(D-145) The Effects of Low-Intensity Vibration and Exercise on Bone Mechanical Properties

Introduction:: Bone loss can occur when bone resorption exceeds bone formation, especially in conditions of limited mobility. Low-Intensity Vibration (LIV) is a therapy known to promote bone health by strengthening bone and increasing its formation [1]. Traditionally, exercise has been used as a non-pharmaceutical intervention to increase bone mass in patients with osteoporosis. However, exercise regimes can be difficult for frail, immobile, or bedridden patients. LIV may present an alternative or supplement to exercise in these individuals. Our aim was to examine the effect of LIV in conjunction with exercise on bone properties, as well as compare the two interventions.

Materials and Methods:: 20-week old female C57Bl/6J mice were randomly assigned to LIV intervention (0.7g, 90Hz, 15mins, 2x/day) or non-LIV control groups until 48 weeks of age. After LIV, a subcohort of each group was randomly selected for voluntary wheel running (+Ex) or sedentary control (-Ex). A one-week acclimation period was allotted followed by a six-week tracked exercise intervention. An additional subcohort was euthanized immediately after completion of LIV to serve as baseline controls (Table 1). Mice were euthanized and the tibias were collected, cleaned of soft tissue, and stored frozen in PBS-soaked gauze until testing. An Instron Universal Testing System model 5967 was used to conduct mechanical testing (Figure 2). The tibias were tested until failure using a 3-point bending technique. Force and deflection data was collected and ran through a MATLAB code in order to determine the mechanical properties of the bone (i.e. linear flexural stiffness, maximum yield force, and maximum force). A Kruskal-Wallis ANOVA was performed to compare the effects of LIV and exercise on the mechanical properties of the bone.

Results, Conclusions, and Discussions:: No significant differences were found between mechanical properties of bone and LIV/Exercise interventions. LIV and exercise interventions were evaluated across linear flexural stiffness (N/mm), yield load (N), energy to yield (mJ), max load (N), energy to max load (mJ), failure load (N), and energy to failure (mJ). Baseline LIV intervention also showed no significant difference in the use of LIV on bone properties. Although there was no significance found between groups, the group that received both LIV and exercise showed the maximum stiffness, and the +LIV/-Ex group showed the minimum stiffness (Figure 1).
The results of this experiment cannot determine if use of LIV is an effective method to simulate exercise conditions, as there is no difference between the negative control group and treatment groups. More research is needed to explore the potential of LIV treatment to improve bone health in patients with low-mobility. Future studies hope to investigate the effects of LIV and exercise intervention on the material properties and mineral composition of bone through spherical-indentation and energy dispersive spectroscopy (EDS).

Acknowledgements (Optional): : We would like to thank the College of New Jersey Mentored Undergraduate Summer Experience Program and grant number AG059923 for funding this experiment.

References (Optional): : [1] Thompson WR. Current Opinion in Endocrinology, Diabetes, and Obesity. 2014. 21:447-453.