asymmetricity of muscle activations

[Hamidreza Aftabi]

Dear all

I have a few questions about running gait analysis using CMC algorithm and I would be grateful if you could help me.
As we know running is a symmetric gait and as a result, activations of muscles should also be symmetric, but for example it is obvious in the Fig4 of "Simulating Ideal Assistive Devices to Reduce the Metabolic Cost of Running" which is written by Prof. Uchida that the activations of the lower extremity muscles are not symmetric ( activation in the 0% of the gait cycle should be close to the activation in the 100% of the gait cycle because running is symmetric, but in some muscles, for example, GAS MEDIALIS, the difference between these 2 points is very high). There are many other papers that confirm this problem, for example, "Full body musculoskeletal model for muscle driven simulation of human gait" written by Apoorva Rajagopal. This problem might happen because of RRA algorithm which modifies the kinematics and also because of CMC algorithm which uses first 0.03 second of the gait cycle to solve muscle equilibrium equation, but it can not justify the high difference between these 2 points. Is this a critical issue? if it is critical how can we justify it? would you suggest any paper about this issue which I can cite in my paper?

please note that the Fig4 of the aforementioned paper is attached.

Once again, I really would like to express my thanks for your time in assisting me.

Sincerely

[Thomas Uchida]

activations of the lower extremity muscles are not symmetric ( activation in the 0% of the gait cycle should be close to the activation in the 100% of the gait cycle because running is symmetric

There are several possible reasons for this, but also note that people are not exactly symmetric in reality and there is some variability between strides. If exactly cyclical results are critical for your study, you could design an algorithm that enforces this constraint (OpenSim does not by default).

Is this a critical issue?

It depends on your research question. In our study, we were interested primarily in trends between unassisted running and running with different idealized devices. There were several limitations of our study (described in the "Study Limitations" section on pages 14 and 15) which should also be considered.

would you suggest any paper about this issue

Hicks et al. (2015) discusses the importance of ensuring that a model and simulation are appropriate for answering a given research question:

Hicks, J.L., Uchida, T.K., Seth, A., Rajagopal, A., Delp, S.L. Is my model good enough? Best practices for verification and validation of musculoskeletal models and simulations of movement. ASME Journal of Biomechanical Engineering 137(2):020905, 2015. https://nmbl.stanford.edu/publications/ ... ks2015.pdf

[Hamidreza Aftabi]

Dear Prof. Uchida
Many thanks for your assistance. I really appreciate the information and advice you have shared.
Sincerely,
Hamidreza