Heterogeneous Spatial and Strength Adaptation of the Proximal Femur to Physical Activity: A Within-Subject Controlled Cross-Sectional Study |
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| Authors: | Stuart J Warden Julio Carballido-Gamio Alyssa M Weatherholt Joyce H Keyak Chenxi Yan Mariana E Kersh Thomas F Lang Robyn K Fuchs |
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| Affiliation: | 1. Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN, USA;2. Department of Radiology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA;3. Department of Kinesiology and Sport, Pott College of Science, Engineering, and Education, University of Southern Indiana, Evansville, IN, USA;4. Department of Radiological Sciences, Mechanical and Aerospace Engineering, and Biomedical Engineering, University of California Irvine, Irvine, CA, USA;5. Department of Mechanical Science and Engineering, College of Engineering, University of Illinois at Urbana-Champaign, Urbana-Champaign, IL, USA;6. Department of Radiology and Biomedical Imaging, School of Medicine, University of California San Francisco, San Francisco, CA, USA;7. Department of Physical Therapy, School of Health and Human Sciences, Indiana University, Indianapolis, IN, USA Indiana Center for Musculoskeletal Health, Indiana University, Indianapolis, IN, USA |
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| Abstract: | Physical activity (PA) enhances proximal femur bone mass, as assessed using projectional imaging techniques. However, these techniques average data over large volumes, obscuring spatially heterogeneous adaptations. The current study used quantitative computed tomography, statistical parameter mapping, and subject-specific finite element (FE) modeling to explore spatial adaptation of the proximal femur to PA. In particular, we were interested in adaptation occurring at the superior femoral neck and improving strength under loading from a fall onto the greater trochanter. High/long jump athletes (n = 16) and baseball pitchers (n = 16) were utilized as within-subject controlled models as they preferentially load their take-off leg and leg contralateral to their throwing arm, respectively. Controls (n = 15) were included but did not show any dominant-to-nondominant (D-to-ND) leg differences. Jumping athletes showed some D-to-ND leg differences but less than pitchers. Pitchers had 5.8% (95% confidence interval [CI] 3.9%–7.6%) D-to-ND leg differences in total hip volumetric bone mineral density (vBMD), with increased vBMD in the cortical compartment of the femoral neck and trochanteric cortical and trabecular compartments. Voxel-based morphometry analyses and cortical bone mapping showed pitchers had D-to-ND leg differences within the regions of the primary compressive trabeculae, inferior femoral neck, and greater trochanter but not the superior femoral neck. FE modeling revealed pitchers had 4.1% (95% CI 1.4%–6.7%) D-to-ND leg differences in ultimate strength under single-leg stance loading but no differences in ultimate strength to a fall onto the greater trochanter. These data indicate the asymmetrical loading associated with baseball pitching induces proximal femur adaptation in regions associated with weight bearing and muscle contractile forces and increases strength under single-leg stance loading. However, there were no benefits evident at the superior femoral neck and no measurable improvement in ultimate strength to common injurious loading during aging (ie, fall onto the greater trochanter), raising questions as to how to better target these variables with PA. © 2019 American Society for Bone and Mineral Research. |
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| Keywords: | BONE EXERCISE FALLS FEMORAL NECK FRACTURE OSTEOPOROSIS |
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