Document Type

Article

Publication Date

2026

DOI

10.20338/bjmb.v20i1.527

Publication Title

Brazilian Journal of Motor Behavior

Volume

20

Issue

1

Pages

e527

Abstract

BACKGROUND: The structure of variability in postural sway reflects the adaptability and health of the postural control system. Entropy quantifies this structure by measuring the regularity of repeated fluctuations over time. Although entropy has been used to examine sway in neurological populations, little is known about how sway complexity changes following anterior cruciate ligament reconstruction (ACLR). Attentional focus may also influence postural control, with external focus typically promoting more efficient and automatic regulation than internal focus.

AIM: To examine how attentional focus (internal vs. external) influences the structure of postural sway in individuals with and without ACLR.

METHODS: Forty-three participants (20 ACLR, 23 controls) completed quiet standing trials on a force plate under three attentional focus conditions: internal focus on the injured or non-injured limb, and external focus. Sample entropy was calculated to assess sway complexity, and traditional linear sway variables (mean velocity, path length) were also examined.

RESULTS: Participants with ACLR exhibited lower sample entropy than controls, indicating more regular and less adaptable sway patterns. In the ACLR group, external focus instructions significantly increased sample entropy relative to internal focus conditions. Linear sway measures also reflected improved control under external focus, with lower mean sway velocity and reduced path length.

INTERPRETATION: Individuals with ACLR demonstrate reduced complexity in postural control, but external focus instructions can enhance adaptability. These findings suggest that attentional focus modulates sway dynamics after ACLR. Incorporating external focus into rehabilitation may facilitate more automatic and flexible postural control strategies.

Rights

© 2026 Natalie L. Ferguson, Brian L. Cone, Christopher K. Rhea, Anne Beethe, Breanna Studenka.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) License.

ORCID

0000-0001-7256-4508 (Rhea)

Original Publication Citation

Ferguson, N. L., Cone, B. L., Rhea, C. K., Beethe, A., & Studenka, B. (2026). Nonlinear differences in postural sway across attentional focus conditions in individuals with and without anterior cruciate ligament reconstruction. Brazilian Journal of Motor Behavior, 20(1), Article e527. https://doi.org/10.20338/bjmb.v20i1.527

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