Influence of a School-based Physical Activity Intervention on Cortical Bone Mass Distribution: A 7-year Intervention Study.

Cortical bone mass and density varies across a bones length and cross section, and may be influenced by physical activity. This study evaluated the long-term effects of a pediatric school-based physical activity intervention on tibial cortical bone mass distribution. A total of 170 children (72 girls and 98 boys) from one school were provided with 200 min of physical education per week. Three other schools (44 girls and 47 boys) continued with the standard 60 min per week. Tibial total and cortical area, cortical density, polar stress-strain index (SSI), and the mass and density distribution around the center of mass (polar distribution, mg) and through the bones cortex (radial distribution subdivided into endo-, mid-, and pericortical volumetric BMD: mg/cm3) at three sites (14, 38, and 66 %) were assessed using peripheral quantitative computed tomography after 7 years. Girls in the intervention group had 2.5 % greater cortical thickness and 6.9 % greater SSI at the 66 % tibia, which was accompanied by significantly greater pericortical volumetric BMD compared to controls (all P < 0.05). Region-specific differences in cortical mass were also detected in the anterior, medial, and lateral sectors at the 38 and 66 % tibial sites. There were no group differences at the 14 % tibia site in girls, and no group differences in any of the bone parameters in boys. Additional school-based physical education over seven years was associated with greater tibial structure, strength, and region-specific adaptations in cortical bone mass and density distribution in girls, but not in boys.

A 5-year exercise program in children improves muscle strength without affecting fracture risk.

PURPOSE: High level of physical activity (PA) is associated with great muscle strength and high fracture risk. This prospective controlled population-based study evaluated how a pediatric PA intervention program influenced muscle strength and fracture risk. METHODS: We carried out a school-based exercise intervention program with 200 min of PA per week for 5 years in 335 girls and 408 boys aged 6-9 years at study start. An age-matched control cohort including 756 girls and 782 boys continued with 60 min of PA per week. We registered fractures during the study period and calculated rate ratio. In a sub-sample, including 74 girls and 107 boys in the intervention and 51 girls and 54 boys in the control group, we measured knee flexion and extension strength by a computerized dynamometer and leg composition by dual energy X-ray absorptiometry. Group comparisons were adjusted for differences in age, baseline value for the measured parameter and changes in height. RESULTS: Children in the intervention group had a rate ratio to sustain a fracture of 1.03 (0.78, 1.36) (mean and 95 % confidence interval) (p = 0.79). The annual gain in flexion peak torque muscle strength was greater in both girls (at 60°/s) [1.1 Nm (0.5, 1.8), p < 0.01] and boys (at 180°/s) [0.7 Nm (0.1, 1.2), p < 0.05] in the intervention than in the control group, while leg composition was similar. CONCLUSION: Increased PA during a 5-year period, starting in the pre-pubertal period, improves the gain in muscle strength without affecting the fracture risk.

A seven-year physical activity intervention for children increased gains in bone mass and muscle strength.

AIM: This study evaluated the musculoskeletal effects of increased physical activity on children, starting at six to nine years of age. METHODS: In one school we increased the physical education of 72 girls and 100 boys to 200 minutes per week over seven years. In three other schools, 45 girls and 47 boys continued to receive 60 minutes per week. We measured areal bone mineral density (aBMD) with dual energy X-ray absorptiometry and muscle strength with computerised dynamometer at baseline and after seven years and tibial cortical thickness with peripheral quantitative computed tomography after seven years. RESULTS: Girls in the intervention group gained 0.04 g/cm(2) (0.01-0.08) more total spine aBMD (p < 0.05) and 6.2Nm (1.6, 10.7) more knee flexion strength (p < 0.01) than control group girls and had a 0.1 mm (0.0, 0.3) higher tibial cortical thickness at follow-up (p < 0.05). Boys in the intervention group gained 7.3Nm (0.4, 14.2) more knee extension strength (p < 0.05) and 7.4Nm (2.3, 12.4) more knee flexion strength (p < 0.01) than the control group boys, but their aBMD was no higher than the control group. CONCLUSION: A seven-year, population-based moderately intense exercise intervention enhanced gains in spine bone mass in girls and knee muscle strength in both genders.

Daily School Physical Activity Improves Academic Performance.

Physical activity (PA) may improve brain development, cognition, concentration and academic performance. In this prospective controlled intervention study, we increased the level of PA in 338 children aged 6-8 years at study start, from the Swedish standard of 60 min per week to 200 min per week (40 min daily). The intervention continued in all nine compulsory school years until the students graduated between 2007-2012. All other 689,881 Swedish children who graduated the same years were included as a control group. We registered at graduation eligibility rate for upper secondary school and the final grade score (from 0 to 320 grade points). We also registered the same end points in the 295 students in the index school and in all other 471,926 Swedish students who graduated in 2003-2006, that is, those who graduated before the intervention study started. Before the intervention, academic performance was similar among children in the index school as for all other Swedish boys and girls. With the intervention, the eligibility rate increased for boys in the index school by 7.3 percentage points and the mean grade scores by 13.3 points. This should be compared with a decrease of 0.8 percentage points in eligibility rate and an increase by 2.7 points in grade score in other Swedish boys. No changes were seen for intervention girls, neither in eligibility rates or grade scores. By introducing daily school-based PA in compulsory school, more boys would probably reach the eligibility rate for higher education.

[Daily physical activity during the nine compulsory school years improves academic school results in boys but not girls - a prospective controlled intervention study]. / Daglig fysisk aktivitet på schemat: bättre skolresultat hos pojkarna - Men för flickorna var det ingen skillnad ­ Bunkefloprojektet följde grundskoleelever under nio år.

One aim of the Bunkeflo project is to evaluate if daily school physical activity (PA) is associated with higher final school grades and improved eligibility for upper secondary school. One elementary school extended PA throughout elementary school to 200 minutes/week while control schools continued with in mean 60 minutes/week. We then registered final school grades and eligibility for upper secondary school in children who began first grade in the intervention school during the years before the intervention (1994-1997) and in the children who started 1998-2003 (that is, who had daily PA during the 9 compulsory school years). We also registered final school grades and eligibility for upper secondary school in all Swedish children who started school 1998-2003. We found that boys in the intervention group had higher eligibility rates and higher grade scores than boys who finished the same school before the intervention was implemented as well as higher in all Swedish boys. These differences in were not seen in girls. Daily school PA through elementary school is associated with higher final grade scores and higher eligibility rates for upper secondary school in boys.

How does a physical activity programme in elementary school affect fracture risk? A prospective controlled intervention study in Malmo, Sweden.

OBJECTIVES: Recent evidence from the 7-year follow-up of the Pediatric Osteoporosis Prevention (POP) study indicates an inverse correlation between years of participation in a physical activity (PA) intervention and fracture risk in children. However, we could not see a statistically significant reduction in fracture risk, which urged for an extension of the intervention. SETTING: The study was conducted in 4 neighbouring elementary schools, where 1 school functioned as intervention school. PARTICIPANTS: We included all children who began first grade in these 4 schools between 1998 and 2012. This resulted in 1339 children in the intervention group and 2195 children in the control group, all aged 6-8 years at the state of the study. INTERVENTION: We launched an 8-year intervention programme with 40 min of moderate PA per school day, while the controls continued with the Swedish national standard of 60 min of PA per week. PRIMARY OUTCOME MEASURE: We used the regional radiographic archive to register objectively verified fractures and we estimated annual fracture incidences and incidence rate ratios (IRRs). RESULTS: During the first year after initiation of the intervention, the fracture IRR was 1.65 (1.05 to 2.08) (mean 95% CI). For each year of the study, the fracture incidence rate in the control group compared with the intervention group increased by 15.7% (5.6% to 26.8%) (mean 95% CI). After 8 years, the IRR of fractures was 52% lower in the intervention group than in the control group (IRR 0.48 (0.25 to 0.91) (mean 95% CI))]. CONCLUSIONS: Introduction of the school-based intervention programme is associated with a higher fracture risk in the intervention group during the first year followed by a gradual reduction, so that during the eighth year, the fracture risk was lower in the intervention group. TRIAL REGISTRATION NUMBER: NCT00633828.