Bone Mineral Density In Male Runners And Climbers

Abstract

While in running the weight-bearing bones are stressed predominantly by high-impact ground-reaction forces, in climbing bones of the total skeleton are stressed by vigorous muscle contractions. Purpose To determine the influence of two disciplines of sport which are characterised by different loading patterns and a different anatomical distribution of the loads on bone mineral density (BMD) of male athletes. Methods We compared the BMD of age-, weight-, and height matched competitive male runners, competitive climbers, and controls. Total body (TB) and regional (upper extremity, lower extremity) BMD were measured by dual-energy X-ray absorptiometry (DXA). Quantitative computed tomographic (QCT) scans were made from the femoral neck (FN) and the lumbar spine (LS). Quantitative ultrasound (QUS) measurements were performed at the calcaneus. ResultsTableRunners and climbers had about the same TB BMD value which was significantly higher than in the control group. The regional analysis showed significant differences between runners and climbers in favour to the mechanically loaded sites. At the FN the runners had a significantly higher trabecular BMD than the climbers and the controls, while the climbers had a significantly higher cortical BMD than the runners and the controls. At the LS the runners and the climbers had similar values for trabecular BMD, which differed significantly from the controls. As expected, runners had the highest QUI value at the calcaneus. Conclusion The results indicate that both, sports producing impact loading as well as sports producing forces by vigorous muscle contraction have beneficial effects on BMD. The bone adaptation is site specific. The inhomogeneous results at the FN (QCT) might be due to the different loading pattern. We suggest that bones that are loaded by compression due to ground reaction forces preliminary adapt by increasing the trabecular BMD while bones loaded by bending resulting from muscle contraction, adapt by increasing the cortical BMD.