Weight knowledge and weight magnitude: impact on lumbosacral loading

Abstract

Several factors can impact lumbosacral loads during lifting, including weight knowledge and weight magnitude. However, interaction between them has never been tested. This study investigated the interaction effect of these variables on lumbosacral forces and moments. Participants performed symmetrical lifts using three different weights. Weight knowledge involved known and unknown weight conditions. A biologically assisted dynamic model was used to calculate spinal loading parameters. Weight impacted all variables, while knowledge impacted only compression, by a moderate amount (5%), and spinal moments. Lifting a lightweight resulted in a difference of 16% and 7.2% between knowledge conditions for compression and anterior-posterior shear forces, respectively, compared with a negligible difference of < 1% when lifting a heavy weight. Increased spinal loading with light unknown weight can be attributed to increased muscular co-contraction. Weight knowledge is important to consider at low weight levels as it can increase tissue loading to values equivalent to lifting a heavier weight.

Abstract

Practitioner Summary: Impact of weight knowledge and magnitude on lumbosacral loading was investigated. The results suggest that subjects changed their lifting manner when handling unknown lightweight that increased spine loading to levels equivalent to handling heavier weights. This may be important for high frequency lifting tasks common in modern distribution centres.

Keywords::

• knowledge of weight
• magnitude
• low back loads
• manual lifting

Acknowledgements

The authors would like to thank Drs. Sue Ferguson, and Gary Allread for their valuable comments and suggestions. The authors also wish to thank Riley Splittstoesser, Greg Knapik and Gang Yang for their assistance in data collection and analysis.