Implementation and Validation of Human Kinematics Measured Using IMUs for Musculoskeletal Simulations by the Evaluation of Joint Reaction Forces

Abstract

The gold standard for the analysis of human kinematics and kinetics is a camera-based motion capture system in combination with force measurement platforms. Alternatively, inertial measurement units can be utilized to obtain human kinematics, while ground reaction forces are computed from full body dynamics. This setup represents a system independent from the spatial confinement of a gait laboratory. The aim of this study is the comparison of the two methods by the investigation of lower limb kinematics and the resulting joint reaction forces within the ankle-, knee-and hip joints. For this purpose, human motion during gait was captured simultaneously by both measurement techniques. 13 trials from 8 different test subjects were evaluated in total. IMU data was processed with a quaternion based Kalman Filter. The data sets were implemented into a musculoskeletal simulation program in order to drive a virtual human body model. Each sensor was aligned to the gravitational and magnetic field vectors of the earth. The angles of flexions, extensions and rotations were analyzed to determine kinematic differences. Joint reaction forces defined kinetic dissimilarities. The overall kinematic differences of both models yielded root mean square errors of 7.62°, 6.02°, 4.95°, 2.79°, 2.38° and 3.56° for ankle flexion, subtalar eversion, knee flexion, hip external rotation, hip abduction and hip flexion, respectively. The proximo-distal differences in force peaks between the models yielded overall for the ankle, 57.33 %Bodyweight(BW) ± 46.86 %BW (16.66 %(Maximum peak to peak) ± 13.62 %) for the knee 37.09 %BW ± 29.33 %BW (17.65 % ± 15.44 %) and 32.03 %BW ± 24.33 %BW (15.6 % ± 12.54 %) for the hip. The overall outcome of this work investigated an approach independent of the common setup of the gait laboratory, thus enabling a cheaper and more flexible technology as an alternative. However, kinematic and thus kinetic differences remain rather large. Future work aims to improve the contact criterion for the calculation of the ground reaction forces and the implementation of a full-body calibration algorithm for the IMU system in order to counteract magnetic field disturbances.

Indirect Measurement of Ground Reaction Forces and Moments by Means of Wearable Inertial Sensors: A Systematic Review

“…A more advanced anatomical model is the one used by Aurbach et al [ 60 ] that implemented a musculoskeletal model ( Figure 11 ) taking advantage of the software AnyBody™ (AnyBody Technology A/S, Aalborg, Denmark). The model could rely on a detailed anatomical representation of the skeleton and on an inverse kinetic engine to reconstruct forces from the measured kinematics.…”

“…The comparison is shown in Figure 12 . The OS data displayed a longer period of one sided loading of the feet and a difference in curve progression [ 60 ].…”

“…This study showed that the IMU based model yields the possibility to estimate the GRF independently of gait labs, however IMU performance was poor when compared to the OS [ 60 ]. The main sources of errors were attributed to the fluctuations within the magnetic field that could not completely be removed by calibration procedure.…”

“… Musculoskeletal model designed by [ 60 ]. The coordinate frame within the hip represents the reference system for the IMUs.…”

Kinematic and Kinetic Analysis of Horticultural Activities for Postural Control and Balance Training

“…To investigate the characteristics of motor and postural control during human movement, the kinetics and kinematics of movement are described using various measurement instruments, such as a 3D motion analysis system, a GRF platform, and an electromyography (EMG) device. The gold standard for the analysis of human kinematics and kinetics is using a camera-based motion analysis system in combination with measurement devices such as GRF and EMG (Aurbach et al, 2017). On the basis of the characteristics of the movement and postural control identified through kinetic and kinematic analyses, rehabilitation experts (e.g., occupational therapists, clinical rehabilitation specialists, exercise prescribers) develop appropriate rehabilitation plans and methods (Murphy et al, 2006).…”