Vibratory Stimulation to Improve Balance Recovery

Investigators implement stochastic vibratory stimulation (SVS) to alter proprioceptive performance by increasing excitement of type Ia afferents in muscle spindles. Based on previous preliminary data, vibration frequencies around 40Hz may provide adequate noise for enhancing aging-related proprioceptive deficits. To make a subsensory noise investigators set it to 90% of the sensory threshold amplitude, which has been effectively used previously for influencing mechanoreceptor sensation in older adults. Stimulation will be imposed bilaterally on: 1) distal ankle (tibialis anterior, peroneus longus, soleus, gastrocnemius); and 2) proximal hip (quadriceps, gluteus medius, and paraspinals). Investigators use Gaussian noise to reduce the anticipative and preemptive adjustments of muscle spindles to the vibration. For SVS investigators use a magnetic actuator system and a Universal Controller (C-2HDLF Tactor/TDK), to provide programmable frequency ranges.