For many NHLers, it’s a long-accepted pre-game ritual: In the moments before puck drop at the Air Canada Centre on Sunday night, it’s a good bet Maple Leafs teammates Mitch Marner and Matt Martin will indulge in an enthusiastic sniff of a freshly cracked ammonia capsule — commonly known as smelling salts. Marner and Martin, like legions of fellow pros, have both been hyping themselves up by inhaling the stuff for years.

“The first sniff, it clears up your nostrils a little bit,” Marner, 20, said in a recent interview. “The second one, it feels like it gives you a little more go power — adrenalin.”

Said Martin, 28: “It burns the hell out of your nostrils sometimes. But it gives you a bit of a wake-up. It’s like, ‘OK. Let’s do this.’ ”

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Smelling salts have been around for centuries. Once a Victorian-era remedy for fainting and later a boxing-ring fixture used to revive dazed fighters, they have more recently become a go-to pick-me-up everywhere from football sidelines to baseball dugouts. Never mind that there is no compelling scientific evidence that they actually enhance performance, or that they’re safe. Even Tom Brady, the five-time Super Bowl-winning quarterback famous for treating his 40-year-old body like a sacred temple, has acknowledged using them.

“We all do it,” Brady once told a Boston radio station, speaking for his NFL brethren.

Said Morgan Rielly, the veteran Toronto defenceman: “I think most of the guys (on the Maple Leafs) do it.”

The concept is simple enough. A rancid-smelling mixture of ammonia and alcohol is stored in a vial inside a padded pouch about the size of a stick of gum. When the capsule is cracked and the liquid released, a whiff irritates the membranes of the nose and lungs. Players say this triggers a physical reaction that heightens alertness, increases heart rate and accelerates breathing.

“It just kind of shocks the system,” Nazem Kadri, the Maple Leafs centreman, said. “Mentally, it just kind of makes you a little sharper.”

Some experts have theorized that inhaling the pungent smell can trigger the body’s fight-or-flight response, which, as much as it might flood the bloodstream with adrenalin, could possibly impair fine motor skills and hinder the decision-making process. Frederik Andersen, the Maple Leafs goaltender who does not count himself among the ammonia-snorting crowd, laughed at the thought.

“Maybe that’s why they all make so many mistakes,” said Andersen, smiling as he spoke.

Two Maple Leafs defencemen, well aware of their team’s reputation for occasional defensive-zone brain cramps that test Andersen’s skills, laughed when informed of their goaltender’s zinger.

“Freddie might be on to something there — there could be a direct correlation there,” Rielly said with a smile.

Added Connor Carrick: “There’s a little bit of truth behind most jokes.”

Certainly there are truth seekers residing in the Maple Leafs dressing room. And there are those who’ve come to the conclusion that the practice of inhaling ammonia — a toxic chemical intended for use as a cleaning product — doesn’t pass the smell test.

“I used to use it. Then I put some thought into it, and that was the end of that,” said Carrick. “It’s ammonia, right? I’ve never heard of the health benefits of ammonia.”

One NHL trainer, who spoke on the condition of anonymity, said that, while the science is scant — and at least one study found no correlation between inhaling ammonia and improved athletic performance in weightlifting — there’s “power in the placebo effect.” In other words, if the players believe they’re getting more “go power,” to use Marner’s phrase, it’s conceivable they are.

The trainer added that it’s “widely accepted” that the occasional sniff of an ammonia capsule is “relatively harmless.” The exception surrounds players suffering the symptoms of a concussion. Terry Bradshaw, the Hall of Fame NFL quarterback who has acknowledged a post-career struggle with the effects of multiple concussions, including memory loss, anxiety and depression, wrote in a 2011 column for FoxSports.com that it was commonplace during his 1970s heyday to treat a head injury with a snort of ammonia — something that would be considered gross malpractice today.

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“When I played for the Steelers and I got my bell rung, I’d take smelling salts and go right back out there. All of us did that,” Bradshaw wrote.

Such is the copycat nature of sports that small habits with alleged benefits, no matter how absurd, are often widely adopted. Still, the list of Toronto’s ammonia abstainers also includes Dominic Moore and Andreas Borgman. And even some players who partake in the uptake are dubious about the possible effects.

“It can’t be good for you,” Rielly said.

That was the thought behind James van Riemsdyk’s decision a few years back to stop relying on smelling salts for his game-time jolt.

“I just kind of thought, ‘OK, if you’re using this 82-plus times a year, through the course of a long career, it’s like, how much impact is that going to have? How many brain cells is it killing? I need to hang on to every one I can get,’” said van Riemsdyk, the ninth-year veteran.

Van Riemsdyk, an enthusiast of sports-performance literature, eventually hit upon a less caustic substitute: Rosemary oil. In the lead-up to the opening faceoff, van Riemsdyk said he dabs a few drops on his palms before cupping his hands toward his face to breathe in the essence.

“It’s not quite as intense as the salts, obviously. But it’s probably a little bit better for you,” van Riemsdyk, 28.

Which is not to say it’s better for his dressing-room cool factor; van Riemsdyk acknowledged he is regularly mocked for his alternative choice.

“We do make fun of him for that,” Rielly said. “But seriously, I like what James does. It’s more body-friendly than smelling chemicals.”

Even so, Rielly said he’ll likely continue his pre-game wont to share an ammonia capsule with longtime friend and teammate Jake Gardiner. Rielly said it’s been part of his hockey life since was introduced to the practice as a member of the Western Hockey League’s Moose Jaw Warriors.

“We had one (ammonia capsule) for the whole team in Moose Jaw — I’m not even joking, I swear to God this is true — so the guy that was at the end of the bench in the locker room would crack it and he’d take the first smell. And we’d all take our turns smelling it and pass it around the room,” said Rielly, 23. “Now, I do it just as a routine. Not for the effect, really … I don’t really like it. I don’t think there’s science behind it. I don’t think it’s that good for you.”

Still, old habits are hard to break. Which partly explains why Martin, who is equally unsure of ammonia’s actual usefulness, would partake as per usual before facing the Edmonton Oilers on Sunday night.

“Whether the smelling salts have an effect or not, I don’t know. But it’s part of my routine,” Martin said. “There’s so many things to worry about in this world when it comes to health effects. Taking Tylenol’s dangerous, taking Advil. Not everything we take is obviously good for us. And maybe one day if the results come back that it’s really bad for you, we’ll stop. But I’m not too concerned. We’re not sniffing it 12 times a day every day of the year, so I don’t think it’s that big a deal.”

Said Marner with a shrug: “I don’t know if it does anything much. But it feels like it does.”