title: Estimating 3D L5/S1 moments and ground reaction forces during trunk bending using a full-body ambulatory inertial motion capture system.
abstract: Inertial motion capture (IMC) systems have become increasingly popular for ambulatory movement analysis. However, few studies have attempted to use these measurement techniques to estimate kinetic variables, such as joint moments and ground reaction forces (GRFs). Therefore, we investigated the performance of a full-body ambulatory IMC system in estimating 3D L5/S1 moments and GRFs during symmetric, asymmetric and fast trunk bending, performed by nine male participants. Using an ambulatory IMC system (Xsens/MVN), L5/S1 moments were estimated based on the upper-body segment kinematics using a top-down inverse dynamics analysis, and GRFs were estimated based on full-body segment accelerations. As a reference, a laboratory measurement system was utilized: GRFs were measured with Kistler force plates (FPs), and L5/S1 moments were calculated using a bottom-up inverse dynamics model based on FP data and lower-body kinematics measured with an optical motion capture system (OMC). Correspondence between the OMC+FP and IMC systems was quantified by calculating root-mean-square errors (RMSerrors) of moment/force time series and the interclass correlation (ICC) of the absolute peak moments/forces. Averaged over subjects, L5/S1 moment RMSerrors remained below 10Nm (about 5% of the peak extension moment) and 3D GRF RMSerrors remained below 20N (about 2% of the peak vertical force). ICCs were high for the peak L5/S1 extension moment (0.971) and vertical GRF (0.998). Due to lower amplitudes, smaller ICCs were found for the peak asymmetric L5/S1 moments (0.690-0.781) and horizontal GRFs (0.559-0.948). In conclusion, close correspondence was found between the ambulatory IMC-based and laboratory-based estimates of back load.
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands; Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Liberty Mutual Research Institute for Safety, Hopkinton, MA, USA. Electronic address: gertfaber.sci@gmail.com.
authors.forename: G S
authors.initials: GS
authors.lastname: Faber
authors.affiliation: Liberty Mutual Research Institute for Safety, Hopkinton, MA, USA; Department of Industrial Engineering & Engineering Management National Tsing Hua University, Taiwan, ROC.
authors.forename: C C
authors.initials: CC
authors.lastname: Chang
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: I
authors.initials: I
authors.lastname: Kingma
authors.affiliation: Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Department of Physical Therapy, Movement, and Rehabilitation Sciences, Northeastern University, Boston, MA, USA.
authors.forename: J T
authors.initials: JT
authors.lastname: Dennerlein
authors.affiliation: Department of Human Movement Sciences, Faculty of Behaviour and Movement Sciences, Vrije Universiteit Amsterdam, MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: J H
authors.initials: JH
authors.lastname: van Dieën
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D006801:Humans; D021621:Imaging, Three-Dimensional; D008159:Lumbar Vertebrae / Q000502:physiology*; D008161:Lumbosacral Region / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D009068:Movement; D011187:Posture; D012447:Sacrum / Q000502:physiology*
keywords: Inertial measurement unit (IMU); Inertial sensors; Low back loading; Occupational biomechanics; Physical exposure