الفهرس 
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Abstract
Man is an expensive means of transport, for, in manual carrying, the entire muscles of the body are brought into action. Since the efficiency of the human motor system is rather low, this makes the human machine an expensive source of energy. Mechanical devices are considerably cheaper to operate in terms of overall costs.
Although manual handling 0f loads is expensive and inefficient, it is often necessary. This may be due to the type of task performed, the space available which does not permit mechanical handling equipments, or other restrictions which may be present. Therefore, it is necessary to improve the operator’s efficiency and reduce fatigue and injury during manual handling of loads. The necessity of manual lifting and the resulting associated problems dictate a need for studies which are directed towards a better understanding of the physical stresses imposed on the musculo¬skeletal system during lifting activities.
1.1 SCOPE
Various methods have been used in studies to determine stresses acting upon parts of the human body in work situations. Among these are the following:
(1) Mathematical models devised to predict the magnitude of external forces which cause partial or complete destruction of the vertebral or supporting structures.
2 (2) Use of electromyography to determine the role of the back muscles with respect to posture and motion.
(3) Use of a force platform to measure changes in location of the center of body mass during simulated tasks.
(4) Measurement of physiological responses such as oxygen consumption. respiration. and heart rate during physical work in a controlled atmosphere as an indication of body stress.
All of these methods have some merit. but in general none is considered the ultimate solution for measuring the forces acting upon various parts of the human body during lifting tasks.
1.2 OBJECTIVES
The main objective of this research is the development of a methodology for ana1yzing the amount of physical stress imposed on a person’s musculoskeletal system by infrequent material handling tasks. The methodology is based upon the concept that the physical stress incurred by the musculoskeletal system can be analyzed by applying the well-known laws of engineering mechanics to the human body.
A need appears to exist for the formulation of a biomechanical dynamic model for lifting in the sagittal plane. The proposed model will:
1. Provide data on the mechanical stresses on the body when performing lifting task in the sagittal plane.
2. Determine whether a lift can be performed by an individual