Between-Day Reliability of Kinematic Variables Using Markerless Motion Capture for Single-Leg Squat and Single-Leg Landing Tasks.
Matias Yoma, Lee Herrington, Chelsea Starbuck and 2 others
PMID 40756794WHAT IT FOUND
Markerless video motion capture measured single-leg squat and landing movements with day-to-day error mostly under 5 degrees, similar to marker-based systems.
Hip flexion and hip rotation were less reliable, so use caution with those angles.
Key findings
01Most markerless motion capture variables had day-to-day error under 5 degrees, except hip flexion.
02Hip rotation during the single-leg squat was the main markerless variable with low day-to-day consistency.
03The marker-based system had similar discrete landing values to markerless motion capture.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Measurements were made in a controlled lab, not in the field or clinic where athletes might normally be screened. Results apply to Theia3D specifically and may not transfer to other markerless systems. Markerless and marker-based comparisons used different participants and different sample sizes (19 vs 10). Only single-leg squat and landing tasks were tested, not running or cutting. Tasks were submaximal, so they may not match high-risk sport movements. The paper does not report dropouts or how many participants were excluded after recruitment. Participants were recreational athletes, so the paper does not show results for injured athletes or elite squads.
Declared interests
The authors declared no commercial or financial conflicts of interest. The study was funded by the University of Salford.
The easy way to misread this
Do not conclude that markerless motion capture can diagnose or reduce injury risk. This paper only tested day-to-day measurement consistency in a lab for Theia3D in recreational athletes, and hip flexion and hip rotation were less reliable.