The relationship between isometric strength of Cantonese males and the US NIOSH guide for manual lifting

A laboratory study was undertaken to assess the relationship between the maximal voluntary isometric strength (MVIS) of a group of Hong Kong Cantonese males and recommended limiting values for lifting proposed in the Work Practices Guide for Manual Lifting (NIOSH, 1981). Forty-one male subjects were required to apply a 'free-style' vertical 'lift' force to a horizontal bar located 150 mm from the ground. Forces were applied with the horizontal location of the midpoint of the ankles at 200, 400, 600 and 800 mm from the bar. The results were compared with the Maximal Permissible Limit (MPL) and the Action Limit (AL) values proposed in the NIOSH guide. The results showed that the mean MVIS of the Hong Kong subjects lay between the MPL and AL when the load was 200 mm and 400 mm from the ankles, but was significantly below the AL at 600 mm. At 800 mm more than half of the subjects were unable to apply any measurable positive vertical force. The compressive force at the L5/S1 disc of four subjects was estimated using a static biomechanical model. The relationship between the disc pressure and the force exerted was largely in accordance with NIOSH guide values. The results are discussed in terms of differences in subject population and lifting technique. Comments on the applicability of the NIOSH standards internationally, are also presented.