An electrical current is pumping into T.J. Oshie when he is working out, when he is warming up before games, when he is recovering after them and when he is sleeping, roughly 12 hours a day in all.

The Washington Capitals forward is one of roughly 75 NHL players who make the Accelerated Recovery Performance (ARP) machine part of their daily routine. Electrodes are attached to him as often as shoes are.

In large part because of player testimonials — proponents include Chicago’s Jonathan Toews and Duncan Keith and Minnesota’s Zach Parise — the ARP has become a more common sight in NHL locker rooms, though teams don’t endorse the machine. It is approved by the Food and Drug Administration, but a neurologist and a physical therapist interviewed for this story said that while the ARP doesn’t do any harm, the evidence for it being a benefit is empirical and anecdotal.

In the Capitals’ locker room, Oshie and defenseman Taylor Chorney are the most avid ARP users, even putting electrodes on their forehead because “it feels like you’ve had five cups of coffee,” Chorney said. Their enthusiasm eventually spread to defensemen Karl Alzner and John Carlson.

The device releases an electrical impulse to signal the brain to lengthen certain muscles, with the intent of increasing flexibility and blood flow and breaking down scar tissue. The sensation is one of prickling or tingling. One machine is intended for therapeutic purposes, while a variation is designed for training. Each is portable, small enough to fit in a backpack. Cords hang from each machine, connecting the electrodes to it, and a touch screen at the front has a timer and settings to control the pulse frequency and flow of the current.

A detail photo of the ARP device T.J. Oshie is attached to as many as 12 hours a day. (Ricky Carioti/The Washington Post)

“Last year we were the outcasts, and everybody was kind of looking at us like we were idiots,” Chorney said. “You’re putting it on your forehead, and they’re wondering what the heck is going on. Guys get curious.”

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Oshie had been having chronic lower-back pain when his roommate and St. Louis Blues teammate Chris Porter suggested he try using the machine as a way to warm up before a game. The pain went away almost instantly, and Oshie was hooked.

When Oshie broke his ankle in November 2010, he rented an ARP to use throughout his rehab. Electrodes were attached to him between 16 and 20 hours a day. He was back on the ice in January, a month ahead of schedule.

“That kind of sold me there,” Oshie said.

When Oshie was traded to Washington in the summer of 2015, he started working with EVO UltraFit and owner Jay Schroeder, and a lot of the training program involved the ARP. Schroeder uses the ARP on himself and also said his dog sleeps with electrodes attached to it every night. (Schroeder cautioned that the ARP is unsafe for cats.)

Schroeder is available on call for Oshie, and if Oshie wakes up from a pregame nap with a stiff neck, for example, he can text Schroeder for immediate instructions about how to work out the stiffness with the ARP.

Part of Schroeder’s service to Oshie is occasional visits, and he was in town this fall when Oshie injured his shoulder against the Detroit Red Wings on Nov. 18. Oshie said he was using the ARP 13 to 14 hours a day when he was injured, attaching the electrodes as soon as he put his two daughters to sleep. That, coupled with the work of Washington’s training staff, had him back in the lineup after seven games, slightly earlier than expected, Capitals Coach Barry Trotz said.

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Alzner used the ARP about a month before training camp as he was recovering from sports hernia surgery and a groin injury. But he admitted to being nervous to try it.

“It doesn’t seem right, you know?” Alzner said. “It’s weird to see what your muscle does when it’s on, how it moves and it contracts. It just doesn’t seem right. Then once you figure out exactly what it’s doing and get some more information on it, then it starts to make more sense.”

As Capitals center Jay Beagle recovered from a broken hand last season, he was struggling to get the swelling to go down, so Oshie suggested Beagle try using his ARP for a few weeks. It seemed to work, but Beagle still remained slightly skeptical.

“I just don’t know if it actually works,” Beagle said. “I don’t like doing things that don’t help, you know what I mean? But I think it did help. It helped the swelling get out. Would it have been the same thing — you know, it was a two-week process — so would it have been the same with ice and all that?”

Research on the ARP and similar electrical stimulation devices is sparse. The lone independent study of the ARP was conducted at the University of Hawaii medical school, which tested 25 patients recovering from anterior cruciate ligament reconstruction. It concluded that the ARP “significantly improves” quadriceps strength after ACL surgery.

“A lot of it is the anecdotal evidence that the players really, really stand by it and say, ‘This seems to give me an edge,’ ” said John Bottoms, a physical therapist at TRIA Orthopaedic Center in Minnesota. “If they feel that ARP gives them that, that’s beneficial to them . . . I haven’t seen any negative effects, so if I have an athlete that says, ‘I want to do ARP,’ I would never say, ‘I don’t think you should do that.’ ”

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Beagle isn’t against the ARP and respects the teammates who use it every day, but he also isn’t shy in teasing them about it, joking that it’s “a toaster.”

“Sometimes a certain player — I’m not going to say who — will sit there with it on and say, ‘I’m getting so warm right now,’ ” Beagle said. “He’s doing a warmup mode on it. I’ll be riding the bike, like hard. And I’ll be like, ‘No, this is warm,’ you know what I mean? I’m getting my body warm, and he’ll just be sitting there with it on his head.”

Along with using the ARP for therapeutic purposes, many players work out with electrodes on their forehead or body. Cords dangle from them as they’re squatting or lunging. Some sleep with it because “it’s a great time to train,” Schroeder said. Alzner initially heard “that you could pretty much sit there and strap it on and it’d be your workouts and you didn’t have to do anything.

“Of course, that piqued my interest,” Alzner said. “That’s a game-changer then, obviously. I can watch TV and work out.”

In reality, it’s the opposite. Oshie and Chorney are part of a group of players who train with Schroeder and EVO UltraFit in Minnesota during the summer. Oshie said the offseason training with it was so intense that he wasn’t sure he could continue on after two weeks.

“It’s a lot of stuff you don’t normally see in a gym,” Islanders forward Anders Lee said. “It’s a lot of iso holds, and you’d be expected to do these lunge holds for five minutes. You’re not allowed to fail basically.”

Schroeder said he has gotten resistance from some NHL teams who aren’t comfortable with him coming to their practice facility. The Capitals don’t endorse the machine, but they understand that players have certain preferences.

“At first, definitely, everyone’s like, ‘What are you doing?’ ” Lee said. “So many guys now around the NHL are using it. I think the number is growing each year. I guess now we’ve gotten past the initial shock value.”