Variability in patterns of muscular activity during a fatiguing repetitive task
2016 (English)Conference paper, Abstract (Refereed)
Background. Muscle fatigue develops at markedly different rates among individuals. The pattern of variation in muscle activity has been suggested as a determinant of the rate of fatigue development. This variation can occur between muscles or between compart-ments of a muscle. Thus, we investigated the pattern of muscular activity in shoulder and arm regions during a fatiguing repetitive work task.
Methods. 21 healthy young women performed a repetitive pipetting task at 2.8 seconds/cycle. The session continued until the subject rate of perceived exertion reached 8 on Borg CR-10 scale. High density (HD) surface electromyogram (EMG) over upper trapezius, and bipolar EMG from extensor carpi radialis, flexor carpi radialis, biceps, triceps, deltoi-deus anterior, serratus anterior, upper and lower trapezius were collected to investigate intra- and inter-muscle variation patterns. EMG amplitude and mean power frequency (MPF) were obtained for all the recorded EMG signals. The barycenter of activity over the HD-EMG grid was also determined. Normalized mutual information (NMI) was determined for each pair of muscles. The extent of variability of the outcomes was also assessed.
Results. As fatigue developed, EMG amplitude increased and the MPF decreased for all muscles except the MPF for upper trapezius and deltoideus. The activity of trapezius was higher on the lateral side of HD-EMG grid than on the medial side and the barycenter showed a lateral shift across time. NMI between the muscle pairs also increased with fatigue. The variability of the investigated outcomes was not associated with the time to the task ending.
Discussion. Myo-electrical manifestations of muscle fatigue were observed but none of the outcomes had an association with the rate of fatigue development. Using multivariate approaches, synergistic pattern of muscular activity is yet to be investigated.
Place, publisher, year, edition, pages
Environmental Health and Occupational Health
IdentifiersURN: urn:nbn:se:hig:diva-21894OAI: oai:DiVA.org:hig-21894DiVA: diva2:942386
Ninth International Conference on the Prevention of Work-Related Musculoskeletal Disorders (PREMUS), June 20-23, 2016, Toronto, Canada
Projectsmuscle fatigue, muscle activity, repetitive work task, repetitive task