What This Means
This research suggests that breaking down the Timed Up and Go (TUG) test — a standard clinical mobility assessment where a person stands up from a chair, walks a short distance, turns, walks back, and sits down — into specific movement phases can reveal early signs of Parkinson's disease (PD) that are missed when only looking at total test time. Using body-worn motion sensors alongside a camera-based motion capture system, researchers studied 38 people with early-stage PD and 41 healthy adults. They found that even in the earliest stages of PD (Hoehn and Yahr stages 1 and 1.5, meaning symptoms appear on only one side of the body), the turning portion of the test and an asymmetry in elbow movement were already abnormal compared to healthy adults. In more advanced early-stage PD (stage 2, where both sides of the body are affected), a much wider range of problems emerged, including slower walking, shorter steps, longer time spent with both feet on the ground, and reduced movement in the trunk, hips, and ankles.
Importantly, gait variability — often considered a hallmark of PD — did not significantly differ between groups at these early stages, suggesting it may not be a reliable early marker. Among the two PD subgroups, only the range of trunk motion in the sagittal plane (forward-backward bending) on the less-affected side distinguished stage 1-1.5 from stage 2, highlighting how subtle the differences between early PD stages can be.
This research suggests that sensor-based, phase-specific analysis of the TUG test could provide more detailed and objective information about how Parkinson's disease affects movement even in its earliest stages. Turning, in particular, appears to be an early and sensitive indicator of functional mobility changes. This approach could support clinicians in tracking disease progression and tailoring rehabilitation programs more precisely, without requiring expensive or complex laboratory setups.