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Journal of Osteoporosis
Volume 2017, Article ID 5219541, 9 pages
https://doi.org/10.1155/2017/5219541
Research Article

The Femoral Neck Mechanoresponse to Hip Extensors Exercise: A Case Study

1School of Computer Science, Engineering and Mathematics, Flinders University, Adelaide, SA, Australia
2North West Academic Centre, The University of Melbourne, St Albans, VIC, Australia
3Department of Orthopedic Surgery, Harvard Medical School and Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA
4Department of Mechanical Engineering, Melbourne School of Engineering, University of Melbourne, Parkville, VIC, Australia
5Australian Institute for Musculoskeletal Science, St Albans, VIC, Australia
6St Vincent’s Department of Surgery, The University of Melbourne, Fitzroy, VIC, Australia
7Department of Medicine, School of Clinical Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC, Australia

Correspondence should be addressed to Saulo Martelli; ua.ude.srednilf@illetram.oluas

Received 16 August 2016; Revised 21 November 2016; Accepted 6 December 2016; Published 11 January 2017

Academic Editor: Merry Jo Oursler

Copyright © 2017 Saulo Martelli et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Physical activity is recommended to prevent age-related bone loss. However, the proximal femur mechanoresponse is variable, possibly because of a muscle-dependant mechanoresponse. We compared the proximal femur response with the femoral strain pattern generated by the hip extensor muscles. A healthy participant underwent a six-month unilateral training of the hip extensor muscles using a resistance weight regularly adjusted to the 80% of the one-repetition maximum weight. DXA-based measurements of the areal Bone Mineral Density (aBMD) in the exercise leg were adjusted for changes in the control leg. The biomechanical stimulus for bone adaptation (BS) was calculated using published models of the musculoskeletal system and the average hip extension moment in elderly participants. Volumetric (ΔvBMD) and areal (ΔaBMD) BMD changes were calculated. The measured and calculated BMD changes consistently showed a positive and negative effect of exercise in the femoral neck (ΔaBMD = +0.7%; ΔvBMD = +0.8%) and the trochanter region (ΔaBMD = −4.1%; ΔvBMD = −0.5%), respectively. The 17% of the femoral neck exceeded the 75th percentile of the spatially heterogeneous BS distribution. Hip extensor exercises may be beneficial in the proximal femoral neck but not in the trochanteric region. DXA-based measurements may not capture significant aBMD local changes.