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Collecting Heart Rate Data (Beats per Minute and R-to-R Intervals)

Last Updated: Jul 26, 2016 05:55PM CDT

ActiLife 6.5 and later combined with wGT3X+ devices running firmware 3.0 or newer are capable of providing measurements of Heart Rate R-to-R intervals.  

Collecting Heart Rate Data

Heart rate data is captured from the wireless ANT+ enabled heart rate chest strap and is transmitted in real time to the wGT3X+.  In order to capture heart rate data, the following must occur:

  1. Initialize a wGT3X+.  Be sure to enable "ANT+ Wireless" and "Heart Rate".  Setting a PIN code is optional.  The PIN code is required when communicating with the wGT3X+ from one of ActiGraph's mobile applications.
    • init-hr.png
  2. Position the ANT+ enabled heart rate strap around the chest area.  Instructions for wearing the heart rate strap are available here.
  3. The wGT3X+ will pair over the ANT+ wireless channel with the first heart strap that it detects and will lock to that heart strap.  As of ActiLife 6.5.0, there is no way to pair a single heart strap directly to the wGT3X+.  This feature is coming soon.
    • If the wGT3X+ loses connection with the heart strap, it will begin searching immediately for another one.  If no heart strap is detected, the wGT3X+ will wait 15 seconds before performing another scan.  If no heart straps are detected, it will wait another 30 seconds before performing another scan.  If no heart straps are detected, it will wait another 60 seconds before performing another scan.  If no heart straps are detected after that waiting period, the wGT3X+ will search for nearby heart straps once every 2 minutes.  This method prevents the wGT3X+ from completely depleting its battery life if the heart strap is no longer present.
  4. Wear the wGT3X+ and the heart strap for the desired amount of time.

Downloading Activity and Heart Rate Data

  1. Connect the wGT3X+ to the computer running ActiLife and download the data.  The *.agd file can be created at time of download.  Be sure to check the "HR" option during download to ensure that the raw Heart Rate data collected on the wGT3X+ gets exported to the *.agd file for use in ActiLife.
    • Download.png
    • Alternatively, the *.agd file can be created after download by clicking "finished downloading" from the device list or later by simply opening the raw *.gt3x file that is generated at time of download.
  2. The resulting *.agd file will contain basic beats per minute data for each epoch.  This can be viewed by opening the *.agd file in ActiLife (simply double-click on the *.agd file).  
    • Heart.png

Extracting R-to-R Heart Rate Data

  1. To extract more detailed heart rate data (R-to-R values), either a) select the "Heart Rate R-R" option from the File->Import/Export menu in ActiLife or b) select "Export Heart Rate R-R" from the AGD File Viewer export menu as shown below 
    • RtoR.png        OR        rr.png
  2. Select the *.agd file that contains the heart rate data you wish to examine.  A *.csv file will be created in the same directory.

Understanding the R-to-R Heart Rate Data

Bluetooth R-R Heart Rate Data

The Bluetooth R-R heart rate data can be examined in Microsoft Excel. There are three columns:

  • Timestamp
  • Heart Rate
  • RR Interval in seconds

More information can be found at Bluetooth's official documentation on Heart Rate.

ANT+ R-R Heart Rate Data

The ANT+ R-to-R heart rate data can be examined in Microsoft Excel®. There are three columns:

  • Timestamp - the long date and time (with millisecond resolution) at which a heart beat was detected
  • Time since last beat (milliseconds) - the number of milliseconds since the last beat
  • Beat count - A consecutive beat counter that resets at 255.  This helps when examining missing beats.
To view the Timestamp at millisecond resolution in MS Excel, right-click on the Timestamp column and choose "Format Cells..".  Select the "Number" tab and choose the "Custom" option.  Set the format to m/d/yyyy h:mm:s.000 and click "OK."  This will set the Timestamp column to display the timestamp down to the millisecond resolution.
An ANT+ sample file containing R-to-R data can be downloaded here.

How Heart Rate Data is Captured

The ANT+ heart strap polls the wearer's heart at a rate of approximately 4Hz.  Each sample is transmitted to the wGT3X+ and is stored upon receipt.

If you need any further assistance, please visit our support portal at From there, you can view many helpful FAQ's and Troubleshooting Articles; log in to check any existing Support Requests; or create a new Support Ticket if you are unable to find a solution. You can also email us at or give us a call at (877) 497-6996, Monday through Friday, 8 am to 5 pm CST.

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