Agreement between An Inertia and Optical Based Motion Capture during the VU-Return-to-Play- Field-Test.

Chris Richter,Andrew Franklyn-Miller,Katherine A J Daniels,Enda King

doi:10.3390/s20030831

Chris Richter, Andrew Franklyn-Miller + Show 2 more

Open Access

https://doi.org/10.3390/s20030831

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Abstract

The validity of an inertial sensor-based motion capture system (IMC) has not been examined within the demands of a sports-specific field movement test. This study examined the validity of an IMC during a field test (VU®) by comparing it to an optical marker-based motion capture system (MMC). Expected accuracy and precision benchmarks were computed by comparing the outcomes of a linear and functional joint fitting model within the MMC. The kinematics from the IMC in sagittal plane demonstrated correlations (r2) between 0.76 and 0.98 with root mean square differences (RMSD) < 5°, only the knee bias was within the benchmark. In the frontal plane, r2 ranged between 0.13 and 0.80 with RMSD < 10°, while the knee and hip bias was within the benchmark. For the transversal plane, r2 ranged 0.11 to 0.93 with RMSD < 7°, while the ankle, knee and hip bias remained within the benchmark. The findings indicate that ankle kinematics are not interchangeable with MMC, that hip flexion and pelvis tilt higher in IMC than MMC, while other measures are comparable to MMC. Higher pelvis tilt/hip flexion in the IMC can be explained by a one sensor tilt estimation, while ankle kinematics demonstrated a considerable level of disagreement, which is likely due to four reasons: A one sensor estimation, sensor/marker attachment, movement artefacts of shoe sole and the ankle model used.

Highlights

Motion capture systems are frequently used to assess athletic performance or to support return to play decisions, as they provide an objective insight into the kinematics of athletes, which can be compared with, either previously captured data or other benchmarks.A commonly used technology to capture movements is marker-based optical motion capture (MMC)systems—Systems that combine cameras and active or passive markers
inertial sensor-based motion capture system (IMC) and MMC were no larger than differences between OSSCA and Plug-In Gait, we concluded that the accuracy/precision of the IMC system for the relevant variable was acceptable, i.e., within the accepted error resulting from differences in model assumptions
Joint kinematics in the sagittal plane demonstrated very high correlations, except for the trunk segment, with all mean root mean square differences (RMSD) smaller than 4.44 degrees (7% of range), while mean bias ranged from 4.11 degrees to 16.60 degrees, with all joint angles over-estimated by the IMC approach

Summary

Introduction

A commonly used technology to capture movements is marker-based optical motion capture (MMC). Systems—Systems that combine cameras and active or passive markers. MMC systems record the positions of reflective markers that are attached to an object and are considered to be state of art in motion capture, due to their high accuracy when tracking rigid objects [1]. MMC systems are bound to a capturing volume, often requiring considerable manual post-processing, and are sensitive to disturbances of the recording cameras and infra-red interference from other sources. MMC systems are often found only in research laboratories. A limitation of capturing movements, within a laboratory setting, is that the assessed individual is fully aware of the assessment and there is a lack of external distraction (e.g., opponents) due to the restricted capturing volume

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