Do fitness trackers really help people move more?

About one in five people has a smart watch or fitness tracker, according to a recent survey. These wrist-worn monitors are a handy way to track your daily steps, and they're probably more accurate than the tally from your smartphone, which you might not carry with you every waking moment. Most wearable gadgets also offer an array of other data, such as your heart rate, walking pace, and more.

But does using one affect how active people are? According to the largest study to date on the topic, the answer is yes (see "Fitness trackers and activity levels: What's the evidence?"). Regular physical activity is vital for a healthy heart, and the improvements seen in this study could potentially make a difference, says Dr. Megan Wasfy, a cardiologist at the Cardiovascular Performance Laboratory at Harvard-affiliated Massachusetts General Hospital.

"The increase in moderate-to-vigorous physical activity was close to 50 extra minutes per week, which is one-third of the 150 minutes recommended by the federal activity guidelines," says Dr. Wasfy. The extra 1,200 daily steps taken when people were wearing trackers is about the same number that's been linked to a longer life in several studies. While 10,000 steps has long been touted as a daily goal, research suggests that 8,000 steps a day is nearly as effective longevity-wise, particularly in older populations.

No long-term data yet

The key, however, is to keep being physically active throughout your life, Dr. Wasfy says. Because many of the studies in the review lasted just a few months, it's impossible to know whether wearing a fitness tracker will promote lasting change in a person's behavior, she adds. And using a fitness tracker to change behavior requires a few more steps than simply being active — you also have to remember to keep the tracker charged, wear it consistently, and check your data.

Many people who might be motivated to use these devices are already regular exercisers, Dr. Wasfy points out. Such people tend to use them to step up their program or train for a race, rather than to transition from being mostly sedentary to more active. But if you're in that latter camp, a fitness tracker can be a useful tool, says Dr. Wasfy. "For people who are motivated to start exercising more, sometimes the day-to-day feedback on their progress helps keep them engaged," she says.

Tracker info

Activity monitors contain various sensors to track your movement and other health parameters. One basic feature is a sensor that shines a light through the skin to detect blood flow, revealing your heart rate. Another is the accelerometer, which tracks movement and velocity and enables the device to count steps. For people who want extra detail to help boost their performance, a global positioning satellite (GPS) sensor provides a more accurate assessment of your speed, distance, and pace during a walk, run, or ride.

For the average person, being able correlate how intensely you're exercising with your heart rate can be interesting, although it's certainly not mandatory, Dr. Wasfy says. If you're not interested in using a fitness tracker, the old-school "talk test" is an easy way to gauge exercise intensity. During moderate-intensity exercise, you should still be able to speak in full sentences but unable to sing.

However, if you've recently recovered from a heart attack or heart surgery or if you have other heart issues, you may need to monitor your exercise intensity more closely, and the heart rate function on a fitness tracker offers an easy way to do that. "High-intensity exercise may come with some added risk, so ask your doctor about a heart rate goal that makes sense for you," she advises.

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