Association between numbers of long periods with sustained low-level trapezius muscle activity and neck pain

Abstract

The purpose of this prospective cohort study was to evaluate relationships between sustained low-level muscle activity (SULMA) in the neck and pain after 1 year among machine operators of forest harvesters (n = 19), forwarders (n = 20) and forest researchers (n = 20). Surface electromyography of the right upper trapezius muscle was measured during one working day. Continuous muscle activity (SULMA periods) were analysed in predetermined time intervals. Neck pain was assessed by the Borg's category-ratio scale and the Standardized Nordic Questionnaire (dichotomised into pain duration ≤30 or >30 d). Harvesters reported significantly more pain than researchers. A higher number of long SULMA periods >8 min duration increased the risk of neck pain >30 d during the successive year (odds ratio 3.0, 95% CI 1.2–7.8). Perceived personal economy above average was associated with less pain, while other potential confounders or intermediate variables were not significant. Low-level trapezius muscle activity in periods longer than 8 min may constitute a risk for neck pain.

Keywords:

• Surface electromyography
• control levers
• forest vehicles
• musculoskeletal disorders
• epidemiology
• cohort

Acknowledgements

We express our gratitude to the Research Council of Norway for financial support. The authors would also like to thank the volunteering forest machine operators and researchers for participating and the help and assistance from Ola Ro and the staff at the Norwegian Forest and Landscape Institute during the initial data collection.