Enhancement of the adolescent murine musculoskeletal system using low-level mechanical vibrations.

Mechanical signals are recognized as anabolic to both bone and muscle, but the specific parameters that are critical to this stimulus remain unknown. Here we examined the potential of extremely low-magnitude, high-frequency mechanical stimuli to enhance the quality of the adolescent musculoskeletal system. Eight-week-old female BALB/cByJ mice were divided into three groups: baseline controls (BC, n = 8), age-matched controls (AC, n = 12), and whole body vibration (WBV, n = 12) at 45 Hz (0.3 g) for 15 min/day. Following 6 wk of WBV, bone mineralizing surfaces of trabeculae in the proximal metaphysis of the tibia were 75% greater (P < 0.05) than AC, while osteoclast activity was not significantly different. The tibial metaphysis of WBV mice had 14% greater trabecular bone volume (P < 0.05) than AC, while periosteal bone area, bone marrow area, cortical bone area, and the moments of inertia of this region were all significantly greater (up to 29%, P < 0.05). The soleus muscle also realized gains by WBV, with total cross-sectional area as well as type I and type II fiber area as much as 29% greater (P < 0.05) in mice that received the vibratory mechanical stimulus. The small magnitude and brief application of the noninvasive intervention emphasize that the mechanosensitive elements of the musculoskeletal system are not necessarily dependent on strenuous, long-term activity to initiate a structurally relevant response in the adolescent musculoskeletal system. If maintained into adulthood, the beneficial structural changes in trabecular bone, cortical bone, and muscle may serve to decrease the incidence of osteoporotic fractures and sarcopenia later in life.