Abstract
Background:
Neurocognition plays an essential role in the organization of movement patterns. Evaluation of competition readiness could be improved by incorporating dual tasks, including decision-making and/or divided attention, to simulate competition-like environments. While recent reports have highlighted kinematic adaptations, the influence of dual task testing on muscle activation remains unknown.
Hypothesis:
We hypothesized that introducing a cognitive load would result in earlier onset and decreased peak activation of lower extremity muscles involved in joint stabilization, reflecting compensatory neuromuscular strategies under divided attention.
Methods:
Healthy adolescents (14-18 years) performed lateral shuffle, run-plant, and run-cut tasks with and without dual task conditions, including verbal memory (Verbal; reciting numbers backwards), visual memory (Visual; reporting observed colors), and visual motor response (Motor; unanticipated directional change). Electromyography sensors were placed on the rectus femoris (RF), vastus medialis obliquus (VMO), semimembranosus (HAM), tibialis anterior (TA), and gastrocnemius (GAS). Peak activation was extracted across the weight acceptance phase and normalized. Peak values during Baseline (no dual task) were subtracted from each dual task condition to compute the muscle activity deficit. Friedman’s tests with post hoc paired comparisons (Wilcoxon) were performed for each movement task to identify differences in deficits between dual task conditions.
Results:
Fifty-three limbs from 29 participants (16.1±1.2years) were analyzed. During the run-cut, greater deficits were observed under the Visual condition compared to Motor for the RF (27.3% vs. 11.5%, p=0.008) and HAM (36.7% vs. 22.1%, p=0.008). The VMO also demonstrated larger deficits during both Verbal (110.1%, p=0.001) and Visual (108.1%, p=0.001) compared to Motor (63.0%). For the run-plant, RF deficits were significantly higher during Verbal (22.4%, p=0.001) and Visual (21.5%, p<0.001) compared to Motor (5.3%), with similar patterns observed for VMO (Verbal:76.6%, p<0.001; Visual:75.6%, p=0.001; Motor:9.5%). HAM also exhibited greater deficits during Verbal (38.1%) versus Motor (22.1%, p=0.002). Additionally, RF peak activation timing differed across conditions, with Visual eliciting earlier activation (+13ms relative to Baseline), while Motor resulted in delayed activation (-22ms, p=0.015). During the shuffle, RF deficits varied significantly between conditions (p<0.001–0.015), with Verbal producing the greatest deficit (32.1%) and Motor the smallest (9.5%). HAM deficits were similarly higher during Verbal (14.1%) compared to Motor (5.5%, p=0.011).
Conclusion:
These findings demonstrate that increasing cognitive load alters neuromuscular activation patterns during change-of-direction movements. The observed earlier activation and greater deficits in key stabilizing muscles suggest a loss of neuromuscular control under divided attention that may have implications for injury risk during sport-specific tasks.