Specifications

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Not only is the shape of the graph different; the maximum activity is also significantly higher. An error of
10% in an anthropometric data value is not uncommon considering the accuracy of measurement methods
and variation between individuals, and if the influence on the final result is as strong as this, we would not
be able to trust our results. The problem is even more difficult if we desire to scale models up and down in
size: Muscles pass along complex paths from origin to insertion, and the lengths of these paths do not scale
in a simple fashion with, for instance, overall subject height.
As usual in biomechanical modeling, the solution can be found by relying on nature's ability to make the
best of its resources. Nature has not equipped humans with tendons whose lengths are very
disadvantageous for our normal activities. We can use this knowledge to calibrate the tendon lengths for an
individual of a certain size. Quite simply, we shall presume that the tendon lengths are calibrated by nature
to provide the muscles with optimum fiber lengths at certain postures. The AnyBody Modeling System
provides two ways to do that: One is cheap and dirty, and the other one requires additional information. Let
us take a closer look at them:
Cheap and dirty
Cheap and dirty is readily available. If you take a closer look at the list of operations in the study tree, you
will find one called MuscleCalibrationAnalysis.
If you run it, you will see the model moving as it does in the InverseDynamicAnalysis. But when the analysis
is done, the following message appears in the message window:
<address>The tendon length of muscle Main.MyModel.Muscle2 was calibrated. The muscle properties have
been updated. </address>