A NEW COMPREHENSIVE APPROACH FOR BONE REMODELING UNDER MEDIUM AND HIGH MECHANICAL LOAD BASED ON CELLULAR ACTIVITY

Abstract

Most of the last century, bone remodeling models have been proposed based on the observation that bone density is dependent on the intensity of the applied mechanical loads. Most of these cortical or trabecular bone remodeling models are related to the osteocyte mechanosensitivity, and they all have a direct correlation between the bone mineral density and the mechanical strain energy. However, experiments on human athletes show that high-intensity sport activity tends not to increase bone mineral density but rather has a negative impact. Therefore, it appears that the optimum bone mineral density would develop for “medium”-intensity activity (or medium mechanical loads) and not for the highest-intensity one. In this work, we propose a new continuum approach based on bone cell activity being either positive or negative as a function of the intensity of the applied mechanical load. At standard earth gravity without exercise, bone homeostasis is observed with cell activity being at equilibrium. When “medium loads” such as “low-intensity” or “optimized” sport activity are applied, cells are activated and an increase of bone density occurs. On the other hand, “high-intensity loads” such as over-training lead to bone density decrease or bone degradation. Our results are in agreement with the literature and enable us to foresee applications such as optimal sport training for best physical conditions.