Psychophysical estimate of plantar vibration sensitivity brings additional information to the detection threshold in young and elderly subjects.

Objective: Vibration detection threshold of the foot sole was compared to the psychophysical estimate of vibration in a wide range of amplitudes in young (20-34 years old) and elderly subjects (53-67 years old).
Methods: The vibration detection threshold was determined on the hallux, 5th metatarsal head, and heel at frequencies of 25, 50 and 150 Hz. For vibrations of higher amplitude (reaching 360 μm), the Stevens power function ( Ψ  =  k  *  Φ ⁿ ) allowed to obtain regression equations between the vibration estimate ( Ψ ) and its physical magnitude ( Φ ), the n coefficient giving the subjective intensity in vibration perception. We searched for age-related changes in the vibration perception by the foot sole.
Results: In all participants, higher n values were measured at vibration frequencies of 150 Hz and, compared to the young adults the elderly had lower n values measured at this frequency. Only in the young participants, the vibration detection threshold was lowered at 150 Hz.
Conclusion: The psychophysical estimate brings further information than the vibration detection threshold which is less affected by age.
Significance: The clinical interest of psychophysical vibration estimate was assessed in a patient with a unilateral alteration of foot sensitivity.