Is Apple Watch Heart Rate Monitoring Spot-On?

If you’ve ever googled how accurate the heart rate monitoring of the Apple Watch is, you would know it’s at the top of the rankings. It detects heart rate throughout the day and night, during workouts, performs ECG, and even has the ability to detect atrial fibrillation. 

But is your Apple Watch really accurate if you have a serious health condition? Let’s find out.

Here’s What the Studies Say About Apple Watch’s Heart Rate Accuracy:#

• An independent study comparing four fitness trackers against a chest strap and an EKG on 50 healthy adults in three different conditions– rest, walking, and running on a treadmill. It was found that the Apple Watch was the most accurate amongst commercial fitness brands, with 91% accuracy, only beating the chest strap at 99% accuracy with the EKG. 

• A study from 2019 published in the IEEE Journal of Translational Engineering in Health and Medicine found the Apple Watch and telemetry data to indicate a strong correlation of 0.7. This correlation was higher in patients with atrial fibrillation, 0.86, than in patients without atrial fibrillation, 0.64.

• Another study testing The Reliability of the Apple Watch’s Electrocardiogram found the ECG to be highly accurate, with a 0.903 correlation and atrial fibrillation with a 99.54% sensitivity. It was, however, moderately accurate in detecting other heart rhythm abnormalities.

• The Quantified Scientist on YouTube also found the Apple Watch to be highly reliable in terms of heart rate, even during workouts such as weightlifting. He also pointed out that the accuracy is not very different in versions Series 6 and above.

• In another test conducted by the Quantified Scientist in his video with the Apple Watch Ultra, he recorded a lag of 4-5 seconds in the heart rate displayed across all workouts. Even though a lag of a few seconds doesn’t make much difference, it is still one of the most accurate heart rate trackers on the market.

How Does the Apple Watch Detect Heart Rate?#

The Apple Watch has optical heart sensors, which use its green LED with light-sensitive photodiodes to detect blood flow. The watch flashes its LEDs a hundred times per second, which is absorbed by the blood, calculating beats per minute. The sensors support a range of 30-120 beats per minute and increase brightness and sampling rates in order to enhance accuracy even during low signal conditions.

Barring the Apple Watch SE models, an ECG reading can also be performed on the Apple Watch Series 4 and later, and the Apple Watch Ultra models.

This is done by resting a finger on the Digital Crown of the watch and keeping it still for a precise recording. The Digital Crown and the back of the watch have built-in electrodes that measure electrical signals between the heart and arms, creating a closed circuit and measuring every second for a detailed heart rhythm reading.

These reports can be accessed via the Apple Health app and should be consulted with a doctor if these reports signal any abnormalities.

How Important are the Apple Watch Heart Rate Readings?#

Even though I know that there’s a lag of a few seconds in the heart rate that shows up on the screen, what really matters to me is consistency. The watch provides consistent measurements of my heart rate during my workouts; sure, it may be more accurate for some workouts than others, but for the purpose of staying fit and reaching my activity goal, I don’t need pinpoint accuracy.

The best part about the Apple Watch is how it continues to measure my heart rate 3 minutes after I finish a workout to determine a recovery rate. For people with heart conditions, the Apple Watch can be a great source to monitor the heart rate constantly since it detects AFib, which generally doesn’t have any visible symptoms. To ensure the best readings, a good, snug fit of your Apple Watch on the wrist is necessary. That being said, there are certain factors that affect the readings of your heart rate on your Apple Watch. 

Factors Affecting Your Heart Rate Readings#

Personal information is not updated#

Remember when you recently bought your iPhone, and the Health app asked you for details like your age, gender, weight, and height? Yeah, they need to be updated for the algorithm to correctly judge various measurements from your Apple Watch. If you suspect an incorrect reading of your heart rate, consider updating this information regularly.

Watch app > Health > Health Details

Wrist detection is off#

Background heart rate readings, such as resting and walking heart rate, and stand notifications are disabled when Wrist Detection is off. To ensure that this is not the case,

Watch app > Passcode > Toggle on ‘Wrist Detection’

Loose-fitting strap#

Ensuring a perfect fit of your Apple Watch strap, not too tight and not too loose, will be the perfect way to let the sensors do their job and do it right. This also ensures the watch won’t swing around during a workout and gives accurate measurements.

Not earning Move and Exercise credit#

Allowing your arm with the watch to swing naturally will not only burn slightly more calories but will also earn you Exercise credits during your walks. For activities that require both hands in a stagnant position, such as pushing a stroller or a shopping cart, the workaround could be to choose Outdoor Walk on your Workout app.

Activity on your Apple Watch relies on movement and arm motion to count steps throughout the day. On the other hand, the Workout app can be used because it uses an accelerometer, a heart rate sensor, as well as GPS. 

Choosing an incorrect workout#

Speaking of using the Workout app, selecting the correct form of workout you’re doing will help the algorithm correctly interpret the data collected. This should be fairly easy since the Apple Watch provides a number of workouts to choose from. In case the workout is not available, choose the closest option available for the best results.

Not calibrating your watch#

Walking at a normal pace with the Outdoor Walk set on your Workout app is all you need to calibrate your Apple Watch. This helps in improving the watch’s accuracy in the distance, pace, and calories burned it calculates.

Other factors#

• Certain factors, such as the ink from tattoos on the skin, can affect how much light from the sensors is absorbed by the blood. This affects the reliability of the readings.
• Skin perfusion varies from person to person. Environmental factors such as extreme cold weather can also affect the heart rate sensors.
• Irregular movements during certain workouts, such as boxing or volleyball, will affect the readings slightly more than rhythmic movements, such as walking, running, or cycling.
• Cleaning your watch regularly with a soft cloth so that the sensors don’t get dirty or damaged due to clogging dirt is a good practice to ensure correct readings from your heart rate sensors.

Wrap Up#

For someone to have a device that monitors their heart rate throughout and picks up on irregularities, such as an abnormally high or low heart rate or atrial fibrillation, is a game-changer. Personally, I love using my Apple Watch to see my heart rate during a workout and how quickly it recovers from the same. It helps me so much in training and staying healthy, even if it lags, showing the heart rate by a few seconds.

Even for people with underlying heart conditions, having such a device handy can be a blessing. While no device can be 100% accurate at all times, Apple Watch still remains the cream of the crop, and for a good reason.

FAQs#