View Full Version : coupled motion/cross-talk

12-26-2002, 01:52 AM

Recently (Clin Biomech 16 (2001) 455-458) Hof et al. identified
'cross-talk' in the coupled cervical motion described by Feipel et al
(Clin Biomech 14 (1999) 462-470) and subsequently suggested a more
preferred Euler sequence that would minimize this 'cross-talk'.
However, Hof stated that their recommendation would work for one
sequence of motions, eg, flexion + axial rotation, (performed using a
'dummy' head and neck) but would not work for a different sequence, eg,
flexion + sidebending, of motions. Hof et al went on to conclude that
'as long as no solution is available that can exclude cross-talk
effects, any reported coupling effect in cervical spine motion should be
interpreted with extreme caution'.

I am investigating the 3D kinematics of the thoracic spine, and am
particularly interested in the coupling patterns of sidebending and
axial rotation. I would like to be able to describe with some degree of
confidence what these patterns are knowing that the issue of
'cross-talk' is ever present. Additionally, I would like to be able to
explain the mathematical phenomenon that causes this problem.

Hof el al has suggested that 'cross-talk' is a mathematical problem not
related to measurement methodology but does not say what the
mathematical problem is. So I am wondering if anyone in the
biomechanics community can more precisely describe the mathematical
problem (when using Euler angles) that causes 'cross-talk'?

I will post all responses.

Thank you.

Gordon J. Alderink, PT, MS
Program in Physical Therapy
School of Health Professions
319 Henry
Grand Valley State University
Allendale, MI 49401
Phone: 616.331.2674
Fax: 616.331.3350
Email: aldering@gvsu.edu

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