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EMG integration in MVN

MVN 2020.2 has the ability to integrate EMG data with the MVN software. 

This integration allows you to record EMG data and motion capture data using only MVN. You will also be able to plot live graphs in MVN and export the data into different formats.

In this article, you will find the steps on how to integrate EMG signals with MVN. 

 

We recommend placing the EMG sensors first and then placing the Xsens sensors. This is due to the precision needed for the placement of the EMG sensors whereas the placement of the Xsens is more flexible.                 

 

Skin interface" adhesives for Delsys Trigno EMG system                                    Cometa Systems | Wireless EMG and IMU solutions

 

 

First time use

If you are using EMG integration with MVN for the first time, you will need to complete the following steps.

 

Cometa: 

If using the Cometa system for the first time with the MVN software, you will need to install the drivers from the USB flash drive included with your Cometa system. After installation, the USB flash drive will no longer be needed.

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More details on Cometa system: https://base.xsens.com/hc/en-us/articles/360017536700-EMG-Integration-in-MVN-Cometa

 

Delsys: 

For the Delsys system, the required drivers will be automatically installed when installing MVN 2020.2 or above. Then, you can only run Xsens to record EMG data and motion capture data. However, it is important to notice that after installing MVN 2020.2, you will no longer be able to run the Delsys software. This is currently due to an incompatibility between both software, which will be fixed with the new release of the Delsys software. 

 

More details on Delsys system: https://base.xsens.com/hc/en-us/articles/360017588279-EMG-Integration-in-MVN-Delsys

 

Set up the EMG system

First, connect the receiving station for the EMG system to the computer.  Then, follow guidelines about skin preparation and sensor placement for EMG systems. The most common guidelines to follow in Europe are provided by Seniam project (http://www.seniam.org/). However, you can also follow other guidelines that are suitable for EMG sensor placement. 

 

1 - Skin Preparation:

The skin of the participant needs to be prepared in order to get a good electrode-skin contact. A good electrode-skin contact is important to obtain better SEMG-recordings (in terms of amplitude characteristics), fewer and smaller artefacts (electrical interference), less risk of imbalance between electrodes (smaller common mode disturbance signal), and less noise (better S/N ratio). Different skin preparation techniques are used and reported in literature: shaving, cleaning with alcohol, rubbing with gel, and abrasion with sandpaper.

 

2 - Sensor Placement:

Depending on the EMG system you use, different guidelines may be applied. However, it is important that in surface EMG the recommended muscles to measure are the larger and more superficial muscles. It is important to know how to palpate the muscles to ensure that the sensor is placed in the belly of the muscle. On the Seniam website you can find information about the exact placement and how to find the correct placement of each sensor for each muscle.

For further information on sensor placement, please visit the corresponding website:

- Cometa system: https://www.cometasystems.com/resources/video

- Delsys system: https://delsys.com/support/documentation/#qsg

 

Set up Xsens hardware

The most convenient Xsens motion capture system to use with an EMG system is the Awinda system, since all the sensors communicate wirelessly. However, you can also use the Link system and use a strap set to fix the sensors instead of the full body suit. 

Follow the guidelines below to place the sensors:

- Awinda: https://base.xsens.com/hc/en-us/articles/360014450119-Sensor-Placement-in-Xsens-Awinda-System

- Link: https://base.xsens.com/hc/en-us/articles/360014450799-Sensor-Placement-in-Xsens-Link-System

 

Software set-up

Ensure that you have the USB of the EMG system as well as the EMG and Xsens receiving stations connected to your computer before opening MVN.

1 - Enable the corresponding plugin in the Options Tab.

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For more details on the specific plugin visit:

- Cometa integration: https://base.xsens.com/hc/en-us/articles/360017536700-EMG-Integration-in-MVN-Cometa

- Delsys integration: https://base.xsens.com/hc/en-us/articles/360017588279-EMG-Integration-in-MVN-Delsys

 

2 - In the motion capture configuration window, you will find a tab labeled "External Data." 

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2 - After checking the box labeled "Use External Data", you will be able to see any EMG systems that will be connected at that moment to the MVN software. 

Note: You can connect multiple systems simultaneously from different companies. If the sensors are not listed, click "Hardware Scan". This scan can take up to 10 seconds to detect hardware.

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3 - Depending on the number of sensors you have, you will need to check the box of the corresponding sensors that you would like to use. Each sensor can be named.

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4 - Before recording can begin, you need to perform a calibration of the Xsens system. 

calibration Awinda: https://tutorial.xsens.com/video/calibrating-awinda

calibration link: https://tutorial.xsens.com/video/calibrating-link

best practices for calibration: https://base.xsens.com/hc/en-us/articles/360013886580-MVN-Calibration

 

5 - The EMG data will be shown within the External Data tab. Verify that you are receiving EMG signals in the software before you start recording by opening the graph in MVN and dragging and dropping the EMG signal. 

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6 - Begin recording by clicking on the mceclip7.png button.

Note: The live EMG data in the MVN graphs will be shown at the same sampling frequency as the Xsens kinematic data (240Hz, 120Hz, 100Hz, 80Hz, 60Hz, 40Hz or 30Hz). However, the EMG data will still be saved during the recording with the original sampling frequency (2000Hz (Cometa) and 2148Hz (Delsys) or 4370Hz (Delsys)).

 

After recording

When you record data with EMG sensors, 3 different files will be saved:

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The EMG data will be saved in an mvne file and the kinematic Xsens data will be saved in an mvn file. In order to see the EMG and the kinematic data simultaneously in the MVN software, you will need to open the mvns file in MVN. This mvns file will combine the information of the previous two files to display in the MVN software. 

 

Cut MVNS file

It is possible to cut the MVNS file, which includes the mvn file with the Motion Capture data plus the mvne file with the EMG data, into a new MVNS file. 

1 - Select in the time frame the part of the file you want to cut to a new mvns file.

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2 - Go to "Edit"->"Copy to a new MVN file"

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3 - Select the folder you want to save it in and click "Save".

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Export data

It is possible to export the data in mvnx and in excel format. When exporting in these two formats the EMG data will be saved with the same sampling frequency in which it was recorded. For each Xsens frame there will be multiple values of EMG data, since EMG sensors have a higher sampling frequency than the Xsens sensors. 

1 - To export the data into a preferred format, go to "File" -> "Export" -> "Export File". Then select the format that you would like to export. Do not forget to select External Data in "Show options" to also export the EMG data.

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Troubleshooting

  1. There is no EMG data being plotted in the graphs:
    1. Delsys: If you have the option "Hardware sync check" turned on, data will not be streamed into MVN until you press the start button. 
    2. Cometa: Check that the lights of the corresponding sensors are on in the Cometa receiving station. Go to the Motion Capture Configuration window -> "External data" and reconnect the sensors. 
  2. The Delsys software no longer opens:
    1. Find the answer and workaround in the article: https://base.xsens.com/hc/en-us/articles/360017588279-EMG-Integration-in-MVN-Delsys

 

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