The Interaction of Cognitive Interference, Standing Surface, and Fatigue on Lower Extremity Muscle Activity

Area of Science:

• Biomechanics
• Human Physiology
• Neuroscience

Background:

• Muscle activity in the lower extremities increases during cognitive tasks and muscular fatigue in quiet standing.
• Softer shoe-surface interfaces are common interventions for muscular fatigue.
• The effect of softer interfaces on muscle activity during static standing is not well understood.

Purpose of the Study:

• To evaluate lower extremity muscle activity during erect standing.
• To assess the impact of three different standing surfaces.
• To investigate changes before and after an acute workload and during cognitive tasks.

Main Methods:

• Surface electromyography (sEMG) was used to measure muscle activity in ankle and knee muscles of 15 male participants.
• Key variables included mean, peak, root mean square, and cocontraction index.
• A 2x2x3 within-subject repeated measures analysis of variance was employed for data analysis.

Main Results:

• No significant differences in pre-workload muscle activity were observed across surfaces or cognitive conditions.
• Post-workload balance assessment revealed greater muscle activity, particularly during the cognitive task.
• Cognitive task errors remained consistent across surface and workload conditions.

Conclusions:

• A cognitive task performed after a workload significantly elevates lower extremity muscle activity compared to quiet standing.
• This effect is independent of the shoe-surface interface condition.
• Both fatigue and cognitive load increase the demand on the postural control system.