New aspects of physical work load as a risk factor for musculoskeletal disorders

Sammanfattning: ABSTRACT This study investigated new aspects of physical load factors as risk factors for musculoskeletal disorders among industrial employees. The following issues were in focus: the effect of physical work load and job experience on morbidity from musculoskeletal disorders, the incidence rates and induction times for these disorders, and the triggering factors for incident low back pain. Furthermore, the applicability of telephone interview in the assessment of physical work load and the effects of an ergonomic intervention were investigated. The studies were conducted in two Finnish factories: a middle-sized trailer assembly factory and a large forest industry enterprise. To investigate the effects of physical work load and job experience on morbidity from musculoskeletal disorders, and to assess the incidence rates of these disorders among newly employed workers, dynamic cohorts were followed. Case-crossover and case-control designs were used for investigating triggering factors for acute low back pain. A 'before-after' design was used in the intervention study. The data were collected with questionnaires, interviews, diaries, observations, and direct measurements. Medical diagnoses and sick leaves were obtained from medical records. The results showed that newly employed workers had a higher rate of sick leave due to upper limb disorders compared to experienced ones, especially in the tasks with high physical work load. The women had a higher rate than the men. New male workers in physically strenuous tasks had a high rate of sick leave due to neck and shoulder disorders. The workers sought medical advice due to the disorders for the first time typically after some months from the beginning of employment. The study on triggering factors for acute low back pain showed these factors to be associated with both work and leisure activities. Acute low back pain was also associated with daily job exposures, such as the handling of heavy loads, squatting or kneeling, and accident risk. Valid and reproducible information of work contents of regular work tasks was obtained via telephone interview. After an ergonomic intervention in assembly work most employees worked less with deviated wrist and the cumulative exposure on the upper extremity was lower. Lifting with twisted torso was reduced.In conclusion, newly employed workers in hand intensive tasks having a high risk of sick leave due to upper limb and neck-shoulder disorders suggests an etiologic role of activities involving high force demands in these disorders. In the prevention of these disorders, special attention should be paid to newly employed workers. The risk of acute low back pain seems to increase via both cumulative loading and acute physical overload. For the assessment of physical load factors, a single telephone interview can give reproducible and valid information of work in daily occurring tasks. For occasional tasks interview methods should be further developed. Exposure to importan.t risk factors of upper extremity and low back disorders can be reduced with relatively simple and low-cost solutions