A Physiology-Based Approach for Detecting Vibration Perception Threshold in the Plantar Foot

Abstract

Stochastic-resonance-based vibration therapies have demonstrated the potential to improve balance in persons with somatosensory deficiencies to help prevent fall incidents. These vibrations must remain below vibration perception threshold (VPT) to be safe and effective. Several concerns exist regarding current approaches of detecting VPT, including inconsistent unit scales, limited knowledge of the physiological reliability of the methods, or potential effects they may have on standing balance. Recent assumptions that threshold detection tests have no impact on subsequent vibratory stimulations warrant further investigation. The purpose of this study was (a) to develop a new modified 4-2-1 VPT detection method (M421) based on existing approaches and underlying physiological principles, and (b) to identify potential effects the M421 may have on balance during or after threshold testing. To address the need for greater comparability between patient populations and across vibration systems, a common scale for expressing VPT was also established. Our results indicate that, among healthy adults, the M421 test does not significantly alter balance during or following threshold testing, and that a single trial conducted on both feet is comparable to separate tests of each foot. M421 demonstrates repeatable results and can be completed efficiently. Future studies will seek to further validate M421 through direct comparisons against existing methods to determine the optimal approach for detecting VPT prior to stochastic vibration interventions.