You probably think of the Apple Watch as a wrist-worn accessory. However, a new study has suggested that wearing the Apple Watch on your arm won’t affect the accuracy of its heart rate monitor.
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This may come as a surprise, given that Apple designed its watch to read your heart rate while it’s on your wrist. However, a new observational study published on PubMed indicates that the heart rate monitor still provides accurate data despite the alternative placement.
Here’s what you should know.
Quick background on Apple Watch heart rate monitoring
The Apple Watch uses an optical heart rate sensor to measure your vitals. It relies on a technique known as photoplethysmography, which basically boils down to the fact that blood absorbs green light.
As such, the Apple Watch heart rate sensor uses flashes of green light to detect the amount of blood flowing through your wrist at any one time. From there, it uses light‑sensitive photodiodes to measure that amount.
The other facet of understanding the Apple Watch heart rate monitor is to know how your heart works. When your heart beats, the amount of blood flowing through specific body parts — such as your wrist — increases. Between heartbeats, the blood volume is less.
By flashing this green light hundreds of times per second, the Apple Watch can calculate your heartbeat.
What the study found
The study used a pair of identical Apple Watch Series 8 devices to monitor the heart rates of surgeons performing robotic-assisted surgery. The study authors affixed one Apple Watch to a surgeon’s wrist and the other to a surgeon’s arm.
Using statistical analysis, the study found that there were not any systematic errors between the wrist-worn Apple Watch and the arm-worn Apple Watch when it came to heart rate monitoring. In other words, the two heart rates were close enough for either measurement to be considered accurate.
“The findings of this study suggest that the upper arm is a viable alternative site for monitoring heart rate during surgery using an Apple Watch,” the study reads. “The agreement and reliability between the measurements obtained from the upper arm-worn and the wrist-worn devices were good, with no systematic error and a high level of accuracy.”
Although the study set out to determine heart rate accuracy for surgeons in the operating room, the results have practical applications for anyone. It also suggests that the Apple Watch’s heart rate sensor even works with blood flowing through the arm.
Options for wearing an Apple Watch on your arm
There are certainly times when wearing an Apple Watch on your wrist isn’t an ideal solution. For example, the surgeons in the study couldn’t do so because of sterility concerns while in the operating room.
Other situations where an arm-worn Apple Watch could come in handy include:
- Tracking activity during jobs that don’t allow any wrist-worn accessories
- During physical activities when an Apple Watch on the wrist could be damaged.
Although wearing an Apple Watch on the arm isn’t as common as wearing it on the wrist, there are still a number of Apple Watch armband accessories on the market that can make wearing your Apple wearable on your arm that much easier.
For example, you can find options as inexpensive as $10 on Amazon, such as this arm or ankle band.
The best option, in our opinion, is likely this TwelveSouth Action Sleeve, which costs $39.99 and is made by a highly reputable and respected accessory maker.