Effect of full-body immobilization on center of pressure complexity in open- and closed-eyes conditions.

Background: Recent research has shown that center of pressure (COP) variability increases during full-body immobilization, suggesting that sway may be exploratory, with the central nervous system attempting to generate movement to gather sensory information. However, most studies have focused on COP magnitude, and its effect on COP complexity remains unclear.

Research question: This study aimed to assess the effect of full-body immobilization in both open- and closed-eye conditions on COP behavior, with a certain focus on COP complexity.

Method: Nineteen young adults participated in the study, performing four trials per eye condition using an apparatus that allowed for "locked" and "unlocked" body positioning. The COP variability, regularity, and frequency were analyzed.

Results: Full-body immobilization increased COP variability for most participants in both open- and closed-eye conditions. It also increased COP regularity and shifted the signal toward lower frequencies, suggesting the presence of COP drifts. Additionally, intraclass correlation coefficients (ICC(2,k)) revealed fair to excellent reliability across most COP variables, supporting the use of multi-trials in immobilization studies.

Significance: As previously observed, full-body immobilization increases COP variability, but it also alters its complexity, leading to what appears to be a "drifting" behavior. Since no effect of visual condition was found, the role of sensory input in this exploratory behavior remains unclear.