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.

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

Trends in BMI among Belgian children, adolescents and adults from 1969 to 1996.

OBJECTIVE: To document secular data on changes in the distribution of body mass index (BMI), to determine the probability of overweight at 40 y of age in Belgian males in relation to the presence or absence of overweight at different ages in adolescence, and to estimate tracking of BMI in Belgian males in Belgium aged 12-40 y. DESIGN: Cross-sectional and mixed longitudinal surveys in nationally representative samples of Belgian males and females. SUBJECTS: Cross-sectional-more than 21 000 boys and 9698 girls; to examine secular trends-3164 boys and 5140 girls; to examine tracking-161 males. MEASURES: Body mass and height to determine BMI. RESULTS: In Belgian children the degree of overweight has increased between 1969 and 1993. Tracking of BMI is high in adolescence (r=0.77) and adulthood (r=0.69-0.91) and moderate from adolescence to adulthood (r=0.49). In Belgian males, the probability of overweight at 40 y of age in the presence of overweight at different ages in adolescence is important (odds ratios 5.0-6.9). CONCLUSIONS: Cross-sectional and longitudinal data, trends and tracking of BMI from 1969 until 1996 in Belgium indicate an increase in the degree of childhood overweight and obesity. Moreover, the risk of an overweight male adolescent becoming an overweight adult is substantial. Measures to restrict the Belgian overweight and obesity epidemic should be taken.

Anthropometric characteristics of elite female junior rowers.

During the 1997 Federation Internationale des Sociétés d'Aviron (FISA) World Junior Rowing Championships, the anthropometric characteristics of 245 female junior rowers aged 17.5 +/- 0.8 years (mean +/- s) were assessed. Twenty-seven body dimensions (body mass, 6 heights or lengths, 4 breadths, 10 girths and 6 skinfolds) were measured in total. The elite female junior rowers were taller (174.5 +/- 6.2 cm) and heavier (69.5 +/- 6.2 kg), with greater length, breadth and girth dimensions, but lower skinfold thicknesses than a representative sample of Flemish (Belgian) girls of the same chronological age. An anthropometric profile chart was constructed that was rowing-specific and norms were established. Compared with scullers, sweep rowers were heavier (+4.2 kg) and taller (+2.8 cm), with greater length, breadth (except for femur width) and girth dimensions (except for calf girth). Sweep rowers also had greater skinfold thicknesses (except for the thigh and calf skinfolds). Finalists were heavier (+3.6 kg) and taller (+3.9 cm), with greater length, breadth (except for femur width) and girth dimensions (except for calf girth) than non-finalists. No significant differences were found for skinfold thicknesses between finalists and non-finalists.

Anthropometric characteristics of elite male junior rowers.

During the 1997 Federation Internationale des Sociétés d'Aviron World Junior Rowing Championships, anthropometric data on 383 male junior rowers were assessed. With 430 participating athletes, the sample represented 89% of the population. In addition to age, 27 dimensions were measured: body mass, six heights or lengths, four breadths, 10 girths, and six skinfolds. The elite male junior rowers were tall (187.4 (5.8) cm; mean (SD)) and heavy (82.2 (7.4) kg), with larger length, breadth, and girth dimensions than a nationally representative sample of Belgian boys of the same chronological age. A rowing specific anthropometric profile chart with norms was constructed. The stature of the junior rowers is similar to that of adult heavyweight elite rowers, except that the junior rowers are lighter. Compared with non-finalists, finalists are heavier (but still lighter than the adult heavyweight elite rower) and taller, with greater length, breadth (except for the bicristal diameter), and girth dimensions.

Metabolic and cardiorespiratory responses in young oarsmen during prolonged exercise tests on a rowing ergometer at power outputs corresponding to two concepts of anaerobic threshold.

A group of ten young experienced oarsmen [mean age 17.5 (SD 1.7) years, height 182.5 (SD 5.9) cm, body mass 77.0 (SEM 10.6) kg] exercised in a progressive incremental test (PIE: 50W x 3 min[-1]) on a rowing ergometer to determine the power output corresponding to the 4 mmol lactate x l(-1) anaerobic threshold (AT4) and the individual anaerobic threshold (IAT). Within 10 days they performed at random two 30-min prolonged exercise tests (PET) at power outputs corresponding to AT4 and IAT to demonstrate whether or not a steady-state blood lactate concentration [La-]b could be maintained. Oxygen uptake (VO2), heart rate (HR) and [La-]b were measured. The PIE revealed significant lower values at IAT compared to AT4 for power output (P < 0.01), HR (P < 0.01) and VO2 (P < 0.01). Coefficients of correlation between AT4 and IAT were 0.68 for power output, 0.79 for HR and 0.70 for VO2. All the subjects could complete the PET at IAT and only six out of the ten at AT4. The [La-]b at the end of PET was significantly higher at AT4 compared to IAT (P < 0.01). Similar results were found for VO2 (P < 0.01) and for HR (P < 0.01). A steady state of mean blood lactate concentration ([La-]ss was found only for the power output at IAT. From the results of this study, we concluded that both concepts of anaerobic threshold gave different information about submaximal endurance capacity. Only IAT represented on average [La-]ss. It is suggested that more research is needed to elicit optimal guidelines for the intensity of endurance training.

The Conconi test: a controversial concept for the determination of the anaerobic threshold in young rowers.

In order to examine the validity of Conconi's heart rate threshold (ATHR) during rowing ergometry, in accordance with the new recommendations of Conconi, ten young rowers (age 17.5 [SD 1.7] years; height 182.5 [SD 5.9]cm; body mass 77.0 [SD 10.6] kg) were submitted - at random and within 48-72 h - to two progressive incremental exercise tests on a rowing ergometer. In the first test, the heart rate threshold (ATHR) was determined during a ramp-like incremental test. In a second test, the lactate method (150W + 50W x 3 min(-1)) was used to determine the 4 mmol x l(-1) threshold (AT4) and the individual anaerobic threshold (IAT). Subsequently, each subject performed within 48-72 h after the second progressive incremental exercise test a 30 min prolonged exercise test (PET) at the power output corresponding to ATHR to demonstrate whether or not a steady state in blood lactate concentration ([La-]bSS) could be maintained. Friedmann's analysis of variance, Wilcoxon signed ranks test and Spearman rank correlation coefficient (rs) were used as statistical tools. Significant lower values for power output (p < 0.01 ) and heart rate (HR) (p < 0.01) were found at IAT as compared to AT4 and ATHR. No relationships were found between ATHR on the one hand and AT4 and IATon the other hand, neither for power output (rs=0.27 and -0.09), nor for HR (rs=0.08 and -0.08). Coefficients of correlation between AT4 and IAT were respectively 0.68 (p < 0.05) for power output and 0.79 (p < 0.01) for HR. During PET only four out of 10 rowers reached the target time of 30 min at ATHR power output and only one rower showed a lactate steady state. From our results we can conclude that power output at ATHR is overestimated and cannot be used for the prescription of endurance training in rowing. The ATHR does not reflect the anaerobic threshold and is therefore not relevant for monitoring continuous endurance training in rowing.

Effect of specific test procedures on plasma lactate concentration and peak oxygen uptake in endurance athletes.

Plasma lactate accumulation during submaximal work and VO2peak were determined on the bicycle ergometer and on the treadmill in all round trained control subjects (n = 9) and in specifically trained athletes such as distance runners (n = 9) and racing cyclists (n = 8). Plasma lactate concentration at equivalent levels of oxygen uptake was lower during treadmill exercise than during bicycle exercise in the controls and in the runners, but the difference between the two work modalities was more pronounced in the runners. In contrast to the runners, the cyclists had a higher plasma lactate concentration on the treadmill. VO2peak values on the two ergometers were similar in the controls, while the specifically trained athletes reached the highest value when they were tested with the exercise test which is specific to the training conducted. In the runners VO2peak was 14% higher on the treadmill than on the bicycle ergometer and in the cyclists VO2peak was 11% higher on the bicycle ergometer. It is concluded that the difference in plasma lactate concentration during submaximal work and in VO2peak between treadmill and bicycle exercise can be affected by the training conditions of the subjects.

Cardiorespiratory response to bicycle and rowing ergometer exercise in oarsmen.

Maximal aerobic power and related variables during submaximal work were determined on the bicycle and on the rowing ergometer in 9 oarsmen and in 9 control subjects. During submaximal work, heart rate and pulmonary ventilation were similar with the two exercise procedures in each group, but the oarsmen had lower values than the control subjects. Oxygen uptake at a given workload was higher on the rowing ergometer than on the bicycle ergometer for both the oarsmen and the control subjects. During maximal exercise, the control subjects reached significantly lower values on the rowing ergometer than on the bicycle ergometer for maximal oxygen uptake and maximal oxygen pulse. The oarsmen however attained practically the same values on the two ergometers, with a rank difference correlation coefficient of 0.94. The difference between the results obtained in control subjects and in oarsmen supports the concept of training specificity.

Cardiorespiratory response to treadmill and bicycle exercise in runners.

Maximal aerobic power and related variables during submaximal work were determined on the bicycle ergometer and on the treadmill in nine long-distance runners and in nine control subjects. During submaximal work, heart rate and pulmonary ventilation were similar with the two exercise procedures in each group, but the runners had lower values than the control subjects. During maximal exercise, oxygen uptake and pulmonary ventilation reached higher levels on the treadmill than on the bicycle egometer. The difference in VO2max was not significant in the control subjects (4.4%), but was more pronounced (12.8%) and highly significantly (p < 0.01) in the runners. The intergroup differences for VO2max between runners and controls were more marked during treadmill running (17.3%) than during bicycle exercise (8.5%). It is concluded tht the differences between the VO2max values obtained on the bicycle ergometer and on the treadmill are influenced by the training conditions of the subjects and that bicycle ergometry leads to a marked underestimation of maximal oxygen uptake in runners.

Effects of training on maximal working capacity and haemodynamic response during arm and leg-exercise in a group of paddlers.

Maximal oxygen uptake and circulatory adaptation to work with legs and arms were studied in a group of 5 paddlers members of the Belgian national squad and a control-group of 9 trained subjects. The results showed that the specific armtraining of paddlers induced changes in the arm-to-leg ration of physiological parameters at submaximal and maximal work. In the group of paddlers maximal oxygen intake and workload during arm-exercise averaged respectively 88.6% and 80.3% of the scores obtained with leg-exercise. In the control group the arm to leg ratio varied between 81.2% and 65.2%. At a submaximal load of 100 W the difference in heartfrequency was 21 beats/min in the canoe group and 35 beats/min in the control group. Oxygen consumption and ventilation during work with the arms was lower in the group of paddlers. The data of our study suggest that the specific training of paddlers do result in a effect on the haemodynamic adaptations to arm work.