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. 2019 Sep;10(3):321-326.
doi: 10.1016/j.shaw.2019.06.002. Epub 2019 Jun 12.

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

Christopher M Hill  1 , Hunter DeBusk  2 , Jeffrey D Simpson  3 , Brandon L Miller  4 , Adam C Knight  4 , John C Garner  5 , Chip Wade  6 , Harish Chander  4
Affiliations

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

Christopher M Hill et al. Saf Health Work. 2019 Sep.

Abstract

Background: Performing cognitive tasks and muscular fatigue have been shown to increase muscle activity of the lower extremity during quiet standing. A common intervention to reduce muscular fatigue is to provide a softer shoe-surface interface. However, little is known regarding how muscle activity is affected by softer shoe-surface interfaces during static standing. The purpose of this study was to assess lower extremity muscular activity during erect standing on three different standing surfaces, before and after an acute workload and during cognitive tasks.

Methods: Surface electromyography was collected on ankle dorsiflexors and plantarflexors, and knee flexors and extensors of fifteen male participants. Dependent electromyography variables of mean, peak, root mean square, and cocontraction index were calculated and analyzed with a 2 × 2 × 3 within-subject repeated measures analysis of variance.

Results: Pre-workload muscle activity did not differ between surfaces and cognitive task conditions. However, greater muscle activity during post-workload balance assessment was found, specifically during the cognitive task. Cognitive task errors did not differ between surface and workload.

Conclusions: The cognitive task after workload increased lower extremity muscular activity compared to quite standing, irrespective of the surface condition, suggesting an increased demand was placed on the postural control system as the result of both fatigue and cognitive task.

Keywords: Anti-fatigue; Dual-task; Postural control; Standing surface.

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Figures

Fig. 1
Fig. 1
The footwear displayed was outfitted with over-shoe attachment of ErgoMates. Velcro attachments sites were secured over the top of the laces and at the heel of the footwear.
Fig. 2
Fig. 2
Pre- and post-workload mean muscle activity for the hamstring with and without the cognitive task on the three standing surfaces (SS, solid surface; FM, fatigue mat; EM, ErgoMates). ❖Significant task time interaction simple effect, where greater mean muscle activity was found in post-workload cognitive task than pre-workload quite standing muscle activity. ★ Significant task time interaction simple effect, where greater mean muscle activity was found in the in post-workload cognitive task than pre-workload cognitive task. § Significant main effect for time, where greater muscle activity was found after workload than before workload.
Fig. 3
Fig. 3
Pre- and post-workload mean muscle activity for the quadricep with and without the cognitive task on the three standing surfaces (SS, solid surface; FM, fatigue mat; EM, ErgoMates). ❖Significant task time interaction simple effect, where greater mean muscle activity was found in post-workload cognitive task than pre-workload cognitive task muscle activity.
Fig. 4
Fig. 4
Pre- and post-workload mean muscle activity for the tibialis anterior with and without the cognitive task on the three standing surfaces (SS, solid surface; FM, fatigue mat; EM, ErgoMates). ♯Significant task main effect, where greater muscle activity was found during the cognitive task than during quiet standing.
Fig. 5
Fig. 5
Pre- and post-workload mean muscle activity for the quadricep with and without the cognitive task on the three standing surfaces (SS, solid surface; FM, fatigue mat; EM, ErgoMates). ♯Significant task main effect where greater muscle activity was found during the cognitive task than during quiet standing.
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