OpenHRV

A desktop application for heart rate variability (HRV) biofeedback training with ECG chest straps.

Compatible sensors

• Polar H7, H9, H10
• Decathlon Dual HR (model ZT26D)

Installation

It is highly recommended to install the project in a virtual Python environment, e.g., using conda or venv. The required Python version is specified in pyproject.toml.

In your Python environment, clone the repository, and subsequently run

pip install .

in the root of the repository. Alternatively, you can skip cloning by running

pip install git+https://github.com/JanCBrammer/OpenHRV.git

You can now start the application with

python -m openhrv.app

or alternatively, with the shortcut

openhrv

I tested OpenHRV on Ubuntu 24.04. It should run on Windows and macOS as well, however, I haven't confirmed that myself. If you have problems running OpenHRV have a look at docs/troubleshooting.md.

Ubuntu executable

On Ubuntu, download and run OpenHRV.bin, no installation required.

User Guide

Connect your ECG sensor

First make sure the sensor is paired with your computer (i.e., find and pair the sensor in your computer's Bluetooth settings). Then search the sensor in OpenHRV by clicking Scan. The addresses of all paired sensors show up in the drop-down menu. Select your sensor from the drop-down menu and click Connect in order to establish a connection. You can disconnect the sensor anytime by clicking Disconnect. Disconnecting is useful if you want to connect to another sensor, or if an error occurs with the connection. Should you have problems with the connection try disconnecting, and then reconnecting the sensor.

Set an HRV target

You can personalize the HRV target using the Target slider. After you've been training for a while you will have a good idea of what's an attainable target for you (this can vary depending on how much sleep or coffee you had etc.). You can adjust the target anytime if you find the current target too easy or difficult.

Set a breathing pace

The breathing pacer can help you increase your HRV. Breathe out as the blue disk shrinks and breathe in as it gets larger. Explore how different breathing rates affect your HRV by adjusting the Rate slider anytime during a session. Everyone has a personal breathing rate at which their HRV is at its highest. Usually that rate is somewhere between 4 and 7 breaths per minute. You can also hide the pacer by unchecking the Show pacer box if you want to practice regulating HRV without pacing.

Biofeedback training

Below you can watch heart rate variability (HRV) biofeedback training in action. Note how the blue heart rate curve rises and falls. These fluctuations are the "variability" in HRV. Your goal is to get the fluctuations large and regular. As you get better at this, the white HRV curve will go up. There is no "ideal" HRV, as in "everyone should achieve an HRV of 500 msec". Try to increase HRV relative to what you have achieved before and be aware that it can take a fair bit of practice to improve.

Record a session

You can record a session to a .csv file using the controls in the Recording panel. Click Start and choose where to save the file. The dialog suggests a name based on the current date and time (e.g. OpenHRV_2025-12-19-14-30.csv); recording only begins if the file doesn't exist yet, so each session is written to its own file. Click Save to stop recording and close the file. The session is also saved automatically when you close OpenHRV while a recording is running.

While recording, OpenHRV appends one row per data point. Each row has three columns, event,value,timestamp, where timestamp is in ISO 8601 format. The following events are logged:

event	value
InterBeatInterval	latest inter-beat interval (msec)
HeartRateVariability	latest (smoothed) HRV (msec)
HrvTarget	HRV target whenever you move the Target slider
PacerRate	breathing rate whenever you move the Rate slider
Sensors	sensor that became available or connected
Annotation	a note you added (see below)

Annotate a recording

Use the annotation field next to the Annotate button to mark moments of interest in a recording, for example the start of an exercise or a change in how you feel. Type a label (or pick a previously used one from the drop-down) and click Annotate to write an Annotation row with your label and the current timestamp. Annotations are only recorded while a recording is running.