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


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.


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


Supported by : 교육과학기술부, 한국연구재단


  1. Wells N., "Back Pain", Office of Health Economics: London, 1985.
  2. Okunribido O., "Lower limb MSD-scoping work in help inform advice and research planning", Health and Safety Excutive(HSE), 2009.
  3. 이인석, "쪼그려 앉은 작업자세에서의 작업부하 평가", 포항공과대학교 대학원 석사학위 논문, 1996.
  4. Chung M.K., Lee I., Kee S., Kim S.H., "A Postural workload evaluation system based on a macropostural classification", Human Factors and Ergonomics in Manufacturing, Vol. 12, No. 3, pp. 267-277, 2002.
  5. 이인석, 정민근, 기도형, "심물리학적 방법을 이용한 다양한 하지 자세의 부하 평가", 대한인간공학회지, 제21권, 제4호, pp. 47-65, 2002.
  6. Kirby R.L., Price N.A., MacLeod D.A., "The Influence if foot position on standing balance", Journal of Biomechanics, Vol. 20, No. 4, pp. 423-427, 1987.
  7. Van Wely P., "Design and disease", Applied Ergonomics, Vol. 1, No. 5, pp. 262-269, 1970.
  8. Grandjean E., Hüunting W., "Ergonomics of postures review of various problems of standing and sitting postures", Applied Ergonomics, Vol. 8, No. 3, pp. 135-140, 1977.
  9. Cooper C., McAlindon T., Coggon D., Egger P., Dieppe P., "Occupational activity and osteoarthritis of the Knee", Ann. Rheum. Dis., Vol. 53, No. 2, pp. 90- 93, 1994.
  10. Coggon D., Croft P., Kellingray S., Barrett D., Mc- Laren M., Cooper, C., "Occupational physical activities and osteoarthritis of the knee", Arthritis and Rheumatism, Vol. 43, No. 7, pp. 1443-1449, 2000.<1443::AID-ANR5>3.0.CO;2-1
  11. Nahit E.S. Macfarlane G.J., Pritchard C.M., Cherry N.M., Silman A. J, "Short-term influence of mecha nical factors on regional musculoskeletal pain: A study of new workers from 12 occupational groups", Occupational and Environmental Medicine, Vol. 58, pp. 374-381, 2001.
  12. Baker P., Reading I., Cooper C., Coggon D., "Knee disorders in the general population and their relation to occupation", Occupational and Environmental Medicine, Vol. 60, No. 10, pp. 794-797, 2003.
  13. Zhang Y., Hunter D.J., Nevitt M. C., Xu L., Niu J., Lui L.Y., Yu W., Aliabadi P., Felson D.T., "Association of squatting with increased prevalence of radiographic tibiofemoral knee osteoarthritis The Beijing osteoarthritis study", Arthritis and Rheumatism, Vol. 50, No. 4, pp. 1187-1192, 2004.
  14. Felson D. T., Hannan M. T., Naimark A., Berkeley J., Gordon G., Wilson P.W., Anderson J., "Occupational physical demands, knee bending and knee osteoarthritis: Results from the Framingham study", Journal of Rheumatology, Vol. 18, No. 10, pp. 1587-1592, 1991.
  15. Roelen C.A.M., Schreuder K.J., Koopmans P.C., Froothoff J.W., "Perceived job demands relate to self-reported health complaints", Occupational Medicine, Vol. 58, pp. 58-63, 2008.
  16. McAtamney L., Corlett E. N., "RULA: a survey method for the investigation of work-related upper limb disorders", Applied Ergonomics, Vol. 24, No. 2, pp. 91-99, 1993.
  17. McAtamney L., Corlett E, N.., "RULA: A rapid upper limb assessment tool", Ergonomics for all, pp. 286- 291, 1994.
  18. Dul J., Douwes M., Smitt P., "Ergonomic guidelines for the prevention of discomfort of static postures on endurance data", Ergonomics, Vol. 37, No. 5, pp. 807- 815, 1994.
  19. Nag P.K., "Endurance limits in different modes of load holding", Applied Ergonomics, Vol. 22, No. 3, pp. 185-188, 1991.
  20. Putz-Anderson V., Galinsky T.L., "Psychophysically determined work durations for limiting shoulder girdle fatigue from elecated manual work", Interna tional Journal of Industrial Engineering, Vol. 11, No. 1, pp. 19-28, 1993.
  21. Chaffin D. B., "Human strength capability and low back pain", Journal of Occupational and Medicine, Vol. 16, No. 4, pp. 248-254, 1974.
  22. Magora A., "Investigation of the relation between low back pain and occupation", Industrial Medicine and Surgery, Vol. 39, No. 12, pp. 504-510, 1970.
  23. Caruntu D.I., Hefzy M.S., Goel V.K., Goitz H.T., Dennis M.J., Agrawal V., "Modeling the knee joint in deep flexion: thigh and calf contact", Transactions of the Summer Bioengineering Conference, pp. 459- 460, 2003.