The Relationship Between Bone and Muscle Measures in Elite Adolescent Male Cross-Country Skiers Compared to Normally Active Matched Controls

Abstract

Exercise associated muscle induced bone strain has potential osteogenic effects that may increase skeletal density, bone cross-sectional area and structural strength. Whether the effects of exercise and the muscle-bone relation are similar in weight bearing and nonweight bearing bones remains to be determined. This study compared bone density, geometry and biomechanical properties, and bone and muscle cross-sectional areas of 13 elite adolescent male cross-country skiers with height, weight, age and maturity matched non-athletic controls. Total bone mineral density (BMDror), and trabecular bone mineral density and total bone cross-sectional area (CSAror) were measured at the distal 4% of the radius (DR) of the dominant (D) and non-dominant (ND) arms, and tibia (DT) using peripheral quantitative computed tomography (pQCT); BMDror, CSAror, cortical BMD, cortical thickness (CrtTH) and area (CSAcoRr), stress-strain index polar, x, y, polar moment of inertia, axial moment of inertia, and muscle cross-sectional area (mCSA) were measured at the 66% length of the proximal tibia (PT) and proximal radius (PR) of the D and ND arms. Whole body BMD, whole body bone area, and hip areal bone mineral density were measured using dual energy X-ray absorptiometry (DXA). Speed of sound along the bone was measured using quantitative ultrasound (QUS) at the 1/3 DR and PT. There were no differences between the skiers and controls for any of the descriptive measures, however, there was a trend (p=0.06) for skiers to have lower percent body fat than controls. There were no differences between skiers and controls for the bone outcome measures using pQCT, DXA or QUS, except for CrtTH at the PT which was significantly higher in skiers (5.42±0.25mm, p=0.03) than controls (5.18±0.28mm). Cross-country skiers had increased CrtTH at the PT suggesting little differential effect of mechanical loading on bone density, geometry or biomechanical properties associated with skiing.