Spinal loads during two-person team lifting: effect of load mass distribution
Author(s)
Dennis, GJ
Barrett, RS
Griffith University Author(s)
Year published
2003
Metadata
Show full item recordAbstract
The purpose of this study was to examine the relationship between load mass distribution (LMD) and spinal load during team lifting tasks. Two-person lifting teams were required to lift a box containing a mass of 30 or 60 kg from the floor to standing knuckle height. Adjusting the position of the centre of mass within the box by ᱵ and ᷮ5 cm relative to the evenly distributed position (0 cm) yielded three LMD ratios (69:31, 59:41 and 50:50), which represented the percentage of the total mass lifted by each team member. The external force acting on the hands and sagittal plane segmental kinematics were measured and used in a ...
View more >The purpose of this study was to examine the relationship between load mass distribution (LMD) and spinal load during team lifting tasks. Two-person lifting teams were required to lift a box containing a mass of 30 or 60 kg from the floor to standing knuckle height. Adjusting the position of the centre of mass within the box by ᱵ and ᷮ5 cm relative to the evenly distributed position (0 cm) yielded three LMD ratios (69:31, 59:41 and 50:50), which represented the percentage of the total mass lifted by each team member. The external force acting on the hands and sagittal plane segmental kinematics were measured and used in a simple dynamic biomechanical model to calculate the torque, compression and shear forces experienced at L4/L5. Spinal load estimates (i.e. maximum and average L4/L5 torque, compression force and shear force) significantly increased with load mass and were positively correlated with LMD (r=0.86-0.99, p<0.05), indicating that the person at the heavier end of the asymmetrical load experienced higher spinal loads than their lifting partner. However, the asymmetry in spinal loads between the two team members was found to be significantly lower than the asymmetry in the LMD ratios. This result was primarily due to: (i) a significant positive correlation between LMD and the horizontal "pulling" force acting on the hand and (ii) a significant negative correlation between LMD and the moment arm of the vertical force acting through the hand relative to L4/L5. Thus, when lifting an unevenly balanced load a two-person lifting team seems to adopt a lifting strategy that partially alleviates the larger spinal loads experienced by the team member at the heavier end of the load.
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View more >The purpose of this study was to examine the relationship between load mass distribution (LMD) and spinal load during team lifting tasks. Two-person lifting teams were required to lift a box containing a mass of 30 or 60 kg from the floor to standing knuckle height. Adjusting the position of the centre of mass within the box by ᱵ and ᷮ5 cm relative to the evenly distributed position (0 cm) yielded three LMD ratios (69:31, 59:41 and 50:50), which represented the percentage of the total mass lifted by each team member. The external force acting on the hands and sagittal plane segmental kinematics were measured and used in a simple dynamic biomechanical model to calculate the torque, compression and shear forces experienced at L4/L5. Spinal load estimates (i.e. maximum and average L4/L5 torque, compression force and shear force) significantly increased with load mass and were positively correlated with LMD (r=0.86-0.99, p<0.05), indicating that the person at the heavier end of the asymmetrical load experienced higher spinal loads than their lifting partner. However, the asymmetry in spinal loads between the two team members was found to be significantly lower than the asymmetry in the LMD ratios. This result was primarily due to: (i) a significant positive correlation between LMD and the horizontal "pulling" force acting on the hand and (ii) a significant negative correlation between LMD and the moment arm of the vertical force acting through the hand relative to L4/L5. Thus, when lifting an unevenly balanced load a two-person lifting team seems to adopt a lifting strategy that partially alleviates the larger spinal loads experienced by the team member at the heavier end of the load.
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Journal Title
International Journal of Industrial Ergonomics
Volume
32
Publisher URI
Copyright Statement
© 2003 Elsevier : Reproduced in accordance with the copyright policy of the publisher : This journal is available online - use hypertext links.
Subject
Sports science and exercise