Table 4 Summary of geometrical scaling techniques

I

Anthropometric Measurements

The lengths of the segments (\(\:{L}_{S}\)) needed for the calculation of \(\:{k}_{L}\) in the length-mass scaling law are measured externally from the subjects using measuring tape.

This is an easy-to-implement, low-cost approach.

However, measurement errors for segment lengths are significant.

II

Linearly Scaled Model

This model scaling process involves minimizing the sum of residuals between the marker locations on the subject and those on the generic model.

The primary drawback of this method is its inability to accommodate nonlinear differences between the generic model and the subject.

Anatomical Landmark Scaled Model

In this approach, a stick figure is initially generated from a standing reference trial, with joint centers determined from markers on bony landmarks. Subsequently, the generic model undergoes morphing to align with the stick figure utilizing radial basis functions.

This method offers the advantage of not necessitating extensive functional trials to identify bony landmarks or parameters.

Nonetheless, its accuracy is dependent upon precise marker placement.

Kinematically Scaled Model

This approach utilizes both static and dynamic functional trials to generate a stick figure representation of the subject, enabling automatic identification of joint centers without dependence on markers located on bony landmarks. Subsequently, the generic model is adjusted to match the stick figure using radial basis functions.

One drawback of this method is its reliance on extended functional trials of the subject, which may not always be feasible.

III

Medical Imaging Scaling

This cutting-edge scaling technique uses the MRI or CT scan images of the subjects to determine joint centers, segment lengths, and other data.

Despite its excellent accuracy, this is a time-consuming and expensive procedure.