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Background: Optoelectronic systems and force platforms represent the gold standard for postural sway assessment, but pose disadvantages in terms of equipment, cost and preparation time., Objective: Wearable inertial measurement units (IMUs) have been proposed to overcome these issues, but have never been compared to an optoelectronic system. The study aim was therefore to investigate agreement between inertial measurement unit and optoelectronic system in postural sway assessment., Methods: Thirty healthy volunteers performed four balance tasks. IMU was placed on the sacrum (S2) with a retroreflective marker over the sensor and subjects' performance was simultaneously recorded by both systems. Total (TOT), anterior-posterior (AP) and medial-lateral (ML) length of trace, range, speed, root mean squared (RMS), and confidence ellipse were computed., Results: ICCs revealed excellent correlations for Length-TOT, Length-AP and Speed-AP, good correlation for Length-ML, Speed-ML, Confidence Ellipse, Range-AP and RMS-AP, and moderate correlation for range-ML and RMS-ML. Bland-Altman plot showed greater estimation for Length-TOT, Length-AP, Speed-AP, confidence ellipse and RMS-AP using optoelectronic system, and for Length-ML, Range-AP, Range-ML, Speed-ML, RMS-ML using IMU. Both systems revealed the same differences among tasks., Conclusion: The excellent to good agreement of IMU for length of trace and speed parameters and its user-friendly application suggest its potential implementations in clinical practice.

The ability to carry out two tasks at once is critical to effective functioning in the real world and deficits are termed Dual-task interference or effect-DTE. DTE substantially compromised the gait of subjects with Parkinson's disease and freezing of gait (PD + FOG), leading to exaggerated slowing, increasing gait dysrhythmicity, and inducing FOG episodes. This study aimed to investigate the DTE in gait variability of subjects with PD and freezing of gait (PD + FOG). Thirty-three patients with PD + FOG and 14 healthy individuals (REFERENCE) took part at this study. Two gait conditions were analyzed: usual walking (single task) and walking while taking the word-color Stroop test (dual task). The computed variables were as follows: gait velocity, step length, step timing, gait asymmetry, variability measures and DTE of each variable. The PD + FOG group has presented negative DTE values for all analyzed variables, indicating dual task cost. The REFERENCE group has presented dual-task benefits for step length standard deviation and step time. Differences between both groups and conditions were found for all variables, except for step time. Taking the word-color Stroop test while walking led to a larger dual-task cost in subjects with PD + FOG.

The Timed Up and Go test (TUG) is used to assess individual mobility. It evaluates static and dynamic balance by means of the total time required to complete the test, usually measured by a stopwatch. In recent years tools based on portable inertial measurement units (IMU) for clinical application are increasingly available on the market. More specifically, a tool (hardware and dedicated software) to quantify the TUG test based on IMU is now available. However, it has not yet been validated in subjects with Parkinson's disease (PD). Thus, the aim of this study is to compare measurements from instrumented TUG tests (or iTUG) acquired by an IMU with those obtained using an optoelectronic system (the gold standard) and by a stopwatch, to gain an in-depth understanding of IMU behavior in computing iTUG in subjects with PD. To do this, three TUG test trials were carried out on 30 subjects with PD and measured with all three systems simultaneously. System agreements were evaluated using Intraclass Correlation Coefficient and Bland-Altman plots. The device tested showed excellent reliability, accuracy and precision in quantifying total TUG test duration. Since TUG is a widely used test in rehabilitation settings, its automatic quantification through IMUs could potentially improve the quality of assessments in the quantification of PD gait ability., (Copyright © 2017 Elsevier Ltd. All rights reserved.)