Research Article: Effects of a cognitive–motor dual task on neuromuscular and biomechanical control during single-leg drop landing in individuals with chronic ankle instability

Abstract:
To compare lower-extremity neuromuscular and biomechanical characteristics during single-leg drop landing under single-task and cognitive–motor dual-task conditions in individuals with chronic ankle instability (CAI). Twenty-three male participants with unilateral CAI completed single-leg drop landings from a 30-cm platform under single-task and auditory 2-back dual-task conditions in randomized order using a within-participant repeated-measures design. Whole-body three-dimensional kinematics, ground reaction force (GRF), and surface electromyographic (sEMG) signals from eight muscles of the affected limb were recorded synchronously. Outcomes included GRF and dynamic-stability measures, hip, knee, and ankle joint angles and internal moments, muscle activation, and co-contraction indices (CCIs). Depending on the distribution of paired differences, two-sided paired-samples t -tests or Wilcoxon signed-rank tests were used. Effect sizes were reported as Cohen's dz or rank-biserial correlations (rrb), respectively. Compared with the single-task condition, the dual-task condition produced a higher peak vertical GRF (vGRF; p = 0.004, dz = 0.66) and smaller hip flexion angles at peak vGRF ( p = 0.033, rrb = ?0.507) and maximum knee flexion ( p = 0.012, rrb = ?0.587). At maximum knee flexion, the internal hip extension moment was lower ( p < 0.001, dz = ?0.80), whereas the internal ankle plantarflexion moment was higher ( p = 0.028, dz = 0.49). The dual-task condition was also associated with lower lateral gastrocnemius root-mean-square activation ( p = 0.002, dz = ?0.75), higher peak tibialis anterior activation ( p = 0.015, dz = 0.55), higher peak vastus lateralis activation ( p = 0.001, dz = 0.77), and a lower peroneus longus–medial gastrocnemius CCI ( p = 0.030, dz = ?0.48). No significant between-condition differences were observed in average vertical loading rate, time to stabilization, time to peak vGRF, hip flexion at initial contact, the measured knee and ankle joint angles, or frontal-plane joint angles. In individuals with CAI, a concurrent working-memory task was associated with higher peak impact, reduced hip flexion at selected post-contact events, and selective changes in net internal joint moments and lower-extremity sEMG measures. These findings indicate that dual-task effects on landing control are outcome- and event-specific rather than uniform across biomechanical and neuromuscular domains.

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