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The purpose of this study was to determine if physical activity, aerobic fitness and isometric strength during adolescence were predictors of cardiovascular risk factor levels in young adulthood. The following measurements were carried out: maximal oxygen uptake (VO(2)max), maximal voluntary contraction (MVC) in four muscle groups, physical activity (questionnaire), blood pressure (BP), total cholesterol, high density lipoprotein cholesterol (HDL-C), triglycerides, anthropometric variables and body fat % (sum of four skinfolds). The data were collected from the Danish Youth and Sports study, an observational longitudinal study in which two measurements were carried out over an eight-year period. The findings in this study indicated that the relationships between the absolute levels of physical fitness and activity in adolescence and the subsequent level of CVD risk factors are weak. However, the changes in physical fitness and physical activity were related to the absolute levels of CVD risk factors in young adulthood, especially in men. Weak relationships were found between the changes in physical fitness/activity and changes in CVD risk factor levels in both sexes. In conclusion, many subjects changed their levels of physical activity and physical fitness between adolescence and young adulthood and the changes, especially in aerobic fitness, seemed to be the best predictor of CVD risk factor levels in young adulthood.

The aim of this study was to evaluate the effect of increasing the amount of time spent in physical education classes on bone mineral accrual and gain in bone size in prepubertal Danish children. A total of 135 boys and 108 girls, aged 6–8 years, were included in a school-based curriculum intervention program where the usual time spent in physical education classes was doubled to four classes (180 min) per week. The control group comprised age-matched children (62 boys and 76 girls) recruited from a separate community who completed the usual Danish school curriculum of physical activity (90 min/week). Dual-energy X-ray absorptiometry was used to evaluate bone mineral content (BMC; g), bone mineral density (g/cm2), and bone width at the calcaneus and distal forearm before and after 3 years of intervention. Anthropometrics and Tanner stages were evaluated on the same occasions. General physical activity was measured with an accelerometer worn for 4 days. In girls, the intervention group had a 12.5% increase ( P = 0.04) in distal forearm BMC and a 13.2% increase ( P = 0.005) in distal forearm scanned area compared with girls in the control group. No differences were found between the intervention and control groups in boys. Increasing the frequency of physical education classes for prepubertal children is associated with a higher accrual of bone mineral and higher gain in bone size after 3 years in girls but not in boys. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the association between objectively measured habitual physical activity and calcaneal and forearm bone mineral density (BMD, g/cm2), one mechanically more loaded and one less loaded skeletal region, in children aged 6–8 years. BMD was measured in 297 boys and 265 girls by peripheral dual-energy X-ray absorptiometry in the forearm and calcaneus. An accelerometer registered the level of physical activity during 4 days (2 weekdays and the weekend). Weight, height, and skinfold thickness were measured. In order to establish thresholds (count · min−1) for bone-stimulating physical activity, we evaluated different definitions of vigorous physical activity. The boys had 3.2% higher distal forearm bone mineral content (BMC, P < 0.001) and 4.5% higher distal forearm BMD ( P < 0.001) than the girls. They also carried out 9.7% more daily physical activity and spent 14.6–19.0% more time in vigorous physical activity (all P < 0.05) compared to the girls. In contrast, the girls had 3.8% higher calcaneal BMC ( P < 0.01) and 2.5% higher calcaneal BMD ( P < 0.05) than the boys. Both calcaneal and forearm BMD were significantly related to total time of daily physical activity as well as with intense physical activity above all the chosen cut-off points (all P < 0.05). The β value for mean count · min−1 physical activity was significantly lower than that for all the chosen cut-off points of vigorous activity both for calcaneal and distal forearm BMD. This study suggests that both habitual daily physical activity and amount of vigorous physical activity in children aged 6–8 years are associated with appendicular BMD. [ABSTRACT FROM AUTHOR]