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9 Surprising Things Your Fitness Tracker Knows About You

An activity tracker can reveal way more than just your step count. Here, what your tracker is secretly keeping tabs on—from pregnancy status to chronic pain management.

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Your fitness tracker knows: If you're pregnant

Okay, so your fitness tracker can't see inside your womb (yet) but one couple found out from their gadgets they were expecting. David and Ivonne Trinidad of New York City discovered the happy news after Ivonne's FitBit showed a sharp spike in her resting heart rate that lasted for several days. At first they thought the activity tracker was broken, but someone suggested that pregnancy can raise a woman's heart rate, as the heart must work harder to get extra blood to the uterus. So Ivonne took a test; their baby is due in November. Now, we're not saying FitBit would make a good name for a child, but it could be a cute nickname?

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Your fitness tracker knows: If you'll die in three years

Your heart rate variability (HRV), or the variation in the intervals between your heart beats, is an important health stat that most people don't know—but your fitness tracker may tell you. The more variation in your heart rate, the healthier you are, as researchers say it shows that your ticker is resilient and strong. Studies have shown that low HRV is linked with heart disease, metabolic syndrome, and even a higher risk of dying in the next three years.

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Your fitness tracker knows: How intimate you get

It's not just your workout that can send your heart rate racing, discovered one FitBit user known only as "Jess" (for reasons which will soon become apparent). After looking at her daily readout, she realized that her fitness tracker was tracking her sexy times as well as her sweaty times. No big deal—it’s personal data, right? But many activity tracker users make their data public through social media platforms. "What workout were you doing last night at 10:30, Bob? It looked intense!" probably isn't what you want to hear the next day at work.

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Your fitness tracker knows: If you've committed a crime

Last year, Jeannine Risley, then 43, of Saint Petersburg, Florida, reported that she was raped by an intruder while staying in her boss’s Lancaster, Pennsylvania home for work. But her fitness tracker told another story, and ultimately helped get Risley charged with crimes including false reports to law enforcement and tampering with evidence. Police quickly spotted holes in her story when they realized that the data on her FitBit was wildly different than what she said she was doing. Specifically, it showed her heart rate elevated (as she trashed the home) instead of even and slow (as it would have been had she been sleeping, as she claimed). This isn't a one-off case, says Adrianne McMahon, a public defender in Minnesota's third judicial district. "You have to assume that anything you put online is potentially available to the police, even if you think it’s private,” she says, "and that includes fitness tracker data."

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Your fitness tracker knows: If you're in pain

Chronic pain is one of the most difficult problems facing modern medicine. It can be tricky to pinpoint what triggers a person's pain, when it happens, and how intense the pain is. But now professionals are using fitness trackers to find answers. Trackers can capture spikes in your heart rate and your activity patterns, which doctors can combine with a quick texted pain survey to find out the specifics of your particular pain cycle. They can use this info to help come up with an effective plan for managing it. Here’s how one psychologist uses activity trackers to help his patients manage their pain.

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Your fitness tracker knows: How well you're sleeping

Just because you crawl into bed at 10 p.m. doesn’t mean you’re getting solid sleep. (Oh hello, Netflix! How did you get on my phone?) Yet getting enough quality sleep can be one of the best things you can do for your health, which is why fitness trackers now track not just the duration of your actual sleep but also how well you’re sleeping. Depending on the make and model, your activity tracker can tell you how many times you wake up at night, how long it takes you to fall asleep, how much you move in your sleep, and how many times you hit the snooze button before getting up. (For example, here’s how the FitBit tracks your sleep.) Then you can makes changes to make sure you’re getting all the rest your body needs.

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Your fitness tracker knows: If you're cheating (on it, not your partner)

Who hasn't been tempted every once in a while to shake their fitness tracker while lounging on the couch, just to make sure you hit your 10,000 "steps" for the day? Those cheat days may be over as researchers have strengthened the computer algorithms to recognize dishonest activity. While previous trackers were only able to tell a faker 38 percent of the time, the latest versions are now near 90 percent. This is important not just to keep you honest with yourself but may also help your health as insurance companies and doctors rely more and more on this type of information.

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Your fitness tracker knows: Where you are

Many fitness trackers come with GPS capabilities. This can tell you where are at any given moment as well as provide an accurate timeline and map of where you've been—even when the device is not actively "on." It works similar to the location service on cell phones, but many people don't realize their fitness tracker also does that, or they don't know they can turn it off.

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Your fitness trackers knows: Your blood work (soon)

Tracking technology is advancing faster than an Olympic sprinter. Several companies have gadgets on the horizon that will make it possible for our fitness trackers to give us even more detailed biometric information. Jawbone recently announced a tracker in pill form that can be swallowed. Chaotic Moon says they've developed tracker tattoos that adhere semi-permanently to your skin. Both companies say the new devices will be able to track things like digestion, blood sugar, cholesterol, and even test for certain diseases.

Originally Published in Reader's Digest