EMG Normalization

Hello everyone,

You cannot generally compare EMG of one muscle with another muscle or one trial with another trial without normalization. Normalizing data sounds difficult, but its computation is simple indeed. A common procedure of EMG normalization is normalizing pre-processed EMG data with task-related MVC (Maximum Voluntary Contraction) EMG. The task-related means that a movement of trials should be similar with a movement of MVC trials. I collected EMG of hamstring curls, so the MVC trial should be the maximum contraction in hamstring curl. 

Procedure

1, Pre-processing

I am explaining how to pre-process data on my other blog and YouTube video, so please go check them out !!

Takashi's Study Abroad

EMG on Nordic Hamstring Curl - Filtering, Rectifying, Enveloping -

https://ryuugaku-abc.site/emg-on-hamstring

Hello everyone, Have you ever imagined visualizing muscle forces ?? There are many ways, but electromyography aka EMG is just one way. It detects action potentials on muscles and shows signal waves as an output. As a simple example, the bigger waves, the more muscle force. In this blog, I will show you how to collect and analyze EMG data.  What does EMG look like ??You can watch the video applying EMG on hamstring. On the video, 2 small poles detect action potentials, and 1 blue box...

Raw data looks like this …

2, Normalization

Procedure is simple. We just need to divide pre-processed EMG data with peak pre-processed MVC EMG data. Therefore, y-axis is now in % of peak MVC EMG. The plot looks like this …

The plot above is normalized data, and the plot below is just pre-processed data. As you can see not so much different, but you cannot compare right bicep femoris with left semitendinosus on the plot below. However, you can make the comparison with the plot above. 

My YouTube video

I am explaining all procedures on my YouTube video, so please check it out!!

MATLAB code and EMG data

MATLAB code and EMG data

Enjoy!