Physical performance capacity of children in Norway. Part IV. The rate of growth in maximal aerobic power and the influence of improved physical education of children in a rural community - population parameters in a rural community

Physical Fitness Percentiles of German Children Aged 9-12 Years: Findings from a Longitudinal Study

Background

Generating percentile values is helpful for the identification of children with specific fitness characteristics (i.e., low or high fitness level) to set appropriate fitness goals (i.e., fitness/health promotion and/or long-term youth athlete development). Thus, the aim of this longitudinal study was to assess physical fitness development in healthy children aged 9–12 years and to compute sex- and age-specific percentile values.

Methods

Two-hundred and forty children (88 girls, 152 boys) participated in this study and were tested for their physical fitness. Physical fitness was assessed using the 50-m sprint test (i.e., speed), the 1-kg ball push test, the triple hop test (i.e., upper- and lower- extremity muscular power), the stand-and-reach test (i.e., flexibility), the star run test (i.e., agility), and the 9-min run test (i.e., endurance). Age- and sex-specific percentile values (i.e., P₁₀ to P₉₀) were generated using the Lambda, Mu, and Sigma method. Adjusted (for change in body weight, height, and baseline performance) age- and sex-differences as well as the interactions thereof were expressed by calculating effect sizes (Cohen’s d).

Results

Significant main effects of Age were detected for all physical fitness tests (d = 0.40–1.34), whereas significant main effects of Sex were found for upper-extremity muscular power (d = 0.55), flexibility (d = 0.81), agility (d = 0.44), and endurance (d = 0.32) only. Further, significant Sex by Age interactions were observed for upper-extremity muscular power (d = 0.36), flexibility (d = 0.61), and agility (d = 0.27) in favor of girls. Both, linear and curvilinear shaped curves were found for percentile values across the fitness tests. Accelerated (curvilinear) improvements were observed for upper-extremity muscular power (boys: 10–11 yrs; girls: 9–11 yrs), agility (boys: 9–10 yrs; girls: 9–11 yrs), and endurance (boys: 9–10 yrs; girls: 9–10 yrs). Tabulated percentiles for the 9-min run test indicated that running distances between 1,407–1,507 m, 1,479–1,597 m, 1,423–1,654 m, and 1,433–1,666 m in 9- to 12-year-old boys and 1,262–1,362 m, 1,329–1,434 m, 1,392–1,501 m, and 1,415–1,526 m in 9- to 12-year-old girls correspond to a “medium” fitness level (i.e., P₄₀ to P₆₀) in this population.

Conclusions

The observed differences in physical fitness development between boys and girls illustrate that age- and sex-specific maturational processes might have an impact on the fitness status of healthy children. Our statistical analyses revealed linear (e.g., lower-extremity muscular power) and curvilinear (e.g., agility) models of fitness improvement with age which is indicative of timed and capacity-specific fitness development pattern during childhood. Lastly, the provided age- and sex-specific percentile values can be used by coaches for talent identification and by teachers for rating/grading of children’s motor performance.

Longitudinal study of maximal aerobic power in teenagers

On the basis of measurement of maximal aerobic power (VO2max) over a period of four years in a teenage population of boys (N = 102) and girls (N = 133), we studied the growth of VO2max in absolute values and in relative values: relative to whole body mass (VO2max/BM), to fat-free mass (VO2max/LBM) and to height squared (VO2max/H2). The changes in VO2max were studied in relation to chronological age (CA), skeletal age (SA), and age relative to peak height velocity (PA). Since no significant testing or measuring effects could be demonstrated and the reproducibility was high, the longitudinal design seems adequate to trace individual growth curves of VO2max. With CA VO2max increases in boys from 2.41/min at age 12+ to 3.81/min at age 17+. The increase in girls is less, from 2.31/min to 2.71/min over the same age range. VO2max/BM remained constant in boys (591/min.kg) and in girls it gradually decreased from 50 at age 12+ to 45 ml/min.kg at age 17+. The decrease in girls has been caused partly by an increase in body fat. When VO2max is aligned on PA, the results show that the peak increase coincides roughly with the age at peak height velocity. It demonstrates that in general in boys and girls during their teens no discrepancy between structural and functional growth occurs as far as VO2max is concerned.

Maximal oxygen uptake, anthropometry and physical activity in a randomly selected sample of 8 and 13 year old children in Sweden

Maximal oxygen uptake was assessed in 101 randomly selected 8 and 13 year old children. In both age groups a significantly higher aerobic capacity was found in boys than in girls, both in absolute terms and when maximal oxygen uptake was related to body weight, lean body mass and lean leg volume. Among girls, maximal oxygen uptake per kg body weight was lower in the older than in the younger (p less than 0.05). Estimation of spontaneous physical activity, by means of a questionnaire and the actometry method, indicated that physical activity was greater in children with a high than in those with a low aerobic capacity.

Functional aerobic capacity and body size

An endurance treadmill exercise test protocol of two minute stages of increasing speed and gradient has been designed and evaluated for children under 10 years of age. There was a significant relation between test protocol time and oxygen uptake measured in ml/kg/min in tests performed on 20 subjects. One hundred and sixty exercise tests performed in a semi longitudinal study of healthy primary schoolchildren were used to assess the relation of functional aerobic capacity with age and size. In boys functional aerobic capacity measured by predicting maximal oxygen uptake from endurance time in the treadmill test increased from 33.8 ml/kg/min at age 5 to 50.5 ml/kg/min at age 9.5 and was most closely related to age. The variables of size were not significant in predicting functional aerobic capacity for boys. In girls functional aerobic capacity increased from 34.9 to 43.5 ml/kg/min at the same ages and was related positively to lean body mass and age but negatively to weight. For girls lean body mass contributed 53.9% to the variance of functional aerobic capacity in stepwise multiple regression, weight 7.7%, and age 3.5%. A significant difference between the sexes was found.

Physical activity and sports involvement in 8- and 13-year-old children in Sweden

The physical activity of randomly selected 8- and 13-year-old children, living in four different regions of Sweden, was investigated by means of a questionnaire. The younger children of each sex were found to be physically more active than the older ones, and within each age group the boys were physically more active than the girls. The results points to higher sports involvement today compared with 10-15 years ago, especially among younger children. It was also shown that regular physical training constituted a smaller proportion of the total physical activity among the younger children than among the older ones. At both ages and in both sexes the rate of regular physical training was lower in municipalities of less than 1,000 inhabitants, and in the 8-year-old children it was also lower in municipalities of less than 5,000 inhabitants. Among the girls regular physical training was more common in those whose fathers had a high educational level compared with the girls who had fathers of a lower educational level.

Longitudinal comparison of aerobic power in active and inactive boys aged 7.0 to 17.0 years

Height and maximal aerobic power (VO2 max) were analysed longitudinally in 14 active and 11 inactive boys from the Saskatchewan Longitudinal Growth Study. VO2 max values were obtained from a treadmill run repeated each year. The Preece-Baines Model I was fitted to height and VO2 max values over the duration of the study. No significant differences were found for height attained between the two groups. VO2 max comparisons revealed no significant differences before the take-off point for the adolescent growth spurt. Significant differences occurred in the VO2 max attained by the age of peak adolescent velocity in VO2 max, the increase from take-off to peak and in the adult value, with active boys having higher values. It is concluded that activity before adolescence causes no significant increase in VO2 max, but that adolescence is the critical period during which consistently higher rates of increase in the VO2 max of active boys result in a significantly greater adult value.

[Comparative study of four effort tests on nine-year-old children. The value of systolic tension time (author's transl)]

Simple effort tests were carried out on 9-year-old children to measure the systolic tension time (STT) and to judge the accuracy and limitations of such a test by comparing it with other measures more commonly employed in France for the same age group: Pachon-Martinet, Ruffier-Dickson, and maximal oxygen uptake (VO2max), the latter (estimated indirectly) serving as the standard of reference. Subjects stepped onto and off a stool 40 cm high, 24 times per minute; immediately thereafter the heart rate per minute and the arterial systolic pressure (mm Hg) were measured, and the product (the systolic tension time) was obtained. At the age of 9 years, 95% of children have an STT of between 13 000 and 25 000. This test, besides the ease with which it can be performed in daily experimentation, has the advantage of giving results that are at once more precise and more significant than the two standard tests of Pachon-Martinet and Ruffier-Dickson because the quality of the experiment is more satisfactory, because autonomic factors have less impact, and because its discriminative value is higher since only the STT provides a satisfactory correlation with VO2max. The test also fulfills the various requisites of an effort test: it can help to trace a poor cardiovascular response to effort and, because of its selective nature, it can also provide a convenient means of supervision of young athletes. In practice, the test should be complemented by a study of the first 3 min of recovery, as this was the only part of the test showing a difference between boys and girls, whether trained or not.

The effect of exercise on diabetic control and hemoglobin A1 (HbA1) in children

14 children with juvenile diabetes mellitus (mean age 11 years, mean diabetes duration 5 years) were enrolled in a one-hour twice weekly supervised exercise program for 5 months. A group of 8 diabetic children of same age and diabetic duration served as control group. Maximum oxygen uptake was within normal range for all children. With this exercise program the maximum oxygen uptake of the training group did not change significantly compared with the control group. The physicians rating of degree of the metabolic control based on blood-glucose measurements and urinary glucose excretion did not change in any of the groups. The insulin dosage per kilo body weight remained unchanged in both groups. In the training group the HbA1 values decreased during the exercise period from 15.1 +/- 2.2 (mean HbA1 % +/- 1 S.D.) to 13.8 +/- 1.9 (2p less than 0.001). In the control group the HbA1 values did not change significantly (13.4 +/- 1.9 to 12.9 +/- 1.6; 2p = 0.20). In a co-study the effect of freezing and storage of hemolysates, resulting in increased levels of HbA1, was demonstrated.

Activity pattern, smoking habits, and somatometric variables of the Czechoslovakian population

A total of 3762 subjects of both sexes, natives of Czechoslovakia, ranging in age from 12--55 years, were examined. Both anamnestic data and selected anthropometric variables were evaluated. The proportion of non-smokers for adult males was 47--56%, and for adult females was 54--74% of the population. The proportion of subjects not engaged in any type of physical activity decreases in boys between 12 and 18 years from 28 to 16%, in girls between 12 and 15 years from 25 to 22%; from then on the trend reverses and the percentages rises up to 42% in men and 65% in women. The number of subjects participating in competitive sporting activity reaches its peak at 18 years, when 46% of boys annd 43% of girls compete, but then decreases quickly. 12 year old girls are taller and heavier than boys but at 15 years the relationship is reversed. The LBM at the age of 12 is equal in boys and girls, but from then till 18 years the increase is larger in boys. The LBM weight in adults remains steady, women attaining 77% of the value found in men. The skinfold increases with age similarly in both sexes, except for an interval between 12 and 18 years, when girls show a steeper increase. Adult women attain 121--160% of the values characteristic for men. The grip strength of the right hand equals about 50 kp in adult men and 30 kp in adult women. Within the age range followed, it remains unaffected by age.