In the beginning there was god-given brawn: Babe Ruth could go carousing until the sun came up and then smack a baseball beyond the horizon with a flick of his wrists. Or there was god-given talent: Ted Williams and his eyesight so perfect that when he enlisted in World War II, doctors were astounded by his 20-10 vision. The heroes of old, like all mythic characters, were born heroes. It’s hard to picture the Great Bambino lifting weights or the Splendid Splinter struggling with his swing. It’s even harder to picture them meditating.

But times have changed. The days of athletes inhaling pregame cheeseburgers and exhaling halftime cigarettes are long gone, and our understanding of performance has grown exponentially. In the arms race for an edge that is professional sports, teams and players have found ways, both legal and illegal, to optimize the body’s potential. But as anyone who has seen superstar quarterback Tom Brady’s surprisingly unimpressive draft photo knows, athleticism alone may not separate you from the pack at the upper echelon of sport.

“The last frontier now is the mental part of the game,” Bob Tewksbury, a major league pitcher for 13 seasons and the current mental skills coordinator for the Chicago Cubs, told me. “Everyone’s got a certain amount of talent to be a pro, but it’s the mental part that separates the good from the great.”

For Tewksbury and others in his field, incorporating mental skills is the next step in the evolution of athletics.

“When I came up to the big leagues . . . you didn’t really lift weights. You ran, you played catch,” he said. But today, major-league teams have multiple strength and conditioning trainers and nutritionists on their payrolls, he said, and now many athletes are turning to mindfulness.

In locker rooms across the country, players are sitting and working with their minds, something once unheard of in a profession based on results. Still, many athletes and organizations have been reluctant.

“I think there’s been a long-standing stigma with mental health in general going back to counseling and psychotherapy years ago,” said Tewksbury. “When you’re talking about a culture of alpha males, the last thing they want to be seen doing is talking to the mental skills guy.”

But as we learn more about the power of the body and mind working in concert with one another, those walls are collapsing. As many of the trainers and mental skills coaches I spoke with explained, mindfulness isn’t what’s next; by definition, it’s what is happening right now.

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Patient zero of the mindfulness boom in sports, or at least in baseball, may have been Barry Zito. In 2006, after the San Francisco Giants awarded Zito what was at that time the largest contract in baseball history for a pitcher, the media began to take note of his idiosyncrasies, such as his tendency to take deep breaths on the mound before releasing his pitches.

An article for the New York Times described his wacky methods under the guidance of trainer Alan Jaeger: “Jaeger’s regimen lasts five hours a day, and for the first four hours, no one touches a baseball. The pitchers meditate, stretch, listen to music, perform yoga poses, meditate again and listen to more music. They talk about dreams and visualize games.” All this time dedicated to activities that seemed at best tangentially related to baseball was written off as yet another example of pitchers being the oddest species of athlete.

Related: Are the Cubs America’s Buddhist Baseball Team?

Jaeger, who has worked with a number of professional athletes over the years, had been a pitcher in college but had to leave the team due to his own mental struggles. He discovered Zen practice and began to see similarities with the state meditation produced and the state every athlete seeks when competing. “Here’s a simple statement I make all the time to people when I try to help them understand how important and profound looking into the mental game is,” Jaeger explained. “Would you be a better player if you were more relaxed by 30 percent than you are now? Everybody right away says, ‘Of course.’”

But Jaeger’s initial ventures into the field of sports psychology were awkward. “When I first met with a junior college in 1990 they looked at me like I had seven eyes,” said Jaeger. “Even as recently as five years ago, people still associated mental training and sports psychology with, ‘You have to have a problem. You need to get fixed.’”

Overcoming this stigma has been a major hurdle for mental skills coaches, especially those with a mindfulness bent. Dr. Gregory Cartin, a performance consultant, has had to use workarounds to getting athletes interested in meditation.

“With mindfulness a lot of it’s about getting your foot in the door with the client, introducing it, having it take hold, and letting them see for themselves how powerful and beneficial it can be,” said Cartin. “I never introduce the word meditation or mindfulness until they start to ask for more. I get creative and find different ways to teach it.”

Cartin uses mindfulness to bring a player to a place of acceptance. He believes that understanding the inner workings of one’s mind is the first step toward learning how to compete regardless of whatever mental state is present at any given moment. Cartin is aware that looking inward can be an uncomfortable process, but becoming comfortable with discomfort is exactly the point.

“When someone tells you to calm down what do you do? You usually get more upset. The same idea applies in sports,” explained Cartin. “I’m helping athletes embrace difficult mental states instead of fighting them or blocking them or trying to do something with them. You can simply be with it. It’s a skill-access business. I tell my athletes all the time [that] I’m not trying to make them better athletes, I’m trying to help them compete with a sense of freedom and access the skills they’ve already developed.”

This concept, once seen as a fringe idea being taught by a few rogue trainers, is now being implemented by entire organizations.

Ben Freakley, the head of mental performance for the Toronto Blue Jays, said, “For a long time we’ve heard terms like focus or calm down or relax . . . but [mindfulness] is a way to help guys really tap into that.”

In order to harness the power of mental skills the Blue Jays have developed what they call the “Mind Gym.” They’ve brought in mental-performance coaches like Rob DiBernardo to facilitate Mind Gym sessions. A typical session might involve a discussion of a key idea, a meditation, and an opportunity for a debrief and processing. The sessions are optional, but DiBernardo, in his first year with the team, has been encouraged by the response.

Related: The Gods of Baseball

“One of the neat things about [the Mind Gym] is it’s experiential, so a player gets to sample the merchandise, so to speak. There’s an opportunity for them to vote with their feet,” said DiBernardo, who is also the associate head coach at MIT. “I’ve been really impressed with how many people will show up to attend these sessions. Some mornings it’s cold outside and the guys are there and they’re ready to go.”

The players using mindfulness to seek a competitive edge have told DiBernardo that they are seeing results.

“Players often reference the ability to slow the game down,” he said. “The game may not change speed, but I think slowing themselves down with breathing could be one piece of the puzzle, and perhaps an important piece that enhances others.”

But mindfulness training has another appeal: It doesn’t ask of players that they show no weakness and feel no pain, rather it tends to embrace the whole spectrum of their experience. Athletes have long been treated like pieces of equipment, specimens to be chewed up and spit out in service of the best outcome for the organization, their personal health be damned. For many players, the Mind Gym is a space where their own thoughts and feelings are not only welcomed but honored.

“The practice has been around for a long time, but as a team we’re just scratching the surface of what we might be able to explore with our players,” said Freakley. “We feel it can help improve a player’s performance, but also his well-being—and we care a lot about both.”

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Russ Rausch was once a successful businessman in Chicago. A small town kid from Kansas and the first in his family to go to college, he’d risen to a place of material comfort. He’d traveled the world, he owned a home, he even owned a vacation home. And yet Rausch found himself unfulfilled.

“I’ve done all this stuff that really is beyond my dreams,” said Rausch, reflecting on that period. “And I’m having this feeling of, ‘Is this all there is?’ It felt like no matter what I did externally I ended up in the same place. I’d made friends with a couple of pro baseball players at that point and they felt the same way and that was shocking to me. I couldn’t see how that could even be possible.”

If professional athletes, making exorbitant sums of money and living out their childhood dreams, could also feel unfulfilled, something seemed amiss. Rausch spent years researching and soul-searching—studying neuroscience, psychology, and meditation. He said these disciplines changed his life, which led him to found Vision Pursue, a company that helps people develop a performance mindset that also enhances their personal well-being. Vision Pursue’s clients include the Atlanta Falcons, Miami Heat, and Seattle Mariners, as well as with a number of individual athletes. Rausch believes that if athletes learn to enjoy the process, the results will come.

“I think what we’re good at is taking some of these concepts and explaining them in ways that performers can understand,” explained Rausch. “We’re trying to let them keep their goals, keep the things that they want, but change the way they’re looking at them. When you start to realize that fulfillment is an internal thing you shift from [a] wanting-and-getting [mindset] to connecting, contributing, and creating. Not because someone told you to or it sounds good but because that’s what’s coming out of you.”

Rausch and his team have developed an app for Vision Pursue clients that features a daily mindfulness based activity. Through the app clients also report on their progress, and the results have been dramatic. After 60 days of using Vision Pursue clients show a 23 percent decrease in the amount of time during the day in which they feel stressed, bored, or a desire to escape their circumstances, and a corresponding 23 percent increase in the amount of time in which they feel good. But does this improvement in well-being translate into increased performance?

This is the million (or perhaps billion) dollar question of the mindfulness performance movement. Dr. Amy Baltzell, author of The Power of Mindfulness: Mindfulness Meditation Training in Sport, and a professor at Boston University, admitted that as of now the research has not proven anything significant. “There have been a couple of dozen studies around mindfulness and sport in some way,” said Baltzell, and indeed, several of these studies have established a correlation. “But most don’t have performance markers,” continued Baltzell. “It’s difficult to have enough controls to claim impact on performance.”

“There’s not a groundswell of evidence,” agreed Coach DiBernardo. “There’s a few studies where there’s enhanced focus, there’s enhanced self-ratings of performance. There’s certainly some out there involving well-being and increased mindfulness, but there’s a lot more to be done there in the academic space.”

In the meantime, some teams, like the Blue Jays, are forging ahead under the assumption that mindful athletes perform best. And they say other teams are lagging behind.

“Everybody’s kind of sticking their toe in the water,” said Rausch. “I’m old enough to remember when people didn’t lift weights for basketball. Now you couldn’t even imagine not doing it. I think that’s where mental training will be in five years. People will look back and say, ‘Can you believe we didn’t use to do this?’”

According to Alan Jaeger, that time has already come, and any team that doesn’t meditate is making a huge mistake: “At the end of the day this game is 99 percent mental at the major league level,” he said. “Until a team not only brings in a meditation teacher for all of spring training but has a meditation teacher at every affiliate they’re kidding themselves.”