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I ride a recumbent bike while wearing my smartwatch, hoping that tracking my fitness and health metrics will inspire me to exercise more.

The smartwatch is no longer just for texting, music and time (how old school), but instead has become an integral part of some people’s health routines. So can it detect heart problems, such as irregular heartbeats or even heart attacks? How about using it to measure oxygen or blood sugar levels? And can it help with sleep?

More than a quarter of the US population wore a smartwatch or other connected device used to track health and fitness in 2023, according to Insider Intelligence/eMarketer. By 2026, more than 100 million Americans are projected to use a smart wearable device.

To answer my smartwatch health and fitness questions, I spoke with CNN wellness expert Dr. Liana Wen. Wen is an emergency physician and clinical associate professor at George Washington University who has a smartwatch and enjoys sports. She previously served as Baltimore’s health commissioner.

CNN: Let’s start with the basics. How do you define a smartwatch and how can people use it to track exercise and fitness?

Dr Liana Wen: A smartwatch is a type of wearable technology device that resembles a wristwatch. Many are Bluetooth enabled and can connect the watch to a smartphone. This allows the user to access some of the phone’s capabilities, such as receiving text messages, listening to music, or even answering phone calls and emails.

Many smartwatches also allow tracking of fitness and health data. One feature I really like is step tracking. Studies show that setting daily step goals can reduce the risk of heart disease and early death.

A study published in March, for example, found that in people who were sedentary most of the day, taking 9,000 to 10,000 steps a day reduced the risk of developing cardiovascular disease by 21% and the chance them for premature death by 39%. Another study published last year found that even just 4,000 steps a day can reduce the risk of early death.

Wearing a smartwatch helps keep track of how many steps you’ve taken throughout the day. It can remind people of their goals and can be a way to motivate people to take more steps.

CNN: You’re a runner and triathlete. How do you and others who are already active use your smartwatches to help with your workouts?

Wen: What many active people do is track their heart rate during exercise to keep their heart rate in a certain range. Many endurance athletes such as runners, cyclists and triathletes spend most of their time training in what is known as zone two, or the endurance zone. This is where your heart rate is below 70% to 75% of your maximum heart rate. You feel like you’re working, but not so hard that you can’t sustain the exercise.

A smartwatch with a heart rate monitor can help athletes monitor their heart rate so they can stay in their target zones. More advanced smartwatches have more fitness features, such as tracking pace, distance and running cadence, and some can even detect the type of sport being played for people switching between different disciplines. Some have GPS data and can provide the user with directions.

CNN: I’ve seen smartwatches that say they can detect heart problems. Can they really be used to mark heart attacks?

Wen: Smart watches are not approved for diagnosing heart attacks. If you have chest pain and your smartwatch shows that your heart rate and electrocardiogram are normal, that doesn’t mean you’re fine. You should seek medical attention immediately.

It is important to remember that smartwatches are not a substitute for medical monitoring equipment. People who have been told by their doctors that they need a specific heart monitoring device should heed this advice.

CNN: What about the irregular heartbeat?

Wen: There are many smartwatches that claim to detect an irregular heart rhythm called atrial fibrillation. This heart rhythm can increase the risk of stroke if left untreated and is important to diagnose.

The Apple Watch, Fitbit Sense and Samsung Galaxy are among the few smartwatches that have received approval from the US Food and Drug Administration for their ability to detect irregular heartbeats in a subset of adults who have no history of atrial fibrillation.

If someone with no prior heart abnormalities receives such a notification, they should contact their primary care provider and ask about next steps, which may include an in-office EKG and ongoing medical monitoring.

Again, I want to point out that you should also listen to your body. If you experience palpitations, shortness of breath, chest pain, dizziness, or other strange sensations, you should contact your doctor, even if your smartwatch says your heart rate and rhythm are normal.

CNN: What about using smartwatches to measure oxygen levels or blood sugar?

Wen: The accuracy of smartwatches in measuring oxygen levels is variable. My opinion is that if you are someone who needs to measure oxygen levels because you have lung problems, for example, you should use special equipment for that purpose. A pulse oximeter is inexpensive and easily portable. In general, they are reliable, although recent studies show that they are less so in people with dark skin.

When it comes to blood sugar, the FDA issued a strong warning this year, advising consumers not to “purchase or use smart watches or smart rings that claim to measure blood sugar levels.” These devices can give inaccurate measurements of blood sugar levels.

People with diabetes who need accurate measurements to dose their medications may end up giving themselves too little or too much medication if their blood sugar measurements are inaccurate. This can be dangerous. They should continue to use the measuring devices as prescribed by their clinicians, knowing that smartwatches cannot yet duplicate the accuracy of this medical equipment.

CNN: Can using smartwatches help sleep?

Wen: Possibly. Many smartwatches track sleep and can tell you how long you slept and how much time you spent in each stage of sleep.

I personally find this information helpful. I’ve always had trouble sleeping, so I’m constantly experimenting with different things, like meditating before bed, reading a book, and sleeping in different positions. I like the data my smartwatch gives me about sleep quality and duration. I can try to correlate this with the changes I make to my sleep environment to see which changes work and which don’t.

I also like the feature on my smartwatch that tracks heart rate variations during sleep. This is a measure of the variation in time between each heartbeat. Everyone’s baseline heart rate variability is different. By knowing your own baseline, you can track changes over time.

I’ve found, for example, that when I’m not sleeping well or have had recent heavy training blocks, my heart rate variability decreases—a sign of more stress and less recovery. I can then work to prioritize extra sleep time or adjust my training based on this data.

My main takeaway from smartwatches is that they’re good for data-loving people. This is me and I like my smartwatch because it gives me data that can help inform and motivate me. There are also people who may find all the data useless or even stressful. The key is to do what works for you. Smart watches are a tool that can help you with your health and fitness goals; they should not add more pressure and stress to your life.

CNN: I’ve heard that smartwatches aren’t always good for people who have a compulsive urge to exercise.

Wen: There are some people who could benefit from a break from tracking data. Exercise should be fun and enjoyable, and if all the data adds to the tension and stress, it’s worth leaving the smartwatch at home a few times to see if it makes the activity more enjoyable. Also, it’s always important to listen to your body.