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Hi all, I set up the CMC and Static Optimization (SO) study with a subject performing a full gait cycle. The resulting muscle forces, matches pretty well with those presented in the literature. However, the result from CMC seem to have a lot more muscle activities during the swing phase, compare to the result from SO. In order to reduce the muscle forces in the swing phase of these muscles, activation constraints were needed. I attached the resulting muscle force from GMED muscle (combination of 'glut_med1_r','glut_med2_r','glut_med3_r'), see Figure 1. This figure shows the muscle force resulting from SO, CMC without activation constraints, and CMC with activation constraints added. The model we used in this study is a scaled model of Gait2345. I also attached the result from Lin's study (Figure 3 in Yi-Chung Lin, et al. "Comparison of different methods for estimating muscle forces in human movement", Journal of Engineering in Medicine), as a reference. See the "GMED" muscle. We have tried changing other settings in CMC, including changing the optimization routine used, the step size, trying different weighting on body segments, but they don't change the muscle activities significantly (and did not remove the excessive muscle activities in the swing phase). To make sure that this is not due to our collected subject data, I performed the same SO and CMC study on the data given in Gait2345 repository, and we obtain similar result. It appears that activation constraints is the only way in CMC to 'suppress' the unusual muscle activities during the swing phase.

My questions are:
1. Is activation constraint always needed for CMC and if this is a typical/normal practice to set up and run CMC?
2. Is there any other settings that I have missed in setting up the CMC study?