The aim of this study was to evaluate a general school-based one-year exercise intervention program in a population-based cohort of girl at Tanner stage I. Fifty-three girls aged 7 to 9 years were included. The school curriculum based exercise intervention program included 40 minutes per school day. Fifty healthy age-matched girls assigned to the general school curriculum of 60 minutes physical activity per week served as controls. Bone mineral content (BMC; g) and areal bone mineral density (aBMD; g/cm 2 ) were measured with dual X-ray absorptiometry (DXA) of the total body (TB), lumbar spine (L2-L4 vertebra), the third lumbar vertebra (L3), the femoral neck (FN) and the leg. Volumetric bone mineral density (vBMD; g/cm 3 ) and bone width were calculated at L3 and FN. Total lean body mass and total fat mass were estimated from the total body scan. No differences were at baseline found in age, anthropometrics or bone parameters when the groups were compared. The annual gain in BMC was in the cases 4.7 percentage points higher in lumbar spine and 9.5 percentage points higher in L3 than in the controls (both p<0.001). The annual gain in aBMD was in the cases 2.8 percentage points higher in lumbar spine and 3.1 percentage points higher in L3 than in the controls (both p<0.001). The annual gain in bone width was in the cases 2.9 percentage points higher in L3 than in the controls (p<0.001).A general school-based exercise program in 7 -9-year-old girls enhances the accrual of BMC and aBMD and increases bone width.

This non-randomized prospective controlled study evaluates a daily school-based exercise intervention program of 40 min/school day for 1 year in a population-based cohort of 81 boys aged 7-9 years. Controls were 57 age-matched boys assigned to the general school curriculum of 60 min/week. Bone mineral content (BMC; g) and areal bone mineral density (aBMD; g/cm(2)) were measured with dual X-ray absorptiometry (DXA) of the total body, the third lumbar vertebra (L3) and the femoral neck (FN). Bone width for L3 and FN was calculated from the lumbar spine and hip scan. No differences between the groups were found at baseline in age, anthropometrics or bone parameters. The mean annual gain in L3 BMC was 5.9 percentage points higher (P<0.001), L3 aBMD a mean 2.1 percentage points higher (P=0.01) and L3 width a mean 2.3 percentage points higher (P=0.001) in the cases than in the controls. When all individuals were included in one cohort, the total duration of exercise including both school-based and spare-time training correlated with L3 BMC (r=0.26, P=0.003), L3 aBMD (r=0.18, P=0.04) and L3 width (r=0.24, P=0.006). The study suggests that exercise in pre-pubertal boys influences the accrual of bone mineral and bone width and that a 1-year school-based exercise program confers skeletal benefits, at least in the lumbar spine.

The results indicate a higher rate of overuse injuries in low back/pelvic region and shoulders than in comparable studies.

This 8-year controlled, follow-up study in 66 Swedish soccer women evaluated the effect of training and reduced training on BMD. The players who retired during the follow-up lost BMD in the femoral neck, whereas the controls did not.Introduction: Physical activity during adolescence increases BMD, but whether the benefits are retained with reduced activity is controversial. Materials and Methods: At baseline, DXA evaluated BMD in 48 active female soccer players with a mean age of 18.2 ± 4.4 (SD) years, in 18 former female soccer players with a mean age of 43.2 ± 6.2 years and retired for a mean of 9.4 ± 5.3 years, and in 64 age-and sex-matched controls. The soccer women were remeasured after a mean of 8.0 ± 0.3 years, when 35 of the players active at baseline had been retired for a mean of 5.3 ± 1.6 years. Results and Conclusions:The players still active at follow-up had a higher BMD at baseline than the matched controls in the femoral neck (FN; 1.13 ± 0.19 versus 1.00 ± 0.13 g/cm

Objective. Hypovitaminosis D has been shown to be associated with low bone mineral density in middleaged and elderly women. The aim of this study was to evaluate whether such an association might exist in adolescent and young adult girls, approaching peak bone mass. Design. Cross-sectional study carried out in late winter. Setting. Reykjavik area at latitude 64ЊN. Subjects. Two-hundred and fifty-nine Icelandic Caucasian girls, aged 16, 18 and 20 years, randomly selected from the registry of Reykjavik. Main outcome measures. Bone mineral density in lumbar spine, hip, distal forearm and total skeleton was measured with dual-energy X-ray absorptiometry (DEXA) and compared with 25-hydroxyvitamin D levels [25 (OH)D] in serum, measured by radioimmunoassay. Calcium and vitamin-D intake were also assessed by a questionnaire. Results. 18.5% of the girls were below 25 nmol L Ϫ1 in serum 25 (OH)D which has been recognized as the lower normal limit for adults. No significant association was found between 25 (OH)D levels and bone mineral density. Conclusions. Normal calcium and phosphate concentrations in plasma and normal bone mineral density are maintained in adolescent and young adult girls at lower 25 (OH)D levels than published 'normal' levels for middle-aged and elderly.

Objective. The aim of the study was to quantify the inter-relationship between bone mineral density and physical activity, muscle strength, and body mass composition in a group of healthy 16]20-year-old women. Design. A cross-sectional study. Setting. Reykjavik area. Subjects. Two-hundred and fifty-four Icelandic Caucasian women aged 16, 18 and 20 years, randomly selected from the registry of Reykjavik. Main outcome measures. Bone mineral content (BMC) and density (BMD) in lumbar spine, hip, distal forearm and total skeleton and lean mass and fat mass were measured with dual energy X-ray absorptiometry (DEXA) and compared with grip strength measured with a dynamometer and physical activity as assessed by a questionnaire. Results. The lean mass had the strongest correlation with BMC and BMD, stronger than weight, height and fat mass, both in univariate analysis (r = 0.41]0.77; P , 0.001) and in linear regression analysis. The total skeletal BMD was logarithmically higher by hours of exercise per week (P , 0.001)). About 30% of variability in total skeletal BMD in this age group can be predicted by lean mass and physical exercise. Conclusions. Modifiable factors, such as exercise and adequate muscle seem to be significant predictors of the attainment of peak bone mass in women.

The aim of the study was to compare bone turnover in male soccer players with controls and to follow bone turnover with changes in activity level. Serum-osteocalcin (OC), carboxy-terminal propeptide of type I collagen (PICP) and total alkaline phosphatases (tALP) were measured to assess bone formation. Bone resorption was detected by carboxyterminal cross-linked telopeptide of type I collagen (ICTP). Bone turnover of 12 male premier league soccer players (mean age 23 years, range, 17-34) exercising 12 hours/week (range, 8-15) were at the last day of the soccer season compared with 27 age- and gender-matched controls. Bone turnover was followed weekly during a 4-week resting period between two seasons, and a further 10 days following resumption of full training. Data are presented as mean +/- SEM. Both OC (22 +/- 12%) and ICTP (34 +/- 17%) were higher in the players compared with the controls at the end of the season (both P < 0.05, respectively). After 2 weeks of reduced physical activity among the athletes, the PICP levels were 21 +/- 4% (P < 0.05) lower and the ICTP levels 8 +/- 12% higher (P = 0.07) compared with baseline. OC, PICP, and tALP was then no different compared with controls and ICTP was higher than controls (P < 0.001). Ten days within the new season, there was a 23 +/- 5% increase in PICP (P < 0.001) and a 4 +/- 4% decrease in ICTP (P < 0.05) compared with the end of the resting period. In summary, male soccer players have higher bone turnover compared with age- and gender-matched controls. Changes in physical activity level were associated with changes in bone formation and resorption as evaluated by bone markers within weeks, and after 2 weeks rest, ICTP was higher in the athletes than the controls. We conclude that the higher age-related diminution in BMD, previously reported in former soccer players compared with age- and gender-matched controls, may be the result of increased bone resorption, evaluated by ICTP, compared with the controls.

This study is consistent with the hypothesis that a threshold effect of calcium intake on BMD might exist. Above this threshold (1000-1200 mg) no further effect on BMD was seen. The results show a strong association between grip strength, a measure representative of total body strength, and BMD.