Adjusted Zatsiorsky-Seluyanov's segment inertia parameters

While the original Zatsiorsky-Seluyanov segment inertia parameters (1983) used bony landmarks as reference points, de Leva (1996) adjusted these parameters using joints centres instead, more commonly used in biomechanics. This page lists these adjusted parameters and describes how to used them in Visual3D.

Segment Mass

Relative to total body mass.

Segment	Female	Male
Head	0.0668	0.0694
Trunk	0.4257	0.4346
Upper arm	0.0255	0.0271
Forearm	0.0138	0.0162
Hand	0.0056	0.0061
Thigh	0.1478	0.1416
Shank	0.0481	0.0433
Foot	0.0129	0.0137

Segment Centre of Mass Location

Relative to the segment's proximal endpoint.

Segment	Female	Male
Head	0.4841	0.5002
Trunk	0.4964	0.5138
Upper arm	0.5754	0.5772
Forearm	0.4559	0.4574
Hand	0.7474	0.7900
Thigh	0.3612	0.4095
Shank	0.4352	0.4395
Foot	0.4014	0.4415

Segment Radii of gyration

Segment	Female			Male
	IXX	IYY	IZZ	IXX	IYY	IZZ
Head	0.271	0.295	0.261	0.303	0.315	0.261
Trunk	0.307	0.292	0.147	0.328	0.306	0.169
Upper arm	0.278	0.260	0.148	0.285	0.269	0.158
Forearm	0.261	0.257	0.094	0.276	0.265	0.121
Hand	0.631	0.454	0.335	0.628	0.513	0.401
Thigh	0.369	0.364	0.162	0.329	0.329	0.149
Shank	0.267	0.263	0.092	0.251	0.246	0.102
Foot	0.299	0.279	0.139	0.257	0.245	0.124

Modifying the Inertial Values using the Adjusted Zatsiorsky-Seluyanov's parameters

Below images show the default segment properties (on left) and the modified segment properties (on right). The modified segment properties reflect Zatsiorsky's adjusted segment properties for a female's right thigh.

ORIGINAL
This is an example of the original properties using Hanavan's geometric model.

MODIFIED
This is an example of the modified properties using De Lava's values.

1. Change the segment geometry to CUSTOM_SEG

2. To modify the Mass, replace the mass factor from the current equation (0.1* Mass) to Zatsiorsky-Seluyanov mass value(For example: “0.1478 * Mass” for a female thigh segment).

3. To modify the Inertia Values, the expression has to be entered as: “m*r^2”
Where m is the segment's mass parameter, and r is the IXX, IYY or IZZ radius of gyration parameter. The radius of gyration in De Lava's paper is presented as a percent of segment length, so this value must be multiplied by the length of the segment.

For example, to use the Zatsiorsky-Seluyanov's Inertia Values for the right thigh for a female subject, the following expressions would have to be entered in the IXX, IYY and IZZ fields.

IXX = ( 0.1478*Mass ) *((RTH_SEG_LENGTH * 0.369 )^2)
IYY = ( 0.1478*Mass ) *((RTH_SEG_LENGTH * 0.364 )^2)
IZZ = ( 0.1478*Mass ) *((RTH_SEG_LENGTH * 0.162 )^2)

4. To modify the location of the center of mass according to Zatsiorsky-Seluyanov's parameters, replace the factor from the current equation (0.444004 * RTH_Seg_Length in the above image) with the corresponding Centre of Mass location parameter (for example: “0.3612 * RTH_Seg_Length” for a female thigh segment).

The segment length (RTH_SEG_LENGTH) is listed under the Subject Data / Metrics tabs. This value is automatically created when a segment is created.

Reference

de Leva (1996) Adjustements to Zatsiorsky-Seluyanov's segment Inertia Parameters. Journal of Biomechanics Vol.29 No. 9. pp.1223-1230.

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