Wrist postures and forces in tree planters during three tree unloading conditions

Abstract

The aims of this study were to investigate wrist postures and forces while operating the shovel during tree planting and to determine if different tree unloading techniques result in variations in wrist postures and forces. Experienced tree planters performed the planting task in a laboratory environment for three conditions: (1) symmetric tree unloading, and asymmetric unloading resulting in (2) right-loaded planting bags and (3) left-loaded planting bags. An optoelectric system and a shovel instrumented with strain gauges captured wrist posture and forces at the wrist, respectively. Wrist extension of up to 45° was observed, and this posture, in combination with varying degrees of wrist deviation, may be a primary risk factor for musculoskeletal pain. Average resultant forces at the wrist were moderately high (>30 N) for each unloading condition, indicating increased risk for the development of repetitive strain injuries such as carpal tunnel syndrome. No significant differences in wrist posture or forces existed between unloading conditions.

Abstract

Practitioner Summary: Wrist pain is a major musculoskeletal complaint among tree planters. This study measured wrist postures and forces at the wrist while operating the shovel during tree planting. The wrist extension observed, in combination with deviation, may be a key risk factor for musculoskeletal pain. Forces at the wrist indicate increased risk for repetitive strain injuries.

Keywords::

• tree planting
• wrist posture
• wrist forces
• injury
• biomechanics

Acknowledgements

The authors thank Leone Ploeg from Human Mobility Research Centre for her help with data collection set-up and processing, and the Queen's University School of Rehabilitation for use of their laboratory space and equipment. This project was funded by research grants provided by the Workplace Safety and Insurance Board (Ontario) and NSERC Discovery Program. The sponsors of the study had no role in the study design; data collection, analysis and interpretation; writing of the manuscript; or the decision to submit the manuscript for publication.