Biomechanical Stresses as Related to Motion Trajectory of Lifting

Abstract

A laboratory study was conducted to assess the effects of lift angle on biomechanical stresses to the musculoskeletal system, and in particular, on the lower back. Male subjects were required to lift four different tote boxes from the floor to a height of 0.81 m using two different lifting techniques. Maximum acceptable weights were determined using a psychophysical method. The motion trajectory of lift was studied by means of stroboscopic photography. Moments and forces at various body joints were computed using a biomechanical strength model.

Maximum acceptable weights were 16% (range = 9 to 23%) greater for the free-style lifting technique as compared with the squat method of lifting. There were large differences between the maximum acceptable weights and the "maximum permissible limits" recommended by NIOSH. The results showed that the subjects pulled the load toward the body when lifting psychophysically determined maximum weights. The lift angle increased with an increase in box width. The lift angle was greater for the free-style lifting method as compared with the squat lifting technique for lifting compact loads. Lifting at an angle resulted in a decrease in moment at the elbow, shoulder, L₅IS₁ disc, and hips, and an increase in moment at the knees and ankles. The estimated compressive force on the lumbar spine was, on the average, 11% lower for lifting at an angle as compared with a straight vertical lift.

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References

Ayoub, M. M. , Bethea, N. J. , Deivanayagam, S. , Asfour, S. S. , Bakken, G. M., Liles, D., Mital, A., and Sherif, M. Determination and modeling of lifting capacity (DHEW [NIOSH] Report, Grant #R01 OH 005 45-02). Lubbock, TX: Texas Tech University, August, 1978.

Ayoub, M. M. , and El-Bassoussi, M. M. Dynamic biomechanical model for sagittal lifting activities. In: Proceedings of 6th Congress of International Ergonomics Association. Santa Monica, CA: Human Factors Society, 1976.

Brown, J. R. Lifting as an industrial hazard. Ontario: Labor Safety Council, Department of Labor, 1971.

Bureau of Labor Statistics . 1976 SDS Report for Arkansas. Little Rock: Arkansas Department of Labor, Research and Statistics Division, 1978.

Chaffin, D. B. A computerized biomechanical model: Development of and use in studying gross body actions. Journal of Biomechanics, 1969, 2, 429–441.

Chaffin, D. B. On the validity of biomechanical models of the low-back for weight lifting analysis (75-WA/Bio-1), New York: American Society of Mechanical Engineers, 1975.

Chaffin, D. B. , Fisher, B. , Hodges, W. , and Miyamoto, R. A biomechanical analysis of materials handling activities performed in the sagittal body plane. Ann Arbor, MI: Department of Industrial and Operations Engineering, University of Michigan, 1967.

Chaffin, D. B. , Herrin, G. D. , Keyserling, W. M. , and Foulke, J. A. Pre-employment strength testing in selecting workers for materials handling jobs (DHEW [NIOSH) Publication No. 77-163). Cincinnati, OH: NIOSH, 1917. (a)

Chaffin, D. B. , Herrin, G. D. , Keyserling, W. M. , and Garg, A. A method for evaluating the biomechanical stresses resulting from manual materials handling jobs. American Industrial Hygiene Association Journal, 1977, 38, 662–675. (b)

10.

Clarke, H. H. Muscular strength and endurance in man. Englewood Cliffs, NJ: Prentice-Hall, 1966.

11.

Garg, A. , and Ayoub, M. M.

What criteria exist for determining how much load can be lifted safely?

Human Factors, 1980, 22, 475–486.

12.

Garg, A. , and Chaffin, D. B. Abiomechanical computerized simulation of human strength. Transactions of the American Institute of Industrial Engineers, 1975, 7, 1–IS.

13.

Garg, A. , and Herrin, G. D. Stoop or squat: A biomechanical and metabolic evaluation. Transactions of the American Institute of Industrial Engineers, 1979, 11, 293–302.

14.

Garg, A. , Mital, A. , and Asfour, S. S. A comparison of isometric strength and dynamic lifting capability. Ergonomics, 1980, 23, 13–27.

15.

Garg, A. , and Saxena, U. Effects of lifting frequency and technique on physical fatigue with special reference to psychophysical methodology and metabolic rate. American Industrial Hygiene Association Journal, 1979, 40, 894–903.

16.

Garg, A. , and Saxena, U. Container characteristics and maximum acceptable weight of lift. Human Factors, 1980, 22, 487–495.

17.

Keyserling, W. M. Isometric strength testing in selecting workers for strenuous jobs. Unpublished doctoral dissertation, University of Michigan, Ann Arbor, MI, 1979.

18.

Kroemer, K. H. E. Push forces exerted in 65 common working positions (AMRL-TR-68-143). Wright Patterson Air Force Base, OH: Aerospace Medical Research Lab, 1969.

19.

Martin, J. B. , and Chaffin, D. B. Biomechanical computerized simulation of human strength in saggital plane activities. Transactions of the American Institute of Industrial Engineers, 1972, 4, 19–28.

20.

National Safety Council . Accident facts. Chicago: Author, 1975.

21.

Neter, J. , and Wasserman, W. Applied linear statistical models. Homewood, IL: Irwin, 1974.

22.

Park, K. S. , and Chaffin, D. B. A biomechanical evaluation of two methods of load lifting. Transactions of the American Institute of Industrial Engineers, 1974, 6, 105–113.

23.

Pytel, J. L. , and Kamon, E. Dynamic strength test as a predictor for maximal and acceptable lifting. Ergonomics, 1981, 24, 663–672.

24.

Schanne, F. J. A three dimensional hand force capability model for a seated person. Unpublished doctoral dissertation, University of Michigan, Ann Arbor, MI, 1972.

25.

Snook, S. H. The design of manual handling tasks. Ergonomics, 1978, 21, 963–985.

26.

Snook, S. H. , Campanelli, R. A. , and Hart, J. W. A study of three preventive approaches to low-back injury. Journal of Occupational Medicine, 1978, 20, 478–483.

27.

Snook, S. H. , and Irvine, C. H. Maximum acceptable weight of lift. American Industrial Hygiene Association Journal, 1967, 28, 323–329.

28.

Tichauer, E. R. The biomechanical basis of ergonomics. New York: Wiley, 1978.

29.

U.S. Department of Health and Human Services . Work practices guide for manual lifting (DHHS [NIOSH] Publication No. 81-122). Cincinnati, OH: NIOSH, 1981.

30.

Williams, M. W. , and Lissner, H. R. Biomechanics of human motion. Philadelphia: Saunders. 1977