Last Updated on September 28, 2022 by pg@petergamma.org
Whe became interested in consumer grade heart rate monitors (HRM) as we started to practice Shamatha Meditation for calming the mind. sprititual teachings say, that a calm mind leads to a slow breathing rate, and by practicing Shamatha Meditation, whe can master our mind.
Frustrated by the fact, that we found no low-cost and handy device which can measure respiration rate, we started meditating with a Polar watch and a Polar chest strap. Then, we where very happy about the first optical heart rate monitors from Mio to replace the chest strap. The calmer the mind is, the slower the heart rate is roughly worked for us, and we used a Mio Link as a biofeedback HRM device.
As scientists, we wanted numerical and statistical data of the heart rate. Heart rate has also been studied in several papers by meditation reserachers. DC Rainmaker could convince us, that the chest strap is the most accurate device he uses, but how accurate are optical HRMs?
In a PLOS ONE Paper about the Polar OH1, we found that a Polar OH1 can be used instead of an ECG device for the activities studied in the paper. ECG devices are known to be very accurate, and are used for clinical and research applications.
The group of the cardiologist Milind Desai from Cleveland Clinic in Ohio published two papers where they compared consumer grade HRMs to a clinical ECG during sporting activities. There are big differences between different types of clinical and research grade ECG devices, as shown in this table:
Numerical and statistical accuracy data are published in these HRM accuracy studies. The group of Milind Desai studied the accuracy of many differnt HRMs in a single paper and compared them against each other, and use a clinical ECG device as a reference. A cardiolgist like Milind Desai has to be able to handle with ECG devices, else he looses his job.
One paper of the group of Milind Desais showed, that the Polar H7 chest strap is the closest to the ECG, followed by the Apple watch I.
Later on, The Quantitative Scientist Rob ter Horst started to publish HRM accuracy comparison plots on his Yotube channel, as shown here:
We contacted Rob ter Horst and asked him to use an ECG reference device. But soon after that, Rob claimed on his Youtube channel, that his Polar H10 chest strap is more accurate than an ECG device, and reviewed a paper which proved this.
The group of Milind Desai did not test the Polar H10, but only the Polar H7. Why do other studies not use ECG reference devices as well in their studies?
There is a paper which compared the Polar H7 to a Holter ECG device:
[90.x.x] Papers Comparing the Accuracy of Polar H7 to a Mortara Holter ECG with 12-leads, 10 electrodes and 20 bit A/D sampling rate
- Validity of the Polar H7 Heart Rate Sensor for Heart Rate Variability Analysis during Exercise in Different Age, Body Composition and Fitness Level Groups
Reference Device was a H12+ Mortara Holter ECG with 12-leads, 10 electrodes and 20 bit A/D sampling rate:
But during activity, the Polar H7 chest strap was more accurate than the ECG device, we suppose because of movement ECG artifacts. The g.tec support told us, that that g.tec medical does not know of any manufacturer of ECG devices which has solved the problem of ECG movement artifacts. But are novel algorithms published recently to remove noise from PPG and very noise ECG signals:
https://scholar.google.com/citations?user=OOhuA6gAAAAJ&hl=de&oi=sra
The question arrises wether several authors of papers which are disscussed here where aware of the problem of ECG movement artifacts. Not all of the authors are cardiologists, many of those are sports scientists, and we do not know how much they know about ECG devices, which sometimes are difficult to handle.
The group of Milind Desais seemed to know the problem of ECG movement artifacts, and used ECG reference devices only for studies with activities with little movement.
A study of the Swiss Federal Institute of Magglingen compared the Polar H10 to an ECG, and found, that the signal quality of the Polar H10 is better during activity than that of an ECG device:
2. [90.10.1] Polar H10 against Holter ECG comparing the Signal Quality
Rahel Gilgen-Ammann, Theresa Schweizer, Thomas Wyss
Eur J Appl Physiol. 2019 Jul;119(7):1525-1532.
RR interval signal quality of a heart rate monitor and an ECG Holter at rest and during exercise https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiKos3IhuH4AhWF_bsIHfGlD2kQFnoECAIQAQ&url=https%3A%2F%2Fwww.ppdb.ehsm.ch%2Finf2%2Frm%2Ff.php%3Ff%3D20200416162130_5e9869eab833b.pdf%26n%3DGilgenAmmann_RRIntervalSignalQuality_2019.pdf&usg=AOvVaw23MOAobT8so8HFGAdgdcPo
A paper of the US Army found, that the Equivital EQO2 LifeMonitor is accurate, when compared to a Polar H10 chest strap:
3. [90.9.4] Paper Comparing the Polar H10 to an Equivital EQO2 LifeMonitor Sensor Belt
David P. Looney, Sai V. Vangala, Elizabeth M. Lavoie, Lucas D. Holden, Jason W. Hancock, William J. Tharion, William R. Santee, Holly L. McClung, Adam W. Potter
USARIEM TECHNICAL REPORT T22-06, November 2021
Validation of the Equivital (TM) EQO2 LifeMonitor for Continuous Heart Rate Monitoring During Intermittent Military Relevant Tests of Physiological Limits
https://apps.dtic.mil/sti/pdfs/AD1154187.pdf
It is a pitty, that the US Army did not use Adinstruments LabChart software. Adinstruments advertises, that the Adinstruments Equivital together with LabChart software is noise and movement artifact free. But no paper has confirmed this to this date, as far as we know.
Then, another paper was published to compare the Polar H10 to a 12 channel ECG device:
[90.x.x] Comparing the Polar H10 to a 12-Channel ECG (CardioPart 12 Blue)
4. Validity of the Polar H10 Sensor for Heart Rate Variability Analysis during Resting State and Incremental Exercise in Recreational Men and Women
Schaffarczyk, M.; Rogers, B.; Reer, R.; Gronwald,
Sensors 2022, 22, 6536. 30 August 2022
https://www.mdpi.com/1424-8220/22/17/6536
Here the same findings: during activity, the ECG device is inaccurate. Does it make any sense, to use 12 ECG channels for sporting activities? Ask your cardiologist.
One possibility to solve the problem of ECG movement artifacts is to test sensors with two different methods, as this has been done by different studies shown in the tables at the bottom of this page. In the range with little activity, a a high quality ECG device can be used as a reference, while during high acitivy, a Polar H10 strap can be used as a reference, if no motion artifact free ECG device is available.
see also: