Apple Watch is most precise wrist-worn heart rate tracker at 90% accuracy, study says
It appears Apple's bet to pack a bespoke heart rate sensor into Apple Watch instead of off-the-shelf technology paid off, as Cleveland Clinic researchers recently found the wearable to be the most accurate wrist-worn fitness tracker on the market.
The study, which pitted Apple Watch against competitors Fitbit Charge HR, Mio Alpha and Basis Peak, found significant discrepancies between the variance between the consumer devices, reports Time.
Testing involved 50 subjects who were hooked up to an electrocardiogram while walking, running and at rest. Results were compared to to heart rate data from the consumer devices, with Apple Watch showing a 90 percent accuracy rate in most scenarios. The others dropped into the "low 80s," according to Dr. Gordon Blackburn, director of cardiac rehabilitation at Cleveland Clinic.
An unnamed consumer level chest strap monitor, presumably similar to those sold by Polar, was also tested and found to be 99 percent accurate.
"What we really noticed was all of the devices did not a bad job at rest for being accurate for their heart rate, but as the activity intensity went up, we saw more and more variability," Blackburn said. "At the higher levels of activity, some of the wrist technology was not accurate at all."
It is unclear whether Apple Watch accuracy diminished during rigorous exercise, and to what extent, though it is common for wrist-mounted monitors to suffer signal degradation during extreme movement. Since wearables rely on optical sensors to measure blood flow at a single point on the body, accurate tracking becomes a problem when the device shifts or lifts off from the skin.
Apple detailed how its in-house heart rate sensor prevents data anomalies caused by user motion in a recently published patent application. Apple's heart rate sensor is based on existing photoplethysmogram (PPG) technology, which employs a light emitter and sensor array to measure blood perfusion to the skin. With Apple Watch, signal data from at least two light guides are compared and contrasted using special software algorithms to correctly compensate for physiological changes (vasculature expansion and contraction) and device motion.
Even with a highly advanced sensor solution, Apple Watch is still positioned as a consumer device. Rumor has it that Apple is looking to push deeper into the health and medical industries with Apple Watch and its supporting ecosystem of apps. A first step might be providing healthcare professionals with rich data gleaned by HealthKit, a move hinted at by Apple's purchase of digital health records firm Gliimpse.
Most recently, a report in September claimed Apple is working on two new apps for Apple Watch, one for accurately tracking sleep patterns and another that measures heart rate recovery.
The study, which pitted Apple Watch against competitors Fitbit Charge HR, Mio Alpha and Basis Peak, found significant discrepancies between the variance between the consumer devices, reports Time.
Testing involved 50 subjects who were hooked up to an electrocardiogram while walking, running and at rest. Results were compared to to heart rate data from the consumer devices, with Apple Watch showing a 90 percent accuracy rate in most scenarios. The others dropped into the "low 80s," according to Dr. Gordon Blackburn, director of cardiac rehabilitation at Cleveland Clinic.
An unnamed consumer level chest strap monitor, presumably similar to those sold by Polar, was also tested and found to be 99 percent accurate.
"What we really noticed was all of the devices did not a bad job at rest for being accurate for their heart rate, but as the activity intensity went up, we saw more and more variability," Blackburn said. "At the higher levels of activity, some of the wrist technology was not accurate at all."
It is unclear whether Apple Watch accuracy diminished during rigorous exercise, and to what extent, though it is common for wrist-mounted monitors to suffer signal degradation during extreme movement. Since wearables rely on optical sensors to measure blood flow at a single point on the body, accurate tracking becomes a problem when the device shifts or lifts off from the skin.
Apple detailed how its in-house heart rate sensor prevents data anomalies caused by user motion in a recently published patent application. Apple's heart rate sensor is based on existing photoplethysmogram (PPG) technology, which employs a light emitter and sensor array to measure blood perfusion to the skin. With Apple Watch, signal data from at least two light guides are compared and contrasted using special software algorithms to correctly compensate for physiological changes (vasculature expansion and contraction) and device motion.
Even with a highly advanced sensor solution, Apple Watch is still positioned as a consumer device. Rumor has it that Apple is looking to push deeper into the health and medical industries with Apple Watch and its supporting ecosystem of apps. A first step might be providing healthcare professionals with rich data gleaned by HealthKit, a move hinted at by Apple's purchase of digital health records firm Gliimpse.
Most recently, a report in September claimed Apple is working on two new apps for Apple Watch, one for accurately tracking sleep patterns and another that measures heart rate recovery.
Comments
What is amazing me is that to reach the goal of selling as many products and services possible they seems to still be convinced that a good product and hard work behind is the best guarantee for success when you go for margin and not just market share. You get a glimpse of the crazy hard work behind all this seemingly easy tech when the CEO laudes the team during a keynote.
http://jamanetwork.com/journals/jamacardiology/article-abstract/2566167
It would be interesting to see a more comprehensive study with more devices, including more devices that are in the same higher-end category as the Apple watch (Garmin, Suunto, etc). But as the original research letter (ie, not a full-blown study) said, this was just a "convenience sample" (probably the devices the researches already personally owned LOL) of devices and "results should be confirmed with different types of exercises and with other devices."
But interestingly, recently I switched from the Polar H7 being monitored by the ICardio app on my IPhone (aka "DigiFit") to an Apple Watch and the watch always shows a steady, consistent heart rate even if I have linked it to the Polar H7 heart rate strap.
The difference, I believe, lies in sampling rate: while the ICardio app on the IPhone would sample many times a second and then display a graph of my heart rate where the swings showed up, the exercise app on the Apple Watch samples far less frequently (in order to conserve battery) and then only displays average heart rate. Basically, the Apple Watch tends to miss the spikes -- which is (I believe) proven because when I use both the watch (using its wrist sensors) and the strap connected to ICardio on my IPhone simultaneously, the average heart rate on the IPhone is often 5-10 beats higher than the what the watch shows (it has never been lower).
This may also be why Apple has admitted that the heart rate measured by the watch is not overly accurate when it is monitoring exercise such as weight lifting or boxing -- it misses the spikes.
From my experience, if you want an accurate heart rate, you still need to use a chest strap and IPhone. And the study confirmed that saying that the chest strap is 99% accurate. Part of that is due to methodology: the chest strap measures the same electrical signals as an EKG which is the gold standard; while the wrist monitors measure blood flow through the wrist by shining green light through the skin. It sounds to me like the wrist based light sensors are simply inherently less accurate. But, what is also interesting is that it is theoretically possible to measure those same electrical signals that the EKG measures at the wrist rather than the chest. I wonder if Apple looked into that or will look into that?
In the meantime, I know that if I want a highly accurate heart rate I need to use my Polar H7 strap and my IPhone. But, for most runs, just the Apple Watch will give me 'close enough'.
Just so, you know, I do not own an Apple Watch. For the kind of activities I do, mainly the gym, and hiking, I chose Garmin products, the Forerunner 15, and a good GPS, the eTrex Touch 35. I need to have a GPS track for at least 8-10 hours. The Apple Watch is not capable of doing that on a single charge
as for my case usage, it's irrelevant -- I'm just an anonymous commenter on a rumors site, not a publication that presumably has a style guide. guides have value for a reason. thats why the "But you do it too!" argument is a fallacy, an ad homenim, because it's attacking the speaker and not the point raised.