Evaluating the Reliability of Markerless Gait Biomechanics Research: Insights from Theia3D

March 4, 2025
Theia
BIO
Recent Posts
A Major Research Milestone for Theia3D
More than 50 independent, peer-reviewed research publications now cite, evaluate or review Theia3D across domains including gait, sports performance, postural control, upper-extremity movement and other biomechanics applications. These publications are available in world-leading journals including Journal of Biomechanics, Journal of Applied Biomechanics, Gait & Posture and Clinical Biomechanics. Together, they represent a growing body of evidence across different movements, populations and environments, reinforcing Theia3D’s position as the most extensively validated markerless motion capture system.
Beyond The Radar Gun: How Dean Jackson uses Theia3D For Incremental Velocity Analysis
This article is a first in a miniseries that breaks down what motion capture can show beyond radar, ball data, and standard video. In this first installment, Dean breaks down how he uses Incremental Velocity Analysis, or IVA, to study what changes biomechanically as pitchers move closer and closer to max output.
New Research on Theia3D: Comparing Markerless and Marker-Based Shoulder Kinematics Across Full Arm Range of Motion
A 2025 study published in the Journal of Biomechanics compared shoulder kinematics measured with Theia3D markerless motion capture against gold-standard marker-based motion capture across full arm ranges of motion. The results show strong agreement for many movements, particularly in the coronal plane, while also highlighting where caution is still required, especially at the extremes of ranges of motion and in transverse-plane rotations.

Summary

A recent study published in PeerJ assessed the reliability of Theia3D's markerless motion capture system for gait biomechanics research, comparing repeated-measures outputs against established marker-based benchmarks.

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.

Research Overview

Study Aim: To evaluate the inter-trial and inter-session variation, and the effect of clothing within and between sessions on gait kinematics from Theia3D markerless motion capture software.

‍Methods: Twenty-two healthy adults walked along an indoor walkway while eight video cameras recorded their gait in both tight and loose-fitting clothing, during two sessions within 14 days of each other. Video data were analyzed using Theia3D to obtain the kinematic data for analysis.

‍Key Findings:

  • Inter-trial Variation: Averaged less than 2° across all joints and planes.
  • Inter-session Variation: Averaged less than 3°, indicating high consistency between sessions.
  • Inter-session-Clothing Variation: Averaged less than 3.5°, suggesting minimal impact of clothing type on gait measurements.
  • Root Mean Square Differences (RMSD): Less than 2° between clothing conditions, reinforcing the system’s robustness to clothing variations.

Implications for Biomechanics Research

These findings support the use of markerless motion capture systems like Theia3D in both research and applied biomechanics settings. The low inter-session variability and minimal impact of clothing type simplifies data collection protocols, allowing participants to wear their usual clothing without compromising data quality, even across separate sessions.

Full Study & Further Reading

For a detailed understanding of the study’s methodology and results, read the full article here.

‍Want to explore Theia3D for your biomechanics studies? Contact us for a demo. 

Recent Posts
A Major Research Milestone for Theia3D
More than 50 independent, peer-reviewed research publications now cite, evaluate or review Theia3D across domains including gait, sports performance, postural control, upper-extremity movement and other biomechanics applications. These publications are available in world-leading journals including Journal of Biomechanics, Journal of Applied Biomechanics, Gait & Posture and Clinical Biomechanics. Together, they represent a growing body of evidence across different movements, populations and environments, reinforcing Theia3D’s position as the most extensively validated markerless motion capture system.
Beyond The Radar Gun: How Dean Jackson uses Theia3D For Incremental Velocity Analysis
This article is a first in a miniseries that breaks down what motion capture can show beyond radar, ball data, and standard video. In this first installment, Dean breaks down how he uses Incremental Velocity Analysis, or IVA, to study what changes biomechanically as pitchers move closer and closer to max output.
New Research on Theia3D: Comparing Markerless and Marker-Based Shoulder Kinematics Across Full Arm Range of Motion
A 2025 study published in the Journal of Biomechanics compared shoulder kinematics measured with Theia3D markerless motion capture against gold-standard marker-based motion capture across full arm ranges of motion. The results show strong agreement for many movements, particularly in the coronal plane, while also highlighting where caution is still required, especially at the extremes of ranges of motion and in transverse-plane rotations.
In this blog
Summary