High-phosphorus, low-calcium dietary intakes and bone effects of physical training

Physical training-related bone injuries represent an important concern in young military recruits. Diet inquiries showed changes in calcium and phosphorus intakes. This study is aimed at investigating the effects of physical activity on bone tissue in the context of high-phosphorus and low-calcium intakes. Sedentary (SED) and trained (TR) Dark Agouti rats were raised on four different diets: normal, high phosphorus-normal calcium, normal phosphorus-low calcium and high phosphorus-low calcium. TR animal were submitted to a 6- week voluntary exercise. The experimental phase was achieved without problem. All TR rats ran spontaneously distances corresponding to a high range of performance (14.4+/-1.5 km and 40.5+/-2.5 km for the first and the last week respectively). Analysis of weekly physical activity and running speed showed no significant difference considering the diet. Trained animals (TR) had a 30-40% higher food intake than corresponding sedentary (SED) animals. A slight difference in body growth appeared on the 28th day of the experiment with lower body weight in TR than in SED animals, independently of the dietary group. Bones and blood were sampled at the end of the experiment. The right tibias are aimed to be processed for histomorphometric analysis and the left tibias for analysis of bone mineral content.