Validation of inertial measurement units with an optoelectronic system for whole-body motion analysis

Abstract

The potential of inertial measurement units (IMUs) for ergonomics applications appears promising. However, previous IMUs validation studies have been incomplete regarding aspects of joints analysed, complexity of movements and duration of trials. The objective was to determine the technological error and biomechanical model differences between IMUs and an optoelectronic system and evaluate the effect of task complexity and duration. Whole-body kinematics from 12 participants was recorded simultaneously with a full-body Xsens system where an Optotrak cluster was fixed on every IMU. Short functional movements and long manual material handling tasks were performed and joint angles were compared between the two systems. The differences attributed to the biomechanical model showed significantly greater (P ≤ .001) RMSE than the technological error. RMSE was systematically higher (P ≤ .001) for the long complex task with a mean on all joints of 2.8° compared to 1.2° during short functional movements. Definition of local coordinate systems based on anatomical landmarks or single posture was the most influent difference between the two systems. Additionally, IMUs accuracy was affected by the complexity and duration of the tasks. Nevertheless, technological error remained under 5° RMSE during handling tasks, which shows potential to track workers during their daily labour.

Inertial measurement systems for segments and joints kinematics assessment: towards an understanding of the variations in sensors accuracy

“…This specific methodological choice was made in order to enhance the understanding of the technological limitations themselves. Clinicians and researchers should, however, be aware that the accuracy of any technological equipment used for mobility assessment does not only depend upon the technological capability to measure accurately motion in the context of use, but also on soft tissue artifacts due to the positioning and fixation of the modules as well as errors due to anatomical calibration and referencing [22, 35, 36, 38, 50, 51]. To the authors’ opinion, these issues should be addressed separately as they are of a different nature.…”

“…Their study has shown that biomechanical model difference is a major contributor to the error when assessing joint accuracy from a specific inertial system compared to an optoelectronic camera-based system using both their own biomechanical model. Accuracy studies should therefore define the methodology considering these differences and in accordance with the goal pursued [19, 38]. The study from Robert-Lachaine et al performed on a variety of handling tasks also confirmed that joint accuracy is affected by task duration and complexity, reinforcing the need for in-context accuracy assessment studies.…”

“…Errors in assessing accuracy of the movement include: errors associated to the sensors themselves (conditions of motion, magnetic environment, and position of the sensors), soft tissue artefacts associated with the fixation of the modules and errors associated to the anatomical referencing process [34–37]. Recently, Robert-Lachaine et al have assessed accuracy of multiple segments during a variety of handling tasks [38]. Their study has shown that biomechanical model difference is a major contributor to the error when assessing joint accuracy from a specific inertial system compared to an optoelectronic camera-based system using both their own biomechanical model.…”

Accuracy of identification of low or high risk lifting during standardised lifting situations

“…Other studies suggest to utilise measures of the kinematics of the trunk (Balaguier et al 2017;LagerstedOlsen et al 2016;Lunde et al 2017;Robert-Lachaine et al 2017;Villumsen et al 2016) or a combination of these methods (Samani et al 2012). So far, most studies based on in situ assessments have studied bending and torsion of the trunk but have not provided assessments of the physical loads (Balaguier et al 2017;Villumsen et al 2015Villumsen et al , 2016.…”

Effects of a Participatory Ergonomics Intervention With Wearable Technical Measurements of Physical Workload in the Construction Industry: Cluster Randomized Controlled Trial (Preprint)

“…Technological development has made it possible to obtain field measurements with surface electromyography (sEMG) [10,11], kinematics measured with inertial measurement unit (IMU) [12][13][14][15], or a combination [16]. However, no studies have used sEMG, IMU and video recordings obtained simultaneously to detect events with excessive physical workload (events) during a working day.…”