Human limb vibration and neuromuscular control

Mechanical loading can modulate tissue plasticity and has potential applications in rehabilitation science and regenerative medicine. To safely and effectively introduce mechanical loads to human cells, tissues, and the entire body, we need to understand the optimal loading environment to promote growth and health. The purpose of this research was 1) to validate a limb vibration and compression system; 2) to determine the effect of limb vibration on neural excitability measured by sub-threshold TMS-conditioned Hreflexes and supra-threshold TMS; 3) to determine changes in center of pressure, ankle muscle activity, and kinematics during a postural task following limb vibration; and 4) to determine the effect of limb vibration and whole body vibration on movement accuracy of a weight bearing visuomotor task and muscle responses to an unexpected pertubation. The major findings of this research are 1) the mechanical system presented in the manuscript can deliver limb vibration and compression reliably, accurate, and safely to human tissue. 2) Sub-threshold cortical stimulation reduces the vibration-induced presynaptic inhibition of the H-reflex. This reduction cannot be attributed to an increase in cortical excitability during limb vibration because the MEP remains unchanged with limb vibration. 3) Limb vibration altered the soleus and tibialis EMG activity during a postural control task. The vibration-induced increase in muscle activity was associated with unchanged center of pressure variability but reduced center of pressure complexity. 4) Simulated fallers were able to accommodate extraneous afferent information due to the vibration interventions to maintain similar levels of accuracy but muscle responses to an unexpected pertubation were altered. Taken together, vibration has immediate applications to improve various human tissues.