Specifications

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As you can see, the tendencies are much the same as before, but the muscular synergy is less outspoken in
the quadratic case, and the maximum muscle activity is therefore higher. Muscles recruited according to the
quadratic criterion will tire before muscles recruited according to the min/max criterion, but the difference
particularly for the activation envelope is not very dramatic. In any case, the AnyBody Modeling System
gives you the opportunity to pick the criterion you believe is the best.
The final lesson in the study of studies deals with muscle calibration.
Lesson 5: Calibration Studies
One of the challenges in body modeling is that models must be able to change size to reflect individuals of
different statures. Even if you are working on a model of a particular individual, you will almost always want
to change the dimensions of the model as you are building it. And if you are developing a generic model to
represent a range of body proportions, you are likely to want the model to depend on the anthropometrical
parameters you define. For instance, the weight of a segment is often represented as some fraction of the
full body weight. Such a property you could make parametric by simply defining it as a function of the full
body weight by means of a simple formula.
But other dimensions are more subtle and difficult to establish as a direct functional dependency of other
parameters. Tendon lengths are perhaps the most prominent example. If you are in doubt of the importance
of tendon lengths, just try to bend over and touch your toes with your knees stretched. Some of us have
hamstring tendons that are so short that we can hardly reach beyond our knees, so tendon lengths directly
limit our ranges of motion. But they also influence the working conditions of our muscles even when the
muscle-tendon unit is not stretched to its limit, so it is important that we define the muscle tendon unit so
that it fits the body model.
A muscle-tendon unit is attached to at least two segments at its origin and insertion respectively. To make
things worse, some muscles span several joints, and most muscles wrap over bones and other tissues with
complex geometries on their way from origin to insertion. So, the basic idea behind calibration of tendon