Balance Assessment Using a Handheld Smartphone with Principal Component Analysis for Anatomical Calibration.

Area of Science:

• Biomechanics and Human Movement Analysis
• Wearable Technology in Health
• Sensor Data Processing and Machine Learning

Background:

• Traditional balance assessments using smartphones rely on body straps and fixed alignment, limiting user comfort and practicality.
• Inertial Measurement Units (IMUs) in smartphones offer potential for accessible balance monitoring, but require robust alignment methods.
• Existing methods assume smartphone alignment with anatomical axes, necessitating cumbersome attachments.

Purpose of the Study:

• To develop and validate an anatomical alignment method for handheld smartphones using Principal Component Analysis (PCA) to eliminate the need for body straps.
• To compare angular velocity data from a handheld smartphone (PCA aligned) against a strap-mounted smartphone (assumed alignment) during balance tasks.
• To analyze acceleration data differences across varying balance difficulty levels using the PCA-aligned handheld smartphone.

Main Methods:

• Anatomical alignment was achieved using a calibration maneuver combined with Principal Component Analysis (PCA).
• Participants held smartphones in a comfortable position, eliminating the need for body straps.
• Angular velocity and acceleration data were collected during balance poses of increasing difficulty.

Main Results:

• Angular velocity scores from the handheld smartphone (PCA aligned) showed moderate to strong correlations with the strap-mounted smartphone (r = 0.487-0.983, p < 0.001).
• The PCA-aligned handheld smartphone successfully identified significant differences in anteroposterior, mediolateral, and superoinferior acceleration scores across balance poses (p < 0.001).
• The proposed method demonstrates the feasibility of accurate balance assessment with a comfortably held smartphone.

Conclusions:

• Smartphone-based balance assessment can be performed accurately without body straps using PCA for anatomical alignment.
• This method enhances user comfort and practicality for balance monitoring and assessment.
• The findings support the use of readily available smartphone technology for accessible biomechanical analysis.