Investigation of postural stability applying mathematical optimization theory on posturographic signal in adults

Abstract

Introduction: Postural assessment methods have evolved significantly in recent decades, but their clinical usefulness and applications in Rehabilitation Sciences are still limited. Objective: To investigate postural stability by applying mathematical optimization theory to the posturographic signal in adults. Methods: Study 1: Primary analysis of data from 94 young individuals, by computer simulation of benchmark functions to test the optimization variables (general t and y; local minn, minL, minsd and global ming); secondary analysis of data to investigate main or interaction effects of sensorimotor tasks. Study 2: Secondary analysis of posturographic data from 146 adults, according to methodological recommendations for reliability and robustness studies. Results: The slope property showed a three-way interaction for y (w2 = 0.002), the stability property showed a three-way interaction for minL (w2 = 0.012) and the convergence property resulted in a three-way interaction for ming (w2 = 0.009) and delta gl (w2 = 0.011). Excellent reliability was observed for the stability property (ICC2,k 0.772); excellent to acceptable (ICC2,3 0.540) or excellent to unacceptable (ICC2,1 0.281) for the slope property; and excellent to unacceptable (ICC2,3 > 0.295; ICC2,1 > 0.122) for the convergence property. Robustness analysis showed main effects of signal duration (w2 0.834), sampling frequency (w2 0.526) and low-pass filter cutoff frequency (w2 0.523); two- and three-factor effects ranged from medium to trivial. Conclusion: Visual constraints, support and attention tasks affect slope, stability and convergence properties in the search for orthostatic postural stability. Reliability of optimization properties is excellent or acceptable for deriving slope and stability properties and unacceptable for convergence from the mean of three measures. Optimization properties are robust to interaction, but not to main effects of methodological sources of variation.