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

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~

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

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~

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

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~

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

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~