MinMax or polynomial muscle recruitment


the MinMax criterion should ensure muscle synergism. When we consider the StandingModel the back muscles may have the largest activities as they have to ensure the erect posture. What happens with regions like the hand with much smaller activities than maximum and no contribution to synergism to stand erect? Is it correct that the hand muscles don’t influence the objective and are thus perhaps not optimal?

When the hand muscles’ activities neither influence the maximum muscle activity nor the objective, whould a polynomial muscle recruitment be favourable as for a polynomial objective function all muscles influence the objective value?



Hi Thomaz,

I’m sorry because my answer may not be good to your question.

  1. Even in the StandingModel, if you can apply some amount of external force on the human hand, then the activation levels in the arm will be increased. Then these arm muscles will affect on the Min/Max criteria.

  2. Definitely when you use the polynomial muscle recruitment criteria, it will consider all muscle activation values in the system for the calculation of the objective function.

If you see the ‘Lesson5: Min/max Muscle recruitment’ chapter in the tutorial, there are some sentences like this:

The reason why the MinMaxStrict criterion is not the default in AnyBody™ despite its attractive properties for ergonomic investigations is that it switches muscles in and out very abruptly when they change moment arms from negative to positive. These sudden shifts may sometimes happen faster than physiologically possible and they also mean that muscles with just a marginally positive contribution will be activates to their full potential. As we have seen in the previous sections, lower order polynomial criteria do not have that type of behavior.
So if you don’t like this possible situation in your model, I would recommend you to use polynomial or quadratic muscle recruitment criteria.

Also you can choose the composite recruitment criteria between the min/max and the polynomial.

Best regards,