The Differential Impact of Cognitive Versus Motor Dual-Tasks on Lower Limb Neuromuscular Control during Gait: A Cognitive-Load Perspective

Dual-tasking during gait represents a classic paradigm of cognitive-motor interference, primarily driven by competition for limited central executive resources. While both cognitive and motor secondary tasks disrupt gait, their specific neuromuscular signatures remain poorly differentiated. This study compared the effects of cognitive versus motor dual-tasks on lower limb muscle activity, interpreting findings through cognitive-load theories. Twenty-four healthy adults walked under single-task (normal gait), cognitive dual-task (serial subtraction by threes), and motor dual-task (carrying a full glass of water) conditions. Surface electromyography recorded activity from eight lower limb muscles. Muscle activity intensity was analyzed using repeated-measures ANOVA. Dual-tasking significantly altered muscle activity compared to normal walking (except rectus femoris). A key finding was the distinct pattern elicited by the cognitive task: the medial gastrocnemius, soleus, and tibialis anterior showed significantly higher activity during the cognitive dual-task compared to both the motor dual-task and normal walking. Conversely, the motor dual-task primarily increased activity in the vastus medialis, vastus lateralis, and hamstrings. The pronounced effect of the cognitive task suggests a high demand on central executive resources, leading to compensatory distal stiffening. This underscores cognitive load as a primary driver of gait interference, advocating for task-specific assessment in fall risk evaluation and rehabilitation.