Abstract
Background: Musculoskeletal pain is prevalent both in adolescents and in the general working population. The neck and shoulder region is most commonly affected. Mechanical workload such as work in awkward postures, sustained work with hands above shoulder level, heavy lifting and repetitive work have previously been acknowledged as risk factors in adult working populations. The results have mainly been based on self-reported exposure data and the duration and intensity of the exposure is often disregarded. Young workers report more mechanical work exposures than older workers and the prevalence of musculoskeletal pain among young adults is increasing. It has however been very few studies investigating the mechanical workload as a risk factor for neck and shoulder pain among young workers.
Objective: This dissertation focuses on neck and shoulder pain in a cohort of young adults during their transition from technical school to working life. The aim was to explore the relationship between mechanical workload and neck and shoulder pain, using three different measures of work exposure.
Methods: The cohort consisted of 420 technical school students (representing student hairdressers, student electricians and media/design students) from the greater Oslo area. They were followed over a 6.5 year period from technical school into working life. Every 4th month during the study period neck and shoulder pain was assessed by questionnaire. Approximately halfway in the follow-up period, a technical field measurement was performed assessing the mechanical workload objectively on a subsample of 43 subjects. Paper I included the entire cohort that was followed 6.5 years. The mechanical workload was assessed by questionnaire approximately twice a year in the follow-up period. Paper II was based on the subsample. Surface electromyography on the upper trapezius muscle was measured during a whole working day. The relative time with sustained muscle activity for periods lasting >4minutes was used in the analyses. The neck and shoulder pain was assessed every 4th month during 2.5 years of follow-up. Paper III was also based on the subsample. Mechanical workload was measured using bilateral inclinometers on the upper arms. The relative time of work with prolonged arm elevation >60° and >90° were used in the analyses. The shoulder pain was assessed by pain drawings every year during the 2.5 year follow-up.
Results: An increase in neck and shoulder pain among young workers during their transition from technical school to working life was found. The pain severity levels reported were however relatively low, especially among men. Paper I showed that self-reported mechanical workload was associated with neck and shoulder pain. Stratifying by gender the association was significant among women. Perceived muscle tension was associated with neck and shoulder pain in both genders while clinically tested shoulder muscle endurance was negatively associated with neck and shoulder pain among men. In Paper II the results showed that high levels of sustained trapezius muscle activity during work was associated with neck and shoulder pain. Paper III showed that time with prolonged arm elevation >60° was associated with shoulder pain, however only significant among women.
Conclusions: The main conclusion from the three papers in this dissertation was that both self-reported and objectively measured mechanical workload was associated with neck and shoulder pain in the first years of working life, especially among women. The objectively measured sustained muscle activity during work and perceived muscle tension was associated with neck and shoulder pain in both genders. It was also evident from this dissertation that the neck and shoulder pain increases during the transition from technical school to working life. Even though the reported pain severity levels were relatively low, the findings suggests that mechanical workload is a risk factor already early in working life. This may indicate the need for attention on the work environment among young workers particularly those in manual working environments.