Strain Gradients Correlate with Sites of Exercise-Induced Bone-Forming Surfaces in the Adult Skeleton

Authors

  • Stefan Judex,

    1. McCaig Centre for Joint Injury and Arthritis Research, Departments of Mechanical Engineering and Surgery, University of Calgary, Calgary, Alberta, Canada
    Search for more papers by this author
  • Ted S. Gross,

    1. Department of Orthopaedic Surgery, University of Cincinnati, Cincinnati, Ohio, U.S.A.
    Search for more papers by this author
  • Ronald F. Zernicke

    Corresponding author
    1. McCaig Centre for Joint Injury and Arthritis Research, Departments of Mechanical Engineering and Surgery, University of Calgary, Calgary, Alberta, Canada
    • Department of Surgery, McCaig Centre for Joint Injury and Arthritis Research, University of Calgary, 3330 Hospital Drive NW, Calgary, AB, T2N 4N1 Canada
    Search for more papers by this author

  • Portions of this research have been presented at the annual meetings of the Canadian Society of Biomechanics (1996) and the American Society for Bone and Mineral Research (1996).

Abstract

Physical activity is capable of increasing adult bone mass. The specific osteogenic component of the mechanical stimulus is, however, unknown. Using an exogenous loading model, it was recently reported that circumferential gradients of longitudinal normal strain are strongly associated with the specific sites of periosteal bone formation. Here, we used high-speed running to test this proposed relation in an exercise model of bone adaptation. The strain environment generated during running in a mid-diaphyseal tarsometatarsal section was determined from triple-rosette strain gages in six adult roosters (>1 year). A second group of roosters was run at a high speed (1500 loading cycles/day) on a treadmill for 3 weeks. Periosteal surfaces were activated in five out of eight animals. Mechanical parameters as well as periosteal activation (as measured by incorporated fluorescent labels) were quantified site-specifically in 12 30° sectors subdividing a mid-diaphyseal section. The amount of periosteal mineralizing surface per sector correlated strongly (R2 = 0.63) with the induced peak circumferential strain gradients. Conversely, peak strain magnitude and peak strain rate were only weakly associated with the sites of periosteal activation. The unique feature of this study is that a specific mechanical stimulus (peak circumferential strain gradients) was successfully correlated with specific sites of periosteal bone activation induced in a noninvasive bone adaptation model. The knowledge of this mechanical parameter may help to design exercise regimens that are able to deposit bone at sites where increased structural strength is most needed.

Ancillary