Tecumseh Community Health Study Questionnaire. In conclusion, the questionnaires, and certainly the Baecke Questionnaire, can provide valid data about physical activity. Therefore they are useful in epidemiological studies.

Reliability and validity of three physical activity questionnaires in Flemish males.

The reliability and validity of three physical activity questionnaires were studied using 90 Flemish males (30 aged 30 years, 30 aged 35 years, and 30 aged 40 years). Intraclass correlations (R) and kappa values were calculated to verify within judge and between judges reliability (objectivity) and test-retest reliability (stability) of the Tecumseh Community Health Study Questionnaire, the Five City Project Questionnaire, and the Baecke Questionnaire. Results showed high for within judge and between judges reliability. R coefficients for stability varied between 0.47 and 0.95. Kappa values varied between 0.20 and 0.73. Concurrent validity was investigated by comparing three levels of professional status. Workmen had higher indices concerning physical activity during work than clerks and managers. Congruent validity, studied by means of principal-components analysis, confirmed subdivision of habitual physical activity into three entities, physical activity during work, sports activities, and general leisure time. These results indicate that reliable and valid data can be obtained in Flemish males by three interviewer-assisted physical activity questionnaires.