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Dear Opensim support,
for my thesis project I have to compare the differences in the length of the muscles of children with CP and in the control group. I have scaled the model, loaded the motion and performed the Analyze tool. I want to study the muscle-tendon length but I don't know how to normalize the values between the subjects for comparing the results. I can't understand if I should use the normalized fiber length or not.
Thank you very much
Best regards
Giulia

Hi, for between subject comparison, you need dimensionless quantities. For Length (e.g. stride length or muscle-tendon length), it is suggested to be normalized by the subject's body height or leg length.

In case of rigid tendons, fiber length = muscle-tendon length - tendon slack length. So, they have similar pattern during movement. NORMALIZED fiber length = fiber length / its OPTIMAL length

Hof, A.L. (2018). Scaling and Normalization. In: Handbook of Human Motion. Springer, Cham. https://doi.org/10.1007/978-3-319-14418-4_180

Thank you very much!!!
Best regards
Giulia