An external focus of attention compared to an internal focus of attention improves anticipatory postural adjustments among people post-stroke

Abstract

Background: People after stroke often have postural impairments that can increase their risk of falling. Anticipatory postural adjustments (APAs) are changes in the activity of postural muscles prior to a voluntary movement in order to maintain vertical equilibrium. Previous research suggests that improving APAs leads to better postural control and reduces the risk of falls. Despite the importance of APAs and their impairment among people post-stroke, studies that aim to investigate methods for improving APAs are limited. Consistent evidence supports that an external focus of attention compared to an internal focus of attention, yields superior performance of motor skills that include postural control.

Research question: What are the effects of adopting different foci of attention on measures of APAs and movement parameters when performing a lower extremity Fitts' task among people post-stroke?

Methods: Twelve individuals post-stroke performed a lower extremity stepping movement (Fitts' task) while adopting an external focus or an internal focus of attention in a within-subject design. A motion capture system was used to record participants' movement data. Custom software derived movement time (MT), peak velocity (PV), time to peak velocity (ttPV) and variability at endpoint (SD_T). Electromyography was used to measure muscle activity and determine APAs onset and magnitude. For all dependent variables separate repeated measures ANOVAs were conducted to compare performance between foci of attention.

Results: The results showed that an external focus of attention yielded significantly better performance on all outcome measures. The improvement in performance was seen in shorter MT, higher PV, shorter ttPV, smaller SD_T, earlier APAs onset and more efficient APAs magnitude.

Significance: The changes in outcome measures suggest that adopting an external focus of attention during postural tasks could be an effective strategy for improving balance control among people post-stroke.

Keywords: Balance; Fitts’ law; Focus of attention; Postural control; Stroke.