Ergonomics Evaluation of Manual Lifting Task on Biomechanical Stress in Symmetric Posture

Abstract

Introduction: Manual lifting operations continue to play a key role in the industrial and service sectors, inflicting physical strain on the musculoskeletal system, despite advances in automation. As a result, an experiment is carried out to assess the impact of two lifting task parameters; weight and height, based on the estimation of subjective responses and biomechanical loading, while lifting the weight symmetrically in the sagittal plane. Also to recommend the safe limit for manual lifting tasks. Methods: Twelve volunteer male students in the age group of 21 to 26 years performed lifting tasks from floor to 5 different heights (below the knee to ear level), with 5 different weights (10 to 20 kg) using free-style lifting techniques. The load pan with no handle was used for lifting weight, which is typically adopted in the Indian building construction field. The subjective estimate was obtained using workload assessment by body discomfort chart. The biomechanical loading (loading rate) for each lifted weight and height was collected using a force platform. Results: The results showed that heavier weights produced higher stresses than lower weights. The loading rate was found to be almost similar at waist or knee level. The loading rate was observed to be linearly increasing after waist level. The overall workload rating seems to be a good correlate with the mean loading rate to some extent. Conclusion: It is proposed to keep the maximum acceptable lifting weight from floor to knee, up to the ear level is 15 kg, to prevent any musculoskeletal or chronic injury.

Postural stress and risk conditions in manual load handling of Chilean industrial workers

“…It was observed to be linear- Lifting, lowering and transport Pushing and pulling ly increasing after waist level. 21 The study proposes the following measures which should be adopted by occupational health units to improve working conditions: a) evaluate and train the best technique to perform different tasks to make more efficient use of biomechanics and mechanical advantage 22 , b) evaluate mechanical assistance to push loads of greater magnitude or the conformation of task teams to minimize the initial push and/or drag effort 23 , c) review and incorporate the use of working pauses combined with the rotation of workers in different jobs to reduce the repetitiveness component and improve the recovery of tissues and joint structures involved in the execution of activities, and by reducing the stress imposed on the musculoskeletal system in the tasks performed. 24 A limitation of this study was not to consider or preliminarily assess clinical aspects such as signs and symptoms associated with musculoskeletal disorders and organizational aspects, including those that determine the productive rhythms, criteria that would have allowed to clarify if the detected risks compromise occupational health as well as the development of sustainable work 25 .…”