====== Adjusted Zatsiorsky-Seluyanov's segment inertia parameters ======

While the original Zatsiorsky-Seluyanov segment inertia parameters (1983) used bony landmarks as reference points, [[https://doi.org/10.1016/0021-9290(95)00178-6|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.

===== The Adjusted Parameters =====

^ 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 ^ ^ ^ ^ ^ ^ ^
^         ^Female^     ^     ^Male ^     ^     ^
^Segment  ^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 Inertial Values within Visual3D =====

The images below show the default segment properties on the left and the modified segment properties on the 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.\\ {{:HanavanInertialProperties.png}}  |  __**MODIFIED**__\\ This is an example of the **modified** properties using De Leva's values.\\ {{:deLevaInertialProperties.png}}  |

**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.

===== See Also =====

Visual3D's default segment parameters are derived from [[visual3d:documentation:modeling:segments:segment_mass#default_segment_mass|Dempster's 1955 equations]].

===== Reference =====

  * de Leva (1996) Adjustments to Zatsiorsky-Seluyanov's segment Inertia Parameters. **Journal of Biomechanics** Vol.29 No. 9. pp.1223-1230. [[https://doi.org/10.1016/0021-9290(95)00178-6|DOI]]
  * Dempster, W. T. (1955). Space requirements of the seated operator, geometrical, kinematic, and mechanical aspects of the body with special reference to the limbs (No. WADCTR55159) [[https://hdl.handle.net/2027.42/4540|link]]
  * Zatsiorsky, V. M., & Seluyanov, V. (1983). The mass and inertial characteristics of the main segments of the human body. In H. Matsui & K. Kobayashi (Eds.), Biomechanics VIII-B (pp. 1152-1159). Baltimore: University Park Press.