Thomas Läubli, Michael Schnoz, Joseph Weiss and Helmut Krueger Institute of Hygiene and Applied Physiology, Federal Institute of Technology, Zurich, Switzerland
Although repetitive finger movements are known risk factors for the development of work-related musculoskeletal disorders, the underlying mechanism that causes discomfort and pain is not well understood ( Kuorinka et al, 1995, Läubli and Krueger, 1992, Weiss et al. 1998). Maeda ( 1977) postulated a model on the development of work-related neck-shoulder pain. It stressed the importance of the combined strain resulting from many workload factors such as repetitive finger movements, long working hours, psychological stress, room climate, and others. However, the mechanism in the development of muscle pain at low-intensity work is still not established. Actual guidelines are based on practical experience, performance data and subjective symptoms, and are not deduced from physiological knowledge. A prevailing hypothesis postulates that specific motor units are active continuously during low-level contraction ( Seidel and Bräuer, 1988). Long lasting activity of single muscle fibers may overload their metabolic capacity and finally trigger nociceptive nerves ( Hägg, 1991).
To approach the pathophysiology of work-related musculoskeletal disorders, it is of interest to investigate whether fast repetitive finger movements induce constant activity of neck and shoulder muscles. We therefore examined the muscle activity during a fast and fatiguing tapping task.
9 right-handed subjects participated in the study (7 males and 2 females aged between 24 and 39 years). All test subjects were healthy and did not suffer from musculoskeletal disorders.