Assessment of Postural Sway During Different Attention Focus States in Post-Surgery ACL Tears

The structure of variability in the human neuromotor system can be indicative of its health and function (Stergiou & Decker, 2011). More regular variation in gait is found in those with an ACL injury compared to those without (Decker, et al., 2011). Many things may influence postural and balance control including where the mind is focused during a task. Using an external focus during a balance task induced changes in the variability of balance indicating more automatic control, whereas an internal focus showed a less automatic control (Wulf, et al., 2003). Automatic control is associated with less cognition and more optimal/skilled performance. The purpose of this study was to document the influence of attentional focus on non-linear aspects of postural sway post ACL injury. Participants stood on a force plate standing as still as possible, keeping the injured knee as still as possible, keeping the uninjured knee as still as possible, and keeping a laser beam as still as possible. Sample Entropy was measured for medial lateral sway, anterior posterior sway, and average displacement of the center of pressure from the mean center of pressure. A 2 group (injured vs. non-injured) by 4 task (no focus, internal focus on injured knee, internal focus on uninjured knee, external focus) ANOVA was run to compare groups and tasks. Those in the ACL group had significantly more irregular sway than the non-injured group for both the anterior posterior dimension and average displacement. The ACL group, but not the no-injury group, had significantly more irregular average displacement during the external focus task compared to the internal focus tasks. Through this study, we found an effect of attentional focus in a recovered ACL injury group that may allow more adaptability of control. These results lend support for the influence of attentional focus in rehabilitation settings