Mechanical noise affects rambling and trembling trajectories during quiet standing

Falling is a serious worldwide public health issue, leading to heavy interest in the development of interventions to reduce fall risk. Mechanical noise has been shown to be a promising candidate in this regard - the application of mechanical noise to the foot sole has been shown to improve the sensitivity of the foot sole to pressure stimuli, thereby improving postural control and reducing fall risk. However, the mechanism by which mechanical noise affects the neural drive responsible for postural control is yet unknown. A single-blind randomized controlled study was conducted on the bodily sway of 19 healthy young subjects during quiet standing balance on a firm and compliant surface with and without introduced mechanical noise. The trajectory of the center of pressure (COP) of the subjects during balance was decomposed into its constituent rambling and trembling components, which reflected supraspinal and reflexive neural control respectively. On the compliant surface, the introduction of mechanical noise significantly reduced sway compared to control in the overall COP trajectory as well as the rambling and trembling trajectories. These findings indicate that mechanical noise can improve neural control of balance through both the supraspinal and reflexive neural pathways, leading to tighter bodily control and reduced bodily sway. These findings are particularly promising for the development of targeted noise-based assistive devices to reduce fall risk in demographics with neurological issues impairing motor control and balance.Clinical Relevance- This study demonstrates that mechanical vibratory noise introduced to the foot sole reduces both rambling and trembling of the COP during postural control, thus improving balance, with a wider bandwidth of mechanical noise having a larger effect. This has practical applications in the development of noise-based wearable devices for fall risk reduction.