Your fitness tracker can measure your stress—and help you lower it. Here’s how

Toxic stress during the pandemic has fueled a wave of new stress management trackers. Offered in health monitoring devices by companies such as Fitbit, WHOOP, Oura Ring, Samsung, Garmin, and others, they aim to make users more cognizant of stress and learn tools for handling it.

Measuring stress

These trackers collect information on metrics such as heart rate, skin temperature, and sleep quality through cutting-edge sensors in smart watches, wristbands, and rings. They also continuously assess heart rate variability, or HRV, which is the balance between the body’s systems for ramping up to a challenge and slowing down to rest.

Some, such as Google’s Fitbit and Pixel, measure electrical changes in certain sweat glands that respond to stress and emotional arousal. This invisible “electrodermal” sweat “contains extra information about stress beyond HRV,” says Hugo Posada-Quintero, biomedical engineering professor at the University of Connecticut.

When combined, these metrics reveal psychological stress—like chronic worrying or work aggravation—that erode health and may otherwise escape our awareness. This so-called “unrecognized stress” is common in people with busy lifestyles.

The trackers show how other stressors, like exercise, are beneficial in the right amounts. Although some physical responses to exercise resemble unhealthy stress, the trackers may distinguish good stress from bad. If you’re moving your body in specified ways, they can determine that your fast pulse is from road running, not road rage. 

Stress scores and recommendations

All of this information gets rolled up into a daily stress management score. For example, Fitbit and Garmin offer 1–100 scales, where 100 means you managed stress flawlessly.  Across the various apps, these scores tend to focus on three main factors: mental stress, physical exertion, and sleep quality. 

If you’ve had too much exertion, your app might advise that you dial back on exercise. If anxiety has been dropping your overall score, your app will recommend meditation sessions. In October, Oura teamed with Headspace to add guided breath work and visualizations to its audio library.

These systems also notify you in real time when stress is peaking, with suggestions for decreasing it. This can take some getting used to. When Hananeh Esmailbeigi, a biomedical engineer at the University of Illinois at Chicago, got the first notification from her Apple Watch that she was stressing out, it stressed her out even more. Lately, though, she says the pop-ups have become much-needed reminders to use the stress management techniques she’s learned from books and podcasts.

Quantifying your habits and experiences can encourage behavior changes for stress management. If you eat a large, sugary meal before bed, for example, your stress numbers go up as the digestive overload increases heart rate. The sensors will further detect how the late meal disrupts sleep. 

Objective data makes it harder to overlook or rationalize mistakes, reinforcing motivation to avoid them. Stress trackers also reveal specific triggers of negative emotional stress, so you can mitigate or avoid these situations.

Trackers also reinforce positive stress. This goes beyond exercise to include intermittent fasting, saunas, and cold plunges. These experiences strain us in the moment, but unlike toxic stress, they pack a rebound effect that strengthens bodies and minds. 

“Our bodies need stress,” says Kristen Holmes, VP of performance science at WHOOP. “And understanding the dose and frequency is important.”

Some trackers deploy AI coaches that analyze your stress data to give personalized tips. In September, WHOOP partnered with OpenAI to integrate a large language model. “It’s like texting with a friend about your health, but this friend knows more about you than your doctor,” says Holmes, a Ph.D. candidate in psychology at the University of Queensland. 

In early 2024, Fitbit will start rolling out similar AI coaching. Generally, these models are engaging but nascent, Posada-Quintero says. He thinks they’ll become more effective as they’re designed more specifically for health.

Challenges and workarounds

One challenge when using these trackers is accuracy. People prefer devices designed for the hand area, but the sensors work better in other areas. The constant movement of your hands can skew data. “There’s a reason they haven’t yet been [FDA-approved] as medical devices for certain metrics like HRV,” Esmailbeigi says.

There are some workarounds. Algorithms remove many of the “motion artifacts.” With WHOOP, you can wear the band on the bicep, which produces less movement and more precision. To get more information on electrodermal sweating, you can put your palm on Fitbit’s watch face, which measures more sweat glands while you’re motionless for two minutes.

A remaining issue is distinguishing negative and positive emotions. Say you felt excited after a work promotion. Your device may confuse your happiness with agitation. To address this issue, some apps let you note what was actually happening when stress was detected through journaling tools, such as Oura’s recently launched, AI-enhanced Reflections. 

Rosalind Picard, an MIT Media Lab professor and trailblazer in measuring emotion through computing, says that more research is needed to design labels that people can use to gain awareness of their feelings, including stress. “Consumer devices oversimplify the complexity of stress,” Picard says.

Until then, Esmailbeigi recommends journaling outside the app to reflect on stress levels, what you’re learning from the device, and issues that are affecting measurements—for example, a smart watch slipping down the wrist too far. (Esmailbeigi is researching a solution to that problem: putting the sensors in mouthguards.) 

Picard founded a smartwatch company called Empatica that meets FDA requirements for measuring electrodermal activity, HRV, and more. It’s available to participants in clinical trials. Commercially sold sensors and stress scores still have a long way to go, Picard says, but there’s reason for excitement. “We originally thought this stuff was crazy when we built the first working devices,” she says. “Now, here it is, happening.”