European Journal of Applied Physiology

, Volume 94, Issue 1–2, pp 158–167 | Cite as

A comparison of muscular activity during single and double mouse clicks

  • Stefan ThornEmail author
  • Mikael Forsman
  • Susan Hallbeck
Original Article


Work-related musculoskeletal disorders (WMSDs) in the neck/shoulder region and the upper extremities are a common problem among computer workers. Occurrences of motor unit (MU) double discharges with very short inter-firing intervals (doublets) have been hypothesised as a potential additional risk for overuse of already exhausted fibres during long-term stereotyped activity. Doublets are reported to be present during double-click mouse work tasks. A few comparative studies have been carried out on overall muscle activities for short-term tasks with single types of actions, but none on occurrences of doublets during double versus single clicks. The main purpose of this study was to compare muscle activity levels of single and double mouse clicks during a long-term combined mouse/keyboard work task. Four muscles were studied: left and right upper trapezius, right extensor digitorum communis (EDC) and right flexor carpi ulnaris. Additionally, MU activity was analysed through intramuscular electromyography in the EDC muscle for a selection of subjects. The results indicate that double clicking produces neither higher median or 90th percentile levels in the trapezius and EDC muscles, nor a higher disposition for MU doublets, than does single clicking. Especially for the 90th percentile levels, the indications are rather the opposite (in the EDC significantly higher during single clicks in 8 of 11 subjects, P<0.05). Although it cannot be concluded from the present study that double clicks are harmless, there were no signs that double clicks during computer work generally constitute a larger risk factor for WMSDs than do single clicks.


Computer mouse Muscle activity Motor units Doublets 



The authors wish to acknowledge Dr. Quixia Zhang for invaluable support during the iEMG recordings and Professor Roland Kadefors for fruitful discussions. This work was supported by the Swedish Council for Working Life and Social Research.


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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Stefan Thorn
    • 1
    • 2
    Email author
  • Mikael Forsman
    • 1
    • 2
  • Susan Hallbeck
    • 3
  1. 1.National Institute for Working LifeGoteborgSweden
  2. 2.Department of Product and Production Development/Human Factors EngineeringChalmers University of TechnologyGoteborgSweden
  3. 3.Department of Industrial and Management Systems EngineeringUniversity of NebraskaLincolnUSA

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