The Influence of Physical Activity on Musculoskeletal Characteristics and Fracture Risk at Growth

Abstract: Physical Activity (PA) can improve neuromuscular development. A high level of physical activity can perhaps however lead to more fractures.
This is a longitudinal population-based exercise intervention study where the school-based physical education (PE) in one school is increased from mean 60 min/week to mean 200 min/ week. We registered fractures in all children during 6 years. We annually measured musculoskeletal traits in a subsample by dual-energy X-ray absorptiometry (DXA) and muscle strength by a Biodex dynamometer. At follow-up we used peripheral computed tomography (pQCT) to assess the appendicular skeleton.
The fracture risk was not affected by the intervention, rate ratio 1.12 (0.85, 1.46). Children in the intervention group annually improved their spine BMD more than controls (p<0.05). At follow-up intervention girls had improved 11% in femoral neck BMC and 8% in tibial cortical bone mass (all p<0.05). Intervention children also improved their muscle strength compared to the controls (all p<0.05).
This thesis shows that a long-term PA intervention program in school improves the gain in skeletal traits and muscle strength without increasing the fracture risk.