Dear Marcelo,

I think the 3D motion analysis is an accurate method to estimate COM during gait cycle. In addition, the force platform is a good for estimating stance phase if you want to know more about ground reaction force.

Best regards,

Hello Marcelo,

I agree with Abdelrahman. If you want to estimate the coordinate of COM for wholebody, The 3D motion analysis by using accurate system is the best method

I agree with you. However, tell me about the others possibilities to estimate it. Indeed, for example,  through the COP analysis its possible too or using an accelerometer attached on the pelvis. Can you send me some papers about these methods?

See the following papers:

1- SEJDIĆ, E., LOWRY, K. A., BELLANCA, J., PERERA, S., REDFERN, M. S., & BRACH5, J. S. (2016). Extraction of Stride Events From Gait Accelerometry During Treadmill Walking. IEEE, 4.

2- Querido, A., Castro, M. P., Vilas-Boas, J. P., Corredeira, R., Daly, D., & Fernandes, R. J. (2016). Reliability and accuracy of spatial-temporal gait parameters measured by the WalkinSense(R). Proceedings of the Institution of Mechanical Engineers, Part P: Journal of Sports Engineering and Technology.

3- Mummolo, C., Park, S., Mangialardi, L., & Kim, J. H. (2015). Computational evaluation of load carriage effects on gait balance stability. Comput Methods Biomech Biomed Engin, 1-10.

4- Bolink, S. A. A. N., Naisas, H., Senden, R., Essers, H., Heyligers, I. C., Meijer, K., & Grimm, B. (2015). Validity of an inertial measurement unit to assess pelvic orientation angles during gait, sit–stand transfers and step-up transfers: Comparison with an optoelectronic motion capture system*. Med Eng Phys.

5- STAAB, W., HOTTOWITZ5, R., SOHNS, C., SOHNS, J. M., GILBERT, F., MENKE, J., . . . LOTZ, J. (2014). Accelerometer and Gyroscope Based Gait Analysis Using Spectral Analysis of Patients with Osteoarthritis of the Knee. J. Phys. Ther. Sci., 26, 997–1002.

if you need any help don't hesitate.

Thank you very much!

Oi Marcelo, Tudo Bem

The COM is based on the mass distribution in a segment. For multi segment bodies (the whole person) it is the weighted based on each segments individual mass and geometry.  COM and Center of gravity are also not exactly the same. Do determine the COM you need data on each segment – their length and mass distribution. Motion capture programs that calculate COM have anthropometric data from cadaver studies in their software and you tell them the length of the segments and the body weight of the person – that's how they calculate. To get an accurate estimate for COM you need the anthropometrics of all the body segments. 

Also there are some problems 1. The cadaver studies are very old and have some errors 2. When limbs are moved quickly (swinging your arms) the blood and fluid in the limb may shift so that the mass distribution is not exactly static.3. depends how accurately you can measure segment lengths.

Regarding accelerometers –placing an accelerometer on the limb will not tell you COM without additional data – you need to the length and weight relative to the body wt.

Finally, in many biomechanics classes students calculate COG using the “reaction board” method – you can search for this and see how its done, and there are many good websites that explain these concepts.

Tchau

Kevin

Hello Kevin,

How to use “reaction board” method to estimate COM in walking . you can help us and put the links of this Websites 

I agree with all friends about using 3D motion analysis and the following site will help you

https://www.xsens.com/images/stories/PDF/ambulatory%20estimation%20of%20center%20of%20mass%20displacement%20during%20walking.pdf

http://www.ncbi.nlm.nih.gov/pubmed/16458379

www.clinicalgaitanalysis.com/bodybuilder/Johan.doc

http://journals.humankinetics.com/AcuCustom/Sitename/Documents/DocumentItem/16111.pdf

http://www-personal.umich.edu/~artkuo/Papers/HMS04.pdf

https://www.designsociety.org/download-publication/29655/trajectory_of_the_human_body_mass_centre_during_walking_at_different_speed

http://www.sciencedirect.com/science/article/pii/S016794570300085X

http://www.sciencedirect.com/science/article/pii/0966636295010580

http://www.sciencedirect.com/science/article/pii/S0167945705001004

http://www.gaitposture.com/article/S0966-6362%2802%2900192-3/pdf