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P198 Physiological impact of sit-stand workstations
  1. Stephen Bao,
  2. Jia-Hua Lin
  1. Washington State Department of Labour and Industries, Olympia, USA


Work-related musculoskeletal disorders (WMSD) are common among office workers who often use computers. High static muscle loading has been considered one of the major risk factors responsible for developing WMSDs among office workers. One of the ergonomics intervention strategies in the office environment is to create healthy physical variations. The introduction of sit-stand workstations usually reduces sedentary sitting time during work and is believed to be able to introduce physical variations among office workers. The goal of the present study is to examine systematically several physiological measures on sit-stand workstation use.

An earlier study using surface electromyography (EMG) to examine muscle loadings on four office workers when identical works were performed using both sitting and standing workstations showed that the effect of posture on the upper extremity muscle loadings was not consistent among workers. For trapezius muscles, work in standing resulted in overall greater muscle activities for some subjects, but sitting for others. Since the primary objective of that study was not on the sit/stand workstation, several other variables (such as workstation set-up etc.) were not controlled. The present study will therefore standardise factors that might influence the loading (such as workstation set-up, task activities, and work schedule), but only changing sit-stand workstation related factors, so that the impact of sit-stand workstations can be studied.

The physiological measures that will be compared among several different sit-stand workstation use schedules include muscle activities measured by electromyography (EMG) during work, muscle fatigue (estimated by median frequency shift of EMG), spinal shrinkage, and foot swelling. Four different sit-stand workstation schedules are studied. The hypothesis of the study is that working at sit and stand postures introduce healthy physical variations of muscle activities. Different sit-stand workstation schedules may have different levels of impact in terms of these physiological measures on the human operators.

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