Hi,
I have been using the GaitLowerExtremity and AnyGait models in Anybody. I had a question about 2 of the parameters used without reference in the script.
In the HumanModel.any file there is a variable called StrengthIndexLeg = 1.53. This is multiplied by the max stress in the muscle fiber (27N/cm^2). Is there a reference for where this factor of 1.53 originated and why it is being used?
Also, in the LengthMassFat scaling, the term R_other=0.5 is used to estimate the percentage of body composition that is not fat or muscle. Is there a reference for this anywhere?
as far as I know, John explained that in his WebCast a while back:
Anthropometrical Scaling of Musculoskeletal Models (John Rasmussen, 19. March, 2009) Presentation (0.5Mb), Playback (28Mb), Get WebEx Player
This webcast presents ongoing work on reliable scaling of models to represent individual subjects or percentiles of the population. The scaling is in terms of body dimensions as well as strength, and new results and features are presented in terms of scaling to bony landmarks and scaling based on motion capture data.
Hi Amir,
Yes I have watched the webcast, and there are no references for those terms. I received a reply from John R as to how they came about.
I’m having trouble using the ChartFX in AnyBody. Besides it crashing when I try to manipulate the chart, when I put the mouse over individual curves to see what they are, the box next to the cursor cuts off short so that I can’t see the full name. I have attached a screenshot so that you can see what I mean by this.
I just watched the WEbcast as well and you are right, he is mentioning the values there but not saying where they come from
About ChartFX:
ChartFX is an external software we use in AnyBody, the more advanced AnyBody gets, the more trouble ChartFX is making. We do NOT have under control what CHartFX is doing and we can not change ChartFX’s behavior… I have to warn you, we are even planning in v5.3 or the next release to remove ChartFX. We recommend AnyChart instead, I know it takes some adjustments, but it is worth it…
For other users the answer to the first question from John:
In the case of the strength scaling factor of 1.53, it came about because we had a set of original anatomical data from the TLEM model provided by a cadaver study from the group in Twente. These data led to an unrealistically small strength in the lower extremity, and we experimented with how far it was from published strength data (I do not remember where from). Then we came up with the scaling of 1.53 to put the strength into the realistic domain.
Right now we are working closely with the Twente group to produce new and more realistic sets of original cadaver data, which will hopefully get the strength right without adjustment factors.
The r_other ratio of 0.5 was adapted from several textbooks, references and we tried to find data for the different contributions. I expect it varies quite a bit between individuals, so the number 0.5 is really a guesstimate.
Like anything else in AnyBody, you can of course change these numbers if you think you have more precise values.
