A comparison of vibrotactile thresholds obtained using different diagnostic equipment: the effect of contact conditions

Abstract.

Objectives: Vibrotactile thresholds on the fingers were compared using two alternative methods of controlling contact with a vibrating probe: control of the force of contact with the probe (force control) and control of skin indentation produced by the probe (indentation control). Both systems had the same control of push force on a static surround around the vibrating probe. Method: A group of 14 male subjects (aged 20–27 years) were tested at four frequencies (31.5, 63, 125, 250 Hz) in three separate sessions so as to quantify the repeatability of thresholds. Skin stiffness was also measured. Results: Control of skin indentation gave more repeatable thresholds than control of probe force. There was a practice effect whereby thresholds became more consistent over sessions. There were no systematic correlations between thresholds and skin stiffness. Conclusions: Repeatable and similar vibrotactile thresholds can be obtained with two alternative methods having different contact conditions. Either method may assist the diagnosis of disorders associated with hand-transmitted vibration, but control of skin indentation has the advantage of greater simplicity and, in this study, greater repeatability.