GYKO-Based L-Test Reliability in Parkinson's Disease

This study aims to investigate the test-retest and interrater reliability, as well as the concurrent validity, of GYKO-based postural sway measurements obtained during the L-Test and the Timed Up and Go (TUG) test in individuals with Parkinson's disease. Participants diagnosed with idiopathic Parkinson's disease (Hoehn \& Yahr stages 1-3) will be evaluated using the GYKO inertial measurement unit, which provides quantitative postural sway parameters including ellipse area, mean length, mediolateral and anteroposterior mean length, mediolateral and anteroposterior mean distance, and velocity. Two independent raters will perform GYKO-based assessments of the L-Test and TUG on the same day, with a 20-minute interval between raters, to determine interrater reliability. Participants will return one week later to repeat the same procedures, allowing assessment of test-retest reliability. To examine concurrent validity, participants' functional balance will also be assessed using the Berg Balance Scale, and correlations between GYKO variables and clinical mobility tests (L-Test and TUG) will be analyzed.