Assessment of Pelvic Motion During Single-Leg Weight-Bearing Tasks Using Smartphone Sensors: Validity Study.
Yu Xi, Zhongsheng Li, Surendran Vatatheeswaran and 2 others
PMID 40168648WHAT IT FOUND
Smartphone sensors placed on the lower back accurately measure pelvic motion and exercise duration during single-leg squats and step-downs compared to lab motion capture.
While the phone consistently underestimates tilt and overestimates sway, it reliably detects differences between tasks, offering a low-cost clinic tool.
Key findings
01Smartphone sensors showed good to excellent agreement with motion capture for pelvic orientation in the sagittal and transverse planes, and for exercise duration.
02The smartphone consistently measured less anterior pelvic tilt and shorter squat durations than motion capture across all tasks.
03Smartphone sensors successfully detected significant differences in pelvic kinematics between the single-leg squat and the two step-down heights, matching motion capture findings.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only healthy young adults, so it is unknown if the smartphone works as well for patients with pain, balance impairments, or older adults. The smartphone was held in place by the participant's trouser elastic, which may have shifted during movement, potentially affecting accuracy. The analysis required exporting data and using specialized software for some calculations, meaning it is not yet a simple 'plug-and-play' clinical tool. Agreement was poorer for frontal plane measurements (pelvic drop) compared to other directions.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not treat the smartphone's absolute values as equivalent to motion capture data. The phone consistently underestimates anterior pelvic tilt and exercise duration, so you should use it to monitor trends and relative differences between tasks, not to judge against fixed normative thresholds.