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Han C.G. Kemper

This paper reviews the growth and development of skeletal mass in youth and the effects of physical activity upon the bone mass in young people. The different methods to measure the bone mass are described such as anthropometrics, radiographics, dual energy X-ray absorptiometry, quantitative computed tomography, and ultrasound. Two different mechanisms are important for the formation and plasticity of bone: a central hormonal mechanism (with estrogen production) and a local mechanism (based on mechanical forces of gravity and muscle contractions). This local mechanism is closely connected to physical activity patterns and therefore discussed in more detail. Thereafter the natural course of the development of the bone mass during youth is described, taking into account the pubertal stages of boys and girls and also the age at which the maximal bone mass (peak bone mineral density) will be reached. The last part is devoted to the effects of physical activity on bone mass based on results of randomized controlled trials. Although the number of experimental studies are scarce, significant effects of weight bearing activity and high impact strength training programs are shown on the side specific bone mineral density in both boys and girls.

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Han C.G. Kemper and Willem Van Mechelen

The purpose of this article is to clarify the scientific basis of physical fitness assessment in children and to review the European efforts to develop a EUROFIT fitness test battery for the youth in the countries of the Council of Europe. The development of EUROFIT is based on the efforts made in the United States in the 1950s and in Europe in the 1980s. Physical fitness measurement is not identical to physiological measurement: The EUROFIT tests are aimed at measuring abilities rather than skills. Correlations between physical fitness tests and physiological laboratory tests show varying results and, therefore, need to be continued. Reliability of fitness tests needs to be continually studied. Because of the multipurposes of physical fitness testing, EUROFIT norm- and criterion-referenced scales for EUROFIT have to be developed. Examples of scaling methods are given. Implementation of the EUROFIT fitness tests for educational purposes is urgently needed.

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Han C.G. Kemper and Robbert Verschuur

The purpose of this longitudinal study was to identify factors for coronary artery disease (CAD) in a teenage population in the Netherlands from ages 13.5 to 21.5 years. In a follow-up study 93 boys and 107 girls were measured annually from 1977 to 1980, and a fifth measurement was made in 1985. The CAD factors assessed were total serum cholesterol (TC), high density lipoprotein cholesterol (HDL), TC/HDL ratio, systolic (Psyst) and diastolic (Pdiast) blood pressure, percentage body fat (percent fat) and aerobic fitness (VO2 max/BW). The results indicate that the percentage of subjects at risk for CAD are relatively low in both sexes for all factors except for percent fat. From 20 to 30% of the subjects remain in the upper half of risk factor distribution throughout the 8 years study for TC, TC/HDL, percent fat, and VO2max/BW, indicating stability during the teenage period. Because percent fat combines a high stability with relatively high mean values during the teenage period in both sexes, this parameter seems a particularly important CAD risk factor in youngsters.

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Han C.G. Kemper, Robbert Verschuur and Langha de Mey

In the Amsterdam Growth and Health Study, 103 girls and 97 boys were studied five times on a longitudinal basis over a period of 8 years, covering the teenage years from 12 to 17 until young adulthood at 22/23 years. Measured were anthropometric variables such as height, weight (BW), and body fat, and physiological variables such as maximal aerobic power (V̇O2max) and endurance performance (max slope). During the teenage period, V̇O2max/BW remains constant in boys and decreases in girls whereas endurance performance increases in boys and remains constant in girls. By young adulthood V̇O2max/BW and maximal slope have declined in both sexes, and in the case of females are even lower than at the beginning of their teens. Boys superiority in aerobic fitness and the decline in aerobic fitness in both sexes is mainly caused by the differences in the intensity of daily physical activity level.

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Han C.G. Kemper and Lando L.J. Koppes

The purpose of this study was to test the hypothesis that physical activity (PA), measured over a period of 23 years, is beneficial to aerobic fitness (VO2max) in boys and girls (13-36 years) who were enrolled in the Amsterdam Growth and Health Longitudinal Study (AGAHLS). PA was measured using a standardized activity interview. VO2max was assessed directly with a maximal running test on a treadmill. To assess the longitudinal relationship between PA and VO2max, different longitudinal analyses were carried out over different age periods, correcting for various confounders such as lifestyle parameters, biological parameters, and initial VO2max. Highly significant relationships (p < .05) were observed between PA and VO2max in four of the five analyses. However, in an autoregression analysis, when current PA has been related to the future change in VO2max, the results are not any more significant (p > .05). Analysis of the data of PA and VO2max from the AGAHLS population does not fully support the hypothesis that PA affects VO2max.

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Han C.G. Kemper, Mariëlle Spekreijse, Jaap Slooten, G. Bertheke Post, Desiree C. Welten and Jean Coudert

The main purpose of this study was to measure physical activity of 10- to 12-year-old prepubescent boys and girls living in Bolivia at low altitude (400 m above sea level) and at high altitude (4,000 m) with either a low socioeconomic status (LSES) or a high socioeconomic status (HSES). Habitual physical activity was measured by 24-hour heart rate (HR) monitoring during a normal school day. The mean HR is expressed as a percentage of heart rate reserve (HRR%) and the time spent at 50–85% HRR. Analysis by ANOVA showed no significant effects (p > .05) in HRR%. However, the boys spent significantly (p < .05) more time at 50–85% HRR (M = 51 min) than did girls (M = 34 min), and LSES children significantly (p < .01) more (M = 51 min) than HSES children (M = 32 min). There was also a significant interaction between SES and gender, indicating that the difference between boys and girls was significantly (p < .05) greater in LSES than in HSES, and the difference between LSES and HSES children was significantly (p < .05) greater in boys than in girls.

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Han C.G. Kemper, G. Bertheke Post and Jos W.R. Twisk

This longitudinal study evaluates the relationship of food intake and physical activity with biological maturation of 200 boys and girls during adolescence and young adulthood. The subjects were followed during 9 years from ages 12 to 22 years, with repeated measurements at ages 13, 14, 15, 16, and 21. Biological maturation was estimated four times between ages 12 and 17 as skeletal age by radiographs of the left hand and wrist. Daily nutritional intake (macro- and micronutrients) was assessed with a cross-checked dietary history method. Daily physical activity was assessed through structured interview, whereby average weekly time spent in activity was used to assign a weighted activity score. The 107 girls and 93 boys were divided into three maturity groups: early maturers, late maturers, and average maturers. It was concluded that in both sexes, late maturation seemed to coincide with a higher energetic food intake and a slightly higher activity pattern than early maturation during adolescence.

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Jitske Groothausen, Hanneke Siemer, Han C.G. Kemper, Jos Twisk and Desiree C. Welten

In 83 males and 99 females, the relation between peak strain physical activity (PSPA) from 13 to 27 years and lumbar bone mineral density (LBMD) at age 27 was studied. Physical activity was measured longitudinally by an interview six times between ages 13 and 27. Peak strain scores based on ground reaction forces were developed to quantify all registrated activities for peak strain. LBMD was determined once at age 27. Four PSPA periods were considered: the teenage period (13–17 years), the period between 13 and 21 years, the adult period (21–27 years), and the total period (13–27 years). In multiple linear regression analyses, with body weight and gender as covariates, PSPA appeared to be a significant positive predictor for LBMD at age 27 in both males and females for all analyzed periods. The explained variance of PSPA for LBMD was the highest (25%) for the total period and the lowest (8%) for the teenage period.

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Bareket Falk, Panagiota Klentrou, Neil Armstrong, Thomas Rowland and Han C.G. Kemper

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Han C.G. Kemper, Jos W.R. Twisk and Willem van Mechelen

In the Amsterdam Growth And Health Longitudinal Study (AGAHLS), a group of approximately 650 12- to 14-year-old boys and girls was followed in their growth, and development of their health their lifestyle including diet, physical activity and smoking. One of the main interests was the change in their aerobic fitness. From 12 to 36 years of age in total, eight repeated measurements were performed to measure peak oxygen uptake (peak VO2). In this study the data of peak VO2 are revisited and extended: We made use of all collected data as a mixed longitudinal design including cross-sectionally measured subjects as well as longitudinally measured subjects. This led to the availability of 1,194 boys and 1356 girls. With generalized estimating equations (GEE) the longitudinal changes with chronological age and differences between boys and girls were analyzed. Teenage boys and girls increased their peak VO2 (ml/min) significantly (p < .001) until age 14 in girls and until age 17 in boys. However peak VO2 relative to bodyweight (peak VO2/BW) had significantly (p < .001) decreased over the whole age range from 12 to 36 in both sexes. Vigorous physical activity (VPA) also showed a decrease and was significantly (p < .001) related with lower peak VO2/BW (Beta = 0.001). This relation was stronger in boys than in girls. Because at the start of AGAHLS no fast responding metabolic instruments were available, future longitudinal studies about aerobic fitness should include also measurement of VO2 kinetics.