intro.md

(scaling-intro)=

# Introduction to Scaling

:::{sidebar} Scaling Tutorials

The three tutorials covers the different scaling 
methods shown in the table below:

```{toctree}
:maxdepth: 1

lesson1
lesson2
lesson3

```
:::

Musculoskeletal models must be scalable to sizes of different
individuals to be useful for product design. Scaling pertains not only to the overall geometry,
but also muscle insertion points, muscle parameters, wrapping
surfaces etc. AnyBody has a both generic and user-define scaling laws for models in the repository.

For details on scaling theory behind please take a look at [Rasmussen 2005](https://paperpile.com/shared/4znHWd).

Size related parameters of models in the {doc}`AMMR </index>`
are seldom defined as constant numbers, but instead computed from global measurements
(e.g., total height, weight of human) based on a scaling law. Thus all body models
expect the definition of a scaling law, although user can
choose the actual law.

Currently there are six pre-defined scaling laws available in AnyBody:


```{eval-rst}
.. list-table::
   :widths: 3 7
   :header-rows: 1

   * - Scaling law
     - Description
   * - :any:`ScalingStandard <_SCALING_STANDARD_>`
     - scale to a standard size; i.e. use 50th percentile sizes for a European male
   * - :any:`ScalingNone <_SCALING_NONE_>`
     - do not scale; i.e. use underlying cadaveric dataset as is
   * - :any:`ScalingUniform  <_SCALING_UNIFORM_>`
     - cale segments equally in all directions; input is joint to
       joint distances
   * - :any:`ScalingLengthMass <_SCALING_LENGTHMASS_>`
     - scale taking mass into account; input is joint to
       joint distances and mass
   * - :any:`ScalingLengthMassFat <_SCALING_LENGTHMASSFAT_>`
     - scale taking mass and fat into account; input
       is joint to joint distances
   * - :any:`ScalingXYZ  <_SCALING_XYZ_>`
     - scale taking mass and fat into account; scale segments along X, Y, Z axes;
       input is scale factors along X, Y, Z axes.
```

**Please also notice that each scaling law scales the strength of the
muscles, in addition to the size and mass of the bone.** This strength
scaling is done automatically in most cases. We will come back to it
when needed. Users who need a more comprehensive introduction can view
this recorded previous webcast titled [“Anthropometrical Scaling of
Musculoskeletal
Models”](https://www.anybodytech.com/download/anthropometrical-scaling-of-musculoskeletal-models).

## Overwriting default input parameters

After selecting a scaling law, the user can override the default input
parameters. All input parameters can be accesed in the
`Main.HumanModel.Anthropometrics` folder.

For example, to adjust the height of
the model, the user can add the following code to the `Main` file:

```AnyScriptDoc
Main.HumanModel.Anthropometrics.BodyHeight = 1.8; // overwrites the default value
```

### Using legacy `AnyMan.any` files

To keep backward compatibility with older models, AnyBody still supports using custom `AnyMan.any` files.
You can specify your own file with by setting the `BM_SCALING_ANTHRO_FILE` BM statement:

```AnyScriptDoc
#path BM_SCALING_ANTHRO_FILE "My_Own_AnyMan.any"
```

This method is not recommended for new models, but it is still supported for older models.

:::{admonition} **Next lesson:**
:class: seealso
Now head for {doc}`lesson1`.
:::

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