Portable Biomechanics Laboratory: Clinically Accessible Movement Analysis from a Handheld Smartphone
Journal:
arXiv
Published Date:
Jul 11, 2025
Abstract
The way a person moves is a direct reflection of their neurological and
musculoskeletal health, yet it remains one of the most underutilized vital
signs in clinical practice. Although clinicians visually observe movement
impairments, they lack accessible and validated methods to objectively measure
movement in routine care. This gap prevents wider use of biomechanical
measurements in practice, which could enable more sensitive outcome measures or
earlier identification of impairment. We present our Portable Biomechanics
Laboratory (PBL), which includes a secure, cloud-enabled smartphone app for
data collection and a novel algorithm for fitting biomechanical models to this
data. We extensively validated PBL's biomechanical measures using a large,
clinically representative dataset. Next, we tested the usability and utility of
our system in neurosurgery and sports medicine clinics. We found joint angle
errors within 3 degrees across participants with neurological injury,
lower-limb prosthesis users, pediatric inpatients, and controls. In addition to
being easy to use, gait metrics computed from the PBL showed high reliability
and were sensitive to clinical differences. For example, in individuals
undergoing decompression surgery for cervical myelopathy, the mJOA score is a
common patient-reported outcome measure; we found that PBL gait metrics
correlated with mJOA scores and demonstrated greater responsiveness to surgical
intervention than the patient-reported outcomes. These findings support the use
of handheld smartphone video as a scalable, low-burden tool for capturing
clinically meaningful biomechanical data, offering a promising path toward
accessible monitoring of mobility impairments. We release the first clinically
validated method for measuring whole-body kinematics from handheld smartphone
video at
https://intelligentsensingandrehabilitation.github.io/MonocularBiomechanics/ .
