Clinical Biomechanics
Volume 25, Issue 2 , Pages 147-153, February 2010

Age-differences in the free vertical moment during step descent

  • John G. Buckley

      Affiliations

    • Vision and Mobility Research Lab, University of Bradford, Bradford, West Yorkshire, UK
    • School of Engineering, Design and Technology, University of Bradford, Bradford, West Yorkshire, UK
    • Corresponding Author InformationCorresponding author. Address: School of Engineering, Design and Technology, University of Bradford, Bradford, West Yorkshire BD7 1DP, UK.
    • ,
  • Steven F. Jones

      Affiliations

    • School of Engineering, Design and Technology, University of Bradford, Bradford, West Yorkshire, UK
    • ,
  • Louise Johnson

      Affiliations

    • Vision and Mobility Research Lab, University of Bradford, Bradford, West Yorkshire, UK
    • Division of Rehabilitation Studies, University of Bradford, Bradford, West Yorkshire, UK

Received 7 July 2009; accepted 20 October 2009. published online 18 November 2009.

Abstract 

Background

This study utilises a rarely examined biomechanical parameter – the free vertical moment to determine age-related differences in rotational kinetics of the body about the vertical-axis when stepping down from a stationary position.

Methods

Ten older and 10 young adults completed step-downs from three heights. Free vertical moment impulse and peak during step-initiation double-support and the subsequent step-execution phase, and vertical-axis pelvis angular displacement and velocity at instant of landing were compared.

Findings

The free vertical moment during double-support was directed away from the intended lead-limb side, producing a change in vertical-axis rotational momentum that moved the lead-limb in a forwards-medial direction about the stationary support/trailing limb during the subsequent step-execution phase. The free vertical moment during step-execution was directed towards the lead-limb side and acted to slow/halt the body’s vertical-axis rotation away from lead-limb side. Free vertical moment impulse and peak during double-support were similar between groups (P>0.05), but during step-execution were significantly reduced in older adults (P=0.002). As a result older adults had greater vertical-axis pelvis angular displacement and velocity at instant of landing (directed away from lead-limb side), with significant (P<0.001) group-by-step height interactions indicating that differences between groups became more pronounced with increasing step-height.

Interpretation

These findings highlight that older adults were unable to exert the same vertical-axis control during single-support as young subjects did. Findings also highlight that the analysis of free vertical moment data can be a useful biomechanical tool to highlight age-related differences in how steps/stairs are negotiated.

Keywords: Vertical-axis, Free moment, Stepping, Elderly, Stairs

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PII: S0268-0033(09)00247-2

doi:10.1016/j.clinbiomech.2009.10.008

Clinical Biomechanics
Volume 25, Issue 2 , Pages 147-153, February 2010

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