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Young-tae Lim
02-16-1998, 04:23 PM
Dear BIOMECH-L subscribers,

Currently, I am working on a project which involved the computation of
joint resultant torque and force at the L4-L5 level during a golf swing.
Generally, the inverse dynamics method with ground reaction force (GRF) is
used to calculate these parameters. However, as Dr. Dapena and Dr. Hatze
mentioned these problems last June (1996), this approach may produce a lot
of errors (for example, the errors from joint center digitization, from
estimation of center of mass of each segment, and etc.). The linear and
angular velocities and accelerations from the first and second derivatives
of the displacements would be another source of error.
If then, my questions are:

a) Can I use static (or quasi-static) model with GRF to calculate joint
resultant torque and force at L4-L5? In my case, the golf swing is a kind
of closed loop kinetic chain motion(?). In other words, two feet are on
the ground during the motion. So the influences of moment of inertia and
linear acceleration of each segment would be minimal. I think, the error
occurring from using this static model could compromise the error
introduced from the inverse dynamics approach.

b) What is the definition of quasi-static model? Is this as same as
quasi-dynamic model?

As always, I will post a summary of responses. Thanks in advance.

Sincerely yours,

Young-tae


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Young-tae Lim

Department of Kinesiology Tel: (217) 333-6398
241 Louise Freer Hall (MC-052) Fax: (217) 244-7322
960 S. Goodwin Ave. E-mail: y-lim2@students.uiuc.edu
University of Illinois
Urbana, IL. 61801
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