Motoneuron Function Does not Change Following Whole-Body Vibration in Individuals With Chronic Ankle Instability.

CONTEXT: Following a lateral ankle sprain, ∼40% of individuals develop chronic ankle instability (CAI), characterized by recurrent injury and sensations of giving way. Deafferentation due to mechanoreceptor damage postinjury is suggested to contribute to arthrogenic muscle inhibition (AMI). Whole-body vibration (WBV) has the potential to address the neurophysiologic deficits accompanied by CAI and, therefore, possibly prevent reinjury. OBJECTIVE: To determine if an acute bout of WBV can improve AMI and proprioception in individuals with CAI. DESIGN AND PARTICIPANTS: The authors examined if an acute bout of WBV can improve AMI and proprioception in individuals with CAI with a repeated-measures design. A total of 10 young adults with CAI and 10 age-matched healthy controls underwent a control, sham, and WBV condition in randomized order. SETTING: Biomechanics laboratory. INTERVENTION: WBV. MAIN OUTCOME MEASURES: Motoneuron pool recruitment was assessed via Hoffmann reflex (H-reflex) in the soleus. Proprioception was evaluated using ankle joint position sense at 15° and 20° of inversion. Both were assessed prior to, immediately following, and 30 minutes after the intervention (pretest, posttest, and 30mPost, respectively). RESULTS: Soleus maximum H-reflex:M-response (H:M) ratios were 25% lower in the CAI group compared with the control group (P = .03). Joint position sense mean constant error did not differ between groups (P = .45). Error at 15° in the CAI (pretest 0.8 [1.6], posttest 2.0 [2.8], 30mPost 2.0 [1.9]) and control group (pretest 0.8 [2.0], posttest 0.6 [2.9], 30mPost 0.5 [2.1]) did not improve post-WBV. Error at 20° did not change post-WBV in the CAI (pretest 1.3 [1.7], posttest 1.0 [2.4], 30mPost 1.5 [2.2]) or control group (pretest -0.3 [3.0], posttest 0.8 [2.1], 30mPost 0.6 [1.8]). CONCLUSION: AMI is present in the involved limb of individuals with CAI. The acute response following a single bout of WBV did not ameliorate the presence of AMI nor improve proprioception in those with CAI.