Rules for accurate HRV measurements
Welltory’s heart rate variability measurements can tell you a lot about your body, gadgets like smart phones or heart rate monitors are highly sensitive to how you behave during the measurement. So if you want accurate measurements, follow our simple rules.
1. Put your finger over the camera and flash correctly
If you’re using an HRM sensor, you don’t have to cover your phone’s flash during the measurement.
IMPORTANT: The HRM sensors on some Samsung phones are not accurate enough for measurements. If you’re using a Galaxy Note 4, Galaxy Note 5, Galaxy S5 Neo, Galaxy S6, Galaxy S6 Edge, or Galaxy S6 Edge+, please use the camera and flash instead of the HRM sensor.
2. Don’t move finger and check the lighting
The camera records changes in the color of the frame to track blood flowing in and out of your finger, so moving it around can interrupt the analysis.
If you’re in a space that’s too light or too dark, it can affect the color of the frame and mess up the results as well. So don’t measure with all the lights off or turn on every light source in your house.
If the flash burns, you can cover it half-way, or hold your finger 2-3 mm away from the flash.
3. Always measure in the same position
4. Make sure your heart rate and breathing are stable
5. Don’t talk, move, or control your breathing
Talking or moving can disrupt your breathing, which affects the activity of your autonomic nervous system — the body’s regulatory center that modifies your heartbeat in response to changes in your environment or behavior. These changes can, in turn, alter your heart rate variability measurement.
Just like with talking, trying to control your breathing will affect your heartbeat and can mess with your results.
6. Use the hints on top of the measurement screen
Keep track of the measurement quality hints on top of the screen to always take accurate and reliable measurements.
If you see no hints, you’re doing well. And if something is wrong, we’ll tell you what you need to do. You may be moving too much, pressing the finger too hard into the camera or holding it too far etc. Follow the instruction until the hint disappears.
7. Check accuracy score
We analyze all of your measurements to give you an accuracy score along with your results. You can see it right on top your results screen.
If you see an accuracy score of less than 80%, it’s best to take another measurement.
Measurements with an accuracy score of less than 30% aren’t worth analyzing, so we’ll toss them out automatically and ask you to measure again.
Things that lower accuracy score
High heart rate. If you’ve gone up a flight of stairs before the measurement or were moving too much while you measured, your heart rate will likely be over 90, which is too high for a resting heart rate.
Unstable heart rate. This can happen if your body is in the middle of transitioning between two states. Say you ran up a flight of stairs, waited for your heart rate to go down to 90, and started measurement. Your average heart rate will likely fluctuate between 90 and 60, which will reduce your score.
Incorrect finger placement. If the app can’t see the blood vessels in your finger through the camera, it will affect your score. You may need to experiment with your finger placement: flip your phone over and make sure the flash is illuminating your finger and make sure you’re not pressing down on the camera too hard.
Moving too much or talking. This can make your heartbeat erratic and unstable, which reduces your score.
Bad lighting. If you’re in a space where the lighting is way too bright or there are no lights on at all, the camera may have trouble illuminating your finger properly.
That’s it! Stick to these 7 simple rules and you should get high-quality HRV measurements every time.