No announcement yet.

ASI responses

This topic is closed.
  • Filter
  • Time
  • Show
Clear All
new posts

  • ASI responses

    i originally posted this 12 days ago but didnt appear on the list - so second time lucky

    my original post was with regards to the an asymmetry index (ASI) to assess gait symmetry.

    The asymmetry index or symmetry index (SI), same thing, is a basic equation
    used to determine symmetry

    SI = (Xr-Xl)/0.5(Xr+Xl)*100

    Xr = values of gait variable for right limb
    Xl = value of variable for left limb.

    (Herzog W, Nigg BM, Read LJ, Olsson E. Asymmetries in ground reaction force
    patterns in normal human gait. Med Sci Sports Exerc 1989;21(1):110-4.)

    this equation has been used mainly with regards to GRF, therefore if the
    difference between F1for left and right limb was 5% then this is deemed
    symmetrical. If the difference was 11% then it would be deemed asymmetrical.
    I believe this 10% cut-off, everything below 10% is symmetrical, is purely
    arbitrary . This method also has limitations see H. Sadeghi et al. :Gait and
    Posture 12 (2000) 34-45, But if subject numbers are small then stats cant be used so it may be the
    best option. The vast majority of research that has used this method has
    applied it to GRF and used 10% as a cut-off. It appears not to have been
    used with regards to moments or powers, therefore is the 10% cut-off point
    applicable. This is what I am stuck on, if the 10% was purely arbitrary
    then could another arbitrary figure be plucked out of the air for moments
    and powers

    thanks to those who responded (see below)

    I used an index presented by
    Durwood B and Rowe (1991) Symmetry - not so simple. Proceedings of the World Confederation for Physical Therapy 11th International Congress, London, United Kingdom p447-449

    I think the cut-off point is pretty arbitrary and depends on the variables
    that you're assessing. If you want something more objective, you can
    establish the cut-off based on the range of asymmetry values observed in
    healthy, control subjects.

    -- George

    To unsubscribe send SIGNOFF BIOMCH-L to
    For information and archives:
    Please consider posting your message to the Biomch-L Web-based
    Discussion Forum: