There's a chance your Fitbit, Apple Watch, WHOOP or another smartwatch device could mean more to your health than just counting your steps, recommending you go to sleep earlier or reminding you to get off your couch.
Known as fitness wearables, fitness trackers or simply a smartwatch, the devices are a more elaborate version of the everyday wristwatch, and millions are using them in a pairing with their smartphones to track various body metrics -- from heart rate and temperature to blood oxygen levels.
Dr. Michael Mina, an assistant professor of epidemiology at Harvard University, told ESPN that smartwatches are "incredible devices" -- so incredible that they have the potential to track COVID-19 and other viral diseases if "networked appropriately."
Coronavirus: Postponements and cancellations in sport
Mina is not yet ready to declare smartwatches ready to perfectly detect the coronavirus -- but they can get there, he said.
"What's needed first is to really aggregate that data and do supervised algorithms to essentially take all of this data, and then say OK we know that these people got sick and these people didn't, or we know that there was an outbreak here and there wasn't an outbreak here," Mina said.
He believes "subtle differences" in patterns of breathing or heart rate -- specifically while someone is sleeping, and thus stable over a longer period of time -- can be an indicator of being sick.
And some scientists and researchers are already making progress in wrangling the data.
Fitbit has two ways its users can help. One includes opting to share their data with Scripps Research Translational Institute as part of the DETECT Study. The data shared includes changes in heart rate, activity and sleep patterns.
Fitbit wearers can also opt in to be part of the PROTECT Study at Stanford University. There, researchers are using data collected from users of Fitbit, three other smartwatches -- including Apple Watch -- and one smart ring. Specifically, Dr. Michael Snyder's laboratory at Stanford is studying data from smartwatch users who have a confirmed or suspected case of coronavirus, have been exposed to someone who has a confirmed or suspected case, or are at a higher risk of exposure, such as health care or grocery store employees.
One of the metrics Snyder and his team are focusing on is how a smartwatch can measure heart rate and body temperature.
Heart rate is the number of times a heart beats in one minute. Though it can vary greatly from person to person, the normal resting heart rate for an adult is between 60 and 100. A lower rate means a person is in peak cardiovascular shape. Unusual numbers on the high or low scale could indicate an underlying illness. The challenge is that a heart rate can spike because of various factors including age, smoking, high cholesterol, diabetes, activity, weight and medications.
When you're sick, "your heart rate goes up before you're congested. ... So, worst-case scenario, it goes up around the time you're feeling yucky, but it probably goes up before that, we think," Snyder explained.
Seeing a spike in heart rate coupled with a jump in body temperature -- i.e., a fever -- might be cause enough for someone to stay home, curbing possible transmission of a virus.
There are 30 million Fitbit users around the globe, which puts Fitbit in a very consequential position during outbreaks and this pandemic, Amy McDonough, COO for Fitbit Health Solutions, told ESPN.com. She is not a doctor but leads the team focusing on health outcomes.
"[T]he idea is to [...] look at these early indicators and the power that wearables can have in showing early indications of illness, and eventually early detection and early warning systems is obviously the long-term goal. But even being able to recognize those very early, and being able to do that: detect, track and contain those diseases as early as possible," McDonough said.
Fitbit collects data to estimate a variety of metrics such as number of steps taken, distance traveled, calories burned, weight, heart rate, sleep stages, active minutes and location. The data is then transferred to Fitbit's servers. By agreeing to Fitbit's terms of use, wearers allow the company to use the metrics to improve their services.
"[W]hat we're going to continue to focus on is how do we support our users, how do we help them better understand their health metrics, how do we make that very accessible and very attainable, and how do we show them and point them to the best resources that we have, across our ecosystem," McDonough said.
WHOOP, another wearable that tracks key measurements such as heart rate variability, resting heart rate and sleep staging, has been part of a research effort focusing on changes in respiratory rate and COVID-19 symptoms in collaboration with the Cleveland Clinic and CQ University in Australia.
Emily Capodilupo, the vice president of data science and research at WHOOP, described to ESPN.com how important respiratory rate is in determining whether someone is showing symptoms of coronavirus. Respiratory rate, which is reported in respirations (or breaths) per minute, is recommended to be anywhere from 12 to 20 respirations per minute at rest.
If your typical respiratory rate is 14 but jumps to 17, a doctor might not find anything wrong since you are still between 12 and 20, Capodilupo said. But that is a big enough jump to be worthy of a closer look.
ESPN Daily Newsletter: Sign up now!
"It's really, really significant, and it means that your pulmonary system, your lungs are working a lot harder than they normally are," said Capodilupo, who is not a doctor but studied neurobiology at Harvard University and volunteered as an EMT for years. "But because that is still under 20, a doctor wouldn't necessarily feel particularly alarmed by it because they didn't see you two weeks ago when you were still 'healthy,' and so they don't know this is a massive, massive increase that we should very much be paying attention to."
Users of WHOOP are consistently monitoring their personal health data, giving them the tools to know when they are healthy and then when they could possibly be coming down with a virus. Because COVID-19 is a lower-respiratory infection, picking up on even the smallest change in respiratory rate is crucial.
"And so I think, really, the interesting takeaway from a lot of this is that if we were all monitoring our health with something like WHOOP, you can start to get a lot more valuable early warning signs and different indications when you are sick," Capodilupo said.
There have been previous success stories with smartwatches.
Before the coronavirus pandemic hit the U.S., researchers at Scripps -- and funded by the National Institutes of Health -- tracked data from 200,000 individuals who used a Fitbit between March 2016 and 2018. Focusing on data from more than 47,000 users in California, Texas, New York, Illinois and Pennsylvania, the researches published their work in January and found they were able to improve predictions of the flu at the state level.
"So I think that they're great inventions and I'm excited to see where that data goes and how it ends up becoming used," Harvard's Mina said.