Interaction of awkward working posture and manipulation tasks on physical strain
Awkward body postures are known since long to cause different types of strain reactions. In a real working context, however, awkward body postures normally occur in conjunction with the primary task, i.e. assembly work. Although hand arm movements should have little direct effect on the strain induced by body posture both movements necessarily interact with each other. This is the case for balancing the body against hand-arm-movements and for co-contraction required to stabilise body posture as well as the hand-arm system. On the other hand there is some potential for energy saving by coordinating muscle recruitment for both the movements. In order to study if such interactions have a significant cumulative or compensatory effect a laboratory study was conducted testing two different body postures (sitting, and bent forward) against a reference posture (standing), each for two different task conditions (torque wrenching and precision movement). From the differences between the conditions the contributions of body posture and task performance as well as the interaction effects on strain were calculated. Testing was performed with 18 male and 18 female subjects using EMG of 7 muscles (from upper arm, shoulder, trunk and leg area), physiological measures (HR, Energy consumption, respiration frequency etc.) and subjective discomfort ratings. Results show that 44％ of the tested conditions and parameters show a significant interaction in a way that the performance of the manipulation task significantly reduces the strain induced by awkward body posture (as vice versa). A cumulative interaction was observed only for 3％ of the tested conditions and parameters. No significant differences were found between the different tasks and body postures tested. It can thus be concluded that the interaction effect is mostly of a compensative nature, enabling the human body to balance both activities in order to reduce muscular effort and energy expenditure.
Matthias Goebel Sarah Anne Skelton
Department of Human Kinetics and Ergonomics, Rhodes University, South Africa
国际会议
17th World Congress on Ergonomics(第十七届国际人类工效学大会)
北京
英文
1-10
2009-08-09（万方平台首次上网日期，不代表论文的发表时间）