Balance Assessment Using a Smartwatch Inertial Measurement Unit with Principal Component Analysis for Anatomical Calibration
Abstract
:1. Introduction
2. Materials and Methods
2.1. Participant Recruitment
2.2. Balance Experiment
2.3. Hardware Devices and Data Acquisition Software
2.4. Calibration Algorithm
2.4.1. Gravity Target Vector
2.4.2. PCA Methods for the Forward Flexion Maneuver
2.4.3. PCA Methods for the Lateral Bending Maneuver
2.4.4. PCA Methods for the Chest Tap Maneuver
2.4.5. Cross-Product Utilization
2.5. Statistical Methods
2.5.1. Smartwatch versus SPIMU Correlation Design
2.5.2. Smartwatch versus Force Plate Correlation Design
2.5.3. Smartwatch Repeated-Measures Analysis of Variance across Pose Types
3. Results
3.1. Smartwatch versus SPIMU Correlation Results
3.1.1. AP Correlation Results
3.1.2. ML Correlation Results
3.1.3. 2D Correlation Results
3.2. Smartwatch versus Force Plate Correlation Results
3.2.1. AP Correlation Results
3.2.2. ML Correlation Results
3.2.3. 2D Correlation Results
3.3. Smartwatch Repeated-Measures Analysis of Variance Results
3.3.1. RMANOVA Acceleration-Based Score Results
3.3.2. RMANOVA Rotational Velocity-Based Score Results
3.3.3. Bar Graph and Standard Error Bars of the Smartwatch Scores
3.3.4. Bar Graph and Standard Error Bars of the Force-Plate Scores
3.4. Qualitative Results
4. Discussion
4.1. Summary of Key Findings
- Acceleration scores in the ML, 2D, and 3D directions.
- Rotational scores in the AP direction.
4.2. Limitations of RMANOVA Statistical Results
4.3. Optional Improvement to Calibration Algorithm
4.4. Future Development of IMU-Based Posturography
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Calibration Method (Type of Motion) | Known Axes (Method of Discovery) | Axis Found by Cross Product | Equation |
---|---|---|---|
Forward flexion (rotational velocity) | SI axis (gravity vector) ML axis (PCA vector) | AP axis | |
Lateral bending (rotational velocity) | SI axis (gravity vector) AP axis (PCA vector) | ML axis | |
Chest tap (acceleration) | SI axis (gravity vector) AP axis (PCA vector) | ML axis |
Smartwatch Score | ||||
---|---|---|---|---|
Chest-Tap Calibration | Forward Flexion Calibration | Lateral Bending Calibration | ||
SPIMU score | Pearson correlation | 0.884 | 0.970 | 0.953 |
p-value (two-tailed) | <0.001 | <0.001 | <0.001 | |
Number of Data Points | 84 | 84 | 84 |
Smartwatch Score | ||||
---|---|---|---|---|
Chest-Tap Calibration | Forward Flexion Calibration | Lateral Bending Calibration | ||
SPIMU score | Pearson correlation | 0.901 | 0.887 | 0.861 |
p-value (two-tailed) | <0.001 | <0.001 | <0.001 | |
Number of Data Points | 84 | 84 | 84 |
Smartwatch 2D Score | ||
---|---|---|
(2D Calibration Method) | ||
SPIMU score | Pearson correlation | 0.919 |
p-value (two-tailed) | <0.001 | |
Number of Data Points | 84 |
Smartwatch Score | |||||
---|---|---|---|---|---|
Chest-Tap Calibration | Forward Flexion Calibration | Lateral Bending Calibration | SPIMU | ||
Force-plate score | Pearson correlation | 0.819 | 0.794 | 0.721 | 0.281 |
p-value (two-tailed) | <0.001 | <0.001 | <0.001 | 0.010 | |
Number of Data Points | 84 | 84 | 84 | 84 |
Smartwatch Score | |||||
---|---|---|---|---|---|
Chest-Tap Calibration | Forward Flexion Calibration | Lateral Bending Calibration | SPIMU | ||
Force-plate score | Pearson correlation | 0.729 | 0.758 | 0.799 | 0.711 |
p-value (two-tailed) | <0.001 | <0.001 | <0.001 | <0.001 | |
Number of Data Points | 84 | 84 | 84 | 84 |
Smartwatch 2D Score | SPIMU | ||
---|---|---|---|
(2D Calibration Method) | |||
Force-plate score | Pearson correlation | 0.468 | 0.593 |
p-value (two-tailed) | <0.001 | <0.001 | |
Number of Data Points | 84 | 84 |
Device | Direction | Pose-Type within-Subject Effects on RMS Score | |||
---|---|---|---|---|---|
Error DOF | Factor DOF | F | p-Value | ||
Smartwatch (forward flexion) | AP | 18.44 | 1.09 | 1.73 | 0.205 |
ML | 21.51 | 1.27 | 40.70 * | <0.001 | |
2D | 34 | 2.00 | 8.08 ** | 0.002 | |
3D | 34 | 2.00 | 16.06 ** | <0.001 | |
SPIMU | AP | 34 | 2.00 | 3.31 | 0.048 |
ML | 19.10 | 1.12 | 20.43 * | <0.001 | |
2D | 34 | 2.00 | 15.49 ** | <0.001 | |
3D | 34 | 2.00 | 17.16 ** | <0.001 | |
Force plate (COP Vel.) | AP | 18.15 | 1.07 | 61.27 * | <0.001 |
ML | 18.62 | 1.10 | 83.23 * | <0.001 | |
2D | 17.52 | 1.03 | 52.17 * | <0.001 |
Device | Calibration Method | Direction | Pose-Type Within-Subject Effects | |||
---|---|---|---|---|---|
Error DOF | Factor DOF | F | p-Value | ||
Smartwatch (forward flexion) | AP | 34 | 2.00 | 9.59 ** | <0.001 |
ML | 25.51 | 1.5 | 0.41 | 0.609 | |
2D | 34 | 2.00 | 3.40 | 0.028 | |
3D | 34 | 2.00 | 6.55 | 0.004 | |
SPIMU | AP | 20.59 | 1.21 | 24.74 * | <0.001 |
ML | 34 | 2.00 | 12.23 ** | <0.001 | |
2D | 23.64 | 1.39 | 23.33 * | <0.001 | |
3D | 23.53 | 1.38 | 37.47 * | <0.001 |
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Presley, B.M.; Sklar, J.C.; Hazelwood, S.J.; Berg-Johansen, B.; Klisch, S.M. Balance Assessment Using a Smartwatch Inertial Measurement Unit with Principal Component Analysis for Anatomical Calibration. Sensors 2023, 23, 4585. https://doi.org/10.3390/s23104585
Presley BM, Sklar JC, Hazelwood SJ, Berg-Johansen B, Klisch SM. Balance Assessment Using a Smartwatch Inertial Measurement Unit with Principal Component Analysis for Anatomical Calibration. Sensors. 2023; 23(10):4585. https://doi.org/10.3390/s23104585
Chicago/Turabian StylePresley, Benjamin M., Jeffrey C. Sklar, Scott J. Hazelwood, Britta Berg-Johansen, and Stephen M. Klisch. 2023. "Balance Assessment Using a Smartwatch Inertial Measurement Unit with Principal Component Analysis for Anatomical Calibration" Sensors 23, no. 10: 4585. https://doi.org/10.3390/s23104585
APA StylePresley, B. M., Sklar, J. C., Hazelwood, S. J., Berg-Johansen, B., & Klisch, S. M. (2023). Balance Assessment Using a Smartwatch Inertial Measurement Unit with Principal Component Analysis for Anatomical Calibration. Sensors, 23(10), 4585. https://doi.org/10.3390/s23104585