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Effect of Trunk Flexion and Low Extremity Posture on Maximum Holding Time

허리굽힘과 다리자세가 작업지속시간에 미치는 영향에 관한 연구

  • Lee, Se-Jung (Department of Safety Engineering, Graduate Scool, Pukyong National University) ;
  • Chang, Seong-Rok (Department of Safety Engineering, Pukyong National University)
  • 이세정 (부경대학교 대학원 안전공학과) ;
  • 장성록 (부경대학교 안전공학과)
  • Received : 2011.02.16
  • Accepted : 2011.05.23
  • Published : 2011.06.30

Abstract

Despite most of tasks in manufacturing, construction and agriculture, etc., were currently mechanized and automated, manual materials handling still existed in atypical working condition. In case of manual materials handling, repetitive work, inappropriate working posture, excessive force, contact stress might cause overload, which could lead to work-related musculoskeletal disorders and low back pains. On this basis, the goal of this study is to reveal the effects of various lifting postures of trunk angles and lower extremity postures on maximum holding time(MHT). Twenty two subjects were recruited from a university population. The experiment was designed by a combination of three trunk angle ($0^{\circ}$, $20^{\circ}$, $60^{\circ}$) and three lower extremity postures(straight, bent, kneeling). Before experimental trials, subjects performed MVC(maximum voluntary contraction) exertions in three trunk angles ($0^{\circ}$, $20^{\circ}$, $60^{\circ}$) to calculate 30%MVC at designated postures. In each trial, they were required to hold the handheld load(30%MVC) for a designated posture as long as they could. The results of MVC by trunk angles were measured in $0^{\circ}$ > $20^{\circ}$ > $60^{\circ}$ orders, but those of MHT measured in $20^{\circ}$ > $0^{\circ}$ > $60^{\circ}$ orders. These results showed that straight posture is the ideal working posture in work exerted a strong force for a short time, but the ability to work might be improved in the trunk angle $20^{\circ}$ in work required 30%MVC for a long time. Also, results of MVC and MHT by lower extremity postures measured in straight > bent > kneeling orders.

Keywords

work posture;trunk;lower extremity;maximum voluntary contraction;maximum holding time

Acknowledgement

Supported by : 교육과학기술부, 한국연구재단

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