View Full Version : Re: ISB axis conventions

Scott Tashman
10-02-1995, 01:56 AM
I have been monitoring the discussion of the "standardization" of axis
conventions, and thought I would throw in my humble opinion.

As far as I am concerned, the only convincing argument for the ISB 3D
axis standard is that it maintains compatibility with conventional 2D
axis descriptions. My personal feeling is that 3D analysis is a
completely different world than 2D analysis. A clear example of this
is the difficulty associated with uniquely describing a 3D rotation,
which has no equivalent in the 2D world. I firmly believe that, in
most cases, it is inappropriate to be comparing 2D data to 3D data for
human movement, since truly "planar" natural movement does not exist.

With this in mind, I would suggest that basing a 3D standard on 2D
conventions makes little sense. In most of the 3D dynamics world, the
Z-axis is the axis of gravity (vertical) axis, and I believe that we
should maintain this convention in biomechanics reporting. If a 2D
standard is necessary, it can (and perhaps should) be different than
the 3D standard.

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Scott Tashman, Ph.D.

Head, Motion Analysis Section Assistant Professor
Bone and Joint Center Department of Orthopaedics
Henry Ford Hospital School of Medicine
2799 W. Grand Blvd. Case Western Reserve University
Detroit, MI 48202

Voice: (313) 876-8680 or 876-7572
FAX: (313) 556-8812 or 876-8064
Internet: tashman@bjc.hfh.edu
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