Stability Limits In Extreme Postures: Effects Of Load Positioning,Foot Placement,and Strength

Abstract

Although injuries related to postural stability are prevalent, ergonomic job analyses traditionally have not addressed stability issues. In this research functional stability limits are quantified for persons standing in extreme postures under various external load and foot positioning conditions. Participants were asked to lean and displace their center of gravity (COG) as far as possible in eight directions to the sides and front of the body. Stability measures based on these COG displacements were calculated. All controlled variables significantly affected the stability measures. When standing unladen, participants extended their COG to within 99% of their theoretical maximum. Movement was much more restricted when handling a load (89%), especially when holding it with one hand on the shoulder (84%). On average, increased separation of the feet in a particular direction resulted in larger COG displacements in that direction. The results are discussed relative to their effects on balance and stability modeling.

Get full access to this article

View all access options for this article.

References

Barin, K. (1983). An experimental study of multi-link models of human postural dynamics and control. Unpublished doctoral dissertation, Ohio State University, Columbus, OH.

Chaffin, D. B. , & Andersson, G. B. J. (1991). Occupational biomechanics (2nd ed.). New York: Wiley.

Chaffin, D. B. , & Baker, W. H. (1970). A biomechanical model for analysss of symmetric sagittal plane lifting. IIE Transactions, 2(1), 16–27.

Davis, P. R. (1983) Human factors contributing to slips, trips and falls. Ergonomics, 26, 51–59.

Fernie, G. R. , Gryfe, C. I. , Holliday, P. J. , & Llewellyn, A. (1982) The relationship of postural sway in standing to the incidence of falls in geriatric subjects. Age and Aging, 11, 11–16.

Gollhofer, A. , Horstmann, G. A. , Berger, W. , & Dietz, V. (1989) Compensation of translational and rotational perturbations in human posture: Stabilization of the centre of gravity. Neuroscience Newsletters, 105, 73–78.

Grieve, D. W. (1979a) Environmental constraints on the static exertion of force: PSD analysis in task design. Ergonomics, 22, 1165–1175.

Grieve, D. W. (1979b) The postural stability diagram (PSD): Personal constraints on the static exertion of force. Ergonomics, 22, 1155–1164.

Holbein, M. A. (1993). Ergonomic load-holding and carrying strategies based on the biomechanics of human motion and postural stability. Unpublished doctoral dissertation, University of Pittsburgh, PA.

10.

Holbein, M. A. , & Redfern, M. S. (1997). Functional stability limits while holding loads in various positions. International Journal of Industrial Ergonomics, 19(5), 387–395.

11.

Kerk, C. J. (1992). Development and evaluation of a static hand force exertion capability model using strength, stability and coefficient of fruition. Unpublished doctoral dissertation, The University of Michigan, Ann Arbor, MI.

12.

MacKinnon, C. D. , & Winter, D. A. (1993) Control of whole body balance in the frontal plane during human walking. Journal of Biomechanics, 26, 633–644.

13.

Maki, B. E. , Holliday, P. J. , & Fernie, G. R. (1987). A postural control model and balance test for the prediction of relative postural stability. IEEE Transactions on Biomedical Engineering, BME-34, 797–810.

14.

Martin, J. B. , & Chaffin, D. B. (1972) Biomechanical computerized simulation of human strength in sagittal-plane activities. IIE Transactions, 4, 19–28.

15.

Nashner, L. M. (1975) Adapting reflexes controlling the human posture. Experimental Brain Research, 26, 59–72.

16.

Nashner, L. M. (1977) Fixed patterns of rapid postural responses among leg muscles during stance. Experimental Brain Research, 30, 13–24.

17.

Stobbe, T. J. (1982). The development of a practical strength testing program for industry. Unpublished doctoral dissertation, University of Michigan, Ann Arbor, MI.

18.

Tokita, T. , Miyata, H. , & Fujiwara, H. (1984). Postural responses induced by horizontal sway of a platform. Acta Otolaryngology (Supp. 406), 120–124.

19.

Winter, D. A. (1987, September). Sagittal plane balance and posture in human walking. IEEE Engineering in Medicine and Biology Magazine, 8–11.