Academic journal article Scandinavian Journal of Work, Environment & Health

The Effect of Work-Related Sustained Trapezius Muscle Activity on the Development of Neck and Shoulder Pain among Young Adults

Academic journal article Scandinavian Journal of Work, Environment & Health

The Effect of Work-Related Sustained Trapezius Muscle Activity on the Development of Neck and Shoulder Pain among Young Adults

Article excerpt

Hanvold TN, Wæ rsted M, Mengshoel AM, Bjertness E, Stigum H, Twisk J, Veiersted KB. The effect of work-related sustained trapezius muscle activity on the development of neck and shoulder pain among young adults. Scand J Work Environ Health. 2013:39(4):390-400. doi:10.5271/sjweh.3357

Objective This study aimed to evaluate if sustained trapezius muscle activity predicts neck and shoulder pain over a 2.5-year period.

Methods Forty young adults (15 hairdressers, 14 electricians, 5 students and 6 with various work) were followed during their first years of working life. Self-reported neck and shoulder pain during the last four weeks was assessed seven times over the observational period. Upper-trapezius muscle activity was measured during a full working day by bilateral surface electromyography (EMG) at baseline (winter 2006/7). Sustained trapezius muscle activity was defined as continuous muscle activity with amplitude >0.5% EMGmax lasting >4 minutes. The relative time of sustained muscle activity during the working day was calculated and further classified into low (0-29%), moderate (30-49%) and high (50-100%) level groups.

Results Generalized estimating equations (GEE), adjusted for time, gender, mechanical workload, control-over-work intensity, physical activity, tobacco use, and prior neck and shoulder pain, showed that participants with a high level of sustained muscle activity had a rate of neck and shoulder pain three times higher than the low level group during a 2.5-year period. The association was strongest at the same time and shortly after the EMG measurement, indicating a time-lag of ≤6 months.

Conclusion The results support the hypothesis that sustained trapezius muscle activity is associated with neck and shoulder pain. This association was strongest analyzing cross-sectional and short-term effects.

Key terms electromyography; EMG; musculoskeletal disorder; workload; young worker.

Neck and shoulder disorders are a considerable health problem in the working population with prevalence rates of ≥30% (1, 2). Pain in this region is common also among young adults in their first years of working life (3). Work-related neck and shoulder pain represents suffering for the individual and is a considerable economic challenge for society.

The etiology of work-related neck and shoulder pain has been extensively examined, however the causes are still unclear and regarded as complex and multifactorial (4). Biomechanical and psychosocial workplace factors as well as individual risk factors have all been related to neck and shoulder pain (5-8). The deleterious effect of sustained activity pattern in the trapezius muscle (which is the occurrence of continuous muscle activation without interruptions) has been proposed as a common mechanism for explaining neck and shoulder pain (9). Veiersted and co-workers (10) found that a low frequency of interruptions in trapezius muscle activity during repetitive tasks was associated with future development of neck pain. More recent studies have shown a correlation between trapezius muscle activation and pain. In a cross-sectional study, Szeto et al (11) found that those office workers with high levels of neck and shoulder pain had higher trapezius muscle activity compared to office workers with lower pain levels. A longitudinal study on forest machine operators found that a higher frequency of episodes with sustained trapezius muscle activity lasting for ≥8 minutes was related to future reports of neck pain (12). These studies suggest that reduced muscle rest or sustained muscle activity may be essential factors leading to neck and shoulder pain. In contrast, others have proposed that either pain leads to decreased muscle activity (13) or there is no association between low-level trapezius muscle activity and pain (14-17).

Since there is no consensus concerning trapezius muscle activity and its relation to neck and shoulder pain, we have used a longitudinal design for this study with frequent measurements of neck and shoulder pain to evaluate the long-term effects and time-lag, in addition to cross-sectional effects and reverse relationship, of sustained muscle activity. …

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