Follow-Up: Garmin Vivoactive HR & Polar H10: Which measures heart rate more accurately?

Heart Rate Measurement Using Garmin & Polar Wearables

A study was made of the Garmin Vivoactive HR and Polar H10 chest strap in terms of comparative heart rate assessments. The units are shown in Figure 1 below. The two units involved included a wrist-based sensor (Garmin Vivoactive HR) and a chest strap (Polar H10).

Polar h10 chest strap and garmin vivoactive hr smart watch were used in the comparison

This follow-up focuses on 20 minutes of water rowing using both units in an effort to assess the heart rate measurement consistency and reliability. Both watch and chest strap were properly attached with no movement between these devices and the skin. Data were collected and then downloaded and processed through a Microsoft Excel spreadsheet. The data were time-synchronized so that corresponding data points from each device were associated in time. A summary of the analysis is provided here.

Time-Based Plots of Heart Rate

Overlay scatter plots of heart rate measurements versus time were made and are as shown in Figure 2.

Figure 2: Heart rate measurement while water-rowing approximately 20 minutes. Shown are overlays of Garmin Vivoactive HR and polar h10 heart rate versus time.

A general observation from the data is that the heart rate measurements from the two devices seem to overlap reasonably well as viewed by the naked eye. But there are key drops in measurements, particularly with the wrist-based heart rate sensor, that show as deviations in the overlap of the two signals. This can be seen more readily via the correlation curve shown in Figure 3. The correlation coefficient of 0.91 was determined between the two sets of measurements. It should be noted that the wrist-based sensor was snug with no movement on the wrist. Ambient temperature was approximately 80F.

As I showed in a previous post, there was a serious issue with the wrist-based sensor in which there were data dropouts with some significant time lags between measurements. In the case of the wrist-based sensor for the associated measurements here, this was also experienced. For comparison, I show histogram plots of the time intervals between measurements for both the wrist-based sensor (Figure 4) and the chest strap (Figure 5). The wrist-based sensor experiences a significant number of events in which the time between actual measurements are greater than one second. Indeed, from the figure, only 83 measurements during this interval were obtained within one-second of one another! There were a significant number of measurements in which the interval was > 1 second, with one as high as 40 seconds. The overall quantity of measurements was thus reduced to approximately 430 during the workout. On the other hand, the chest strap consistently measured at one-second intervals for a total of approximately 1320 measurements.

Figure 3: Scatter plot of heart rate as measured between the wrist-based Garmin device and the chest-strap Polar H10. A correlation coefficient of 0.91 was determined between the measurements. Perfect correlation is shown by the diagonal line.
Figure 4: Historgram of time between measurements for Garmin wrist-based sensor. Note the significant quantities of measurements in which the interval is greater than 1 second (the advertised measurement interval). For example, there were 20 instances in which the measurement interval was 6 seconds, and one instance in which the measurement interval was 40 seconds! Note that only 83 measurements were in the one-second interval width!
Figure 5: Historgram of time between measurements for the chest strap polar H10 sensor. All measurements (of which there were more than 1300) were reliably at one-second intervals.

Conclusions

Chest straps are much more reliable for heart rate measurement versus wrist-based sensors. Users of wrist-based sensors for heart rate measurement should be advised that measurements can be in question, as results illustrate here. This is not to say that chest straps are the gold-standard. Clearly, ECG measurement similar to those obtained through stress-testing are of diagnostic quality. Yet, for rate measurement chest straps are quite adequate and seemingly reliable.

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