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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.
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.
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.
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.
Re: Plantar sensory deficits and chronic ankle instability
Altered plantar-receptor stimulation impairs postural control in those with chronic ankle instability.
McKeon PO, Stein AJ, Ingersoll CD, Hertel J. J Sport Rehabil. 2012 Feb;21(1):1-6.
Postural control as assessed via time-to-boundary (TTB) measures has been shown to be impaired in those with chronic ankle instability (CAI). Foot orthotics have been shown to improve postural control, although it is not clear if this is via mechanical or sensorimotor mechanisms.
To assess the effect of textured shoe inserts that provide no mechanical support on postural control as assessed by TTB measures in subjects with CAI.
A crossover design to examine the effects of a textured insole on postural control in individuals with unilateral CAI. The independent variables were vision (eyes open, eyes closed) and texture (textured insole, sham insole, control).
20 physically active individuals, 12 men, 8 women, age 18-45 y (21.5 ± 5.51) with self-reported CAI.
Each subject balanced in shod single-limb stance with eyes open and eyes closed under 3 conditions (control, sham, and textured insole). The order of testing under the 3 shoe conditions and 2 vision conditions was counterbalanced.
MAIN OUTCOME MEASURES:
The mean of TTB minima and the standard deviation of TTB minima in the mediolateral (ML) and anteroposterior directions.
There were significant reductions in TTB ML magnitude and variability found in the textured condition compared with the control and sham conditions. In the textured condition, subjects failed significantly more trials than any other condition.
Stimulating the plantar surface of the foot, via a textured insole, has an effect in the broad spectrum of postural-control maintenance in individuals with CAI.
Re: Plantar sensory deficits and chronic ankle instability
Evaluation of joint position recognition measurement variables associated with chronic ankle instability: a meta-analysis.
McKeon JM, McKeon PO. J Athl Train. 2012;47(4):444-56.
To identify the most precise and consistent variables using joint repositioning for identifying joint position recognition (JPR) deficits in individuals with chronic ankle instability (CAI). Data Sources: We conducted a computerized search of the relevant scientific literature from January 1, 1965, to July 31, 2010, using PubMed Central, CINAHL, MEDLINE, SPORTDiscus, and Web of Science. We also conducted hand searches of all retrieved studies to identify relevant citations. Included studies were written in English, involved human participants, and were published in peer-reviewed journals.
Studies were included in the analysis if the authors (1) had examined JPR deficits in patients with CAI using active or passive repositioning techniques, (2) had made comparisons with a group or contralateral limb without CAI, and (3) had provided means and standard deviations for the calculation of effect sizes.
Studies were selected and coded independently and assessed for quality by the investigators. We evaluated 6 JPR variables: (1) study comparisons, (2) starting foot position, (3) repositioning method, (4) testing range of motion, (5) testing velocity, and (6) data-reduction method. The independent variable was group (CAI, control group or side without CAI). The dependent variable was errors committed during joint repositioning. Means and standard deviations for errors committed were extracted from each included study.
Effect sizes and 95% confidence intervals were calculated to make comparisons across studies. Separate meta-analyses were calculated to determine the most precise and consistent method within each variable. Between-groups comparisons that involved active repositioning starting from a neutral position and moving into plantar flexion or inversion at a rate of less than 5°/s as measured by the mean absolute error committed appeared to be the most sensitive and precise variables for detecting JPR deficits in people with CAI.