View Full Version : Biomechanics in Florida

Herman J. Woltring
11-22-1990, 08:50 PM
Dear Biomch-L readers,

Following Professor Chao's highly interesting and kind response of November 12
to Fabio Catani's posting of November 5 and my reply of November 8, I had the
pleasure to attend the recent ASB meeting in Miami. `New ideas' seldom occur
in isolation, and I am pleased to refer to the paper "An intrinsic parameter
for the study of complex three-dimensional human motion" by Raymond R. Brodeur
& Robert W. Soutas-Little from the Department of Biomechanics at Michigan State
University in East Lansing, MI 48824, U.S.A.

In this paper, the central point of differential kinematics is mentioned in
the context of the so-called distribution parameter which is the ratio of the
first-order IHA's translation speed along and rotation speed about the second-
order IHA. [Note: the second-order IHA is the IHA about which the (first-order)
IHA itself executes an instantaneous, helical movement.] In other words (and
further to a question by Prof. K.-N. An from the Mayo Clinic after Mr Brodeur's
presentation), it is the so-called pitch of the second-order IHA, similar to
the pitch of the first-order IHA which equals the ratio of a rigid-body's
translation speed along and rotation speed about the first-order IHA. While
the authors place all emphasis of their paper on the distribution parameter,
it seems clear from their presentation that they have the central point in
mind for joint centre representation, too.

At the CAMARC meeting in Rome next week, there is another paper on joint centre
estimation from gait data; the authors are unknown to me at this time. Thus,
the time might be ripe for a paradigm change in whole-body movement analysis.

Another, highly interesting paper at the Miami ASB meeting was from Prof. Jack
M. Winters' group (Chemical, Bio & Materials Engineering) at Arizona State Uni-
versity in Tempe, AZ 85060, U.S.A. [where, incidentally, the next ASB meeting
will be held]. In "Head finite screw axis parameters during vertical, horizon-
tal, and oblique tracking movements: normal and injured subjects" (cf. also
the companion poster "Directional and spatial sensitivity of neck muscle acti-
vity during comfortably-spaced 3-D head tracking movements"), the Abstract's
initial part, co-authored with two members from the Fuer Chiropractic Clinic
in Phoenix, AZ, runs as follows:

This study documents how finite screw axis parameters (FSAP) for head
rotation change during voluntary horizontal, vertical, and oblique point-
to-point head tracking movements. Both "normal" (control) subjects (n=9)
and subjects with "whiplash" conditions (n=10) are considered, with each
subject evaluated twice, separated by six weeks. The information collec-
ted here serves to document normal ranges, help validate 3-D computer
models, and assist optimization studies by providing reference data for
a performance criterion. Here we emphasize the first two of these. The
foundation behind the approach rests with the concept that the head is the
most distal link of an open kinematic chain that includes the neck. Con-
sequently, changes in neck kinematics, due to changes in passive neck tis-
sue biomechanics and/or in neuromuscular function, should be reflected in
head kinematics (Chao et al., Abstract 319, XIIth ISB, UCLA 1989). Tradi-
tional clinical measurements (e.g. ranges of motion; radiographs) appear
limited in their information content. In this study changes in head orien-
tation are essentially specified since the subject is asked to track targets
with a laser pointer coupled to the head. By systematically varying target
patterns, variation in helical screw axis parameters, and in particular the
location and direction of the axis of rotation, can be documented for a wide
variety of movements.

Mr Brodeur, Prof. An and Prof. Winters are Biomch-L subscribers; their email
addresses can be retrieved via the REVIEW BIOMCH-L (COUNTRIES command to

During the two days after the Miami ASB meeting, the Ninth Southern Biomedical
Engineering Conference took place at the same location. Also this conference
hosted a considerable number of Biomechanics presentations, and I'd like to
mention in particular the paper by S.K. Mishra & D.B. Goldgof, Department of
Computer Science and Engineering, University of South Florida in Tampa, FL/USA
entitled "Nonrigid motion analysis and its biomedical applications". The
paper "(...) describes a curvature-based approach to nonrigid motion analysis
which uses three-dimensional data". I did not have the opportunity to hear
its presentation, but this work might be extremely relevant in human motion

Finally, I'd like to mention that the next East Coast Clinical Gait Analysis
Meeting will take place at Prof. Soutas-Little's Department from 5-7 December
1990. I understand that the Proceedings will consist of 4-page papers instead
of the 1-page abstracts of the preceeding meetings (1989: Helen Hayes Hospital,
up-state New York; 1988: Penn State University).

Herman J. Woltring, Eindhoven/NL.