Role of Sensory Deficits on Sensorimotor Control in Athletes With Chronic Ankle Instability

Purpose: Chronic ankle instability (CAI), characterized by instances of repetitive sprains and giving way, is a common chronic dysfunction among athletes. Despite well documented evidence showing impaired peripheral sensory and both central and peripheral motor control, little was known regarding how CAI affects somatosensory cortical activation. Traditionally, management of CAI mostly focused on restoration of motor deficits, with less emphasis on sensory pathway deficits. Only few sensory targeted intervention methods including joint mobilization and massage, have been described. However, methods such as joint mobilization provide not only sensory stimulation but also mechanical alignment correction. In addition, these studies showed functional improvement without exploring mechanisms. Therefore we would like to apply for a three year study grant to firstly investigate the effect of CAI on peripheral and central somatosensation and neuromuscular performance; and secondly to examine the immediate effect of sensory-level electrical stimulation on neurophysiological variables and neuromuscular performance; and lastly to determine the short-term effect of intervention (sensory stimulation with exercise, sham stimulation with exercise, and exercise alone) in athletes with CAI. Research design and methods: This is a cross-sectional exploratory and randomized controlled study. For the first year, we plan to recruit 45 young athletes (20-40 years old) with CAI and 15 matched controls to compare the somatosensory evoked potentials (SEPs), corticomuscular coherence (CMC), α- band event-related desynchronization (ERD), proprioception, two point discrimination threshold of the plantar surfaces, muscle activation and reaching distances of the Y balance test. Activity in the sensorimotor cortex will be recorded using a 64-chanel EEG (SAGA 32/64+ for EEG). Muscle activation is measured using an 8-channel electromyography (EMG) system (Noraxon myo METRICS Portable Lab, Noraxon U.S.A.). For the second year, the 45 young adults with CAI will be randomized into the sensory stimulation (TENS) group, the sham stimulation group, or the control group. The TENS group will receive 40 minutes of sensory electrical stimulation, and the sham group will receive 30 seconds of sensory stimulation at the beginning and end of the treatment. The control group will rest for 40 minutes. The assessment items are identical to those in the first year, and will be carried out before and immediately after the intervention. For the third year, the 45 young adults with CAI will be randomized into the exercise with sensory stimulation (EX-TENS) group, exercise with sham stimulation (EX-ss) group, or exercise alone (EX) group. Participants will receive five sessions of intervention (30 minutes neuromuscular training with or without 40 min stimulation) within two weeks and the assessment will be carried out before and after the intervention. Data analysis: Comparisons of all continuous variables are performed using oneway analysis of variance (ANOVA), and repeated measures ANOVA. The significance level is set at 0.05. Significance. Results of this study provide a better understanding for central somatosensory control mechanisms for chronic ankle instability, and help clinicians and trainers to choose the most appropriate training strategy for people with unstable ankles. We plan to present our work in 3-4 international conferences, and publish 2-3 papers in SCI journals in 5 years.