Peroneal Reaction-Time Demonstrates a Greater Influence Than Peroneal Muscle Strength on Lateral Ankle Ligament Strain in People With Chronic Ankle Instability

Background: Lateral ankle sprains often damage the anterior talofibular (ATFL) and calcaneofibular (CFL) ligaments. Delayed peroneal muscle reaction time (reaction-time) and reduced peroneal muscle strength (strength) may increase the risk of recurrent sprains. Relationships between neuromuscular impairments and ligament strains remain unclear due to challenges in directly measuring ligament strains under dynamic conditions. Hypothesis: Reaction-time and strength are correlated significantly with ATFL and CFL strains in people with and without chronic ankle instability (CAI). Study design: Cross-sectional study. Level of Evidence: Level 3. Methods: Participants with CAI (n = 35) and without CAI (n = 35) were recruited. Reaction-time was assessed using a trapdoor test, while strength was measured through a standardized isometric strength test. ATFL and CFL strains were calculated using a 3-dimensional rigid-body foot model during a drop-landing task. Data were analyzed using Pearson’s correlations and multiple regressions. Results: Compared with people without CAI, those with CAI exhibited longer reaction-time ( P < 0.001) and weaker strength ( P = 0.02). Reaction-time correlated with ATFL strain in both CAI ( r = 0.589; P < 0.001) and non-CAI ( r = 0.423; P = 0.01) participants, and with CFL strain only in CAI participants ( r = 0.358; P = 0.04). Strength correlated with ATFL strain in both groups (CAI: r = −0.462, P = 0.005; non-CAI: r = −0.358, P = 0.04), but showed no correlation with CFL strain in either group. Multiple regression analysis revealed that reaction-time and strength were significant predictors of ATFL strain, with reaction-time having a greater impact ( β = 0.565; P < 0.001) than strength ( β = 0.431; P = 0.001). In non-CAI participants, reaction-time and strength had similar predictive contributions ( β = 0.600 and β = 0.552, respectively; all P < 0.001). Conclusion: Both reaction-time and strength were associated with ATFL strain in people with and without CAI. Reaction-time appeared associated more closely with ATFL strain than strength. Clinical Relevance: These findings highlight the importance of targeting neuromuscular reaction time and peroneal strength in rehabilitation programs aimed at reducing lateral ankle ligament strain and risk of recurrent sprains, with particular emphasis on improving rapid neuromuscular activation.