I have been using Apple Watch for the last 3 years. First I had series 1 then I upgraded to series 3. If you are exercising regularly and have an iPhone then I strongly recommend Apple Watch. Usually the latest versions have a high price tag but you can always go with an older model which are usually priced reasonable. The only thing I don’t like about Apple Watch is the battery life. With series 3 the battery lasts around 2,5 days with a single charge but still it does not allow me to monitor my sleep cycle since I need to charge it at night every 2 days. I wish they had a special night mode that is preserving battery but at the same time tracking your sleep. By the way the battery charges pretty quick.
Let’s come to the point. Recently one of my friends purchased a Garmin Fenix 5 and he claimed that he needs a chest strap for accurate heart rate monitoring. It did not make much sense to me because I have been comparing Apple Watch’s heart rate monitor to treadmill hand grip monitors that I have been using and the values are usually in the same range and differs at most 2 bpm(beats per minute). So I decided to compare Polar H10 which looks like the best option on the market currently to my Apple Watch Series 3. I was planning to take a video while doing the test but I couldn’t find a good spot to fix my camera. I am still considering to take a video but that’s for another story.
How did I make the comparison?
I paired Polar H10 to my wife’s iPhone. The readings from the chest strap went to her phone and the readings from my Apple Watch went to my phone. Both phones are the same model (iPhone XS). I used FITIV Pulse on my wife’s phone to track the exercise and used regular Apple Workout App to track the same exercise using my Apple Watch. I run for 34 minutes and my heart rate fluctuated between 75–175 bpm. Then I used QS Access App to export heart rate readings from both phones to my laptop for processing.
Results
One noticeable difference is that Apple Watch is very cautious about its battery life so it gives less readings. For the same duration of time my watch gave 406 readings which is roughly 12 per minute and 1 per every 5 seconds where Polar band had 1041 readings which is around 30 per minute and 1 per every 2 seconds. Having more data is always better but do we really need it that it is up to you. Below I plotted the readings and the difference between them. Before plotting the readings I upsampled the data points and interpolated the values so that I have 1 reading per second for each of the data sets. I didn’t have a ground truth to compare but the readings from both of the devices were very close to each other. Also according to this research Apple Watch have the lowest error rate of 2.0% and according to this research Apple Watch is accurate about 91%.
This first graph is the heart rate readings from both devices plotted on the same figure. Y axis is the HR values and X axis is the time. I started running at 9:25am and finished at around 9:58am.
The second graph is the absolute difference between the readings. The max difference is 5bpm and mostly the difference is around 1bpm.
