Here is part 1 of his responses, and here is part 2. More than 100 readers submitted questions about aging and yoga; because of the volume, not all could be answered. Some questions have been edited for length, and new questions are no longer being accepted.

HEADSTANDS AND GLAUCOMA RISK

Q. Given that I have been told by several ophthalmologists and a retinologist that the pressure system for the eyes is an independent pressure system and will not be affected by doing headstand, forward bends, etc., I would like very much to hear what your comments are regarding contraindications for practitioners who have elevated eye pressure. Thank you. — Kathy Shoemaker, Buffalo, N.Y.

Q. I would like to know more about inversions (specifically, headstand) and glaucoma. I am almost 51 and have been practicing yoga for 15 years or so, at least three times a week for the past five years. I have “borderline high” eye pressure and my doctors have never seemed too concerned when I tell them I practice headstand. I certainly do not want to have to give it up if I don’t have to, but I also don’t want to do anything that is likely to exacerbate things. Could regular headstand make my eye pressure worse? — Equilibrist, N.Y.C.

Q. I am 62. I have been practicing yoga since the age of 16. Is any yoga pose contraindicated for a narrow angle glaucoma condition? — BJT, Florida.

A. Kathy and Equilibrist, the nonchalant attitude of your doctors may harm you. A few years ago, to help resolve the conflicting claims about whether inversion poses can cause risky eye pressure levels in people with glaucoma, I had an ophthalmologist anaesthetize my eyes, and then I stood on my head. He then did tonometric measurements every 15 seconds. My intraocular pressure doubled from 15 and 14 to 29 and 28 within the first 15 seconds, and then stayed at that level for the pressures just held there at double their normal value for every variation I could think of over 25 minutes. In handstand the values went 10 to 20 percent higher still.

So for you two, and other yoga practitioners and teachers, it is unwise to adopt the “try it and let’s see” attitude about headstand or handstand with glaucoma because by the time you’re comfortable in the pose, it may be too late. Therefore, and this is for you, BJT, too, I believe headstand and handstand are contraindicated by wide angle and narrow angle glaucoma.

We then tried shoulder stand, and found that the intraocular pressures went up all right, but only half as much. The pressures in my right and left eyes went from 14 and 15 to 21 and 22, respectively. This may be because the jugular veins and carotid arteries are somewhat compressed in shoulder stand. Viparita karani, the restorative pose, actually lowered the pressures one point below their resting values. The literature confirms this.

I don’t have glaucoma. At that point in my life I had stood on my head for 30 minutes at least once a week for more than 30 years. I had a retinal image taken soon afterward: the blood vessels were totally normal. So the ophthalmologists you saw are probably right about the retinal vessels, but not about the intraocular pressures that are so critical in glaucoma. For more information and references please see “Intraocular pressure and inversion” on my Web site, Sciatica.org

BALANCE AND BREATHING

Q. Can you recommend a suite of yoga poses that concentrates on breathing and balance (easier to harder) for older yoga folks? Thanks. — Steve G., Baltimore

A. Steve G. of Baltimore, I would begin with the tree (vrksasana), breathing in as you raise your arms, culminating as your hands meet above your head, and exhaling as your arms come down, is a very good start. Use a wall behind you or a chair in front of you if you need it at first. You might follow this with warrior I (virabhadrasana I), inhaling as the arms rise. The downward and upward dog (adho mukha and urdhva mukha svanasana) are good, and reasonably gentle. Then you might try twisting poses like marichyasana and matsyendrasana, where your job is to try to equalize the inflation of right and left lung. Finally, headstand (mirsasana), also with suitable props, is another good balance and breathing posture. For every variation, exhale as you bring your legs down; inhale as they come up.

ARTHRITIS, DIZZINESS AND OTHER AILMENTS

Q. Is yoga good for people like myself who suffer from arthritis? If yoga is helpful, what do I need to be aware of to avoid injuring myself? — Cleo, N.Y.C.

A. Whatever else yoga does, Cleo, it stretches. Lengthening your muscles and tendons and expanding the range of motion of your joints has got to relieve the restrictions that arthritis imposes. Further, a 2008 metastudy published in the journal Nature confirms that the type of gentle exercise that yoga is (and Sunday football is not) liberates a potent endogenous anti-inflammatory from your muscles: PGC1-alpha. Because people make this protein in their own bodies, no one is allergic to it. PGC1-alpha actually reduces the inflammation that is at the heart of osteoarthritis, and for side effects, reduces the incidence of Alzheimer’s disease, diabetes type 2 and a host of cancers.

Q. I am over 70 now and a couple of years ago I tried a yoga class. The result was a lot of dizziness from all the up-and-down motion involving my head. Any suggestions? — Ladas2, San Antonio

Q. I have situational vertigo and it is difficult to lower and raise my head when going through positions in yoga without experiencing dizziness. Do you have any suggestions?

A. Ladas2 in San Antonio and Carrie in St. Paul, there are tiny balls in the semicircular canals inside our inner ears (otoliths) that may degenerate or even disintegrate as we approach 80 or 90. There are two ways to go: a good physical therapist may apply the Appley Maneuver, which can miraculously change things for the better, or, you may try yoga meant for people who are less mobile; that will involve much less vertical movement. The sequencing of yoga poses is a subtle business; some teachers intentionally do all the standing poses together, and the same with sitting and lying down. If you want to start again, discuss sequencing with your prospective teachers.

Q. Dear Dr. Fishman, I am a very bendy person. I have been practicing yoga for many years and I am 53. I started having heartburn and there seemed to be no apparent reason. Two endoscopies and five years later, I started to think it could be my intense backbends. My doctor felt there was “no way” I could be back bending that severely. I sustained a neck injury which put my back bends on hold for a year and three months. The heartburn is gone. I have since ceased my intense back bends. Can back bends give one heartburn? — Rosie, Asheville

A. Back bends can indeed give you heartburn, just as forward bends can. If you want to return to them, do them five hours after eating anything, and begin slowly and carefully, watching for any symptoms to appear. When you’re in, say, Urdhva Dhanurasana, work mostly to bring your chest over your palms, not to arch the lumbar spine. One way to do this is to push your feet away from you without moving them. There are other methods to achieve a satisfying back bend: try a private lesson with checkups every month or so as you proceed.

Q. I have piriformis syndrome with sciatic pain ending in my lower right calf. I’ve tried MacKenzie exercises (a lot like up-dog). PT said to avoid yoga poses with flexion, which I did for a while, but now my low back is stiff and tight and I still have the sciatica. I practice yoga two to three times a week and can do most asanas, but my right hip and leg are weak, so balance poses on the right side are tough. Should I keep doing them to strengthen that side? Or does that increase the inflammation? — JJK, Chicago

A. In the syndrome JJK mentions, the piriformis muscle in the buttocks compresses the sciatic nerve, causing pain down the leg. But the advice he has gotten, avoiding forward bends and doing poses like the upward dog, are for herniated disc, not piriformis syndrome. In my opinion he should be doing twisting poses like the twisted triangle, parivrtta parsvakonasana, marichyasana and matsyendrasana.

Q. There has been some minimal research about the benefits of yoga in treating atrial fibrillation. Is it a viable option for improved control of arrhythmias? — Reno, Falmouth

A. Reno in Falmouth, a recent study published in the Journal of the American College of Cardiology, using yoga designed and administered by Joan White of Philadelphia, documented significant reduction in atrial fibrillation and other types of arrhythmias. Incidentally, or perhaps not so incidentally, several measures of anxiety also showed substantial (and significant) reductions.

Q. Hi – I am a yoga teacher in Boston. I was in a head-on collision that fractured my sacrum bilaterally through both sets of holes along with other spinal and rib fractures. Since I used yoga for my recovery I have many other people with injuries and conditions as well as older students who attend my classes. I have a student with right side stenosis, who has undergone surgery with spacers put in and L4 and L5 fused. She is in a lot of pain, and some of the exercises we do help but only temporarily. Would you have a suggestion for this or could you direct me to any of your books for some guidance? — Kim, Boston

A. Kim, I need a little more information to answer the first question: If your student patient’s pain is at the inner calf or top of the foot, it might relate to the fusion itself, and the spacers. In that case, a doctor should probably try epidural steroids, because yoga should not put pressure on the region of the fusion. If her pain is elsewhere, like the front of the thigh, then she might respond to yoga that does not bring forces to bear at L4-5, but farther up the spine. Upward facing dog, keeping the navel on the mat, might be the way to start, with further arching poses afterward in which the patient wears a lumbar corset. I’m thinking of poses like the locust, keeping the legs on the floor. For someone proficient in yoga, then forward bending in lotus or virasana can be combined with a pillow or two under the chest effectively, especially with arms extended and elevated.

Q. In practice for two years now. I have recently been diagnosed with cerebellar ataxia and secondary parkinsonism. Are there poses that will help dysmetria and intention tremor? The instructors at my studio have only responded “listen to my body,” which I do, but can give me no specific guidelines so I might try and retrain my brain, especially the cerebellum. My physicians are pleased that I practice but can offer no specifics either. Maybe you can point me toward some useful information? — cfsic, Tampa

A. I’m not sure I can, cfsic. The mechanism of cerebellar ataxia is usually unknown, and unfortunately, there is scanty evidence that this part of the brain can learn. It is mainly a processing center. However, yoga will powerfully ward off secondary effects: the weakness, stiffness and imbalance that would disable you so much further without yoga.

RESOURCES AND TEACHERS

Q. I practiced yoga daily from age 15 to 52 when I suffered severe tearing of my gastrocnemius, soleus and achilles. I also injured my neck and head. I’ve had multiple-month bouts of vertigo, insomnia and total body pain since then. Now 56, no yoga for over 4 years. I learned of you when I read Mr. Broad’s book “The Science of Yoga.” I grew up in New York near William, and in recent years felt my own yoga practice becoming increasingly unsatisfying the more “popular,” trendy and commercialized yoga was evolving around me here in Oakland (East SF Bay Area) where I’ve lived most of my adult life. There’s a yoga place on every other block here but I want an M.D. like you and to consult with an equally knowledgeable, experienced yoga master/teacher (Iyengar, Hatha, Ashtanga)! I would be so grateful if you would recommend such persons in my area. Thank You. — Omzoc, California

A. To Omzoc in California: I believe Baxter Bell and Timothy McCall, both M.D.s, both yoga experts, are in your neck of the woods. If they’re not available, I recommend superb yoga teachers named Judith Lasater and Osha. You should be able to take up yoga again.

I think William J. Broad’s book “The Science of Yoga” has had at least two good and very important effects: Better reporting of yoga injuries, and greater care by yoga teachers to avoid them.

Q. I am disabled. I bought a sitting yoga CD from PBS. Will this CD help me? — Bobier, Las Vegas

A. It has got to be a good start, Bobier.

Q. I used to do yoga regularly and want to return to it. How do I find an appropriate yoga class for a 60-year-old in Pasadena, Calif.? I know I could google or Yelp this but I would love a recommendation. Thanks. — Elizabeth, California

A. I would try Eric Small in Beverly Hills. Failing that, try the Iyengar Association in Los Angeles.

Q. For fit people without specific health issues in middle age who already practice yoga, it would be nice to have knowledge about and access to a series of poses appropriate for this age group, which can be arranged into routines of various difficulties to form the core of a yoga class. Also targeting areas, like the lower back, with specific poses for this age group would be helpful. We can then take this knowledge to and practice it with our local yoga community. Thanks. — David, Maine

A. Suza Francina has a number of relevant books with excellent sequences.

Previous Ask an Expert columns can be found here.

Booming: Living Through the Middle Ages offers news and commentary about baby boomers, anchored by Michael Winerip. You can follow Booming via RSS here or visit nytimes.com/booming. You can reach us by e-mail at booming@nytimes.com.

Here is part one of his responses. A third and final set will appear on Booming next week. More than 100 readers submitted questions about aging and yoga; because of the volume, not all could be answered. Some questions have been edited for length, and new questions are no longer being accepted.

FIRST, A THANK YOU

To everyone who asked me questions, thank you. Many people start doing yoga when they are young. There is also a large group who begin doing yoga after 50, who become enthusiasts and continue for the rest of their lives. I think yoga is a perfect match for us as we grow older, because it’s no-impact, good for flexibility, balance, coordination, strength and attitude. Answering your diverse, intelligent questions has given me new ideas for research into the fascinating topic of yoga for those over 50.

OSTEOPOROSIS

Q. What about yoga for osteoporosis. I’m 65, have been doing yoga for 20-plus years, and continue to do forward bends, plow, shoulderstand and twists, all presumably not O.K. for osteoporosis. I’m just at the line at 2.5 dexa. I don’t want to give up these postures if I don’t have to. What’s the risk? — Cat, NYC

Q. Hi, Loren. Please share your thoughts on the almost universal advice given to older people with bone density issues that they should avoid any kind of spinal flexion altogether. Clearly, there is a difference between spinal flexion as a normal range of motion that is necessary to do daily movements like tying your shoes, and a “loaded” lumbar flexion that occurs in a pose like halasana, or even a standing forward bending movement with the arms extended from the body. I have seen many people who have been trained to fear fracturing their spines in normal ranges of motion, and they impose tension and restrictions on their movement and breathing that actually worsens their condition.— Leslie Kaminoff, New York City

Q. I used to practice yoga but I found out from a Dexa scan that I have osteoporosis of the spine and although I have not had any fragility fractures I’m concerned about any forward bending or twisting just in the course of every day activities. It’s affecting the quality of my life because I’m thinking about osteoporosis every time I move. It would be wonderful to have some practical guidelines. Thank you. — Maracache, California

A. On Sciatica.org I discuss 12 poses that can be used to prevent and treat osteoporosis and osteopenia.

Many readers wrote in with questions about osteoporosis. Cat in NYC and Mellieone in New Zealand have osteoporosis, and have been doing all the poses that they’ve been told not to: Cat does forward bends, the plow, shoulderstand and twists. Mellieone’s regimen is similar, and neither of them have any pain. Diane in West Hartford and Nancy B from Maryland find that even gentle yoga gives their osteoporotic backs considerable pain. Maracache in California and Leslie Kaminoff in New York want clarification: surely we all have to bend forward, so what are people with osteoporosis supposed to do?

Mehrsheed Sinaki from the Mayo Clinic showed long ago that forward bending does produce more osteoporotic spinal fractures. Once you have one fracture, your spine is inclined even more forward, and the risk of a second fracture is even higher. These fractures are not life threatening, but they are usually quite painful. And a second fracture raises the likelihood of a third.

So forward bends should be done only with a straight back, or, if you’re not confident you can do that, stick with Supta Padangusthasana: lying on your back and raising your straight legs as far as possible. Your back will stay straight, thanks to gravity and the good carpenter that made the floor, but you’ll get all the benefits of a forward bend, and some of the good that comes with inversion.

Twists are a different matter, in fact, just the opposite. Many yoga practitioners, including excellent ones like Sara Meeks and Carole Krucoff, caution against doing twists if you have osteoporosis, but the only research papers addressing this in the literature that I have found actually say the opposite: that they are safer than forward bends.

I recommend going along with the literature. But there is another reason not to avoid twisting:

If you think about it, there are very few other ways to strengthen the vertebral bodies. In a clinical trial I am conducting to examine the possible benefits of yoga for osteoporosis, more than 500 people have used my 12-minute DVD with what I consider safe and helpful yoga poses for osteoporosis. This amounts to over 60,000 hours of people, mainly with osteoporosis or osteopenia, doing three twists, without even one report of a fracture. I repeat, there are no reports of fractures. Many of these people have before-and-after X-rays of the spine that have, at least so far, revealed no new fractures either. This is important because in spite of their often painful nature, some vertebral fractures are “silent.” So twists appear to be safe, provided you keep your back straight. Of course, until the trial is over no definitive conclusions can be stated, but the data so far are promising.

Yoga does not necessarily prevent bone loss altogether. Irene of the Connecticut Valley, who wrote in, is also in our study, and although 80 percent of the people reporting so far have gained bone after two years, she has lost a little in the spine, and held her own (without medicines) in the hip. My criterion for success in the study is no fractures of any kind. A person’s bone mineral density (usually measured through a DEXA scan, which is something like an X-ray) is well correlated with fractures, but is not the same thing: fractures are also reduced by better balance, improved strength, greater range of motion, enhanced coordination and lower anxiety, all of which are produced by yoga, not medicine. No medicine can do that. There are medicines that lower anxiety, but they impair balance. For more information about my study, go to sciatica.org.

SHOULDER PAIN

Q. Four months ago I also hurt my shoulders doing the plank pose into downward dog. Even if I kneel into the plank position first, then go to DD, I reinjure my shoulders. Warrior poses are not as painful. Should I avoid planks/downward dog poses in the sun salutation sequence? — BeauJoe Lais, California

A. Several readers (including Janine K from Seattle and Crone from Oregon) asked about shoulder pain. Downward Dog can be particularly dangerous to shoulders. That’s true even if you have a good teacher. So avoid doing it if you have a shoulder injury. Also avoid plank pose, and the crocodile, Chattaranga.

The triangular forearm support, the headstand and variations, however, can be used to end shoulder pain for people with rotator cuff tears by training the subscapularis muscle to take over for the supraspinatus. This relatively simple solution has helped many of my patients avoid a costly, painful and unnecessary surgery.

REGAINING RANGE OF MOTION

Q. At 5 feet 10 inches tall, 165 pounds and 57 years old, all of my previous exercise regimens (tackle football as a youth and through high school, long-distance bicycling and running), before becoming a professional desk jockey, have formed me into a hunched-over hulk with a variety of injuries resulting from the imbalances imputed by those practices. Currently, muscle and joint tightness keeps me from the level of yoga I desire (I’d like to be able to do a decent forward fold and cobra). . . . All of my back bend-related asanas (cobra, sphinx, up dog, bridge, etc.) are extremely shallow. Enduring discomfort as a part of a method to increase the range of motion limits of these asanas would not be a problem for me, nor would specific strength training exercises, if they were recommended, but I have not been successful in finding a resource I can trust. With professionally modified yoga practice, can one expect to reverse the effects of a lifetime of debilitating physicality and regain significant loss in vertebral column range of motion? — Roe Bear Toe, Cedar Rapids, Iowa

A. Roe Bear Toe in Iowa, as you get older, your intervertebral discs gradually convert some of their water content, into fat, which limits their flexibility some. Otherwise tight ligaments, shortened tendons, stiff muscles and slumpy posture will all yield to gentle pervasive yoga poses and related maneuvers. One other caveat: men injure themselves more than women, largely, I believe, because they pit their greater strength against their lesser flexibility and end up hurting themselves. So reserve the might of the high school tackle for other things, and do the yoga to gain self-control, not to lose it.

OVERWEIGHT BUT INTERESTED

Q. I am extremely overweight, age 56, 270 pounds, 5 feet 6 inches tall. How should I start practicing yoga? Other than the weight I am well. I have done yoga in the past. I practiced along with a TV show (Lilias) when I was much younger and I was the proper weight, 135 pounds. I enjoyed it. I worry about the weight because everywhere I look the people doing yoga are very thin and seem to already be in shape! In the Times photo with this article everyone is tiny! I guess what I am really asking is, are there special instructions/programs for the obese starting out in yoga? — Rational Reformer, Oklahoma

A. There is no special instruction for overweight beginners, apart from being careful not to injure your ankles, knees and hips and the upper extremities. As your weight increases, the area of your feet and the joints of your lower extremities do not. So there are more pounds-per-square-inch in all these places. The joints of the upper extremities have no menisci, no extra padding of the kind you find in the knees. This may be because of their not usually being weight-bearing in human beings. In yoga, though, there are many poses in which the hands, wrists, elbows and shoulders do bear weight. This makes things easier on the legs and feet, but these are reasons to be especially careful of the more delicate joints above.

As William J. Broad points out in his book, “The Science of Yoga,” yoga lowers metabolism, which does not bode well for weight-watchers. But yoga can promote weight loss by stretching the organ, the stomach, that sends “satiety” signals to the appetite centers in the brain. Parsvakonasana (side angle pose), paschimottanasana (extreme forward bend) and matsyendrasana (a twist) all do this, each in a different plane.

MISCELLANY

Q. Great article but you left one name out: Larry Payne’s Prime of Life Yoga of http://www.samata.com. Larry has been promoting this style of yoga for the past 10 years. He is currently teaching at Loyola Marymount in California and is well respected around the world. — Lisa, Austin, Tex.

A. Larry Payne should not be neglected, Lisa. He has helped many people and has been a potent influence in bringing yoga therapy to where it is today, and where it is headed tomorrow.

Q. I am a 50-year-old former professional dancer and current fitness instructor (water, stretch, dance). I am interested in going through a yoga teacher training program, but don’t know how to go about deciding between different programs. I feel my interests lie primarily in teaching older students with more of an emphasis on health, fitness and therapeutic value. Any insights for me? — SH, Chicago

A. Again, I recommend B.K.S. Iyengar’s methods. Many former dancers gravitate to Iyengar yoga because it is rigorous, classical, and precise, with an emphasis on alignment. Also the former Anusa program is good, as is Integral Yoga.

Next week, Dr. Fishman will respond to questions about headstands and glaucoma risk, poses to improve balance and other questions.

Previous Ask an Expert columns can be found here.

Here is part one of his responses. More from Dr. Fishman will be posted next week, but because of the volume, not all questions may be answered. New questions are no longer being accepted.

INTRODUCTION

Is yoga good for the aging population? My answer is yes. A couple of years ago I ran into my yoga teacher, B.K.S. Iyengar, at a conference in India. Though he was over 90 years old, he was capable of traveling to China and giving a three-day workshop consisting of classes that lasted for many hours each day. When he saw me he rose gracefully from his chair and greeted me by name, though we hadn’t seen each other for more than 20 years. I think Mr. Iyengar is an example of what yoga can do for an aging human. To me he seemed like a man 30 years younger. And, in a way, beyond age.

AGING AND YOGA

Q. Are there any aspects to yoga practice that the over-50 practitioner should give up if she/he is healthy and otherwise feeling well? How about after 70? What poses cause the most injuries, and which might help protect or rehabilitate common yoga-associated injuries? — Elizabeth, Lenox, Mass.

A. Yes, there are things you may need to give up in your yoga practice as you get older. People age differently, and yet there are characteristic aspects to aging. Chronic conditions are cumulative. With osteoporosis you can do forward bends to as far as your hips will carry you without pushing, keeping your back slightly arched if possible, and preventing it from slouching forward no matter what. As my fellow yoga devotee Leslie Kaminoff has rightly noted, this avoidance of forward bending too can be carried to phobic extremes: good posture and sensible bending and lifting is an antidote to osteoporotic fractures; flexibility, coordination, balance and strength are the best prevention of hip fractures. Standing poses like the tree, the warrior trilogy, and half-moon promote these positive traits and are among the last poses one should give up as one ages.

Arthritis will respond to yoga. Supta padangusthasana is as safe and as good as a pose gets, and will help with safe forward bending, too, by lengthening the hamstrings and stretching the hips’ capsule. We will come to many more suggestions and caveats in the questions and answers that follow.

Q. For fit people without specific health issues in middle age who already practice yoga, it would be nice to have knowledge about and access to a series of poses appropriate for this age group, which can be arranged into routines of various difficulties to form the core of a yoga class. Also targeting areas, like the lower back, with specific poses for this age group would be helpful. We can then take this knowledge to and practice it with our local yoga community. Thanks. — David, Maine

Q. Which yoga styles are best if you’re starting at age 50? — LOL, Ithaca

Q. I am 61. Very inflexible, have a history of low back and neck pain that are currently minor. I get regular exercise at a gym and I hike in the mountains several times a week. What is the best way to get introduced to yoga? — Burrito’s, Westbrook, Maine

A. Besides these readers, Big Bird from NYC and SH and Pinotman from Chicago wrote in wanting to know the best place and the best way to begin or resume yoga when you are over 50. The absolute best way is to find out what your liabilities are, and this is an individual matter, requiring a medical visit or summary. The next step is an appointment with an experienced and smart yoga teacher, one on one. Group classes are an artifact of urban economics: the teacher cannot afford to live in the city in which she teaches any other way. But chronic conditions are cumulative, by definition: when you’re older you need the individual attention that yoga has traditionally offered.

I believe the teachings of B.K.S. Iyengar are the most anatomically sophisticated and therapeutically oriented, but there are many other good types of yoga. You’ll need a resourceful and sensitive person to get you started, and to introduce you to an appropriate yoga practice that you can do every day. Then, after a month or two or three, you should go back to that person for a reassessment and suggestions about how to progress to the next step. Yoga, practiced consistently, does good things to your temperament and perceptions.

Q. Any age-related additional risk factors with respect to the vertebral artery during shoulder stand and plow poses? — JPT, Ohio

Q. I am 55 and began yoga two months ago. I go every other day, but I still have problems with the balance poses. I did not have these issues in my youth. Is it typical to have more balance issues as you get older? — AJT, Madison

A. Most arteries become more brittle, and are more easily injured, just as the skin gets more delicate with age. Shoulder stand, plow, and poses like the gate should be trimmed back from their extremes for safety after the age of 70. The vertebral artery actually figures in nourishing a number of neurological structures critical to good balance and coordination, so it is worth our care. Our sense of balance can also be degraded with age decreased sensitivity to changes in direction and momentum in the semicircular canals (offshoots of our hearing apparatus that detect changes in speed and direction of movement), decreased proprioception (lowered awareness of position and relative location) in the joints and in one’s feet, and less acute vision. These are the three determinants of balance: the inner ears, proprioception and vision.

Do the precarious poses against or very close to a wall. The wall is a wonderful, supportive teacher.

BACK PAIN AND SCIATICA

Q. I am 48, in good shape cardiovascular-wise (runner), and decided to try yoga recently. All went well initially but of late I have had considerable back pain both when sitting and lying flat. Could I have an injury? If it’s just sore muscles, will it eventually get better if I keep doing it? — MB, Ohio

A. First, much back pain is discovered in yoga class but really has its origins elsewhere. Second, yoga can cause back pain, and then, as always, the question is: what is the diagnosis? Pain is a symptom, not a disease. Without a diagnosis you’re left to guess about proper treatment, for the same pain can have causes so different that treatments are diametrically opposite.

One way to decide if it’s sore muscles or a neurological injury is if the pain goes down one or both legs or radiates. Does anything tingle, is some part of your leg numb? If so, it’s nerve pain, indicating an injury that merits further inquiry. If not, it’s probably a muscle spasm or strain, and stretching should make it feel better. I say probably because someone could also have a spinal fracture, facet arthritis, spondylolysis or other problem. The bottom line is that you need a diagnosis before yoga or anything else can be used rationally to help.

Q. I have sciatica and a herniated disc so bad I want to cry. I’m on prescription pain killers but I’d rather be better, not drugged up. Will yoga help sciatica? — Linda, Oklahoma

A. Sciatica — nerve pain that goes down the leg along the course of the sciatic nerve — can be helped with yoga, but it must be done with extreme care. A herniated disc responds to extension, and may be worsened by flexion; spinal stenosis improves with flexion, and is exacerbated by extension — yet both can cause sciatica, and the same exact distribution of numbness, weakness and pain. And about 5 percent of the time, the treatments reverse: extension helps stenosis, flexion is good for herniated discs. So start tentatively, be sensitive to the changes you feel, and progress slowly.

Economy airplane seat width is usually 17 or 18 inches. The average American man’s waist is about 40 inches (38 for women), according to the Centers for Disease Control and Prevention. Need I even mention the sliver of space between your knees and the seat in front you?

Fliers nowadays expect to walk off planes with stiff hips and strained backs. Desperation for relief has made seats with extra legroom cash cows for airlines. Even top yoga instructors who can fold their bodies like origami say they abhor airplane seats. So how do you emerge from a plane without feeling like Quasimodo? I turned to one of the best-known yoga teachers for advice.

Cyndi Lee, the founder of the “no baloney” Om Yoga brand and familiar to veteran practitioners from her videos and New York City classes, is in her 50s and among the most flexible frequent fliers. A few weeks before spring trips that will take her to Japan, Virginia and Berlin, she shared some airplane-friendly poses that keep her feeling supple and can be done in a seat or in the aisle. Many of the poses can be performed by yoga novices; others are for seasoned yogis — or those who dare to try a tree pose at 30,000 feet.

For Beginners

“A lot of what you’re doing with these stretches is just increasing the circulation,” said Ms. Lee, explaining that fluids “such as water and lymph can tend to pool in lower regions” on an airplane, making fliers “feel sluggish and thick.”

To improve circulation through your lower back on long flights, be sure to twist every so often. While in your seat, plant your feet on the floor and twist to the right (you can put your left hand on the outside of your right knee to deepen the twist). Always include your head and neck in the twist. Switch sides.

If you have enough room and flexibility, from your seat you can also try ankle-to-knee (with one leg) pose, which is a complicated way of saying place your ankle on top of the opposite knee. For most people, simply being in this position is a significant stretch. “That will open your hip and give you a really good stretch around your butt and your hip,” Ms. Lee said. To deepen the stretch, lean forward a little and place your forearms on top of your legs. Then switch legs. To improve circulation while in that position, flex and point your raised foot, and squeeze and spread your toes. Mind the whereabouts of the drinks cart.

Now, on to your upper back. This next pose, the hug, can be done sitting or standing. And it’s perfect if your travels have you feeling stressed: just wrap your arms around yourself and squeeze, aiming to touch your shoulder blades with your fingertips. From there you can stretch your neck by pressing your right ear to your right shoulder; repeat on the other side. Then release and switch arms, this time placing the arm that was on top on the bottom, as you reach across your back.

After the hug, you can go into a modified eagle pose (normally done standing). Put your hands in front of you as if you were about to play peek-a-boo, but instead of covering your face with your hands, cross your forearms and wind your wrists until your palms touch. Move your palms away from your face for a little stretch. (Instructions for some of these poses are on YogaJournal.com.)

Need a bathroom break? In the space near the lavatory, you can counteract rounded shoulders and relieve a tight upper back with a shoulder stretch. Reach behind you with both arms outstretched until your hands meet, then interlace your fingers, and squeeze your shoulder blades together. Look up and lift your chest. Depending on your level of comfort, you can lift your arms up and away from your back a bit. “You’re curving your spine in the opposite direction of the seat,” Ms. Lee said, “which is good.”

Other yoga experts offered similar advice. Alexandria Crow, a yoga instructor and teacher trainer at YogaWorks in Santa Monica, Calif., suggests putting your palms on either side of the aisle wall near the bathroom and leaning forward, as if stretching your chest through an open doorway.

Even simply hanging forward from the waist — folding at the hips and grabbing each elbow with the opposite hand — can make you feel better, Ms. Crow said.

She added that it’s important during long flights to elevate your feet to keep your ankles from swelling. “I’ve gotten off the plane and had those gigantic ankles,” she said. To prevent that, she puts her feet on the bulkhead wall, the back of the seat in front of her or the back edge of the armrest in front of her. That may be good for your ankles, though not necessarily for your relationship with fellow passengers. Some fliers (myself included) think feet belong on the ground.

For Yogis

For regular yoga practitioners, “tree pose is a no-brainer,” Ms. Lee said, referring to the standing pose in which you place the sole of one foot against the inner thigh of your other leg and raise your arms to your chest or over your head. (You can use a wall by the bathroom for balance.) This pose can open up tight hips and relieve lower back pain. A small price to pay for the possible eyebrow raise from another passenger.

“I do these things and nobody even cares,” Ms. Lee said. “In fact, I think some people are thinking, ‘That’s a good idea.’ ”

Another option is a variation on downward dog. Stand at your seat and put your hands on the seat back in front of you (not when your neighbor is occupying the seat). Then step back and lean forward, bending in half. (You’re making a 90-degree angle, so your upper body and arms should be parallel to the floor.) If there’s no room for that (and chances are there isn’t unless you are rather petite), adjust by placing your forearms on the seat and do the same thing. “It’s just a downward dog in a different relationship to gravity,” Ms. Lee said.

You can also modify popular poses like cat and cow (done on your hands and knees) and do them while standing instead. Just bend your knees and place your hands slightly above your knees. Then alternate between rounding your spine like a dome (cat) and curving it like an arch (cow), looking down when you do cat and looking up when you do cow.

“You can do it in a very contained way and get a lot out of it,” Ms. Lee said.

And don’t forget to breathe deeply, which will help you become calmer. Ms. Lee, the author of “May I Be Happy: A Memoir of Love, Yoga and Changing My Mind,” practices sama vritti, equal breathing in and out. She inhales for a count of 4, 5 or 6, then exhales for the same amount of time. She also recommends that travelers try lion pose: scrunching up your face and then, as you exhale, sticking out your tongue and looking up at the space between your eyebrows.

“Try to touch your chin with your tongue,” she said, noting that this is good for waking up and reminding you to breathe.

I was about to suggest that this is also good for making people think you’re nuts, but Ms. Lee seemingly read my mind.

“You can do that one in the bathroom,” she said.

Rick LeBeau Desirée Rumbaugh teaches a yoga class in California for the 50-and-over set.

Ask an Expert

Questions About Yoga in Your Middle Years

While many yoga classes across the country seem to cater to the youthful enthusiast who wants to sweat his or her way through an hour-and-a-half workout, a growing number of longtime yoga devotees are raising questions about the best way to safely continue a yoga practice into midlife and beyond.

“I suspect that yoga was at times an old person’s sport, and that it has prolonged the life and liveliness of people over the millennia,” said Dr. Loren Fishman, a back-pain specialist in Manhattan who uses yoga in his rehabilitation practice and has written extensively about yoga as an adjunct to medical treatment.

“Designed appropriately and taken in proper dose,” he said, “it is certainly safe.”

Carrie Owerko, a New York-based teacher of Iyengar yoga who has been a yoga student for decades, agreed. “Yoga can be practiced fully and deeply at any age,” she said, with an added caution that “the practice has to change as the body changes.”

Dr. Fishman noted that aging brings impairments of range, motion, strength and balance that can require modifications, even among veteran yogis, like using the support of a chair or the wall for many poses. In addition, students may begin to feel the effects of arthritis, injuries and other ailments that may require students skip certain poses altogether.

Someone with osteoporosis, for example, may want to avoid headstands and poses requiring extreme spinal flexion or extension, while someone with glaucoma may want to avoid taking the head below the heart in poses like headstand, handstand, shoulder stand and standing forward bends. When in doubt about the safety of practicing with any specific medical condition, Dr. Fishman recommended working with a doctor.

Generally speaking, a warm-up sequence is important for the veteran yogi, Ms. Owerko said. “Our bodies may need more time to warm up properly, especially if we are experiencing stiffness or arthritic changes in the joints or in areas that may be more vulnerable to previous injuries,” she said.

It is also important to include various one-legged standing poses — Tree Pose or Eagle Pose are examples — that challenge one’s ability to balance, even if you need the support of the wall, Ms. Owerko said. Weight-bearing poses, like Plank Pose and Forearm Plank, and standing poses like Warrior pose variations, are also important to help counteract the decline in muscle mass and strength as we age, she said.

To help maintain flexibility, poses like standing or seated forward bends and hip openers, like Bound Angle Pose or Pigeon Pose, are also important, said Roger Cole, a longtime Iyengar yoga teacher and psychologist in San Francisco.

Mr. Cole emphasized that a regular yoga practice can help the body maintain a high level of flexibility into midlife and beyond. If a student continues the same practice as much as possible without interruption through the 50s and beyond, he or she will see a gradual decline in certain abilities, but not necessarily a decline in flexibility, he said.

“I think the average person probably does get stiffer as they age,” he said, “but I believe that it’s mainly because they stop doing the things that keep them flexible.”

The passage of more and more baby boomer yogis, teachers as well as students, into and past middle age has sparked interest in creating a new kind of peer yoga community as well.

Desirée Rumbaugh, a longtime yoga teacher who passed the 50-year mark a few years ago, started a class in Del Mar, Calif., aimed at yoga veterans 50 and over. Called Wisdom Warriors, it was intended to offer veteran yogis the chance to keep learning in an environment that is comfortable and encouraging.

“People want to be pushed, but not in the same way they did in their 30s,” she said. “They want a little slower pace.”

Slower pace or not, Ms. Rumbaugh includes a full range of poses in her classes, including backbends and inversions. A recent Wisdom Warriors workshop, presented by Ms. Rumbaugh and Cyndi Lee at the Yoga Journal Conference in New York in April, would have been a vigorous day of yoga for students of any age.

Debra Hodgen, 61, of Vista, Calif., is a student in Ms. Rumbaugh’s class. A former dancer, she said that she began a consistent yoga practice when she was 48. She said she has become “stronger and more fearless” as a result of the class, despite having osteoarthritis, no cartilage in her right knee and joint pain throughout her body.

“I may have trouble just sitting in simple cross-legged pose, but I did full Monkey Pose recently,” she said.

The most important way a seasoned student will be able to continue to practice safely, many teachers say, is to listen to signals their body sends them in class, and know when to back off.

“In my experience, older students often bring a mature wisdom to the practice,” said Ms. Owerko, who turned 51 this week and has for many years attended an advanced yoga retreated for women over 40. “They have lived long enough to have a sense of humor about themselves. And they are often more compassionate toward themselves and other students.”

Do you have a question about yoga over 50? Dr. Loren Fishman is answering reader questions on the Booming blog.

“Drop the pubic bone!” she ordered, teaching class during a five-day women’s retreat last month at the Amansala resort in Tulum, Mexico, the long golden hair flowing over her shoulders calling to mind Botticelli’s “Birth of Venus.” “This is going to give you the perineal energy we’ve been talking about so much.”

Another, almost Vreelandesque command: “You can’t let the arches of your feet collapse. The collapse of your arches is the collapse of your sex life.” And another: “Open the groin. The groin gets soft.”

“I thought you said, ‘The lights go off,’ ” muttered one contorted participant.

Thick with estrogen and incense, buffeted by warm Caribbean breezes, the room was indeed dim. But Ms. Saidman Yee, whether perching beatifically in full lotus position before 40-odd prone bodies or prowling among them like a jungle cat, emits at 53 her own curious, almost celestial incandescence. Since marrying Rodney Yee, one of the most popular practitioners of the discipline (which he prefers to call an art form), in 2007, she has brought to it glamour, sensuality without the creepy overtones of recent yoga scandals, and unapologetic commercialism, endorsing wine and posing for Vanity Fair.

“Oh, my God, I’m so not pure,” said Ms. Saidman Yee, a longtime model who favors a line of yoga togs cheekily called Sweaty Betty and sometimes pads to class in gold sequined Uggs. “I never want to be called a guru. All I want to do is guide women into their own bodies so they can be more content.”

The Yees may not be gurus, but they are yoga moguls, oxymoronic though that term may seem. They are directors at Donna Karan’s Urban Zen Integrative Therapy program, lithe Florence Nightingales working with the designer to bring yoga and meditation to hospital patients and disaster victims, Ms. Saidman Yee having refined her caretaking skills alongside Mother Teresa’s disciples in the late 1980s.

“I mean, who wouldn’t want Colleen at their bedside?” asked Ms. Karan over the phone from Parrot Cay in the Turks and Caicos, one of the many exotic locales where the Yees host coed retreats that can cost participants upward of $4,000 each (not including airfare).

More democratically, the couple collaborate on DVDs for Gaiam, the wellness behemoth with which the tawny, muscled Mr. Yee has partnered since 1998. And they are in talks to open a Manhattan outpost of Yoga Shanti, the studio in Sag Harbor, N.Y., where Ms. Saidman Yee has taught Russell Simmons, Christie Brinkley and the literary agent Esther Newberg. It is a move that could be seismic to a tight-knit if perennially (and perineally) relaxed community of instructors and their acolytes.

“I can’t wait,” Ms. Karan said. “To see her evolve as a yoga teacher with Rodney has been one of the most beautiful movies.”

To some, though, it might seem more “Kramer vs. Kramer” than “Royal Wedding.” The felicitous but messy merger of the Yees, who met when she took his teacher-training class, broke up each of their previous marriages. (The couple now have six children and stepchildren between them.)

Ms. Saidman Yee has also severed ties with a longtime business partner, Jessica Bellofatto, who helped her build Yoga Shanti but now has been exiled to East Hampton after a legal tangle. (“I could not be happier,” Ms. Bellofatto wrote in an e-mail.)

Despite prevailing in this conflict, and though her marriage has burnished her personal brand, Ms. Saidman Yee said she still struggles sometimes with asserting her voice. Indeed, this was a theme explored, with “journaling” and tearful dialogue exercises, throughout the gathering in Tulum, formerly an invitation-only affair organized in part by Mary Richardson Kennedy, the late ex-wife of Robert F. Kennedy Jr., that this year was open to anyone who Googled it. “Women’s retreats are about finding that what you have to say is worthwhile and needed,” Ms. Saidman Yee said.

Recently Gaiam released her first solo video for the company, “Yoga for Weight Loss,” a title she dismissed as a sales ploy about which she had no input. “Any way to get a woman on the mat,” she said with a shrug.

And during a March appearance on a “Fit Minute” segment on “The Couch,” a local CBS morning show, Ms. Saidman Yee expressed frustration that the producers wanted her merely for a mute demonstration of the poses her husband was describing. “Just another blonde doing Warrior Two,” she wrote in a weary-sounding e-mail afterward.

But Colleen Saidman Yee, the middle child of seven in a Catholic family raised mostly in Bluffton, Ind., has stood out from the moment she was born.

“Drop the pubic bone!” she ordered, teaching class during a five-day women’s retreat last month at the Amansala resort in Tulum, Mexico, the long golden hair flowing over her shoulders calling to mind Botticelli’s “Birth of Venus.” “This is going to give you the perineal energy we’ve been talking about so much.”

Another, almost Vreelandesque command: “You can’t let the arches of your feet collapse. The collapse of your arches is the collapse of your sex life.” And another: “Open the groin. The groin gets soft.”

“I thought you said, ‘The lights go off,’ ” muttered one contorted participant.

Thick with estrogen and incense, buffeted by warm Caribbean breezes, the room was indeed dim. But Ms. Saidman Yee, whether perching beatifically in full lotus position before 40-odd prone bodies or prowling among them like a jungle cat, emits at 53 her own curious, almost celestial incandescence. Since marrying Rodney Yee, one of the most popular practitioners of the discipline (which he prefers to call an art form), in 2007, she has brought to it glamour, sensuality without the creepy overtones of recent yoga scandals, and unapologetic commercialism, endorsing wine and posing for Vanity Fair.

“Oh, my God, I’m so not pure,” said Ms. Saidman Yee, a longtime model who favors a line of yoga togs cheekily called Sweaty Betty and sometimes pads to class in gold sequined Uggs. “I never want to be called a guru. All I want to do is guide women into their own bodies so they can be more content.”

The Yees may not be gurus, but they are yoga moguls, oxymoronic though that term may seem. They are directors at Donna Karan’s Urban Zen Integrative Therapy program, lithe Florence Nightingales working with the designer to bring yoga and meditation to hospital patients and disaster victims, Ms. Saidman Yee having refined her caretaking skills alongside Mother Teresa’s disciples in the late 1980s.

“I mean, who wouldn’t want Colleen at their bedside?” asked Ms. Karan over the phone from Parrot Cay in the Turks and Caicos, one of the many exotic locales where the Yees host coed retreats that can cost participants upward of $4,000 each (not including airfare).

More democratically, the couple collaborate on DVDs for Gaiam, the wellness behemoth with which the tawny, muscled Mr. Yee has partnered since 1998. And they are in talks to open a Manhattan outpost of Yoga Shanti, the studio in Sag Harbor, N.Y., where Ms. Saidman Yee has taught Russell Simmons, Christie Brinkley and the literary agent Esther Newberg. It is a move that could be seismic to a tight-knit if perennially (and perineally) relaxed community of instructors and their acolytes.

“I can’t wait,” Ms. Karan said. “To see her evolve as a yoga teacher with Rodney has been one of the most beautiful movies.”

To some, though, it might seem more “Kramer vs. Kramer” than “Royal Wedding.” The felicitous but messy merger of the Yees, who met when she took his teacher-training class, broke up each of their previous marriages. (The couple now have six children and stepchildren between them.)

Ms. Saidman Yee has also severed ties with a longtime business partner, Jessica Bellofatto, who helped her build Yoga Shanti but now has been exiled to East Hampton after a legal tangle. (“I could not be happier,” Ms. Bellofatto wrote in an e-mail.)

Despite prevailing in this conflict, and though her marriage has burnished her personal brand, Ms. Saidman Yee said she still struggles sometimes with asserting her voice. Indeed, this was a theme explored, with “journaling” and tearful dialogue exercises, throughout the gathering in Tulum, formerly an invitation-only affair organized in part by Mary Richardson Kennedy, the late ex-wife of Robert F. Kennedy Jr., that this year was open to anyone who Googled it. “Women’s retreats are about finding that what you have to say is worthwhile and needed,” Ms. Saidman Yee said.

Recently Gaiam released her first solo video for the company, “Yoga for Weight Loss,” a title she dismissed as a sales ploy about which she had no input. “Any way to get a woman on the mat,” she said with a shrug.

And during a March appearance on a “Fit Minute” segment on “The Couch,” a local CBS morning show, Ms. Saidman Yee expressed frustration that the producers wanted her merely for a mute demonstration of the poses her husband was describing. “Just another blonde doing Warrior Two,” she wrote in a weary-sounding e-mail afterward.

But Colleen Saidman Yee, the middle child of seven in a Catholic family raised mostly in Bluffton, Ind., has stood out from the moment she was born.

According to legal documents filed this month in Los Angeles County Superior Court, Sarah Baughn, 28, a Bikram student, teacher and international competitor who lives in San Francisco, said she considered Mr. Choudhury her hero until he made advances toward her during a 2005 teacher training course in Los Angeles.

Ms. Baughn, who was 20 at the time, said she was uncomfortable when she first noticed how other female students would brush his hair, wash his feet and give him massages, but she chalked it up to cultural differences. Then, she says, he offered her his diamond Rolex watch, which she did not accept, and told her he had known her in a past life.

“What should we do about this?” the lawsuit claims Mr. Choudhury said. “I have never felt this way about anyone,” he continued, adding, “Should we make this a relationship?”

Mr. Choudhury opened his first yoga studio in the early 1970s in the basement of a bank building in Beverly Hills, Calif. A national yoga champion from Calcutta, Mr. Choudhury was said to sleep on the studio floor, spurn the advances of women and offer classes by donation only. Then Shirley MacLaine, an early student, gave him some advice.

“She said no American respects anything that’s free,” Mr. Choudhury recalled at the 2012 Bishnu Charan Ghosh Cup, the yoga asana competition named after his guru.

Now, Mr. Choudhury, 67, charges $25 per class, oversees hundreds of studios on six continents, owns several Rolls-Royces and is called “Yoga’s Bad Boy” by Yoga Journal. His copyrighted yoga sequence is practiced in a 105-degree room often nicknamed the torture chamber.

“Sarah dropped out of college to study with Bikram, and every penny she had went to him,” said Mary Shea Hagebols, Ms. Baughn’s lawyer. “She was a true believer and student.”

Ms. Baughn says she rebuffed Mr. Choudhury’s repeated advances and at times tried to redirect his attention to his wife, also a teacher and the founder of USA Yoga, a yoga sports federation with Olympic ambitions. The legal document claims that his advances continued; he is accused of pressing his body against hers while adjusting her posture, whispering sexually charged comments into her ear, ordering her to kiss him in front of other trainees, and assaulting her in a hotel room in Acapulco, Mexico, during a teacher training.

Her lawyer declined to say whether Ms. Baughn ever reported any of these accusations to the police, but she did speak with senior teachers at his Los Angeles-based Yoga College of India. “Sarah wants whatever justice the jury decides so that this never happens again — that’s her primary goal,” Ms. Hagebols said.

Neither Mr. Choudhury nor his wife, Rajashree, who is also being sued for her role in running the business and the teacher training program, could be reached for comment. But a spokeswoman for USA Yoga said the group was confident that the court would determine the truth.

“In the interim,” said the spokeswoman, Rachel Golden, “we believe it is vitally important to continue to support the millions of devoted yoga practitioners around the world in reaping the benefits of their practice.”

Reporting Mr. Choudhury’s behavior to the senior teachers did little good, Ms. Baughn says in the suit. They promised that he was harmless and “innocent, like a child,” she said. Ms. Baughn said she was told that she needed to “separate the man from the teacher” and understand that powerful men were often flirtatious.

“Vulnerability and devotion are big parts of the practice,” said Benjamin Lorr, the author of the memoir “Hellbent: Obsession, Pain, and the Search for Something like Transcendence in Competitive Yoga.” “Bikram creates this mentality that the outside is phony. There is no path but this path, and everything that happens in this path is just a part of your yoga, that you have to learn to be strong and get past it.”

Considered a guru to celebrities like Madonna, George Clooney and Jennifer Aniston, Mr. Choudhury wears a Speedo while presiding over teacher trainings that cost $11,000. Over 300 would-be teachers practice three hours of yoga per day in a sweltering hotel conference room. They also study anatomy, Hindu philosophy and Bikram’s views on life, love and ethics.

Ms. Baughn says her financial investment was one reason she continued to study, practice and teach the series despite her accusations that Mr. Choudhury attempted to sabotage her career and competition results when she repeatedly refused his advances.

“There was a culture of fear,” Mr. Lorr said of the Bikram teacher trainings he experienced, where he tried to interview other students. “No one really wanted to go on the record with me. They thought they would lose their certificates, that all the hard work and money they put into it would be taken away.”

Some Bikram studio owners are wondering how to confront the accusations.

Tricia Donegan, the owner of Bikram Yoga on the Lower East Side of Manhattan, explained that some students did not even know that Bikram was an actual person.

“Bikram’s name may be on the door,” she said, “but my particular space is a safe haven.”

According to legal documents filed this month in Los Angeles County Superior Court, Sarah Baughn, 28, a Bikram student, teacher and international competitor who lives in San Francisco, said she considered Mr. Choudhury her hero until he made advances toward her during a 2005 teacher training course in Los Angeles.

Ms. Baughn, who was 20 at the time, said she was uncomfortable when she first noticed how other female students would brush his hair, wash his feet and give him massages, but she chalked it up to cultural differences. Then, she says, he offered her his diamond Rolex watch, which she did not accept, and told her he had known her in a past life.

“What should we do about this?” the lawsuit claims Mr. Choudhury said. “I have never felt this way about anyone,” he continued, adding, “Should we make this a relationship?”

Mr. Choudhury opened his first yoga studio in the early 1970s in the basement of a bank building in Beverly Hills, Calif. A national yoga champion from Calcutta, Mr. Choudhury was said to sleep on the studio floor, spurn the advances of women and offer classes by donation only. Then Shirley MacLaine, an early student, gave him some advice.

“She said no American respects anything that’s free,” Mr. Choudhury recalled at the 2012 Bishnu Charan Ghosh Cup, the yoga asana competition named after his guru.

Now, Mr. Choudhury, 67, charges $25 per class, oversees hundreds of studios on six continents, owns several Rolls-Royces and is called “Yoga’s Bad Boy” by Yoga Journal. His copyrighted yoga sequence is practiced in a 105-degree room often nicknamed the torture chamber.

“Sarah dropped out of college to study with Bikram, and every penny she had went to him,” said Mary Shea Hagebols, Ms. Baughn’s lawyer. “She was a true believer and student.”

Ms. Baughn says she rebuffed Mr. Choudhury’s repeated advances and at times tried to redirect his attention to his wife, also a teacher and the founder of USA Yoga, a yoga sports federation with Olympic ambitions. The legal document claims that his advances continued; he is accused of pressing his body against hers while adjusting her posture, whispering sexually charged comments into her ear, ordering her to kiss him in front of other trainees, and assaulting her in a hotel room in Acapulco, Mexico, during a teacher training.

Her lawyer declined to say whether Ms. Baughn ever reported any of these accusations to the police, but she did speak with senior teachers at his Los Angeles-based Yoga College of India. “Sarah wants whatever justice the jury decides so that this never happens again — that’s her primary goal,” Ms. Hagebols said.

Neither Mr. Choudhury nor his wife, Rajashree, who is also being sued for her role in running the business and the teacher training program, could be reached for comment. But a spokeswoman for USA Yoga said the group was confident that the court would determine the truth.

“In the interim,” said the spokeswoman, Rachel Golden, “we believe it is vitally important to continue to support the millions of devoted yoga practitioners around the world in reaping the benefits of their practice.”

Reporting Mr. Choudhury’s behavior to the senior teachers did little good, Ms. Baughn says in the suit. They promised that he was harmless and “innocent, like a child,” she said. Ms. Baughn said she was told that she needed to “separate the man from the teacher” and understand that powerful men were often flirtatious.

“Vulnerability and devotion are big parts of the practice,” said Benjamin Lorr, the author of the memoir “Hellbent: Obsession, Pain, and the Search for Something like Transcendence in Competitive Yoga.” “Bikram creates this mentality that the outside is phony. There is no path but this path, and everything that happens in this path is just a part of your yoga, that you have to learn to be strong and get past it.”

Considered a guru to celebrities like Madonna, George Clooney and Jennifer Aniston, Mr. Choudhury wears a Speedo while presiding over teacher trainings that cost $11,000. Over 300 would-be teachers practice three hours of yoga per day in a sweltering hotel conference room. They also study anatomy, Hindu philosophy and Bikram’s views on life, love and ethics.

Ms. Baughn says her financial investment was one reason she continued to study, practice and teach the series despite her accusations that Mr. Choudhury attempted to sabotage her career and competition results when she repeatedly refused his advances.

“There was a culture of fear,” Mr. Lorr said of the Bikram teacher trainings he experienced, where he tried to interview other students. “No one really wanted to go on the record with me. They thought they would lose their certificates, that all the hard work and money they put into it would be taken away.”

Some Bikram studio owners are wondering how to confront the accusations.

Tricia Donegan, the owner of Bikram Yoga on the Lower East Side of Manhattan, explained that some students did not even know that Bikram was an actual person.

“Bikram’s name may be on the door,” she said, “but my particular space is a safe haven.”

The company is recalling yoga pants made with a fabric known as Luon that are overly transparent, which make up about 17 percent of all the Canada-based retailer’s women’s bottoms.

Lululemon’s chief executive, Christine Day, said Thursday that the company did not know exactly why the quality had gone awry, as the pants had passed quality-assurance tests. But she added that “the truth of the matter is that the only way that you can actually test for the issue is to put the pants on and bend over,” which the company did not do until too late.

The consequences could be significant for Lululemon, analysts said. The company redefined the athletic-apparel world, making it no big deal for women to spend $100 on yoga pants and wear them throughout the day. Its stores churn out high sales per square foot, offer amenities like yoga classes and running clubs, and cater to hard-core fans by offering store discounts to yoga instructors in exchange for product feedback.

Since its founding, the company has faced competitors, notably Gap Inc.’s Athleta, which has been opening stores near Lululemons and selling similar products, though at slightly cheaper prices. Boutique brands and major sports brands like Nike and Under Armour have also been eager to expand their reach in this market.

Now, analysts say, they may finally have a shot.

“You can’t afford to be potentially inviting your customer to go somewhere else, especially in this environment,” said Sam Poser, an analyst with Sterne Agee. Yoga pants are a main attraction for Lululemon shoppers, who may not visit the store, or buy multiple items there, he said, if their favorite type is missing.

“One thing can be that important,” Mr. Poser said.

Lululemon first talked about the Luon problems on Monday, and its stock had dropped by 7 percent, to $62.16, during trading on Tuesday.

Analysts hurried to downgrade Lululemon stock, and on Thursday, the company quantified the fallout of the sheer-pants problem as it reported its fourth-quarter earnings. Lululemon said the impact from the damaged inventory and lost revenue would reduce first-quarter earnings by 11 to 12 cents a share and by 25 to 27 cents for the year. The company put the lost revenue at about $57 million to $67 million for this year.

The company’s performance for the year ended Feb. 3 was strong: profit rose 34 percent to $762.8 million, while revenue rose 37 percent to $1.4 billion, and the company said it expected sales of more than $1.6 billion this year. The stock closed slightly up on Thursday at $64.70.

Ms. Day did not specify when revamped Luon pants would be in stores. She said the company was taking steps to improve quality control, such as dedicating employees to work with vendors, adding specifications to the Luon production process and stationing employees at mills to observe production.

The Luon issue comes on the heels of other quality problems. Last summer, the company issued an apology to customers after they complained about the colors of some garments bleeding.

At the time, John D. Morris, an analyst for BMO Capital, conducted consumer research that showed shoppers were upset about “bright colors bleeding when washed, pilling and fraying seams problems.” Mr. Morris said then that “we believe LULU’s recently expanded manufacturing partnerships could be partly to blame in terms of isolating the problem.”

On Thursday, Mr. Morris sent a note to clients saying “the issues may not have a quick fix. We would continue to proceed with caution on the name until quality issues are clearly identified, contained and remedied.”

Competitors have long been circling Lululemon, trying to get a bigger piece of its high-margin business.

Athleta, for instance, has 35 Athleta stores in the United States, compared with 211 Lululemons in North America and Australia, and Gap expects to open another 30 Athleta stores in 2013.

“Everyone has wanted to be in Lululemon’s business for a long time,” said Faye Landes, an analyst at Cowen. She said, however, that Lululemon’s store environment was hard to match, from its offer of free hemming to its activities.

“I’m sure Nike and Under Armour and boutique brands are all talking to their retailers right now about how this is an opportunity, but I think they just can’t replicate what Lululemon does,” she said.

Still, reaction — from blogs and personalities like Jimmy Kimmel — was harsh, and some shoppers seemed to be increasingly wary of Lululemon.

Stacey Hanuska, 34, of Pottstown, Pa., said reading about the Lululemon issues had made her even more of a fan of Athleta.

There, “you can return anything at any time for any reason,” she said. And while she had made some returns, “it’s never been a quality issue,” she said.