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In the Bunkeflo project, one elementary school increased duration of school physical activity (PA) to 200 minutes/week while 3 control schools continued with 60 minutes/week throughout the nine elementary school years. We then registered fractures in 3534 children, and evaluated the duration of PA, bone mass and muscle strength in a subsample (n=140) during the intervention and 3 years after. The PA intervention was associated with higher duration of PA both during and 3 years after the intervention. With each year of intervention, the fracture incidence rate ratio (IRR) declined in the intervention children so that it was 0.48 (95% CI 0.25, 0.91) the eighth year of intervention. These findings were accompanied by beneficial gain in musculoskeletal traits in both intervention girls and boys (p0.05). Nine years of daily school-based PA is associated with a progressive reduction in fracture risk, accompanied by beneficial musculoskeletal gains and a more physically active lifestyle.

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.

Observational and case control studies infer that a pregnancy and a period of lactation are followed by loss in bone mass of up to 5%. The reason for this loss is virtually impossible to conclude as so many factors known to influence the bone mass undergo changes during a pregnancy and lactation. The increased calcium demand, changed nutritional habits, reduced smoking and alcohol consumption seen in many women during these periods, the changes in body weight and fat content, the changed level of physical activity and the changed levels of hormones with potential to influence the bone metabolism could all influence the bone mass. Most studies also report that the deficit in "bone mass" normalises after weaning. Multiple pregnancies and long total duration of lactation can not be regarded as risk factors for osteoporosis and fragility fractures as most reports indicate that women with multiple pregnancies have similar or higher bone mass and similar or lower fracture incidence than their peers with no children.