Gaining jacked-up physical powers from frontal-lobe-electrifying headgear sounds like a half-baked superhero origin story. It’s also a premise that athletes are buying as reality. NBA players and Olympians are wearing a brain-stimulation device called Halo Sport in an attempt to transform into champions.

The $649 Halo Sport is sold by a San Francisco startup called Halo Neuroscience. The device looks like a bizarro, limited-edition pair of Beats headphones. Like Beats, the headset can play music; unlike Beats, its primary purpose is to electrically trigger the brain using a method called transcranial direct-current stimulation, or tDCS. The science is knotty, but Halo’s sales pitch is fairly simple: Electric pulses emitted from the headset will jolt the brain’s motor cortex, boosting athletic performance. Without any additional physical effort, and just by adding fancy headgear to their training regimen (they can also be worn while at rest), an athlete can biohack their way to victory.

“Do nothing extra yet improve anyway” is an appealing sell. If Halo assured me its device could prime my mind to make me a superior writer, I’d buy five, stack them on my head like a real psycho, and remove them only to shower. Who would pass up the chance to get better without trying harder?

The Golden State Warriors didn’t refuse. The team wore Halo Sport in training last season. NFL hopefuls used it as they trained for a regional scouting combine. Olympians are putting it on as they prepare for Rio. For the U.S., hurdler Michael Tinsley is using Halo Sport, as are relay sprinters Mike Rodgers and Natasha Hastings. Mikel Thomas, a hurdler competing for Trinidad and Tobago, is also training with the device.

Sierra Leone sprinter Hafsatu Kamara has added Halo to her routine as she prepares for the Summer Games. Kamara uses Halo for two or three training sessions a week. Although she has been using it for only three weeks, she has noticed a difference. “I’m just on point,” she told me over the phone.

“I’ve definitely seen a change in how I’m recovering,” Kamara said. “My coach even mentioned that I’ve basically turned a corner faster in my training and recovery than I have in the past. And I want to say that it’s supplementing … how I recover and get back in sync and [the fluidity] in my movements.”

Using a Halo Sport is not complicated. You can adjust for the intensity of the waves, but other than that, the directions are essentially “put this thing on your head.” (For good measure, Halo instructs athletes how, exactly, to position the headset.) Halo Sport, unlike other exercise gadgets that promise effort-free results — like ab belts — doesn’t pretend that it works out for you. The Halo promise, instead, is that it rejiggers the brain to make it better at receiving signals from your muscles, despite intense fatigue. An athlete still needs to train as hard as they did before, but their body will be better prepared to process and recover from that training.

I haven’t been able to try Halo Sport myself (they’re on pre-order, and the company didn’t have any press units available), so I asked Kamara what it feels like to wear it. “It’s like a tingling sensation,” she said.

Of course, “tingling” doesn’t mean it works.

“The strategy here is applying this electrical wave form to the part of the brain that’s responsible for controlling movement; it’s called the motor cortex. And it happens to sit right above our ears, anatomically, which allowed us to build our neurostimulator into a headphone form factor,” Halo CEO Daniel Chao told me over the phone.

Halo claims that this brain zapping — the tDCS — will put your brain into a special state of “hyperplasticity.” The theory, according to the company’s website, is that the transcranial direct-current stimulation helps “build optimized neuronal circuity for athletic movement — similar to how proper nutrition makes training more productive for the body to build muscle.” In other words, it’s like a “preworkout for the brain,” using electricity instead of creatine dust. That’s how Halo describes it.

Chao, a Stanford-trained neuroscientist, has experience designing and selling other neurostimulators. He was head of business development at NeuroPace, which created an electric “brain pacemaker” to help treat epilepsy. The FDA-approved RNS System, a medical device that requires surgery for it to be implanted into a patient’s skull, is a vastly different device than Halo Sport.

Meanwhile, Halo Sport doesn’t require skull-opening, nor does it need FDA approval. (As long as the products are marketed as recreational and not as therapeutic or diagnostic, their makers don’t have to bother with FDA approval.) Far from requiring implantation, you’re meant to wear it for only a short amount of time. Athletes are advised to wear the device for 30 minutes at a time, and no longer. “There’s diminishing returns, so after 30 minutes, there’s really no reason to wear it any further,” Chao said. “You get the effect after 30 minutes and, if anything, there could be the chance for a little bit of skin irritation or something like that.”

The amplitude of the electric waves is adjustable, from 1 to 10. Chao says most athletes prefer to wear it cranked up to the highest level. That is how Kamara prefers to practice — at maximum tingle.

Halo has aggressively courted elite athletes in its first PR push, but Chao says high-end competitors aren’t the company’s only targets. “We find that it’s actually easier for us to get a result from unskilled athletes than it is for us to get a result from skilled athletes,” he said.

If you go to Halo’s website, you’ll see a section highlighting case studies that are presented as evidence. “Professional and Olympic athletes improve performance after training with Halo Sport,” the site reads.

It’s a bold claim — one that some neuroscientists believe is overblown.

“To put it simply — it’s quite clear that Halo (along with most companies trying to sell neuromodulation devices) are overstating their claims. The evidence is simply not there that tDCS can improve basic motor learning, let alone complex athletic learning,” neuroscientist Jared Cooney Horvath, who studies transcranial direct-current therapy, told me via email.

“The truth is — if you want to become an elite athlete, there still is only one prescription: deliberate practice,” Cooney said, stressing that old-fashioned sweat is far more efficient than strapping on a device.

“Everything we know about tDCS and electrical neuromodulation suggests that, even if tDCS could somehow enhance elite motor skill training (and, again, there’s no evidence it can), there would be no way to determine which athletes would benefit and under which conditions — the reliability and predictability of this device is incredibly weak, to the point of nonexistence,” Cooney said.

UCLA clinical psychology professor Robert M. Bilder has overlapping doubts. Bilder directs the Tennenbaum Center for the Biology of Creativity, which researches innovations in cognitive enhancements. He wasn’t impressed with Halo’s research. “I did take a look at what they call their science on their website, and in support of their product they have three articles, none of which has been published in a peer-reviewed referee journal. It’s just internal documents describing the experiments that they’ve done,” he told me.

“I’m just eager to see a randomized control trial of the use of their device, relative to a good control condition, that shows that it is actually enhancing the outcome of the athletic performances that they claim are going to be benefiting from using their device,” he said. “Then, I’ll be persuaded that it actually works. But so far, I think they’re way short of having that kind of evidence.”

It’s not that Bilder thinks Halo Sport absolutely won’t ever work; it’s that he thinks there isn’t research to prove that it does. “It strikes me that the claims that they’re making are substantially greater than there is evidence to support those claims,” Bilder said.

I asked Chao about the lack of peer-reviewed evidence supporting Halo’s claims. He didn’t seem surprised by the question. “Academics are really interested in us publishing something. As a for-profit company, that’s not our mandate,” he said. Chao said that Halo does intend to publish additional studies to aid scientific research, but that it isn’t his primary responsibility. “As the CEO of the company and also the chairman of the board, I have a fiduciary responsibility to build a business here. Patents come before publications.”

Chao has reason to hurry Halo Sport’s release: It may not stay a novelty much longer. Recreational and non-medical neurostimulators are a relatively new product category, but there’s already blossoming competition among products that claim they can do something to your mood or abilities by electrical stimulation. And the market is paying attention: Red Bull, for instance, is already piqued by the idea that neurostimulators have a role to play in the future of athletics. The company has tested various neurostimulators for its Project Endurance experiment.

Halo has plenty of startup competition, although its focus on fitness enhancement helps distinguish it from other noninvasive neurostimulators. There’s Thync, which claims it can relax or energize users by stimulating the trigeminal nerve, or the Fisher Wallace Stimulator, which is FDA-cleared to treat anxiety, depression, and insomnia. (Although people using it aren’t supposed to stop taking medication.) The foc.us v2 uses transcranial direct-current stimulation, just like Halo Sport, but it aims to improve reaction time for video and computer gamers.

There’s also a DIY transcranial direct-current stimulation community, where people cobble together homemade devices instead of buying the latest equipment, swapping tips on how to make the cheapest gear. Tutorials on how to make a stimulator at home using dish sponges and other household supplies have racked up hundreds of thousands of views on YouTube. This doesn’t necessarily mean that DIY users will flock to Halo Sport, especially since their at-home tDCS devices cost a fraction of the price, but it certainly suggests there is avid interest in the technology.

Something that’s mildly comforting about the new field of brain stimulation is that its known side effects are generally far less scary than your average prescription drug warning. Even a 2014 study urging researchers to be highly cautious when introducing brain stimulation to children noted that its mild side effects are simply “scalp tenderness, headache or dizziness,” and that the more serious risk of seizure is present but very low. Then again, that same study also emphasized that we don’t have much research on the long-term effects of tDCS.

I am not an elite athlete. I’m barely a casual fitness enthusiast. I also have never tested the Halo Sport, as I mentioned earlier (I’m not scientifically minded enough to develop my own criteria for whether it works or not, anyway). I would probably say what Kamara said: It tingles! I was a swimmer in high school, and there’s one performance-enhancing trick I will never forget, mainly because it made me very itchy — we weren’t allowed to shave for months. The theory went like this: Extra hair on our bodies created additional resistance in the water during practice. When swimmers finally shaved down before a big competition, they became faster. This wasn’t unique to my training; it’s a standard swimmer’s ritual. The shaving trick is not yet backed by robust evidence, but swimmers still embrace it. Any edge, no matter how scientifically nebulous, is better than none.

Or so the thinking goes. There’s a difference between athletes performing a DIY hair-removal ritual and spending hundreds of dollars on a device. Only in the latter scenario does a company profit off a shaky promise of an athletic boost. Then again, the Halo may still have value as a placebo, especially for elite athletes who don’t have to personally shell out for the device. As New York Magazine’s Science of Us pointed out in a recent piece on the Halo, a placebo can still have a measurable biological benefit. Perhaps athletes don’t give a shit if they’re improving because of motor cortex priming or because they simply believe that they’re getting better — the important factor may be that, either way, they’re improving.

For its price point, the Halo would be a ridiculously expensive placebo.

There are five Olympians, including Kamara, who are using the Halo as they hone their skills in preparation for Rio. Perhaps they will all win gold medals by boggling margins and effusively thank Halo Neuroscience on the podium. If that happens, it’ll be a fantastic publicity moment for the company — but it won’t end questions about the device. After all, if the Halo is a breakthrough training tool that uses electricity instead of supplements to improve athletic performance, it will fall into a new category of performance-enhancing tactics, one known as “neuro-doping.” And it may eventually be seen and regulated as a performance enhancer that provides an unfair advantage. “Neuro-doping” includes nootropics like Modafinil, an alertness medication. But it also refers to the heightened sense of stimulation that can be achieved by zapping your brain.

I asked performance-enhancing drug expert and Penn State professor emeritus Charles Yesalis what he thought about the Halo and neuro-doping. “I don’t have a clue about that,” he said via email. But other PED experts are catching on. “The World Anti-Doping Agency is concerned with any nontherapeutic use of a therapeutic substance or method, and this includes neuro-doping. In fact, cognitive enhancers are one of the major worries of WAPA,” Andy Miah told me. Miah is an ethics professor at the University of Salford, Manchester, in the UK, and he has written books on doping and the Olympics. He is in Rio researching the doping debate.

“In the last few years, the substance Modafinil has been one of the watch drugs of choice for athletes as it could provide great alertness and capacity to focus for longer. With so much of an athlete’s performance dependent on cognitive abilities, neuro-doping is a large area of concern for the world of sport,” Miah said.

There’s a long list of substances, biohacks, and other trickery that may give an advantage but will definitely cause a scandal if athletes are caught using them: steroids, HGH, blood doping, and equipment tampering, for example. Halo Sport has the advantage of being legal, and not being banned by governing sports bodies.

If Halo proves to be as effective as its promotional materials claim it is — if it crosses over from a promising experimental toy to a demonstrably reliable athletic aid — the company will quell criticism about charlatanism. But it could come under scrutiny because it works.

For now, we’ll watch as world-class athletes who’ve donned the brain-zapping device compete in Rio to see if those “tingles” — placebo or not — can earn them a medal.