B6. General Points

-should foot-line be a fundamental parameter?

-allows for the expression of step/stride/walking base as a 2D and 3D vector equation.

-“induced stress” experiments may help in diagnosis

-static analysis of movements outside points and lines, like lateral knee joint movement and step-out-line, may be revealing

-the point and line projections must be purely vertical wrt the plane of interest

-if time profile-some joint and other rotations give equivalent values in the 2D

-computer modeling-rigid frame and introduce rotations sequentially

-degrees of freedom wrt parameter changes

-standard orientation not along foot-line, but "push-off-line", even though the start and reference foot models' foot-lines are parallel to the straight line at heel-contact.

-for modeling, show how variations in each fund. parameter affects other measured distances like, step, stride, etc.

-have to determine how it fits in, how it can be applied effectively to each area

-the 2D projection of points other than the minimum 4 may show periodicity with respect to changes in the primary elements.

-at first, do measure at heel-strike and heel-point contact, if possible, heel-point not at the bone, but is contact point with the floor. Any of several choices for heel-point, but contact with the floor may be best, since that's most easily measurable without equipment

- for different str in sequential steps, 2 models at heel-point with the different str values, both in standard orientation, each the reference for it's appropriate step, heel-points can then be related like an aberration

-body motions, momentum, etc. have to be studied to determine effect on parameters

-negative step?, no-no step, shortened to 0 carry

-there may be some simplifications which can be applied for quicker analysis, if the required equipment is unavailable. This would have to be determined.

-there are physical constraints relevant which may limit the ranges of one or more of the parameters wrt one or more of the others.

-applied to running - last heel-point position when rear-foot leaves the ground to the rear-pelvic joint at the next heel-contact (two snapshots needed per step, step-heel contact and rear-foot leave ground (ie. the start/stop for aberrations).

- though new, can be immediately applied to all levels of gait analysis because it can track walking patterns over any period of time, without the need to compare to standards, since it's only a measurement system. But, comparison to standards will be important in the full analysis, so a relevant database would be very useful.

-the orientation of the upper body greatly confuses the interpretation of direction changes over the path. But, the upper body pointing "straight ahead" doesn't mean the person is walking a straight line. And, a person who places each foot on it's appropriate straight line for every step isn't necessarily walking straight in each step, and probably usually isn't.

-The lower frame defines both direction and distance through the varied relationship between the 4 minimum points (and foot-line).

C. Quadrupeds

The biped is the simplest normal gait system to model. The same general strategy should apply to quadrupeds, or any multi-ped, but the system is a fair bit more complicated. Modeling would be much more complicated, but the measurements very similar.

It may be best to think of the quadruped as two connected "biped sets". All the parameters would be derived from tracking the 8 minimum points of quadruped gait, the front and rear would both have the same minimum 4 points as for biped gait.

The line of connection, the spine-line, is from the center of the front "shoulder-line" to the center of the rear pelvis-line. Though this represents the spine, it should be a straight line connecting the shoulder and pelvis-line centers, and it may be desirable to define the measures related to this connection as fundamental parameters.

Spine curvature would be seen as an apparent rotation of the spine-line, as well as apparent rotation of the shoulder and /or pelvis-line at the centers, both leading to direction change, as well as a decrease in apparent spine length.

The development of this application would be much better using experimental data. It's easy enough to choose points to track in the 2D plane, but the order of heel-contact may vary, and organizing the direction relationships more complicated.

Comparison of snapshots at each heel-contact, with identification of the 8 points, as well as the time of each foot contact, will make it much easier to determine the proper procedure for application. But, it's still just tracking points in 2D. Each snapshot is a reference grid, and how the various lines and angles are related to overall gait, within each step and over sequential snapshots, requires consideration of what factors are considered important for that study, and what generalizations, standard positions and/or values are desired or available.

The establishment of the 2 “standard start positions” should be similar to biped, but there would be many more “straight lines over the step”, representing sequential direction changes.

This would be a very challenging area of research at the beginning. Once standard procedures are established, though, it should be as easily applied as for biped gait.

D. Acknowledgements

Very many thanks to Walter Muma, Jean Hurrle and Gammon Earhart for their contributions to this effort. Jean and Gammon for very productive discussions to focus and clarify the work on the trapper and clinical sides, resp, and Walter for putting up with a lot to publish the article and revisions on his Wildwood Survival web-site.

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