Evaluating lifting tasks using subjective and biomechanical estimates of stress at the lower back.

The objective of this study was to evaluate five different lifting tasks based on subjective and biomechanical estimates of stress at the lower back. Subjective estimates were obtained immediately after the subjects performed the lifting tasks. Rankings for different tasks were obtained according to the perceived level of stress at the lower back. A biomechanical model was used to predict the compressive force at the L5/S1 disc for the weight lifted considering link angles for the particular posture. The tasks were also ranked according to the compressive force loading at the L5/S1 disc. The weight lifted in these tasks for obtaining the subjective estimate of stress was the maximum acceptable weight of lift (MAWOL). This was determined separately for each subject using a psychophysical approach. Subjective estimates of stress were obtained for infrequent lifting, specifically for a single lift, as well as for lifting at a frequency of four lifts per min. The results showed that a lifting task acceptable from the biomechanical point of view may not be judged as a safe or acceptable task by the worker based on his subjective perception. This may result in a risk of the worker not performing the recommended task or not following the recommended method.

[1]  W. M. Keyserling,et al.  Preemployment strength testing: an updated position. , 1978, Journal of occupational medicine. : official publication of the Industrial Medical Association.

[2]  A Mital,et al.  Psychophysical lifting capabilities for overreach heights. , 1987, Ergonomics.

[3]  A. Mital.  The Psychophysical Approach in Manual Lifting---A Verification Study , 1983, Human factors.

[4]  M. M. Ayoub,et al.  Modeling of Isometric Strength and Lifting Capacity , 1980 .

[5]  J R Brown,et al.  Lifting as an industrial hazard. , 1973, American Industrial Hygiene Association journal.

[6]  A Mital,et al.  Comprehensive maximum acceptable weight of lift database for regular 8-hour work shifts. , 1984, Ergonomics.

[7]  S H Snook,et al.  Maximum frequency of lift acceptable to male industrial workers. , 1968, American Industrial Hygiene Association journal.

[8]  D B Chaffin,et al.  A dynamic biomechanical evaluation of lifting maximum acceptable loads. , 1984, Journal of biomechanics.

[9]  K. S. Lee,et al.  Physical stress evaluation of microscope work using objective and subjective methods , 1988 .

[10]  Anil Mital,et al.  Kinetic analysis of manual lifting activities: Part II—Biomechanical analysis of task variables , 1986 .

[11]  S. Snook,et al.  Comparison of Different Approaches for the Prevention of Low Back Pain , 1988 .

[12]  D B Chaffin,et al.  Ergonomics guide for the assessment of human static strength. , 1975, American Industrial Hygiene Association journal.

[13]  D B Chaffin,et al.  A computerized biomechanical model-development of and use in studying gross body actions. , 1969, Journal of biomechanics.

[14]  Anil Mital,et al.  Relationship between Lifting Capacity and Injury in Occupations Requiring Lifting , 1978 .

[15]  John A. Roebuck,et al.  Engineering Anthropometry Methods , 1975 .

[16]  A. Mital,et al.  Maximum Frequencies Acceptable to Males for One-Handed Horizontal Lifting in the Sagittal Plane , 1983, Human factors.

[17]  Robert Dwayne Dryden.  A predictive model for the maximum permissible weight of lift from knuckle to shoulder height , 1973 .

[18]  R. Knipfer.  Predictive models for the maximum acceptable weight of lift , 1974 .

[19]  R J Robertson,et al.  Metabolic and perceptual responses while carrying external loads on the head and by yoke. , 1986, Ergonomics.

[20]  Stover H. Snook,et al.  The Ergonomics Society The Society's Lecture 1978. THE DESIGN OF MANUAL HANDLING TASKS , 1978 .

[21]  D. G. Beeton,et al.  Engineering Anthropometry Methods. J. A. Roebuck, K. H. E. Kroemer and W. G. Thomson. Wiley-InterScience, London. 1975. Illustrated. £15.00. , 1975, The Aeronautical Journal (1968).