Three dimensional dynamic motor performance of the normal trunk

W. S. Marras, S. A. Ferguson, S. R. Simon

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Traditionally, human strength has been described in terms of the maximum force one could exert under isometric conditions. However, in the past decade ergonomists have attempted to find strength measures that better represent the dynamic aspects of occupational tasks. Recent efforts have focussed upon dynamic motor performance capabilities of the human body that go beyond the traditional measures of isometric strength. The objective of this study was to document the three dimensional dynamic motor performance capabilities of the normal human trunk as subjects flexed and extended their trunks as fast as they could under 'sagittaly symmetric and asymmetric "back lifting" conditions. The results indicated that the range of motion, trunk angular velocity and trunk angular acceleration decreased in the sagittal plane as the trunk became more asymmetric. Dynamic motor performance characteristics increased in the frontal and transverse planes as the trunk became more asymmetric, however, these differences were also dependent upon the device used to measure trunk motor performance.

Original languageEnglish
Pages (from-to)211-224
Number of pages14
JournalInternational Journal of Industrial Ergonomics
Issue number3
StatePublished - Nov 1990
Externally publishedYes


  • Back strength
  • biochemical modeling
  • low back disorders
  • strength testing
  • three dimensional trunk movement


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