Introduction to Scaling

Scaling Tutorials

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

• Lesson 1: Joint to Joint Scaling Methods
• Lesson 2: Scaling based on External Body Measurements
• Lesson 3: Scaling using segmental scaling vectors

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.

Size related parameters of models in the AMMR 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:

Scaling law	Description
ScalingStandard	scale to a standard size; i.e. use 50th percentile sizes for a European male
ScalingNone	do not scale; i.e. use underlying cadaveric dataset as is
ScalingUniform	cale segments equally in all directions; input is joint to joint distances
ScalingLengthMass	scale taking mass into account; input is joint to joint distances and mass
ScalingLengthMassFat	scale taking mass and fat into account; input is joint to joint distances
ScalingXYZ	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”.

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:

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:

#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.

Next lesson:

Now head for Lesson 1: Joint to Joint Scaling Methods.