The Femoral Neck Mechanoresponse to Hip Extensors Exercise: A Case Study.
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.
School of Computer Science, Engineering and Mathematics, Flinders University, Adelaide, SA, Australia; North West Academic Centre, The University of Melbourne, St Albans, VIC, Australia.
Saulo
0000-0002-0012-8122
S
Martelli
Department of Orthopedic Surgery, Harvard Medical School and Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Boston, MA, USA; Department of Mechanical Engineering, Melbourne School of Engineering, University of Melbourne, Parkville, VIC, Australia.
Hossein
H
Mokhtarzadeh
North West Academic Centre, The University of Melbourne, St Albans, VIC, Australia; Australian Institute for Musculoskeletal Science, St Albans, VIC, Australia; St Vincent's Department of Surgery, The University of Melbourne, Fitzroy, VIC, Australia.
Peter
P
Pivonka
Australian Institute for Musculoskeletal Science, St Albans, VIC, Australia; Department of Medicine, School of Clinical Sciences, Faculty of Medicine, Nursing and Health Sciences, Monash University, Clayton, VIC, Australia.
Peter R
PR
Ebeling