Rachel Brathen had no idea of the deluge headed her way when she asked her Instagram followers if they ever had experienced touch that felt inappropriate in yoga.

This was nearly two years ago. Ms. Brathen, 31 and a yoga studio owner in Aruba, heard from hundreds.

The letters described a constellation of abuses of power and influence, including being propositioned after class and on yoga retreats, forcibly kissed during private meditation sessions and assaulted on post-yoga massage tables.

The complaints also included being touched in ways that felt improper during yoga classes — essentially right in public.

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The hands-on teaching practices of some of yoga’s most celebrated gurus raise questions about consent.

More than 130 of the people who responded gave Ms. Brathen permission to turn their stories over to someone who could help bring accountability.

Other professionals whose work can involve touching people, such as massage therapists, are regulated by the government. Yoga teachers are not, and there are no industry trade groups that police these issues.

So Ms. Brathen, the author of “Yoga Girl,” wrote a few blog posts with redacted excerpts from the letters. That’s all that came from it.

About five months later, in April 2018, nine women went public in a magazine article about their treatment at the hands of one of yoga’s most important, influential and revered gurus.

Again, very little happened.

Disregarding complaints about unwanted touch, or much worse, has been the way of yoga for decades. Much of the yoga community has been slow or unwilling to respond, maybe because teachers are loath to discredit those they see as gurus. Additionally, many teachers have built their businesses and personal brands in part from associating with these figures.

The public, awash in terrible stories about abuse and harassment in gymnastics, Hollywood and more, may find yogis easier to dismiss as flaky flower children, or as self-promoting Instagram brand ambassadors.

In reality, yoga is one of the most accessible and popular forms of exercise worldwide, and the centerpiece of a multibillion-dollar apparel-equipment-real-estate industry.

And while a conversation about touch and consent has been taking place in schools, churches, sports and medicine for some time now, the yoga studio remains a place where the simple act of unfurling a mat signals to many teachers — of good repute or not, of good intentions or not — that they can touch you as they see fit.

“A lot of the stories we received were centered around heart chakra, and the heart center, which is also where your boobs are,” Ms. Brathen said, referring to the letters she got. “So is it O.K. for someone to touch my breasts because my heart is there?”

Ms. Brathen said she saw a recurring theme. Students are told that yoga is a spiritual practice, “a big mysterious thing,” she said, so “if there is something we don’t understand, we’re going to trust what the teacher tells us.”

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If you have taken classes called vinyasa, power yoga or flow yoga, you have practiced a version of Ashtanga yoga. Ashtanga was popularized and named by a man named Krishna Pattabhi Jois, who died in 2009, when he was 93 years old.

Ashtanga, a physically arduous series of posture and dynamic moves, attracted celebrity practitioners, like Gwyneth Paltrow, Madonna, Willem Dafoe and Mike D. They helped introduce Mr. Jois (pronounced JOYCE) and Ashtanga to Americans hungry for a Type A workout with a side of spirituality.

“He’s the one living guru of Ashtanga yoga,” Ms. Paltrow says in the 2003 documentary “Ashtanga, NY.”

Mr. Jois also helped to popularize so-called adjustments — how yoga teachers physically manipulate a student’s body. In the average studio today, adjustments can range from forceful maneuvering to get into certain poses to gentle alignments to avoid injury or to show students support during a challenging posture. Some teachers rely almost entirely on verbal cues.

But in many cases, Mr. Jois’s adjustments were not about yoga, some former students say. “He would get on top of me, make sure that his genitals were placed directly above my genitals, and he pushed my leg down to the floor and he would hump me,” said Karen Rain, now 53. “He would grind his genitals into my genitals.”

Because of the power and devotion Mr. Jois commanded, because these adjustments were meted out in public — which somehow normalized them — and because of the role that “letting go” plays in yoga, it took years, in some cases, for the women to make sense of their experiences.

“I tried to frame it that he was just adjusting me and that I was supposed to surrender to the asana” — a word that comes from Sanskrit and refers to yoga poses and movements — “and that there was some reason he was doing it that maybe I didn’t understand yet, that if I kept doing it, it would make sense someday, maybe,” Ms. Rain said.

She first met Mr. Jois in 1993 and became an enraptured disciple. “I was delusional,” she said.

Jubilee Cooke, now 54, studied with Mr. Jois in 1997. He groped her on a daily basis, she said.

“Pattabhi Jois came up from behind me while I was in full lotus position and he grabbed my crotch, he grabbed my genitals and swung me back, lifted me back so that I would land in a yoga push-up,” Ms. Cooke said.

He would lay on top of her, and grind into her, as he did with Ms. Rain. Sometimes he would stand behind her while she was in a forward fold. She could see him simulating sexual motions in the air, thrusting his pelvis at her.

She had traveled from Seattle to practice in India, planning to stay for three months. She stayed the duration, returning daily to his studio. “I was just caught up in the culture and what everyone else was doing,” she said.

Ms. Cooke, Ms. Rain and seven other women went public in 2018 in an article in a Canadian publication called The Walrus written by Matthew Remski, a yoga teacher. It described their experiences of being groped, kissed, even fingered through yoga tights.

During Mr. Jois’s lifetime, some people did try to intervene. Farley Harding, now 58, was in India studying with Mr. Jois in 1995.

After becoming disgusted by what he saw Mr. Jois do to women students — “grabbing their asses and kissing them,” Mr. Harding said — he privately confronted Mr. Jois. “I said, ‘You are a teacher and we are students, and what you’re doing to students is wrong.’”

Mr. Harding said that Mr. Jois acted like he didn’t understand, which Mr. Harding didn’t believe. He stopping studying with Mr. Jois.

Another person who spoke up is Micki Evslin. In 2002, when she was 54, she went to a workshop Mr. Jois led in Hawaii.

At one point, he instructed the 150 or so students to take a forward bend. “I could kind of see behind me,” she said, “his little feet coming up. And, I thought, ‘Oh! Pattabhi Jois is going to correct me.’ And he put his fingers under my coccyx bone and kind of used it as a lever to yank me up.”

It surprised her, but it didn’t offend her. A few minutes later, when Mr. Jois called for the class to do a wide-leg forward bend, she saw his feet approach again. “My head’s on the floor. My feet are far apart,” she said. “And, this time, he jammed his two fingers into my vagina, basically forcefully, because he had to go through tights and underpants.”

She froze. “You don’t want to create a disturbance,” Ms. Evslin said. “You’re not sure what to do. And, you’re processing everything. Like, ‘What do I say? How do I handle this?’”

She reported the event to a workshop organizer, who was dismissive. “She sort of pooh-poohed it,” Ms. Evslin said: “‘Oh! He’s old. He’s a grandfather.’”

Mr. Jois was a figure who was easy to idolize. In Ashtanga, if you trained closely with him once or over the years, you were akin to a Catholic priest trained by the pope.

Mr. Jois’s photo still appears on some yoga studio altars; his name still adorns some websites as a stamp of professional standing. The merits of the women’s statements are debated by some yogis on social media. The photographs that show Mr. Jois with his hands on students’ vulvas get explained away.

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The #MeToo movement may have helped to provide clarity about certain interactions between boss and employee, clergy and believer, doctor and patient.

Yoga teacher laying genital to genital on a student can now be added.

Stark stories of harassment and abuse have also revealed how complicated it can be to navigate more ambiguous situations. I interviewed more than 50 yoga practitioners, teachers and studio owners about touch in yoga. What I came to realize is that there may be no grayer gray zone than a yoga studio, where physical intimacy, spirituality and power dynamics come together in a sweaty little room.

This summer, to steep myself in yoga as I was reporting this story, I attended the Asheville Yoga Festival in North Carolina. What I learned there is that the public conversation about touch and consent that has long eluded yoga is finally starting.

The first class I took was a workshop called Inversions and Adjustments. It was led by Jonny Kest, 52, a star in the yoga world.

In all the ways that the fitness industry is now about apparel brands, scaling the business through teacher training programs and creating the experiences that will drag people out of their houses and away from their phones, Mr. Kest has influence.

He is an investor in the Spiritual Gangster clothing company. (His son Jonah, a yoga teacher with a large social media following, is a face of the brand.)

Mr. Kest’s teacher training curriculum was acquired in 2011 by Life Time Inc., a chain of athletic and fitness centers with nearly 150 locations around the country. Mr. Kest is the chain’s “teacher of teachers.” This year alone he has overseen the training of 800 yogis. By the end of the year, the program will have brought in $2.4 million to Life Time.

His lineage connects him both to Pattabhi Jois and to his brother Bryan Kest, another yogalebrity.

At Jonny Kest’s classes at Center for Yoga, the suburban Detroit studio he founded in 1993, it’s not unusual to find 75 or more students wedged into the very hot, very dark studio.

“He’s awesome at messages, I’ve never had a teacher give messages like he does,” Kelli Harrington, the owner of Red Yoga in Ann Arbor, Mich., and a former student of Mr. Kest. “People connect through the messages, and they feel like this person’s relatable. It’s just a bond.”

Separate from his work at Life Time, he leads retreats and workshops around the country, like the one I attended in Asheville.

In that four-hour class, Mr. Kest explained different types of adjustments to 30 or so yoga instructors and enthusiasts, most of them women.

There are verbal adjustments, in which a teacher instructs a student to move an arm or rotate a shoulder. There are “press point” adjustments, where a very light touch is used as a suggestion, like placing a palm so it is barely touching the top of a student’s head to indicate she should elongate her spine.

Then there are the more hands-on adjustments.

Standing behind a student with one leg lunged around one of her legs, he wrapped an arm around her torso and placed a hand between her breast and collarbone. She was in a pose commonly called triangle. “Again, you want to be careful of the spots that you want to stay away from,” Mr. Kest said. Some students in the class laughed.

Later, he demonstrated an unusual adjustment to a student while in the final resting pose. Yogis who have practiced at Center for Yoga in Michigan say this is commonly referred to as the “Diaper Change.”

“It has some intimacy to it,” Mr. Kest said, after having selected a volunteer who said she experienced lower-back discomfort when lying on the floor. This adjustment, he said, is intended to alleviate that. With the student on the floor, he put his knees under her lower back. Her bottom then rested on Mr. Kest’s lap.

“Then you’re going to take her feet, open her legs up and straddle them around you,” he said, as he did just that with the student’s legs. He recommended rubbing the student’s forearms, leaning forward and pressing on the shoulders, placing hands on the belly or the pelvis. “A lot of times, I’ll even rock a little bit just to relax.”

After Mr. Kest had demonstrated this, Catherine Derrow, a yoga teacher and personal trainer from Columbus, Ohio, approached him to ask if he had ever asked permission before doing this adjustment. He encouraged her to bring her question to the group.

“I would be very surprised if someone gave it to me in a class,” she said to the room. “I would not be happy.”

Mr. Kest said: “That’s a very good, important conversation to have. How do you limit the offensive? Do you ask, ‘May I touch you?’”

“That doesn’t really work,” he said.

“This is different than touching, I think,” Ms. Derrow said. She rephrased the question for him: “‘Can I sit down between your legs and open your legs and sit down.’”

Ms. Derrow said that in the studio where she teaches, there are “consent cards,” with X’s and O’s on them so students can indicate without words if they welcome touch.

“I’ve found over the years that X and O stuff really doesn’t work,” Mr. Kest said.

Another student suggested he ask people at the beginning of class to place their hand on their hearts or bellies if they want to be adjusted. Someone suggested that he could just ask for permission.

“I don’t do any of that,” he said.

Later, Ms. Derrow asked Mr. Kest to pose for a photo with her. She shared it on Instagram. She did this, she said, because she wanted to find a way to end her interaction with him on a positive note.

“I don’t think that Jonny Kest is a terrible person,” she said that night, after a Kirtan concert. “I thought that that was a lapse of judgment.”

She also said she felt alone in confronting him about his techniques. “No one else said, ‘I also agree that that was a weird adjustment,’” she said, “but after class I had about six or seven people come to me and say, ‘Oh my God, I’m so glad you said something. That was so weird. I would never do that in class.’ And I think that speaks to his saying, ‘No one’s objecting, no one’s complaining.’ They’re not enjoying that. They’re just not feeling like it’s an environment where they have a voice to speak.”

Mr. Kest, through a representative at his Center for Yoga studio, declined repeated requests to be interviewed.

In an email sent this week to editors at The New York Times, Mr. Kest said the scrutiny is unfair and expressed concern that this article was a tactic intended to damage his business. “This is despite the fact that our approach aligns with countless other yoga boutiques nationally and beyond,” he wrote.

In the workshop in Asheville, Mr. Kest explained that creating an expectation for hands-on teaching is important, if that’s the type of class you are going to lead. “Giving this kind of adjustment,” he said of the Diaper Change, “really depends on what kind of culture do you create in your class.”

Among suburban Detroit yogis, Mr. Kest is known for prolific use of touch and intimate adjustments, attributes well promoted in photographs and a video on the studio website. And his classes are very popular.

But when he takes his approach to other communities, it can offend students who don’t know what they’re in for. Jenni Donnell, 43, took a class from Mr. Kest at a Life Time studio in Orange County, Calif., in 2014.

During the class, she said, Mr. Kest talked about intimacy and passion. While Ms. Donnell was in one pose, on her back with an ankle over a knee in a figure four, Mr. Kest approached her and took hold of her extended foot.

Facing her, he wedged her foot into his groin. He then leaned toward her and put his open palms on her chest, touching part of her breast.

In the final resting pose, he came by again. “He placed his hand again on my breast, then he moved his hand down to my lower pelvis,” Ms. Donnell said.

She didn’t know what to make of the experience. She wondered if she was being uptight. Even days later, she was confused and upset. Without naming Mr. Kest, she wrote about her experience.

Five years later, she feels more clarity: “If he had walked around and said to me, ‘Is it O.K. if I wedge your foot in my pelvis near my crotch, near my private part?’ I would have said, ‘No, that’s not O.K.’”

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Pattabhi Jois has been dead for 10 years, but Ashtanga leaders are still reluctant to take part in an open dialogue about his legacy.

Sharath Jois, Pattabhi’s grandson — who recently anointed himself on Instagram “Ashtanga Yoga Guru” and also added “Paramaguru” (which translates to “the lineage holder”) to his bio — teaches in India and travels the world leading workshops. This summer, he rebranded the organization his grandfather created. It’s now called the Sharath Yoga Center.

He also broke a public silence this July, publishing an Instagram post that expressed his sorrow for pain caused by his grandfather’s “improper adjustments” and asked for forgiveness. It concluded with prayer-hand emojis.

But he declined repeated requests to be interviewed on the matter for this article. “I’m extremely busy with my teachings,” he said in a WhatsApp message.

In his Instagram post, he questioned why senior students didn’t intervene with his grandfather.

Eddie Stern is considered the ambassador of the New York Ashtanga community and is an author of a hagiographic biography of Mr. Jois. He too has been disinclined to take part in a public discussion. After three months of background conversations, however, he agreed in late October to an interview.

“I was in Mysore when Karen was there. I didn’t see Guruji” — their preferred title for Mr. Jois — “doing the things she described, but I believe her when she says that was her experience.”

He said he traveled to India annually from 1991 to 2009 to study with Mr. Jois and sometimes spent three months at a time practicing with him there. He said he never saw Mr. Jois treat any student differently from another.

Mr. Stern wants to help the community move forward. “I’m trying to get educated about these things myself,” he said.

When pressed to discuss photographs posted online that show Mr. Jois touching students in ways that many consider inappropriate, Mr. Stern said he regretted agreeing to speak and ended the phone call. “I don’t trust you, and I don’t trust The New York Times,” he said.

Change still may be coming. Life Time executives said that they are now reviewing Mr. Kest’s methods and have decided to require all teachers at Life Time’s nearly 150 locations to provide yoga students with cards that they can place on their mats to signal consent to be touched.

“In my conversation with Jonny Kest he is on board with an immediate modification,” said Jeff Zwiefel, the chief operating officer of Life Time. “He is immediately embedding it into his personal instruction.”

It’s just a start, but it’s a positive one, the sort of thing Ms. Brathen hoped would come from her Instagram post two years ago.

“Physical touch can be absolutely, unbelievably amazing and beautiful,” she said. But why not simply ask a student if they feel the same, she suggested. “It takes one second and the answer is yes or no,” she said. “It’s not that hard.”

Jamila Wignot contributed reporting.