Dynamic analysis of forces in the lumbar spine during bag carrying

Abstract

Objective. The intervertebral disc supports axial and shear forces generated during tasks such as lifting and carrying weights. The objective of this study was to determine the forces in the lumbar spine of workers carrying a bag on the head, on the shoulder and on the anterior part of the trunk. Methods. Kinematic measurements were recorded for 10 subjects carrying bags of 10, 20 and 25 kg on each of the three aforementioned positions. A simple dynamic model implemented in a custom program was then developed to determine the lumbar forces using the accelerations and positions obtained from the kinematic analysis. Results. The analyses yielded a maximum compressive force of 2338.4 ± 422 N when a 25-kg bag was carried on the anterior part of the trunk. Conclusion. Carrying bags on the anterior part of the trunk generated higher lumbar forces compared to those developed by carrying the bag on the head or on the shoulder. Force levels suggest that this activity represents a moderate risk for the subjects. However, future biomechanical models should be developed to analyze the cumulative effect in the discs when longer periods of time are spent in this activity.

Keywords:

• bag carriage
• intervertebral disc
• lumbar forces
• lumbar spine

Acknowledgements

The authors appreciate the support of the Universidad del Valle and Universidad Libre-Cali to undertake this study. Thanks are also due to Colciencias for the financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Lessby Gómez http://orcid.org/0000-0003-2338-9410

Carlos A. Díaz http://orcid.org/0000-0002-2295-8848

José J. García http://orcid.org/0000-0003-2580-805X

Additional information

Funding

This work was supported by Colciencias program 245-2010 [contract number 1106-519-29063].