The Effects of Cognitive Load and Postural Demand on Static Balance

Abstract

A growing body of research indicates that measures of static balance (e.g., postural sway) are influenced under cognitive demands. Similar measures are also impacted under different balance demands (e.g., stable vs unstable stances). However, to date, there is little known about how the difficulty of postural demands impact the relationship between balance and cognition. PURPOSE: Within the same individuals, we parametrically compared balance demands and cognitive demands on static balance ability using state-of-the-art inertial sensors. METHODS: 34 healthy young adults completed tasks of static balance with and without a cognitive demand (CD). Six wireless inertial sensors (APDM Opals) were attached to the wrists, feet, chest and lower back. The static balance task involved the participants standing for 30 seconds on a firm surface with their eyes closed in three different postural demand (PD) positions: feet apart (Low PD), feet together (Moderate PD), and feet in tandem (High PD). After completing these tasks alone (Low CD), participants were asked to complete these tasks while doing serial seven subtractions from a randomly presented three-digit number (High CD). RESULTS: We conducted repeated measures ANOVAs with Cognitive Demand (High vs Low) and Postural Demand (High vs. Moderate vs. Low) on measures of Path Length and Jerk. For Path Length, there was a main effect of CD [F(1,32)=13.19, p<.001, High=32.39, Low=18.42] and a main effect of PD [F(2,64)=99.69, p<.001, High=62.32, Moderate=8.19, Low=5.71]; however, there was no interaction between these factors. Path Length was longer under High CD relative to Low CD, and for Tandem PD relative to Likewise, for Jerk, there was a main effect of CD [F(1,32)=4.28, p<.05, High=22.92, Low=17.36] and a main effect of PD [F(2,64)=28.65, p<.001, High=37.08, Moderate=14.07, Low=9.27], but there was no interaction between these factors. CONCLUSION: Using two precise measurements of static balance, we observed that performance was impacted by separate cognitive and postural demands. Since these factors did not interact, our results suggest that adding a cognitive task to a balance assessment may have an impact independent of the balance demands.