Anthropometric, muscle strength, and spinal mobility characteristics as predictors in the rating of acceptable loads in parcel sorting

Abstract

The rating of acceptable load (RAL) attained with a standard test (RAL_st) and a work-simulating test (RAL_w) for postal parcel sorting was related to anthropometric, muscle strength, and spinal mobility characteristics of 18 male sorters. The subjects comprised a subsample of 103 experienced male sorters who carried out the RAL tests at postal sorting centres. The dynamic hand-grip endurance correlated significantly (p=0·036) to the RAL_st results. Correspondingly, there was a significant correlation ( p=0·044) between the ratio of maximal isometric strength of trunk extension to body weight and the RAL_w. The dynamic hand-grip endurance predicted 26% of the variation in the RAL_st; in the RAL_w the maximal isometric strength of trunk flexion to body weight ratio predicted 24%. The subjects who rated heavier weights for RAL_st, tended to have a better trunk mobility. The dynamic endurance of hand-grip muscles, trunk strength, and spinal flexibility seemed to be the most powerful predictors for the psychophysically assessed ‘acceptable loads’ in experienced workers performing manual materials handling tasks.

Keywords:

• Musculoskeletal system
• Psychophysics
• Muscle contraction
• Range of motion
• Weight-lifting
• Manual materials handling