Category: Technology
Objective:
The use of accelerometer sensors offer an opportunity to do precise measurement of upper body postural tremor, and gait and balance. To facilitate the development of a digital biomarker to measure these symptoms, we analyzed 3 device accelerometers to determine their accuracy and analytical validity.
Background:
Motor symptoms in patients with movement disorders are traditionally measured using clinician-reported outcome measures such as the UPDRS. The ability to use a digital biomarker, powered by sensors and accelerometers, for precise measurement of these symptoms could improve signal detection in clinical research. In this study we compared two wrist-worn accelerometer devices with a phone-based device. An iPhone app was developed to collect this data. We compared the iPhone 8 accelerometer and gyroscope to the ActiGraph GT9X Link (GT9X) or Actigraph CenterPoint Insight Watch (CPIW).
Method:
The accuracy of the iPhone and 2 ActiGraph devices is determined by assessing the agreement of the output from the accelerometers with known input across a range of frequencies and amplitudes. To test this, we used the Quanser Shake Table II system controller to define the amplitude and frequency at which a flat surface is oscillated. The frequency range of the table is 0 to 10 Hz and the amplitude range +/- 76.2 mm at up to 2.5 g.
Results: The agreement results for each endpoint are summarized below (g = acceleration in m/s2):
Shake Table vs iPhone:
agreement is excellent (94.6%) or good (5.4%) for all nominal peak accelerations
Shake Table vs GT9X and CPIW:
nominal peak acceleration ≥ 0.1g: excellent (63.7%) or good (22.6%) agreement
nominal peak acceleration < 0.1g: poor agreement (97.7%)
GT9X vs CPIW:
nominal peak acceleration ≥ 0.1g: excellent (49.2%) or good (27.4%) agreement
nominal peak acceleration < 0.1g: poor agreement (97.7%)
Conclusion:
The iPhone accelerometer is suitable for measuring acceleration of functional assessments for gait, balance, and postural tremor. The use of the iPhone in combination with wrist-worn devices may be suitable for use during continuous wear periods detected as walking.
To cite this abstract in AMA style:
P. Kelly, C. Huang, R. Ellis. Comparison of accelerometers used for measurement of upper body postural tremor, and gait and balance [abstract]. Mov Disord. 2020; 35 (suppl 1). https://www.mdsabstracts.org/abstract/comparison-of-accelerometers-used-for-measurement-of-upper-body-postural-tremor-and-gait-and-balance/. Accessed June 15, 2025.« Back to MDS Virtual Congress 2020
MDS Abstracts - https://www.mdsabstracts.org/abstract/comparison-of-accelerometers-used-for-measurement-of-upper-body-postural-tremor-and-gait-and-balance/