Baseline peroneus longus reaction time predicts the response to proprioceptive training in chronic ankle instability: A single-centre retrospective cohort study.

BackgroundChronic ankle instability (CAI) is a common sequel of lateral ankle sprain, and proprioceptive training is its first-line treatment, yet the gain differs widely between patients. A prolonged peroneus longus reaction time (PRT) is a hallmark neuromuscular deficit of CAI, but whether it forecasts the training response is unknown.MethodsWe retrospectively analysed 183 adults with CAI who completed a supervised 12-week proprioceptive programme. Baseline PRT to sudden inversion was measured by surface electromyography. The primary outcome was the change in the Cumberland Ankle Instability Tool (CAIT); the Star Excursion Balance Test (SEBT) was secondary. Associations were tested with Pearson and partial correlation, analysis of covariance, multivariable linear regression and receiver-operating-characteristic analysis.ResultsCAIT improved from 18.4 to 22.2 points (mean change +3.8, p < 0.001). Baseline PRT was inversely related to the CAIT gain (Pearson r = -0.51, 95% CI -0.61 to -0.39; partial r adjusted for baseline CAIT = -0.57). In the adjusted model PRT remained the strongest predictor (partially standardized β = -2.09 CAIT points per SD, p < 0.001). PRT discriminated non-responders with an area under the curve of 0.78 (95% CI 0.71-0.84).ConclusionsA shorter baseline peroneal reaction time was associated with a larger improvement after proprioceptive training. PRT is an inexpensive candidate marker that may help stratify CAI patients, although the retrospective single-centre design warrants prospective confirmation.