Effects of height and load weight on shoulder muscle work during overhead lifting task

Abstract

Few musculoskeletal models are available to assess shoulder deeper muscle demand during overhead lifting tasks. Our objective was to implement a musculoskeletal model to assess the effect of lifting height and load on shoulder muscle work. A musculoskeletal model scaled from 15 male subjects was used to calculate shoulder muscle work during six lifting tasks. Boxes containing three different loads (6, 12 and 18 kg) were lifted by the subjects from the waist to shoulder or eye level. After optimisation of the maximal isometric force of the model's muscles, the bio-fidelity of the model was improved by 19%. The latter was able to reproduce the subjects’ lifting movements. Mechanical work of the rotator cuff muscles, upper trapezius and anterior deltoid was increased with lifting load and height augmentation. In conclusion, the use of a musculoskeletal model validated by electromyography enabled to evaluate the muscle demand of deep muscles during lifting tasks.

Abstract

Practitioner Summary: This study aimed to assess the effect of lifting height and weight lifted on shoulder muscle load. A musculoskeletal model was implemented to calculate the work of shoulder muscles during lifting tasks. The overhead lifting task with the use of a heavy box was the most demanding for the rotator cuff muscles, anterior deltoid and upper trapezius.

Keywords::

• biomechanics
• musculoskeletal model
• handling movement
• rotator cuff muscles

Acknowledgements

We would like to thank the Institut National du Sport (INS) for the loan of the electromyographic wireless system.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was partially supported by the Institut de Recherche Robert-Sauvé en Santé et Sécurité du Travail (IRSST) [grant number 2010-0024] and by the Fond de Recherche Santé Québec (FRQ-S) [grant number #26741].