Movement of loads with trunk rotation

Abstract

Movements with participants standing at a bench and moving loads up to 6 kg were studied, with participants using two hands to hold the load and trunk rotation in order to move the loads to specified locations. Tasks were performed with rapid ballistic movements and also with ongoing visual control. Data for ballistic movements were modelled in terms of a modified form of the (Gan, K.-C. and Hoffmann, E.R. 1988. “Geometrical conditions for ballistic and visually controlled movements.” Ergonomics 5 (31): 829–839) model for ballistic movements, taking into account the inertial properties of trunk rotation. Visually-controlled movements were modelled in terms of Fitts' law and a term that allowed for the ballistic form of the first submovement of the visually-controlled movement.

Practitioner Summary: Movement times to move masses up to 6 kg, for workers at a bench using trunk rotation, are given. Theoretical models fit the experimental data very well and allow prediction of movement times.

Keywords::

• heavy load
• trunk rotation
• Fitts' law
• trunk inertia effects

Acknowledgements

The authors thank Matthew Man for assistance with collection of experimental data.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work described in this paper was fully supported by a grant from City University of Hong Kong [grant number SRG7004250].