Dear Biomch-L readers/posters,

In reply to Karin Rosenberg's question on pelvic orientation (or attitude, as

I would prefer to call it) during stance, a very useful source is David H.

Sutherland, Richard A. Olshen, Edmund N. Biden, and Marilynn P. Wyatt, "The

Development of Mature Walking", MacKeith Press 1988, Blackwell/Oxford and J.B.

Lippincott/Philadelphia. One of the authors is a Biomch-L subscriber, and

the group is with the Children's Hospital in Frost Street, San Diego, Calif-

ornia. Some time last year, I posted a review of this book to the list (Mike

Whittle: my apologies -- I cannot seem to come around reviewing your book!).

Note that their graphs are expressed in terms of so-called `planes of move-

ment' (pp. 65-66):

"We have chosen to consider the familiar, laboratory-oriented planes

of movement used by physicians and physical therapists rather than more

complex concepts such as *Eulerian movement*[*] which would be familiar

only to engineers, mathematicians or physicists. A brief review will be

given for readers who may not be accustomed to the terms. In the context

of the laboratory, *sagittal* movement is in the direction of walk pro-

gression and is best viewed from the side; *coronal* movement is from

side tot side and is best viewed from the front or back; *transverse*

movement is about a vertical axis and the ideal viewpoint, although im-

practical, is from above or below the subject."

"[*] *Eulerian movement* related to the motion of each segment (rigid body)

to another or multiple other rigid bodies in space" [or to the spatial

reference coordinate system -- HJW].

Note that this approach is rather useful if the movement is the classical

paradigm of level, straight walking along, e.g., the X-axis of a laboratory-

defined, Cartesian coordinate system, for *segment* movement in particular

(i.e., segment position and attitude expressed relative to the laboratory

frame of reference). However, it is less attractive for *for joint movement*

as defined in this approach (i.e., differences of corresponding segment angles)

since these so-called `projection angles' will change even for a `fixed' joint

(unless it is in the neutral attitude, with equal projection angles for the

proximal and distal segments) if the subject as a whole -- or the laboratory

reference coordinate system -- changes orientation, e.g., by a rotation about

the vertical axis. Eulerian angles (or helical ones) do not suffer from this

disadvantage. Here, the engineers/mathematicians/physicists do have a mis-

sion, it seems.

An intermediate solution would be to define `projection plane joint angles'

as those angles where the attitude of a distal segment is viewed after re-

aligment of the laboratory reference system with the proximal segment's

coordinate system. This is, however, an interdisciplinary (`political')

compromise ...

Herman J. Woltring, Eindhoven/NL

In reply to Karin Rosenberg's question on pelvic orientation (or attitude, as

I would prefer to call it) during stance, a very useful source is David H.

Sutherland, Richard A. Olshen, Edmund N. Biden, and Marilynn P. Wyatt, "The

Development of Mature Walking", MacKeith Press 1988, Blackwell/Oxford and J.B.

Lippincott/Philadelphia. One of the authors is a Biomch-L subscriber, and

the group is with the Children's Hospital in Frost Street, San Diego, Calif-

ornia. Some time last year, I posted a review of this book to the list (Mike

Whittle: my apologies -- I cannot seem to come around reviewing your book!).

Note that their graphs are expressed in terms of so-called `planes of move-

ment' (pp. 65-66):

"We have chosen to consider the familiar, laboratory-oriented planes

of movement used by physicians and physical therapists rather than more

complex concepts such as *Eulerian movement*[*] which would be familiar

only to engineers, mathematicians or physicists. A brief review will be

given for readers who may not be accustomed to the terms. In the context

of the laboratory, *sagittal* movement is in the direction of walk pro-

gression and is best viewed from the side; *coronal* movement is from

side tot side and is best viewed from the front or back; *transverse*

movement is about a vertical axis and the ideal viewpoint, although im-

practical, is from above or below the subject."

"[*] *Eulerian movement* related to the motion of each segment (rigid body)

to another or multiple other rigid bodies in space" [or to the spatial

reference coordinate system -- HJW].

Note that this approach is rather useful if the movement is the classical

paradigm of level, straight walking along, e.g., the X-axis of a laboratory-

defined, Cartesian coordinate system, for *segment* movement in particular

(i.e., segment position and attitude expressed relative to the laboratory

frame of reference). However, it is less attractive for *for joint movement*

as defined in this approach (i.e., differences of corresponding segment angles)

since these so-called `projection angles' will change even for a `fixed' joint

(unless it is in the neutral attitude, with equal projection angles for the

proximal and distal segments) if the subject as a whole -- or the laboratory

reference coordinate system -- changes orientation, e.g., by a rotation about

the vertical axis. Eulerian angles (or helical ones) do not suffer from this

disadvantage. Here, the engineers/mathematicians/physicists do have a mis-

sion, it seems.

An intermediate solution would be to define `projection plane joint angles'

as those angles where the attitude of a distal segment is viewed after re-

aligment of the laboratory reference system with the proximal segment's

coordinate system. This is, however, an interdisciplinary (`political')

compromise ...

Herman J. Woltring, Eindhoven/NL