When Eric Blue goes to the gym, he sports a wafer-thin shirt that tracks his every move.
Blue's shirt contains tiny sensors woven into the fabric. They monitor his heart rate, the calories he burns and other metrics, like breathing rate. A companion app on his smartphone informs him about the intensity of his workouts.
Blue, a Los Angeles entrepreneur, says regular use of the shirt has pushed him to "up his game" during exercise.
This is no ordinary shirt. It represents the evolution of the wearable-tech trend from accessories, like watches and bands like Fitbits, to clothing.
Blue, 38, was among the first people to buy a biometric shirt from the Montreal-based startup Hexoskin. Blue is a self-professed "fitness junkie" who goes to the gym at least five times each week, so he said the shirt is worth the $399 price tag. For Blue, it's far easier to throw on a Hexoskin shirt and go, rather than fiddle with a smartphone or chest strap.
"My old heart rate monitor is now sitting in the closet, gathering dust," he said. "It sounds very sci-fi right now, but in the future all of the personal data being collected by health and fitness sensors and smart watches will alternatively be readily available in our clothing."
Blue isn't alone in embracing smart clothing.
Athletes, astronauts and Cirque du Soleil performers have espoused the benefits of using Hexoskin and other smart clothing products. Smart shirts, athletic pants and socks started hitting stores last year.
But medical experts say they hope patients with serious or chronic medical conditions also can benefit from smart clothing.
"These companies will hit fitness fans first," said Stephanie Tilenius, founder of Vida, a mobile app that matches sick patients with personal health coaches. "But I see huge potential for chronic care."
It's still early for smart clothing, but the technology is evolving rapidly.
One company, Athos, based in Redwood City, Calif., is developing garments that can track people's muscle activity. Sensors can detect how hard muscles are working and whether a user is putting too much pressure on one side of the body, for instance.
Athos is focused on reaching passionate exercisers who want to make improvements to their exercise regimes, said CEO Dhananja Jayalath. "The people who buy our stuff are into fitness — they typically spent a lot of time working out."
As is the case with many startups, Jayalath started Athos to solve a personal problem.
He came up with the idea while studying electrical engineering in college. Jayalath, who frequently goes to the gym, said he couldn't stop thinking about whether technology could replace a personal trainer.
"After we came up with the idea, people told us we were crazy and it wasn't possible," he said.
It took Jayalath and a fellow electrical engineer five years to build a working prototype. The apparel can track muscle activity, heart rate recovery times and breathing rates. In the past, athletes would have needed to be hooked up to a machine in a performance lab to access all this information.
Like the Hexoskin apparel, these products won't come cheap. Athos shorts or shirts will cost $99 each, and will require a $199 sensor that fits in a pocket on the garment.
Although Jayalath didn't intend the products to be used for sick people, Athos has already received interest from the medical community.
The company anticipates that its clothing will eventually be used in clinical settings such as hospitals and rehabilitation clinics. Smart clothing could benefit patients with a variety of medical conditions, including heart disease and obesity.
"Gradually over the next few years, these low-cost, consumer-focused, data-rich devices and apps will bring to bear vastly more data than physicians have in some circumstances," said Pete Moran, a general partner at the venture capital firm DCM, which invested in Athos.
"Fitness shirts could find a market in rehabilitation and could facilitate home exercises. That's just a thought," said Dr. Molly Maloof, a general practitioner based in San Francisco who has been closely following the wearable tech trend.
But selling wearables as medical devices comes with strings attached.
"It would be far easier for a product like this to remain in the 'wellness' category," said Morgan Reed, executive director at The App Association, a Washington, D.C., nonprofit that works with patient advocates and app developers.
By saying they are helping to improve fitness and wellbeing, Reed said, these companies may hope to avoid stricter regulatory oversight as medical devices by the Food and Drug Administration.
And many physicians are not convinced that the data these devices gather is reliable enough to be used for patient care. This mistrust doesn't just apply to smart clothing, but the wearable-tech trend in general.
"There has been an explosion in patient-generated data, but much of it may not be useful to physicians in the short-term," said Dr. Pat Basu, chief medical officer at Doctor On Demand, an app that connects people to doctors.
"If a patient is showing me their blood pressure or heart rate they gathered from an app or device, I'll always ask myself, 'Is the fidelity of this information accurate or not?' " Basu says.
Wearable-tech makers should produce reports about each patient that doctors and nurses can skim, Basu says. Many physicians are already inundated with the wealth of data that patients are generating from new wearable apps and devices, he said.
Moreover, some doctors fear that they will be liable if they miss something in the growing pile of patient data.
Privacy is another concern. The App Association's Reed says he's satisfied that patient's sensitive health information is protected – for now.
But Reed expressed fears that the next crop of smart clothing companies might opt to offset the high cost of their products by selling people's health data to pharmaceutical companies, insurance providers and even employers.
"Would consumers understand that they're buying the version that is monetizing through data sharing?" Reed said. "That's the problem that everyone in the wearables industry is working on right now."