Comparative effects of various running exercise modalities on femoral bone quality in rats.

BACKGROUND: It is now well established that physical exercise is an effective preventive method to reduce and treat certain chronic diseases, particularly musculoskeletal disorders. At the bone level, running exercise is well known for its positive effects on various parameters of bone quality. There is, however, no consensus regarding the effects of different running exercise modalities on bone quality. AIM: The objective of this study was to compare the effects of three treadmill running modalities: intermittent, moderate continuous, and a combination of both-on bone quality parameters in rats. METHODS: Thirty-nine, 5-week-old, male Wistar rats were randomly divided in 4 groups: sedentary control (SED; n = 10), intermittent running exercise (IE; n = 10), continuous running exercise (CE; n = 10) and combined running exercise (COME; n = 9). Rats in running groups were exercised 45 min/day, 5 days/week, for 8 consecutive weeks. Femoral micro-architectural parameters were assessed by micro-CT; femoral osteocyte apoptosis, osteoclast resorption and bone histomorphometry were assessed by histology. RESULTS: Femoral trabecular thickness in the combined running group was increased (p < 0.0001) compared to respective results in the other running groups (0.13 mm vs 0.11 mm). The cortical thickness, osteocyte lacunae occupancy rate in the whole femur, numbers of apoptotic osteocytes and osteoclastic resorption surfaces were not significantly different between groups. Statistical differences were occasionally noted depending on the femoral anatomical region. CONCLUSION: These results suggest that the femur should not be considered as the better bone to study the effects of running protocols.

Prediction of Cortical Bone Thickness Variations in the Tibial Diaphysis of Running Rats.

A cell-mechanobiological model is used for the prediction of bone density variation in rat tibiae under medium and high mechanical loads. The proposed theoretical-numerical model has only four parameters that need to be identified experimentally. It was used on three groups of male Wistar rats under sedentary, moderate intermittent and continuous running scenarios over an eight week period. The theoretical numerical model was able to predict an increase in bone density under intermittent running (medium intensity mechanical load) and a decrease of bone density under continuous running (higher intensity mechanical load). The numerical predictions were well correlated with the experimental observations of cortical bone thickness variations, and the experimental results of cell activity enabled us to validate the numerical results predictions. The proposed model shows a good capacity to predict bone density variation through medium and high mechanical loads. The mechanobiological balance between osteoblast and osteoclast activity seems to be validated and a foreseen prediction of bone density is made available.

Physical Activity and Bone Vascularization: A Way to Explore in Bone Repair Context?

Physical activity is widely recognized as a biotherapy by WHO in the fight and prevention of bone diseases such as osteoporosis. It reduces the risk of disabling fractures associated with many comorbidities, and whose repair is a major public health and economic issue. Bone tissue is a dynamic supportive tissue that reshapes itself according to the mechanical stresses to which it is exposed. Physical exercise is recognized as a key factor for bone health. However, the effects of exercise on bone quality depend on exercise protocols, duration, intensity, and frequency. Today, the effects of different exercise modalities on capillary bone vascularization, bone blood flow, and bone angiogenesis remain poorly understood and unclear. As vascularization is an integral part of bone repair process, the analysis of the preventive and/or curative effects of physical exercise is currently very undeveloped. Angiogenesis-osteogenesis coupling may constitute a new way for understanding the role of physical activity, especially in fracturing or in the integration of bone biomaterials. Thus, this review aimed to clarify the link between physical activities, vascularization, and bone repair.