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Plantar Vibrotactile Detection Deficits in Adults with Chronic Ankle Instability.
Hoch MC, McKeon PO, Andreatta RD.
Med Sci Sports Exerc. 2011 Sep 27. [Epub ahead of print]
PURPOSE:
The purpose of this study was to investigate the vibrotactile detection thresholds of the plantar cutaneous afferents in subjects with chronic ankle instability compared to healthy control subjects.
METHODS:
Eight adults with chronic ankle instability and 8 adults with no ankle sprain history participated. Vibrotactile detection thresholds were assessed using a mechanical stimulus generator system, mounted onto an articulated microscope arm which delivered sinusoidal vibrotactile inputs to the foot sole at three different sites: head of the 1 metatarsal, base of the 5 metatarsal, and the heel. Vibrotactile stimulation was delivered at a range of test frequencies which corresponded to the known responsiveness of cutaneous mechanoreceptors in the glabrous skin of the foot sole (10, 25, and 50 Hz). Probe displacement measures (dB) from the last eight displacement trials that contained 50% positive detection responses were averaged to obtain a single threshold estimate for each test frequency and site combination.
RESULTS:
The results of this study indicate that no significant group by site interactions were found for any test frequencies (p>0.29). However, group main effects were present at the 10 Hz (p < 0.0001), 25 Hz (p = 0.03), and 50 Hz (p = 0.04) test frequencies indicating subjects with chronic ankle instability had significantly higher detection thresholds or less sensitivity when stimulation sites were pooled.
CONCLUSION:
The results of this study indicate that subjects with chronic ankle instability may demonstrate decreased sensitivity on the plantar surface of the foot. These alterations in plantar cutaneous somatosensation may help explain the underlying mechanisms associated with the prolonged sensorimotor system impairments in postural control and gait commonly exhibited by people with chronic ankle instability.
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