Two linear regression models predicting cumulative dynamic L5/S1 joint moment during a range of lifting tasks based on static postures

Abstract

Previous studies have indicated that cumulative L5/S1 joint load is a potential risk factor for low back pain. The assessment of cumulative L5/S1 joint load during a field study is challenging due to the difficulty of continuously monitoring the dynamic joint load. This study proposes two regression models predicting cumulative dynamic L5/S1 joint moment based on the static L5/S1 joint moment of a lifting task at lift-off and set-down and the lift duration. Twelve men performed lifting tasks at varying lifting ranges and asymmetric angles in a laboratory environment. The cumulative L5/S1 joint moment was calculated from continuous dynamic L5/S1 moments as the reference for comparison. The static L5/S1 joint moments at lift-off and set-down were measured for the two regression models. The prediction error of the cumulative L5/S1 joint moment was 21±14 Nm × s (12% of the measured cumulative L5/S1 joint moment) and 14±9 Nm × s (8%) for the first and the second models, respectively.

Practitioner Summary: The proposed regression models may provide a practical approach for predicting the cumulative dynamic L5/S1 joint loading of a lifting task for field studies since it requires only the lifting duration and the static moments at the lift-off and/or set-down instants of the lift.

Keywords:

• manual materials handling
• low back pain
• cumulative L5/S1 moment
• static moment

Acknowledgements

The authors gratefully acknowledge the help of Jacob Banks and Niall O'Brien for assistance in data collection, and Dr. Rammohan Maikala and Dr. Jin Qin for many useful comments and suggestions.