Seated Human: Disc Pressure and Back Muslce EMG


As the EMG signals or muscle activities change over time for a fixed sitting position either you do anything or not. Without any activities for a fixed posture, do the muscle activities, the inter-vertebral disc pressures or forces produced for back muscles (lumber region) by the Seated Human Model change over time? If it is changed over time, where do I modify the model to manipulate the duration of study?

Note: I am going to evaluate different sitting postures for prolonged data entry tasks in a computer workstation. The study period is 4 hours with 15 minutes break after two hours.



Dear Shaheen,

Currently there is no such setting by default, fatigue is not implemented into the system .
We just had a little brainstorm about your project. We had following idea, however, further complications might appear on the way to success:

You could use the muscle strength of the used muscles and reduce them over time. Intervertebral disc pressure and all forces are affected by the muscles. An idea would be to run the model for a certain time interval, check muscle activities, if they are higher than a certain limit, reduce them for the next time interval.

A useful tool for that might be the AnyDesEvalStudy.

Hope that helps and gives you new ideas…

Thank you very much Amir. I will definitely try that.

Next Question about the “Seated Human Model”.

Here is the scenario: I am going to collected pressure map data for four hours. Each pressure map has total 16X16=256 cells. Each cell is about one inch square size. This system can collect maximum 40 frames per second (40HZ). The data looks like this
Time (seconds) Pressure (Newton/meter square)
0.01 80 100…up to cell 256
0.04 60 100…up to cell 256
0.07 79 95…up to cell 256

as many hours as you want…

I am going to use two pressure maps: one for seat pan and one for seat backrest angle. Is there any way, I can use this data to run the model over time instead of fixed force plate data that is currently included in the model? I believe that this would change the muscle recruitment patters in the “Seated Human” as the pressure is changed either at buttock or at back. I also believe that this would provide muscle activities or disc pressure close to the experimental values.

Any idea? Anything will be highly appreciated.



Dear Shaheen,

In general these force pressure maps can be used. My colleague is currently setting up something similar for feet with pressure-map insoles. I will refer your post to him…

Hi Shaheen,

As Amir said this is perfectly doable. You can recreate the pressure maps on the model with a grid of AnyRefNodes on the seat and back rest representing the center of each cell. Then import your data with AnyFunInterpol and apply the force from each cell/node to the corresponding body part with AnyForce3D class for example.

Best regards, Sylvain.

thanks a lot