The effect of physical training on collagen, ground substance, and nucleic acid concentrations in long bones was studied in male mice of NMRI strain. The mice to be trained and their controls were about 2 wk old at the beginning of training, which took place on a 5 degrees inclined treadmill 5 days/wk for 3–22 wk. The duration of daily exercise was increased progressively over 3 wk. The final daily exercise bouts were 50 and 80 min for moderate programs and 180 min for the intensive program at a speed of 30 cm/s. Increased concentrations of nitrogen and hexosamines were found at both training intensities, especially after prolonged training. No conclusive changes in nucleic acid concentrations were observed after training. The hexosamine-hydroxyproline ratio was higher and the hydroxyproline-nitrogen ratio lower in the long bones of trained animals compared to the controls. In conclusion these data suggest that prolonged physical activity affects the organic matrix of long bones by maintaining above average concentrations of glycosaminoglycans in matured bones.
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