Can Markerless Motion Capture Accurately Track Multiple Athletes at Once?

Summary

A new 2025 study puts Theia3D to the test in dual-athlete sport tasks, and the results may surprise you.

Editor's Note: The following summary details independent academic research conducted in clinical research settings. Theia3D is an offline software solution engineered exclusively for research and human performance analysis.

Motion capture has long been the gold standard for quantifying human movement in research. Traditional marker-based systems require placing reflective markers on specific anatomical landmarks, which is time-consuming, requires trained staff, and can be challenging for some research populations.

This study evaluated whether Theia3D markerless motion capture could accurately track multiple research participants simultaneously in a dual-athlete sport task context, specifically assessing bilateral throwing mechanics in a research setting.

Study Overview

Participants: 10 pairs of research participants performed simultaneous throwing tasks
Comparison: Theia3D markerless vs. marker-based reference system
Metrics assessed: Upper and lower extremity joint kinematics, tracking accuracy per individual in multi-person scenarios

Key Findings

Theia3D successfully tracked both research participants simultaneously without manual labeling or person-specific setup
Agreement with marker-based system was strong for most lower extremity and trunk variables
Upper extremity tracking showed expected variability in transverse-plane variables, consistent with single-participant validation studies

What This Means

This study confirms that Theia3D can accurately capture multi-person biomechanics in applied research environments, enabling team sport biomechanics research, occupational movement studies, and paired-participant research designs that were previously impractical with traditional motion capture systems.

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