Krisanne E. Bothner

02-21-1997, 08:47 AM

THE QUESTION:

What could account for a *dramatic* difference between the ankle

muscle moment when it is calculated using the equation of motion for the

shank compared to the moment when it is calculated from the equation

of motion of the foot?

THE BIOMECHANICAL MODEL

Consider a four segment planar model of a human (two feet, two

legs, two thighs and HAT) for the purpose of an inverse dynamics analysis

of standing balance. The equations of motion for this system can be generated

for each segment, and we are able to solve for the residual torque, as the

generalized muscle moment, acting at each of the three joints. By the

nature of

this approach, one can use either the shank segment or the foot segment

to solve for the generalized muscle moment acting at the ankle. My question

to the list is AGAIN: Given this biomechanical model, what might account for

a *dramatic* difference between the ankle muscle moment calculated using

the equation of motion for the shank compared to the calculated from the

equation of motion of the foot?

As usual, a summary of replies will be posted.

Krisanne Bothner

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--------------

Krisanne E. Bothner Motor Control Laboratory

Dept. of Exercise & Movement Science 330 Gerlinger Hall

1240 University of Oregon voice: 541.346.0275

Eugene, Oregon USA 97403-1240 FAX: 541.346.2841

What could account for a *dramatic* difference between the ankle

muscle moment when it is calculated using the equation of motion for the

shank compared to the moment when it is calculated from the equation

of motion of the foot?

THE BIOMECHANICAL MODEL

Consider a four segment planar model of a human (two feet, two

legs, two thighs and HAT) for the purpose of an inverse dynamics analysis

of standing balance. The equations of motion for this system can be generated

for each segment, and we are able to solve for the residual torque, as the

generalized muscle moment, acting at each of the three joints. By the

nature of

this approach, one can use either the shank segment or the foot segment

to solve for the generalized muscle moment acting at the ankle. My question

to the list is AGAIN: Given this biomechanical model, what might account for

a *dramatic* difference between the ankle muscle moment calculated using

the equation of motion for the shank compared to the calculated from the

equation of motion of the foot?

As usual, a summary of replies will be posted.

Krisanne Bothner

----------------------------------------------------------------------------

--------------

Krisanne E. Bothner Motor Control Laboratory

Dept. of Exercise & Movement Science 330 Gerlinger Hall

1240 University of Oregon voice: 541.346.0275

Eugene, Oregon USA 97403-1240 FAX: 541.346.2841