The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	Biomechanical analysis of asymmetric and dynamic lifting task
Author:	Jiang, Xiaopeng
View Online:	njit-etd2011-074 (x, 57 pages ~ 2.1 MB pdf)
Department:	Department of Mechanical and Industrial Engineering
Degree:	Master of Science
Program:	Occupational Safety and Health Engineering
Document Type:	Thesis
Advisory Committee:	Sengupta, Arijit K. (Committee chair) Bladikas, Athanassios K. (Committee member) Olsen, George W. (Committee member)
Date:	2011-05
Keywords:	Occupational lower back disorders Isometric pulling Electromyography Predicted muscle forces
Availability:	Unrestricted
Abstract:	Lifting tasks is one of the leading causes of occupational lower back disorders (LBD). Aimed at deriving internal forces of human musculoskeletal system during lifting, biomechanical models are utilized to address this problem. This thesis provides an indepth literature review of such modeling, and the results of experiments used to address LBD issues. An isometric pulling experiment was conducted to study the correlation between electromyography (EMG) and predicted muscle forces by AnyBody Modeling System™ with increasing hand loads. An infinite order polynomial (min/max) optimization criterion predicted percentage of maximum muscle forces, which achieved 98% correlation with normalized EMG. In a separate study, motion data during lifting of 13.6 kg (30 lb) weight at 0°, 30° and 60° asymmetry was collected by the OptiTrack™ sixcamera motion capture system to drive the AnyBody™ model. Erector spinae was the most activated muscle during lifting. When the lifting origin became more asymmetric toward the right direction, the right external oblique was more activated, and complementarily the right Internal oblique was less activated. Since oblique muscles can support an external moment more efficiently, and in addition the subject squatted more as the lifting origin became more asymmetric, L5/S1 joint forces decreased. This study contributes to the design and evaluation of lifting tasks to minimize LBD.