J Biomech. 2013 Oct 18;46(15):2736-40. doi: 10.1016/j.jbiomech.2013.07.030. Epub 2013 Jul 30.

Estimating dynamic external hand forces during manual materials handling based on ground reaction forces and body segment accelerations.

Faber GS¹, Chang CC, Kingma I, Dennerlein JT.

Author information

1: Department of Environmental Health, Harvard School of Public Health, 665 Huntington Avenue, Boston 02115, MA, USA; Liberty Mutual Research Institute for Safety, 71 Frankland Road, Hopkinton 01748, MA, USA; Research Institute MOVE, Faculty of Human Movement Sciences, VU University Amsterdam, Van der Boechorststraat 9, 1081 BT Amsterdam, The Netherlands. Electronic address: gertfaber.sci@gmail.com.

Abstract

Direct measurement of hand forces during assessment of manual materials handling is infeasible in most field studies and some laboratory studies (e.g., during patient handling). Therefore, this study proposed and evaluated the performance of a novel hand force estimation method based on ground reaction forces (GRFs) and body segment accelerations. Ten male subjects performed a manual lifting/carrying task while an optoelectronic motion tracking system measured 3D full body kinematics, a force plate measured 3D GRFs and an instrumented box measured 3D hand forces. The estimated 3D hand forces were calculated by taking the measured GRF vector and subtracting the force vectors due to weight and acceleration of all body segments. Root-mean-square difference (RMSD) between estimated and measured hand forces ranged from 11 to 27N. When ignoring the segment accelerations (just subtracting body weight from the GRFs), the hand force estimation errors were much higher, with RMSDs ranging from 21 to 101N. Future studies should verify the performance of the proposed hand force estimation method when using an ambulatory field measurement system.