A CROSS-VALIDATION OF THE NIOSH LIMITS FOR MANUAL LIFTING

The psychophysical, biomechanical, and physiological criteria used in establishing the NIOSH limits for manual lifting were cross-validated against the data published by different researchers in the subject lit erature. Assessment of the 1991 NIOSH lifting equation indicated that: (1) NIOSH-based limits are significantly different from the psychophy sical limits in the (i) low and high frequencies of lift, and (ii) sma ll and large horizontal distances; (2) NIOSH limits are highly correla ted with the data of Snook and Ciriello (1991) in the low frequency ra nge, with the Recommended Weight Limit (RWL) protecting about 85% of t he female population and 95% of the male population; (3) the 3 . 4 kN Limit for compression on the lumbosacral joint cannot protect the majo rity of the worker population on the basis of damage load concept; and (4) energy expenditure limits used in development of the RWL index ca n be sustained by 57 to 99% of worker population when compared to the physiological limits based on previous fatigue studies. Results of the cross-validation for psychophysical criterion confirmed the validity of assumptions made in the 1991 NIOSH revised lifting equation. Howeve r, the results of cross-validation for the biomechanical and physiolog ical criteria were not in total agreement with the 1991 NIOSH model.