Maximum Acceptable Box Width and Box Mass for One-Handed Box Transfers from Three Shelf Heights: A Psychophysical Approach.

Abstract

Background: Effectively using digital human models (DHM) for proactive ergonomics requires estimating how workers interact with objects. One example is guessing when a worker might use one hand rather than two when transferring a box. A better understanding of the determinants for performing one-handed transfers will inform DHM users on when human-object interactions should be modeled with one hand versus two.

Purpose: This work aimed to determine the maximum acceptable box width and mass that would permit a one-handed box transfer from three shelf heights.

Methods: Participants completed a series of box transfers from three shelf heights to a table with their dominant hand. Participants were instructed to grasp the box from the top or front, then adjust the box width (experiment one) or box mass when the box was set at their maximum acceptable grip span (experiment two) until participants reached their maximum acceptable span or mass, respectively, to transfer the box comfortably and safely. Within-subject repeated measure ANOVAs, with an alpha value of 0.05, were used to detect if shelf height or grip orientation affected the maximum acceptable box width and mass, respectively, for a one-handed transfer.

Results: The perceived maximum acceptable box width ranged from 13.3 cm to 13.8 cm. The perceived maximum acceptable box mass ranged from 2.05 to 2.51 kg. The maximum acceptable width and mass for one-handed transfers were lowest when grasping a box from a shoulder-height shelf at the front of the box.

Conclusions: When the box width was less than 70% hand length, and required less than 36.7% wrist strength, participants were more likely to use one hand for box transfers. Findings provide insight into the one-handed lifting capacity of standard cardboard boxes with no handles and help inform DHM users on when to model one-handed or two-handed box transfers.