Investigation of Underlying Association between Anthropometric and Cardiorespiratory Fitness Markers among Overweight and Obese Adolescents in Canada.

BACKGROUND: Adolescents who experience overweight or obesity commonly persist in these conditions into adulthood, thereby elevating their vulnerability to health issues. The focus of this study is on health risk markers such as body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), body surface area (BSA), and cardiorespiratory fitness (CRF). The objectives include updating normative values for BMI, WC, WHtR, and BSA in Canadian adolescents, establishing cardiometabolic risk zones, and developing a composite score considering both anthropometric and CRF markers. METHODS: Involving 1864 adolescents, the study used the LMS method to generate percentile norms, stratified by age and sex. Cardiometabolic risk zones were established for each marker based on Z-scores, and a composite score was created. RESULTS: An increase in WC of 5.8 and 7.4 cm for boys and girls, respectively, was observed since 1981. Forward multiple regression analyses were conducted to assess the robustness and validity of the proposed model. The results indicated that the model explained nearly 90% (R2 = 0.890) of the common variance between the composite score and the retained independent variables. Moreover, the model demonstrated a mean absolute error (MAE) of approximately 6 percentiles, confirming its high precision. Furthermore, these analyses yielded key thresholds for identifying adolescents at risk: the 70th percentile for high cardiometabolic risk and the 85th percentile for very-high risk. CONCLUSIONS: Individually, WC or WHtR seem to be better markers for evaluating cardiometabolic risk than BMI during adolescence. However, CRF showed comparable importance to anthropometric markers in determining cardiometabolic risk. The simultaneous inclusion of anthropometric and CRF markers provides a better picture of the global cardiometabolic risk in adolescents.

Updating normative cross-sectional values and secular trends in body mass, body height and body mass index among Québec children and adolescents.

OBJECTIVE: The main objective of this study was to examine secular trends in body mass, body height and body mass index (BMI) from measured rather than self-reported values between 1972 and 2017. METHODS: A total of 4500 students (males = 51%) were selected from a stratified sampling. The age range varied between 6.0 and 17.9 years. The sample came from 24 elementary schools and 12 high schools located in six urban cities from the province of Québec. All the tests selected were based on standardized procedures that are recognized as valid and reliable. Standardization and modeling of smoothed percentile curves for each variable for both sexes were produced. RESULTS: Regional variations between youth from the province of Québec and those from all other Canadian provinces confirm the relevance of using data specific to the target population. Comparisons with the 1972 and 1982 data show an important increase in body mass (~ 7 kg, i.e. 16.4%) and BMI (~ 1.4 kg·m-2, i.e. 19.9%) with minor change in body height (~ 1.8 cm, i.e. 3.9%). Youth from low-income backgrounds (p = 0.001) as well as those living in large urban cities (p = 0.002) see their probability of developing overweight or obesity greatly increase (low-income = 2.1 times; large urban cities = 1.3 times). However, overweight and obesity rates seem to have stabilized at around 21% since 2004. CONCLUSION: This study provides up-to-date data on factors that contribute to the prevalence of overweight and obesity in youth in urban settings of Québec, and will be instrumental in guiding public health strategies designed to optimize growth outcomes.

RéSUMé: OBJECTIF: L'objectif principal de cette étude était d'examiner les tendances séculaires de la masse corporelle, de la taille et de l'indice de masse corporelle (IMC) de 1972 à 2017 à partir de valeurs mesurées plutôt que de valeurs autodéclarées. MéTHODE: Un total de 4 500 étudiants (garçons = 51 %) ont été sélectionnés à partir d'un échantillon stratifié. La fourchette d'âge variait entre 6,0 et 17,9 ans. L'échantillon provenait de 24 écoles primaires et 12 écoles secondaires situées dans six villes de la province de Québec (Canada). Tous les tests sélectionnés reposaient sur des procédures standardisées, reconnues comme valides et fidèles. Une standardisation et une modélisation des courbes centiles lissées ont été produites pour chaque variable pour les deux sexes. RéSULTATS: Les variations régionales entre les jeunes du Québec et ceux du reste du Canada confirment la pertinence d'utiliser des données spécifiques à la population cible. Les comparaisons entre les données de 1972 et de 1982 montrent une augmentation importante de la masse corporelle et de l'IMC (p ≤ 0,05) sans changement important de la taille corporelle. Les jeunes issus de milieux à faibles revenus (p = 0,001) ainsi que ceux vivant dans les grandes villes (p = 0,002) voient leurs risques de développer un surpoids ou de l'obésité augmenter considérablement (faibles revenus = 2,1 fois; grandes villes urbaines = 1,3 fois). Toutefois, les taux de surpoids et d'obésité semblent s'être stabilisés autour de 21 % depuis 2004. CONCLUSION: Cette étude fournit des données à jour sur les facteurs qui contribuent à la prévalence de l'embonpoint et de l'obésité chez les jeunes des milieux urbains du Québec et contribuera à orienter les stratégies de santé publique afin d'optimiser le suivi sur la croissance physique des jeunes.

Secular trends of cardiorespiratory fitness in children and adolescents over a 35-year period: Chronicle of a predicted foretold.

Background: In the context of concerns regarding the cardiorespiratory fitness (CRF) of youth populations, the aims of this study were: (1) to update reference values for the VO2max for school-aged Canadians and (2) to document secular trends in CRF after a 35-year interval. Methods: Between September 2014 and April 2017, the CRF of 3725 students (53.2% boys; 6.0 to 17.9 yrs) was determined using the 20-m shuttle run test. The sample was collected in 36 different schools from six cities of Québec (Canada). Results: Median values of VO2max decreased with age in both sexes (p ≤ 0.05). By the age of 10, more than 20% of boys showed VO2max values below the recommended value (42 ml·kg-1·min-1). At the age of 17, that proportion reached 56.8%. A similar proportion of 12 yrs girls (20%) were under the recommended minimal value (37 ml·kg-1·min-1) and that value reached 69.9% at the age of 17. Compared to 1982, the VO2max at age 17 has declined by 18% for boys and 12% for girls. The situation is worse in terms of functional capacity (number of stages completed) with an overall decrease of more than 30%. Conclusion: This study demonstrates that, compared to data obtained using the same methodology 35 years ago, the CRF and functional capacity of children and adolescents has declined to levels that should raise concerns from a public health perspective. Thus, the development of strategies to promote a physically active lifestyle in youth is more relevant than ever.

Assessment of On-Ice Oxygen Cost of Skating Performance in Elite Youth Ice Hockey Players.

ABSTRACT: Allisse, M, Bui, HT, Desjardins, P, Léger, L, Comtois, AS, and Leone, M. Assessment of on-ice oxygen cost of skating performance in elite youth ice hockey players. J Strength Cond Res 35(12): 3466-3473, 2021-The purpose of this study was to evaluate the robustness of equations to predict the oxygen requirement during different skating circumstances commonly found in ice hockey game situations (skating forward, backward, with and without controlling a puck, during cornering and stops and starts). Twenty-four male elite ice hockey players from 3 categories (pee-wee, bantam, and midget) participated in this study. Anthropometric measurements were taken, and 4 different on-ice high-intensity and short-duration tests were performed. Execution time, heart rate, oxygen uptake, skating strides, and a skating efficiency index were measured for each test. A regression equation was calculated for each of the 4 tests providing an estimation of oxygen cost. Correlation coefficients ranged from 0.91 to 0.93, and SEE was between 4.5 and 8.4%, indicating that the precision of the regression algorithms was excellent. The results also suggest that execution time alone, which is the traditional manner to measure skating performance, is a bad estimator of oxygen uptake requirement for this kind of effort (average common variance <11%). Furthermore, age proved to be a determining factor with younger players showing an overall lower level of skating efficiency compared with older players. In addition, the introduction of a skating index also helps to better determine which factor of performance needs to be improved. Using simple and easy-to-measure variables, coaches will be able to obtain information that will allow them to intervene more precisely on the training parameters that will optimize the individual on-ice performance of their players.

Updating the Skating Multistage Aerobic Test and Correction for V[Combining Dot Above]O2max Prediction Using a New Skating Economy Index in Elite Youth Ice Hockey Players.

Allisse, M, Bui, HT, Léger, L, Comtois, A-S, and Leone, M. Updating the skating multistage aerobic test and correction for V[Combining Dot Above]O2max prediction using a new skating economy index in elite youth ice hockey players. J Strength Cond Res 34(11): 3182-3189, 2020-A number of field tests, including the skating multistage aerobic test (SMAT), have been developed to predict V[Combining Dot Above]O2max in ice hockey players. The SMAT, like most field tests, assumes that participants who reach a given stage have the same oxygen uptake, which is not usually true. Thus, the objectives of this research are to update the V[Combining Dot Above]O2 values during the SMAT using a portable breath-by-breath metabolic analyzer and to propose a simple index of skating economy to improve the prediction of oxygen uptake. Twenty-six elite hockey players (age 15.8 ± 1.3 years) participated in this study. The oxygen uptake was assessed using a portable metabolic analyzer (K4b) during an on-ice maximal shuttle skate test. To develop an index of skating economy called the skating stride index (SSI), the number of skating strides was compiled for each stage of the test. The SMAT enabled the prediction of the V[Combining Dot Above]O2max (ml·kg·min) from the maximal velocity (m·s) and the SSI (skating strides·kg) using the following regression equation: V[Combining Dot Above]O2max = (14.94 × maximal velocity) + (3.68 × SSI) - 24.98 (r = 0.95, SEE = 1.92). This research allowed for the update of the oxygen uptake values of the SMAT and proposed a simple measure of skating efficiency for a more accurate evaluation of V[Combining Dot Above]O2max in elite youth hockey players. By comparing the highest and lowest observed SSI scores in our sample, it was noted that the V[Combining Dot Above]O2 values can vary by up to 5 ml·kg·min. Our results suggest that skating economy should be included in the prediction of V[Combining Dot Above]O2max to improve prediction accuracy.

Oxygen Uptake, Heart Rate, and Lactate Responses for Continuous Forward Running and Stop-and-Go Running With and Without Directional Changes.

Bekraoui, N, Boussaidi, L, Cazorla, G, and Léger, L. Oxygen uptake, heart rate, and lactate responses for continuous forward running and stop-and-go running with and without directional changes. J Strength Cond Res 34(3): 699-707, 2020-The purpose of this study is to measure and quantify the differences for the gross oxygen uptake (V[Combining Dot Above]O2), heart rate (HR), and blood lactate ([LA]) responses to various modes of in-line running. Twelve healthy participants did an indirect continuous multistage field test to determine the maximal aerobic speed (MAS) before randomly performing in separate sessions 1 of the 3 running protocols at 3 intensities (60, 70, and 80% MAS) (a) in-line continuous running (IR), (b) fractioned running (FR) with stop and go every 20 m, and (c) 20-m shuttle run (SR). V[Combining Dot Above]O2 varied between 34.2 ± 2.5 and 54.6 ± 5.4 ml·kg·min, HR between 141 ± 14 and 184 ± 9 b·min, and [LA] between 4.2 ± 0.8 and 6.6 ± 0.9 mmol·L. In-line continuous running V[Combining Dot Above]O2 was lower than those of SR and FR at all intensities (p < 0.05). However, SR V[Combining Dot Above]O2 were higher than those of FR at 80% MAS only. Heart rate was similar in SR and FR but lower in IR at all intensities (p < 0.05). No significant differences were recorded in [LA]. Because only V[Combining Dot Above]O2 was affected by the introduction of a 180° angle directional change (SR vs. FR) at 80% MAS, the use of HR to assess such activities at such intensities will result in underestimating workloads. This study offers new insights into V[Combining Dot Above]O2, HR, and [LA] associated with accelerations while running with and without directional changes at submaximal speeds.

The 20-m Shuttle Run: Assessment and Interpretation of Data in Relation to Youth Aerobic Fitness and Health.

Cardiorespiratory fitness (CRF) is a good summative measure of the body's ability to perform continuous, rhythmic, dynamic, large-muscle group physical activity, and exercise. In children, CRF is meaningfully associated with health, independent of physical activity levels, and it is an important determinant of sports and athletic performance. Although gas-analyzed peak oxygen uptake is the criterion physiological measure of children's CRF, it is not practical for population-based testing. Field testing offers a simple, cheap, practical alternative to gas analysis. The 20-m shuttle run test (20mSRT)-a progressive aerobic exercise test involving continuous running between 2 lines 20 m apart in time to audio signals-is probably the most widely used field test of CRF. This review aims to clarify the international utility of the 20mSRT by synthesizing the evidence describing measurement variability, validity, reliability, feasibility, and the interpretation of results, as well as to provide future directions for international surveillance. The authors show that the 20mSRT is an acceptable, feasible, and scalable measure of CRF and functional/exercise capacity, and that it has moderate criterion validity and high to very high reliability. The assessment is pragmatic, easily interpreted, and results are transferable to meaningful and understandable situations. The authors recommend that CRF, assessed by the 20mSRT, be considered as an international population health surveillance measure to provide additional insight into pediatric population health.

Making a Case for Cardiorespiratory Fitness Surveillance Among Children and Youth.

We review the evidence that supports cardiorespiratory fitness (CRF) as an important indicator of current and future health among school-aged children and youth, independent of physical activity levels. We discuss the merit of CRF measurement for population health surveillance and propose the development of CRF guidelines to help support regional, national, and international surveillance efforts.

International variability in 20†m shuttle run performance in children and youth: who are the fittest from a 50-country comparison? A systematic literature review with pooling of aggregate results.

OBJECTIVES: To describe and compare 20 m shuttle run test (20mSRT) performance among children and youth across 50 countries; to explore broad socioeconomic indicators that correlate with 20mSRT performance in children and youth across countries and to evaluate the utility of the 20mSRT as an international population health indicator for children and youth. METHODS: A systematic review was undertaken to identify papers that explicitly reported descriptive 20mSRT (with 1-min stages) data on apparently healthy 9-17 year-olds. Descriptive data were standardised to running speed (km/h) at the last completed stage. Country-specific 20mSRT performance indices were calculated as population-weighted mean z-scores relative to all children of the same age and sex from all countries. Countries were categorised into developed and developing groups based on the Human Development Index, and a correlational analysis was performed to describe the association between country-specific performance indices and broad socioeconomic indicators using Spearman's rank correlation coefficient. RESULTS: Performance indices were calculated for 50 countries using collated data on 1 142 026 children and youth aged 9-17 years. The best performing countries were from Africa and Central-Northern Europe. Countries from South America were consistently among the worst performing countries. Country-specific income inequality (Gini index) was a strong negative correlate of the performance index across all 50 countries. CONCLUSIONS: The pattern of variability in the performance index broadly supports the theory of a physical activity transition and income inequality as the strongest structural determinant of health in children and youth. This simple and cost-effective assessment would be a powerful tool for international population health surveillance.

Estimating VO2max in children aged 5-6 years through the preschool-adapted 20-m shuttle-run test (PREFIT).

PURPOSE: (1) To examine the comparability, i.e., discriminatory power, in a preschooler test (PREFIT 20-m shuttle-run test) and the 20mSRT-Original in 5-6-year-olds; (2) to provide an equation to estimate VO2max from the 20mSRT-PREFIT. METHODS: 138 participants aged 5-6 years performed the 20mSRT-PREFIT and the 20mSRT-Original in a counterbalanced order. Total test duration, completed stages, maximum speed and maximum heart rate were registered. RESULTS: Participants finished stages from 2-10 in the 20mSRT-PREFIT, whereas stages 1-5 were completed in the 20mSRT-Original and a null was registered, showing the original version a lower discriminatory power. We also observed that the higher the cardiorespiratory fitness level the more comparable were the tests, i.e., - 0.04 km h-1 difference between tests in the fittest participants (i.e., maximum speed ≥ 9.5 km h-1). Using the original equation proposed by Leger and colleagues in 1988 and based on the estimation regression of maximum speed in the 20mSRT-Original from the PREFIT version, we computed a new equation to estimate VO2max from the 20mSRT-PREFIT: Y = 44.657 + 1.795X 1 - 2.601X 2 + 0.0852X 1 X 2 (r = 0.77; r 2 = 0.59; SEE = 1.25 ml kg-1 min-1 or 2.59% of estimated mean VO2max = 48.38 ml kg-1 min-1), where X 1 is the 20mSRT-PREFIT maximum speed (km h-1) and X 2 is the age of participants. The 20mSRT-PREFIT resulted in a significantly higher maximum heart rate than the 20mSRT-Original. CONCLUSIONS: The 20mSRT-PREFIT has higher discriminatory power than the 20mSRT-Original. Our study provides for the first time an opportunity to estimate VO2max in preschoolers and children based on the 20mSRT-PREFIT maximum speed and the age of participants.

International normative 20†m shuttle run values from 1†142†026 children and youth representing 50 countries.

OBJECTIVE: To develop sex-specific and age-specific international norms for the 20 m shuttle run test (20mSRT) in children and youth (aged 9-17 years), and to estimate the prevalence meeting the FITNESSGRAM criterion-referenced standards for healthy cardiorespiratory endurance (CRE). METHODS: A systematic review was undertaken to identify papers explicitly reporting descriptive 20mSRT (with 1 min stages) data on children and youth since 1981. Data were included on apparently healthy (free from known disease/injury) 9-17 years old. Following standardisation to a common metric and for protocol differences, pseudo data were generated using Monte Carlo simulation, with population-weighted sex-specific and age-specific normative centiles generated using the Lambda Mu and Sigma (LMS) method. Sex-related and age-related differences were expressed as per cent and standardised differences in means. The prevalence with healthy CRE was estimated using the sex-specific and age-specific FITNESSGRAM criterion-referenced standards for [Formula: see text]. RESULTS: Norms were displayed as tabulated centiles and as smoothed centile curves for the 20mSRT using 4 common metrics (speed at the last completed stage, completed stages/minutes, laps and relative [Formula: see text]). The final data set included 1 142 026 children and youth from 50 countries, extracted from 177 studies. Boys consistently outperformed girls at each age group (mean difference±95% CI: 0.86±0.28 km/h or 0.79±0.20 standardised units), with the magnitude of age-related increase larger for boys than for girls. A higher proportion of boys (mean±95% CI: 67±14%) had healthy CRE than girls (mean±95% CI: 54±17%), with the prevalence of healthy CRE decreasing systematically with age. CONCLUSIONS: This study provides the most comprehensive and up-to-date set of international sex-specific and age-specific 20mSRT norms for children and youth, which have utility for health and fitness screening, profiling, monitoring and surveillance.

Oxygen uptake and heart rate response of 6 standardized tennis drills.

The purpose of this study was to compare the oxygen uptake of various on-court tennis drills. Eleven tennis players were monitored with a portable metabolic device to measure oxygen uptake of 6 different tennis drills at low and high speeds. The 6 drills were done with or without striking the ball, over half or full-width of the court, in attack or defense mode, using forehand or backhand strokes. Oxygen uptake values (mean ± SD) ranged from 33.8 ± 4.2 to 42.3 ± 5.1 mL·kg⁻¹·min⁻¹ when running at low speed on the full-width court in defense mode without striking the ball and when running at high speed on the full-width court in attack mode while striking the ball, respectively. Specific differences were observed. Attacking mode requires 6.5% more energy than defensive playing mode. Backhand strokes demand 7% more energy at low speed than forehand ones. Running and striking the ball costs 10% more energy than running without striking the ball. While striking the ball, shuttle running on half-width court costs 14% more energy than running on full-width courts. The specificity of the oxygen uptake responses obtained for these various tennis drills gives an improved representation of their energy cost and could be used to optimize training loads.

Comparison of two aerobic field tests in young tennis players.

This study compares the maximal responses of a new aerobic tennis field test, the NAVTEN to a known aerobic field test, often used with young tennis players, that is, the continuous multistage 20-m shuttle run test (20-m SRT). The NAVTEN is an intermittent (1-minute/1-minute) multistage test with side-to-side displacements and ball hitting. Ten young elite tennis players aged 12.9 ± 0.3 (mean ± SD) randomly performed both tests and were continuously monitored for heart rate (HR) and oxygen uptake (V[Combining Dot Above]O2) using the Vmax ST (Sensormedics). The 20-m SRT and NAVTEN show similar HRpeak (202 ± 6.1 vs. 208 ± 9.5, respectively) and V[Combining Dot Above]O2peak (54.2 ± 5.9 vs. 54.9 ± 6.0 ml·kg·min). Pearson correlations between both tests were 0.88 and 0.92 for V[Combining Dot Above]O2peak and maximal speed, respectively. The NAVTEN yielded V[Combining Dot Above]O2peak values that are typical for active subjects of that age and are similar to the 20-m SRT supporting its use to measure aerobic fitness of young tennis players in specific and entertaining field conditions. The fact that two-thirds of the tennis players achieved a different ranking (±1 rank) with the NAVTEN and the 20-m SRT suggests that the NAVTEN may be more specific than the 20-m SRT to assess aerobic fitness of tennis players. From a practical point of view, the NAVTEN test is more specific and pedagogical for young tennis players even though both tests yield similar maximal values.

Repeated-sprint ability and aerobic fitness.

The purpose of this study was to reinvestigate the relationship between aerobic fitness and fatigue indices of repeated-sprint ability (RSA), with special attention to methodological normalization. Soldiers were divided into low (n = 10) and high (n = 9) fitness groups according to a preset maximal aerobic speed (MAS) of 17 km·h(-1) (∼60 ml O2·kg(-1)·min) measured with the University of Montreal Track Test (UMTT). Subjects' assessment included the RSA test (3 sets of 5 40-m sprints with 1-minute rest between sprints and 1.5 minutes between sets), a 40-m sprint (criterion test used in the computation of fatigue indices for the RSA test), strength and power measurement of the lower limbs, and the 20-m shuttle run test (20-m SRT) and the UMTT, which are measures of maximal aerobic power. The highest correlation with the RSA fatigue indices was obtained with the 20-m SRT (r = 0.90, p = 0.0001, n = 19), a test with 180° direction changes and accelerations and decelerations. The lower correlation (r = 0.66, p < 0.01, n = 19) with the UMTT (continuous forward running) suggests that some aerobic tests better disclose the importance of aerobic fitness for RSA and that aerobic power is not the sole determinant of RSA. However, neither strength nor vertical jumping power was correlated to the RSA fatigue indices. Subjects with greater MAS were able to maintain almost constant level of speed throughout series of repeated sprints and achieved better recovery between series. A MAS of at least 17 km·h(-1) favors constant and high speed level during repeated sprints. From a practical point of view, a high aerobic fitness is a precious asset in counteracting fatigue in sports with numerous sprint repetitions.

VO2 requirements of boxing exercises.

The purpose of this study was to quantify the physiological requirements of various boxing exercises such as sparring, pad work, and punching bag. Because it was not possible to measure the oxygen uptake (VO2) of "true" sparring with a collecting gas valve in the face, we developed and validated a method to measure VO2 of "true" sparring based on "postexercise" measurements. Nine experienced male amateur boxers (Mean ± SD: age = 22.0 ± 3.5 years, height = 176.0 ± 8.0 cm, weight = 71.4 ± 10.9 kg, number of fights = 13.0 ± 9.5) of regional and provincial level volunteered to participate in 3 testing sessions: (a) maximal treadmill test in the LAB, (b) standardized boxing training in the GYM, and (c) standardized boxing exercises in the LAB. Measures of VO2, heart rate (HR), blood lactate concentration [LA], rated perceived exertion level, and punching frequencies were collected. VO2 values of 43.4 ± 5.9, 41.1 ± 5.1, 24.7 ± 6.1, 30.4 ± 5.8, and 38.3 ± 6.5 ml·kg⁻¹·min⁻¹ were obtained, which represent 69.7 ± 8.0, 66.1 ± 8.0, 39.8 ± 10.4, 48.8 ± 8.5, and 61.7 ± 10.3%VO2peak for sparring, pad work, and punching bag at 60, 120, and 180 b·min⁻¹, respectively. Except for lower VO2 values for punching the bag at 60 and 120 b·min⁻¹ (p < 0.05), there was no VO2 difference between exercises. Similar pattern was obtained for %HRmax with respective values of 85.5 ± 5.9, 83.6 ± 6.3, 67.5 ± 3.5, 74.8 ± 5.9, and 83.0 ± 6.0. Finally, sparring %HRmax and [LA] were slightly higher in the GYM (91.7 ± 4.3 and 9.4 ± 2.2 mmol·L⁻¹) vs. LAB (85.5 ± 5.9 and 6.1 ± 2.3 mmol·L⁻¹). Thus, in this study simulated LAB sparring and pad work required similar VO2 (43-41 ml·kg⁻¹·min⁻¹, respectively), which corresponds to ~70%VO2peak. These results underline the importance of a minimum of aerobic fitness for boxers and draw some guidelines for the intensity of training.

Generalized self-efficacy and performance on the 20-metre shuttle run in children.

It has been argued that motivation significantly affects the measurement of aerobic capacity when using field tests with children. In this study, the impact of generalized self-efficacy on performance (Stage Completed) in the Léger shuttle run is examined in a cohort of children (N = 2,245, 9.38 +/- 0.52 years old) in Grade 4 from 75 elementary schools. Children completed the Children's Self-perceptions of Adequacy in and Predilection for Physical Activity scale (CSAPPA) to establish levels of generalized self-efficacy toward physical activity, were measured for height and weight, and then completed the Léger Shuttle run to predict aerobic capacity. Regression analysis was used to study the impact of self-efficacy on test performance. After adjusting for age, gender, and BMI, two of the three CSAPPA factor subscales, higher perceived adequacy regarding physical activity (beta = 0.196, P < 0.001) and greater predilection to select physical over sedentary activities (beta = 0.123, P < 0.001), were independently associated with better test performance as indicated by stage completed. Together, self-efficacy accounted for 9% of the total variation in Léger shuttle run performance. A significant interaction between BMI and perceived adequacy was found (beta = -0.106, P < 0.005). Children with both high BMI scores and below average perceived adequacy had the poorest performance results. Generalized self-efficacy, as measured by the CSAPPA, is significantly related to Léger shuttle run performance. Moreover, self-efficacy influences the relationship between other known factors affecting test performance (BMI), suggesting that self-perception of ability/competence has a complex effect on test performance. These results illustrate the importance of considering psychological factors when interpreting physiologic assessments in children.

Prediction of one-hour running performance using constant duration tests.

Critical velocity (CV) represents, theoretically, the highest velocity that can be sustained without fatigue. The aim of this study was to compare CV computed from 5 mathematical models in order to determine which CV estimate is better correlated with 1-hour performance and which model provides the most accurate prediction of performance. Twelve trained middle- and long-distance male runners (29 +/- 5 years) performed 3 randomly ordered constant duration tests (6, 9, and 12 minutes), a maximal running velocity test for the estimation of CV, and a 1-hour track test (actual performance). Two linear, 2 nonlinear, and 1 exponential mathematical models were used to estimate CV and to predict the highest velocity that could be sustained during 1 hour (predicted performance). Although all CV estimates were correlated with performance (0.80 < r < 0.93, p < 0.01), it appeared that CV estimated from the exponential model was more closely associated with performance than all other models (r = 0.93; p < 0.01). Analysis of the bias +/- 95% interval of confidence between actual and predicted performance revealed that none of the models provided an accurate prediction of the 1-hour performance velocity. In conclusion, the estimation of CV allows us to rank middle- and long-distance runners with regard to their ability to perform well in long-distance running. However, no models provide an accurate prediction of performance that could be used as a reference for coaches or athletes.

Worldwide variation in the performance of children and adolescents: an analysis of 109 studies of the 20-m shuttle run test in 37 countries.

This study is a meta-analysis of 109 reports of the performance of children and adolescents on the 20-m shuttle run test (20-mSRT). The studies were performed in 37 countries and included data on 418,026 children, tested between 1981 and 2003. Results were expressed as running speed (km x h(-1)) at the final completed stage of the 20-mSRT. Raw data were combined with pseudodata using Monte Carlo simulation. The 20-mSRT performances were expressed as z-scores relative to all children of the same age and sex from all countries. An overall "performance index" was derived for each country as the average of the age- and sex-specific z-scores for all children from that country. Factorial analysis of variance was used to compare scores among countries and regions, and between boys and girls of the same age. There was wide and significant (P < 0.0001) global variability in the performance of children. The best performing children were from the Northern European countries Estonia, Iceland, Lithuania, and Finland (0.6 - 0.9 standard deviations above the global average). The worst performing children were from Singapore, Brazil, USA, Italy, Portugal, and Greece (0.4 - 0.9 standard deviations below the global average). There is evidence that performance was negatively related to being overweight, as well as to a country's average temperature.