Dear Arno,

In order to avoid relative displacement of marker points with respect to the
underlying skeletal structures (due to skin movement), we use WLRT imaging
techniques to capture the entire back surface in 3D, and active contour
techniques to trace the skeletal structures from surface data [1]. Thanks to
the fact that you have more information available - the entire back surface
instead of marker points - a better estimation of vertebral rotation is

Dr. Hierholzer (Muenster, Germany) has published some articles on this
subject for static applications (e.g. scoliosis detection), and Diers
International (Wiesbaden, Germany) is commercializing the technique
(Formetric II). A European project (4D Bodyscan) has just started to extend
the applicability of the technique to dynamic applications in general;
furthermore several Belgian labs are currently involved in a study to
measure whole body vibration with this technique (Vibracom,

Please contact me if you need more information.

Best Regards,
Bart Haex

[1] T. Huysmans, B. Haex, R. Van Audekercke, J. Vander Sloten, G. Van der
Perre, R. Van Haute, J. Baeteman. 3D-postural analysis for the evaluation of
spinal deformations during sleep. Ergonomic software tools in product and
workplace design. A review of recent developments in human modeling and
other design aids. Edited by K. Landau, Verlag ERGON GmbH. Stuttgart, 2000,
ISBN 3-932160-11-8, 2000, pp 72-85.

Dr. Bart Haex
Div. of Biomechanics and Engineering Design
Department of Mechanical Engineering
Faculty of Applied Sciences
Katholieke Universiteit Leuven
Celestijnenlaan 200 A
B-3001 Heverlee
Tel: +32/16327057
Fax: +32/16327994

-----Original Message-----
From: Biomechanics and Movement Science listserver
[mailto:BIOMCH-L@NIC.SURFNET.NL]On Behalf Of Arno Grunendahl
Sent: woensdag 22 januari 2003 16:19
Subject: [BIOMCH-L] whole-body vibration

Dear colleagues,

today we measured the relative displacement of marker points, placed
along the spine, during jumping with a VICON-system.
The question is how can we calculate the relative displacement of single
vertebrae from the collected data, as it contains the displacement of
skin etc.
The global aim is to measure whole-body vibration, i.e. accelleration
and displacement would be relatively low.

Maybe somebody has dealt with the same problem and will share his/her

Thanks in advance,

A. Grunendahl
The king said sail, but the wind said no.

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