Optimal Heart Rate Recordings

Wattson Blue uses your smartphone’s camera and flash to calculate your resting heart rate (HR) and heart rate variability (HRV). In an earlier post, we discussed how we use the latest scientific literature and our expertise to detect these variables via the analysis of the photoplethysmography signal (PPG). Once you have completed your recording for the day, Wattson Blue will display your HR and HRV, such that you may compare these recordings with your long and short term trends.

It is important that HR recording is carried out, at rest and in as similar conditions as possible to past recordings, e.g. you should ensure that you are always lying down, or sitting in the same position. You should make sure you are in a rested state (e.g. you have not just climbed two flights of stairs), and you should avoid any movements during the recording.

The app will also warn you if the signal detection was optimal or sub-optimal, recommending that you re-take your HR recording if the signal quality was poor.

Despite all your efforts, the recording might still not be optimal. Here are some tips on how to improve the signal quality:

  • Avoid pressing too hard or too lightly on the camera and flash, or moving your finger. Use the live trace to guide you.
  • Make sure you are covering both the camera, and the flash. This may be difficult on some Android phones in which case ensure the camera is completely covered at the very least.
  • If you have a large phone case, ensure it is not stopping your finger from resting directly on the camera and flash. You might have to remove the case if you cannot do that.
  • Ensure that your surroundings are not too bright.
  • Ensure you are well hydrated and your fingers are not too cold. Anything that reduces the blood flow to your fingers can negatively impact the signal.

Don’t worry if the live trace moves around a little bit, as long as at least 40-50 seconds of the recording is of reasonable quality, then Wattson Blue should be able to calculate your HR and HRV accurately.

If you are following these tips but continue to get warnings about the signal quality in the app, please drop us a line.

A note on older phones

If the quality of your camera is too low, or your phone is too slow, the HR recording sadly might not work for you.