Stochastic resonance in osteogenic response to mechanical loading.

Stochastic resonance, in which noise enhances the response of a nonlinear system to a weak signal, has been observed in various biological sensory systems. We speculated that bone formation in response to mechanical loading could be enhanced by adding noise (vibration) to a standard exercise regimen. To test this hypothesis, three different loading regimens were applied to the ulnae of mice: (1) high amplitude, low frequency sinusoidal loading at 2 Hz with an amplitude of 3 N to simulate exercise; (2) low amplitude, broad frequency vibration with frequency components 0-50 Hz and 0.3 N of mean amplitude; (3) the sinusoidal wave combined with vibration (S+V) to invoke stochastic resonance. The simulated exercise regimen induced new bone formation on the periosteal surface of the ulna, however the addition of vibration noise with exercise enhanced the osteogenic response by almost 4-fold. Vibration by itself had no effect on bone formation. It was concluded that adding low magnitude vibration greatly enhanced bone formation in response to loading, suggesting a contribution of stochastic resonance in the osteogenic response.