Accuracy Study

HeartZone has been shown to be as accurate as a standard pulse monitor when used correctly. When compared with a standard pulse monitor, HeartZone was accurate to within an average of 0.8 beats per minute (which was more accurate than a common $130 running monitor also tested for comparison).

HeartZone Compared with Other iPhone Apps

The iPhone / iPod microphone and accelerometer, as shown in reviews for other heart rate iPhone apps, are not sensitive enough to accurately capture heart rate readings. Errors of up to 20 beats per minute are reported, making the data meaningless for many users, and dangerous for users who cannot tell if the readings are accurate.

HeartZone Compared with Using a Watch

HeartZone is easier and more accurate than using the second hand of a watch. When you start counting with a watch you are likely to start and end counting mid beat leading to inaccuracy. With HeartZone your heart rate is determined when you tap, removing this source of error. In addition it is easy to miss a beat, which can lead to inaccurate measurements when using a watch. When using HeartZone missing beats are automatically corrected.
 

HeartZone Error Correction

If after tapping a couple of good beats you miss a beat, HeartZone's error correction will discard the missing beat and still give you an accurate reading (heart rate number turns red, but remains accurate, if you miss a beat).

Ensuring Accuracy

To make sure HeartZone, or any other heart rate app, is working correctly take your heart rate twice in a row while relaxed and sitting down (at least an hour after any strenuous exercise). Your heart rate is constantly changing (see the Somatic Vision breathing for relaxation article) but under these conditions the two measurements should be within 5 beats of each other.

If needed you can improve accuracy by finding your average heart rate for 15 seconds or longer. Alternatively to specifically view your moment to moment heart rate changes from stress and breathing choose Single beat mode.