Table 2 Explanation and clinical correlates of kinematic variables in Parkinson’s disease

From: Computer vision uncovers three fundamental dimensions of levodopa-responsive motor improvement in Parkinson’s disease

Feature

Clinical Interpretation

Mean amplitude

Average extent of movement, a decrease suggests hypokinesia

Mean speed

Overall movement quickness; low values may suggest bradykinesia.

Mean RMS velocity

Average velocity of movement; low values may suggest bradykinesia.

Mean opening speed

Speed of fingers or hand opening; decreased in bradykinesia.

Mean closing speed

Speed of fingers or hand closing; decreased in bradykinesia.

Mean cycle duration

Duration of a complete movement cycle; longer durations suggest bradykinesia.

Frequency

Frequency of repetitive movements, with lower rates potentially indicating bradykinesia.

SD amplitude

Variability in movement amplitude, indicating inconsistency in motor control.

SD speed

Variability in speed, reflecting inconsistency in movement quickness.

SD RMS velocity

Variability in RMS velocity, showing fluctuation in movement velocity.

SD opening speed

Variability in opening speed, indicating inconsistent speed during extension movements.

SD Closing speed

Variability in closing speed, showing inconsistent speed during movements.

SD cycle duration

Variability in cycle duration, indicating inconsistent timing in task performance.

Range cycle duration

The difference between the longest and shortest cycles, reflecting inconsistency in movement execution.

Amplitude decay

Reduction in movement amplitude over time, indicative of a sequence effect

Velocity decay

Decrease in movement speed over time, indicative of a sequence effect

Frequency decay

Reduction in movement rate over time, indicative of a sequence effect

CV amplitude

Coefficient of variation for amplitude, indicating relative variability of amplitude.

CV cycle duration

Coefficient of variation for cycle duration, showing relative variability in movement timing.

CV speed

Coefficient of variation for speed, reflecting relative consistency of movement speed.

CV RMS velocity

Coefficient of variation for RMS velocity, indicating variability in overall movement velocity.

CV opening speed

Coefficient of variation for opening speed, showing consistency in speed.

CV closing speed

Coefficient of variation for closing speed, reflecting consistency in speed.

  1. This table shows the kinematic variables measured in PD patients during motor task assessments and outlines their clinical interpretations. It serves as a guide to understanding these variables from a clinical perspective, linking features such as Mean Speed and Mean Amplitude to symptoms like bradykinesia and hypokinesia, respectively. The interpretations provided in the ‘Clinical Interpretation’ column are intended to aid the reader by connecting the measured kinematic variables to established clinical concepts and phenomena relevant to Parkinson’s disease motor function (such as bradykinesia, hypokinesia, variability, and sequence effects, as reviewed in ref. 1). These serve as a general guide to the potential meaning of each feature within a clinical context.
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