Muscular rest and gap frequency as EMG measures of physical exposure: the impact of work tasks and individual related factors

Catarina Nordander, Gert-Åke Hansson, Lars Rylander, P Asterland, J U Bystrom, Kerstina Ohlsson, Istvan Balogh, Staffan Skerfving

Research output: Contribution to journalArticlepeer-review

87 Citations (SciVal)

Abstract

Owing to an orderly recruitment of motor units, low threshold type I fibres are presumed to be vulnerable in contractions of long duration. To study load on these fibres muscular rest was registered as the time fraction of electromyographic (EMG) activity below a threshold. Moreover, the frequency of periods with muscular rest, EMG gaps, was derived, since a low gap frequency has been shown to be a risk factor for musculoskeletal disorders. Trapezius EMG was registered in 24 female hospital cleaners, 21 female office workers and 13 male office workers during one working day. Cleaners have a high risk of neck/shoulder pain and had much less muscular rest than office workers measured as a percentage of total registered time (median value = 1.5%, range = 0.2-13% vs. median value = 12%, range = 0.0-32%, respectively). Gap frequency showed no difference between the two occupational groups. Both measures displayed a wide inter-individual variation. For the cleaners, some of the variance was explained by body mass index (BMI) and age, with lower values of muscular rest for older subjects with a high BMI. Among the office workers, low values of muscular rest and a high gap frequency were registered in subjects with a low subjective muscular tension tendency. Gender, strength, smoking, job strain, employment time and musculoskeletal symptoms had no impact on either EMG measure.
Original languageEnglish
Pages (from-to)1904-1919
JournalErgonomics
Volume43
Issue number11
DOIs
Publication statusPublished - 2000

Subject classification (UKÄ)

  • Production Engineering, Human Work Science and Ergonomics

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