Is yoga dangerous?

Every day, my inbox overflows with questions from people asking me to verify claims they've seen on social media. I appreciate their trust. After nearly thirty years of studying flexibility and stretching, I've honed an instinct for spotting falsity. It helps me separate truth from fiction with ease. Some jokingly call me the 'Sherlock Holmes of stretching.' Like the famous detective, I aim to uncover the truth. I pay close attention to details in my quest for facts. Whether I'm dispelling the myth that static passive stretching makes joints unstable or proving that stretching prevents specific injuries, I feel a duty as an educator to ensure the knowledge I share is accurate and backed by evidence.

A lot of the questions I get are about yoga. I don’t claim to be an expert, but I’ve taken many classes. I even got certified as an instructor once. I’m not here to tell you yoga is the be-all and end-all. But it is a beneficial way to exercise. Like static passive stretching, yoga has plenty of scientific backing and personal accounts to support it. But it has its critics, too. They argue yoga’s benefits are overblown, maybe even harmful. Most of these critics have their own agendas. They want to make money or promote their brand of fitness. They say yoga doesn’t work or that it’s dangerous. They claim it could cause injuries or make existing problems worse. This misinformation undermines yoga’s actual benefits. Yoga increases flexibility, reduces stress, and clears the mind. It’s an ancient practice, well-respected, yet this kind of talk might turn people away from trying it.

Not long ago, someone from the Flexibility Research community asked for my opinion on a video clip that had made its rounds on Facebook over a year ago. The video shows a conversation between Vishen Lakhiani, the founder and CEO of Mindvalley, and Steven Kotler, a well-known author and journalist. The clip can be viewed on Facebook here.

The caption to the video reads:

"Yoga can be dangerous and this is why! Steven Kotler | Mindvalley

"Sometimes what we've been told may not necessarily be true... check these insights from human performance expert Steven Kotler. Thoughts?

"Discover the latest science behind physical performance and longevity in Steven's full interview on Ep.10 of The Mindvalley Show."

I have provided a full transcript below in case you can't access the clip, or it gets removed.

Steven Kotler (SK): I'm going to say something incredibly controversial, and I've done yoga for 30 years and I think yoga is foundational for peak performance aging, and I will come out and advocate for it but there are a lot of studies now that are looking at the benefits of yoga and they're not finding them in comparison to a bunch of other sports. And they're finding some dangers around like the slow stretching of muscles. A healthy body has fascia that rebounds quickly, right?

Vishen Lakhiani (VL): Right.

SK: And if you're doing 30 second into a minute-long stretches, you're sort of stretching out the fascia. A good body worker who works with fascia will say never hold a stretch for longer than 15 seconds.

VL: That's – that's interesting because in the book 'Body by Science' by Doug McGuff, he basically says stretching is useless.

SK: Other people say that as well. There's a whole movement because they figured out that stretching is not about the muscles, it's actually about the nervous system. So, when I anaesthetise you, I can bend your leg behind your head. Yeah, you're totally flexible when anaesthetised. Same thing with babies [they] have that flexibility, and so something about stretching has to do with the nervous system more than the musculature. So there's this big controversy around stretching in the physical therapy world. That said, in my experience, I think it really matters and certainly maintaining flexibility is one of those five core aspects of functional fitness.

The importance of context

Establishing the full context of what someone says isn't just a luxury; it's a necessity. Without context, we risk missing the real meaning behind their words. Stripped from their setting, words can be twisted, losing the subtle shades that give them depth. Context is essential; it uncovers the speaker's true intentions, the influences shaping their words, and the people they speak to. It shows us whether a comment was made in earnest or jest, whether it was meant to support or criticise, to include or exclude. In today’s fast-moving world, where quick soundbites and rash judgments prevail, ignoring context breeds misunderstandings and needless conflict and spreads falsehoods. I must stress that the video I received was a fragment of a longer conversation. So, before forming an opinion about what Lakhiani and Kotler said, I made sure to watch the whole discussion. You can watch it yourself by clicking here.

In the full episode of the Mindvalley Show, the talk centred on Kotler's book, Gnar Country: Growing Old, Staying Rad. The book takes on a question that has puzzled folks for years: how can we extend our lives and improve the quality of those extra years? Kotler puts forth the concept of "peak performance aging," offering ways to keep our spirits and bodies alive as the years pile on. He points to five key areas: strength, stamina, agility, balance, and flexibility. These are vital for staying physically capable, backed by solid research in human movement sciences. They form a strong foundation for staying fit as we age. Yet, Kotler overlooked the role of speed, a crucial element of motor skills. Also, while agility matters, it often fits better under the umbrella of coordination, another critical skill Kotler doesn’t seem to explore fully.

In the video clip, the talk about yoga begins when Lakhiani asks Kotler to rate different sports and activities on a scale from one to ten. The focus is on how well these activities help people build crucial skills for reaching peak performance in life. Yoga might not be Kotler’s top-rated choice, but its many benefits, especially for older people, are widely recognised. In this article, I will review the points raised in the video, following the order in which they are discussed.

Claim 1: Yoga is not as effective as other sports or activities at developing the pillars of fitness in aging populations.

Reality: Yoga is an effective way for older adults to build strength, maintain flexibility, and keep their balance. Surprisingly, it might rival traditional exercise methods regarding these benefits or even surpass them. Yet, its impact on cardiovascular endurance, what Kotler terms "stamina," appears less pronounced.

In one study, older adults who participated in 16 yoga sessions showed a 12.5% increase in muscle strength, particularly in their legs, as measured by the 30-second chair stand test [1]. Notably, yoga proved just as effective as traditional stretching and strengthening exercises in enhancing muscle strength, balance, flexibility, and overall mobility, even among older adults who had not been active before [2]. Moreover, a systematic review indicates that yoga may offer more significant benefits than typical exercise, particularly in improving strength, balance, and flexibility [3]. This evidence points to yoga being more effective than standard exercises at enhancing how older adults perceive their health and physical strength.

Yoga has a way of improving balance. Studies show it clearly. People score better on tests like the Berg Balance Scale, Functional Gait Assessment, and Dynamic Gait Index [4]. Those who do yoga regularly find their balance holds steady. Their legs become more flexible [5,6]. Yoga strengthens our posture and helps us relax. All these things matter if we want to keep from falling [7-9]. A meta-analysis shows yoga builds muscle strength, improves balance, and makes the lower body more flexible in older people. These findings back the advice to include yoga in physical activity plans for this age group [10]. People doing yoga also say they fall less after their sessions. This suggests yoga may cut down the risk of falls among older people [11].

But how does yoga stack up against the sports Kotler rated higher in his talk with Lakhiani? The truth is, we don’t know. While plenty of evidence shows yoga enhances performance in many sports, there hasn’t been a direct comparison with skiing, snowboarding, tennis, or martial arts. It’s also crucial to remember that Kotler’s rankings in their discussion were entirely subjective. He admitted this himself, showing a hint of reluctance even to give any scores at all.

What does the research tell us? When we look at skiing, we see that skiing and yoga both offer great benefits, each honing in on different parts of physical fitness. Yoga, especially Hatha and Iyengar, is known to boost flexibility. A study with elderly participants showed that those who practiced Hatha yoga three times a week for a year saw a marked increase in flexibility. They outperformed those who did callisthenics or didn’t exercise at all [12]. Skiing, by contrast, focuses on building aerobic fitness, strengthening the lower body, and enhancing endurance. It’s a demanding activity that pushes the heart rate up, making it highly effective for improving cardiovascular endurance [13]. Yet, until yoga faces direct comparison with other sports in rigorous trials, we can’t say for sure if yoga is more or less effective in developing specific fitness traits.

Claim 2: Yoga is dangerous.

Reality: Practicing yoga is safe for most people. But like any activity, it carries risks, especially if precautions aren't taken.

A study on yoga-related injuries showed few reported cases. Serious injuries were rare and less common than in other physical activities. Most injuries were minor or moderate, such as sprains or general discomfort that didn’t need medical care [14]. Doing warm-up exercises before yoga can cut down the risk of injury, especially for beginners or those trying more intense styles [15]. Another study on older women found no link between regular yoga and joint problems. This suggests that when done properly, yoga does not harm joint health [16].

Adverse events from yoga are rare, but they do happen. They usually involve the muscles, nerves, and eyes. There are times when intense yoga breathing exercises, known as pranayama, carry risks. Yet, these risks can be lessened by sticking to traditional safety guidelines and mastering the basics before moving on to more advanced levels. A systematic review of case reports and series found that, while some adverse events were recorded, most people recovered fully or partially. This shows the importance of practising yoga under the guidance of a qualified instructor [17].

For those dealing with anxiety, yoga has proven to be safe and effective, with research showing no increased risk of harm [18]. In the context of breast cancer, yoga not only avoids causing severe negative effects but also improves the quality of life, eases fatigue, and helps with sleep [19]. For individuals with schizophrenia, yoga has shown some benefits without any harmful effects reported, though the evidence remains somewhat limited [20]. The available research suggests that yoga is generally safe, especially when practiced under proper supervision and with the necessary precautions. This is particularly crucial for beginners and those with existing medical conditions. Although adverse events can occur, they are rare and often preventable with correct instruction and proper warm-up exercises.

Claim 3: Static passive stretches should be held for no longer than 15 seconds because they stretch the fascia.

There are some problems with this claim. First is the idea that a 15-second stretch can't lengthen fascia. But even a 1-second stretch will extend the fascia. But what is fascia, really? It's the connective tissue in muscles. Muscles are complex structures. They're made of bundles of fibres, each wrapped in layers of connective tissue. These layers support the muscle and help it transmit forces. A thin layer called the endomysium surrounds each fibre. These fibres are grouped into bundles called fascicles. Another layer, the perimysium, wraps around each bundle. Finally, the whole muscle is covered by the epimysium. Together, these layers form the fascia. It's like a web that covers each muscle and links them to other parts of the body, creating a network throughout.

When you stretch a muscle, the force spreads through the connective tissues, making the muscle longer in different ways. First, the muscle fibres themselves stretch. Inside them are sarcomeres, the tiny units responsible for contraction. These sarcomeres have actin and myosin filaments, which slide past each other to contract the muscle. But when you stretch, these filaments are pulled apart. They create more space between them, which makes the muscles longer. As you stretch, the tension moves to the connective tissues – the endomysium, perimysium, and epimysium. These tissues aren't as flexible as muscle fibres but can still stretch some. When you apply tension slowly, like in static passive stretching, these layers can lengthen without tearing. This makes the muscle longer overall. In short, holding a stretch for less than 15 seconds doesn't stop the fascia from stretching along with the muscle fibres because the fascia is a vital part of those fibres.

The second issue with this claim is that there’s nothing hazardous about holding a stretch for 30, 45, or 60 seconds – or even longer. In fact, a well-known study by William Bandy, a Professor of Physical Therapy at the University of Central Arkansas, and Jean Irion, an Assistant Director of Clinical Education at the University of South Alabama, showed that holding a stretch for 30 seconds was more effective in improving range of motion than holding it for just 15 seconds [21]. However, when focusing on the fascia – the connective tissue that contributes to muscle stiffness – longer stretching durations are more effective. The fascia, along with neural reflexes, is a major barrier to improving flexibility. Recent studies suggest that to reduce stiffness significantly stretches need to be held for three minutes or more [22]. Interestingly, this is the exact duration used in yin yoga, where stretches are held for long periods.

Claim 4: Doug McGuff stated that stretching is useless in his book 'Body by Science.'

Reality: Doug McGuff is an unreliable source of information for stretching and flexibility. Here is what he wrote in his book:

"In most instances, people consider flexibility to be the third leg of the fitness tripod, the other two being cardiovascular stimulation and strength building. While enhanced flexibility is desirable, you don't have to enrol in a yoga class or stretch constantly (or at all) to safely achieve flexibility.

"There is widespread confusion, even among fitness authorities, between stretching and flexibility. What you want is not increased flexibility so much as enhanced flexibility. This goal is achieved by an application of resistance at the safe extremes of a muscle's range of motion.

"In a study conducted on young people who performed a strength-training program, the experimenters concluded that the strength-trained subjects were able to improve their range of movement far more than were the control subjects. In another study, forty-eight subjects who performed Nautilus strength training over a period of eight weeks improved their hip-trunk flexibility by two and a half inches without performing any stretching exercises, while simultaneously increasing muscle strength by 50 percent.

"In setting up an appropriate resistance-training program, the selected exercises should track muscle and joint function and apply resistance through full flexion to full extension. Built into proper resistance exercise is an application of force at the extremes of a muscle's (or muscle group's) safe range of motion. For some joints, this may mean that we're going to improve or increase the range of that joint, but for other joints, an enhanced flexibility may actually result in a decrease in that joint's range of motion. Most of the problems and derangements that occur in the shoulder joint, for example, are a result not of inadequate flexibility but of excessive flexibility. The increased strength and development of the surrounding rotator cuff muscles, as well as the deltoid musculature, may diminish the range of the shoulder joint somewhat, but in a way that is protective to the joint.

"It follows that by performing appropriate exercise with resistance through a full range of motion, you will be doing everything that you should (and could) to improve your flexibility. Yoga or stretching exercises are not going to enhance your flexibility. Instead, either they will induce a state of sufficiency, which is a pulling or tugging sensation in the muscle that occurs because you've put it in a position in which it cannot contract (such as occurs with your quadriceps in a hurdler's stretch), or you are essentially trying to pull the joint apart by its connective tissue-and that's not healthy.

"While many folks may look back wistfully to a time in their younger days when they believed themselves to be "more flexible," because they could "execute a full side split," the reasoning behind such beliefs is faulty. We are no longer able to perform the impressive manoeuvres that we could execute when we were younger because the capsules in the hip have now matured, and our femurs (upper-leg bones) have become bigger. With bigger bones, the movement potential in the hip capsule is now more restricted, as it should be to accommodate adult-size bones. Note that many martial artists who fanatically stretch are not immune from hip replacements and knee replacements as they age, which is a direct result of their attempting to force their joints into vulnerable positions. Similarly, children on sports teams are told to stretch all the time by their coaches, and many develop pulled groin muscles as a result.

"Often adults who believe they have suffered a loss in flexibility have actually suffered a loss of functional strength. If they attempt to perform a full split, they won't make themselves any stronger, but, as with other such stretches, they may produce some improvement in their ability to perform this maneuver by virtue of both practicing and creating enough damage at the joint to allow it that degree of laxity. It is neither desirable nor necessary to do so to enhance your flexibility."

McGuff is probably a skilled physician, and his advice likely comes with good intentions. But his writing highlights a common problem: most medical doctors aren't specialists in the science of flexibility. This is true even for doctors of physical therapy, who don't rank as top experts in flexibility and stretching exercises. In his book, McGuff introduces the term "enhanced flexibility" and tries to set it apart from "increased flexibility." There are two issues here. First, the scientific literature usually treats "increased flexibility" and "enhanced flexibility" as the same. Second, it's unclear if McGuff understands the difference between these terms as he defines them. At first, it seems he uses "enhanced flexibility" to refer to applying resistance at the safe limits of a muscle's range of motion, which is the method he prefers. But then he claims this method will improve – not enhance – flexibility. This indicates even he may be unsure of the difference between the two terms.

We’ve known for decades that strength-based flexibility training works. It shouldn’t surprise anyone. In recent years, these strength-based methods have gained ground, often under the name 'mobility training.' Because of this shift, some now argue these approaches work as well as, if not better than, traditional stretching. Recent systematic reviews back up this claim. They report that resistance training is as effective as stretching for improving range of motion [23].

However, there are two things to remember when discussing those systematic reviews. First, many studies grouped non-static stretching techniques, which are still types of stretching, under the label of 'resistance training.' Because of this, some readers and so-called experts have come to believe that traditional strength training – often linked with bodybuilding – is just as effective as, or even better than, stretching for improving flexibility. Second, the stretching in most of these studies was only of light intensity. Why does that matter? Because high-intensity stretching is generally much more effective than low-intensity stretching [24-28]. This difference is vital. As flexibility gets close to the limits of joint range, the intensity of stretching – whether it's static, passive, or resistance-based – increases sharply. So, being willing and able to do high-intensity stretching is necessary if you want to keep making progress.

McGuff mistakes weakness in a certain range of motion for what he terms "excessive flexibility." But this isn't excessive flexibility; it's merely a lack of strength. There's no such thing as excessive flexibility. Flexibility is only the measure of how far a joint can move, and not having the strength to exert a particular force doesn't make flexibility excessive. Still, like many doctors before him, McGuff fails to understand this. He blames flexibility when, in reality, the actual issue is a lack of strength.

McGuff states, "Yoga or stretching exercises are not going to enhance your flexibility." Here, by 'enhance,' he means 'increase.' He argues that these activities only lead to a "state of sufficiency," describing it as a muscle feeling tension because it's positioned where it can't contract, and the joint is being "pulled apart" by its connective tissue. His explanation has problems, and I'll address them as clearly as I can. First, "a state of sufficiency" is not a recognised term in biomechanics or exercise science literature. The term "insufficiency" is used to describe a muscle spanning multiple joints that either can't produce effective force due to being overly shortened (active insufficiency) or can't stretch enough to allow full range of motion across all joints it crosses (passive insufficiency). From McGuff's choice of words, he’s not referring to either. He wrongly criticises stretching and flexibility rather than acknowledging that weakness stems from a lack of strength. Static passive stretching, which improves flexibility, doesn’t lead to weakness. The absence of resistance training does. Would anyone argue that long-distance running weakens a person simply because a marathon runner might lack strength from not engaging in resistance training? No, we wouldn't say that. It's also important to note that just five minutes of static passive stretching daily for six weeks can boost muscle strength [29].

McGuff says adults can't move like they did as children, and there's some truth in that. But splits don't fall into that category. Yes, adult bones are shaped differently, but that doesn't mean splits are out of reach. It just means the journey takes longer, and the final pose might not look the same. A six-year-old child might master the side split in a month, hitting a perfect 180° between the hips. A 45-year-old man, though, might need two years and max out at 165° of hip adduction. Look at photos of adult men doing side splits, and you'll often notice a gap of several inches between the pelvis and the floor. Yet, you can still push your body to its natural limit without risking harm. Anyone with average hip joint structure can do the splits – or come very close – if they train with care.

McGuff’s claim that stretching enthusiasts often need hip and knee replacements doesn’t hold much water. Sure, some martial artists might need joint replacements later in life. But so do marathon runners, cyclists, swimmers, weightlifters, tennis players, bodybuilders, golfers, and even those who never exercise. The reasons for needing such surgeries vary widely, yet stretching has never been singled out as a cause in any epidemiological studies. Simply put, stretching alone does not directly lead to joint replacement surgery. The main reasons for these surgeries are advanced osteoarthritis and other forms of arthritis, which wear down the cartilage in the joints. These conditions come from age, genetics, joint injuries, and chronic stress on the joints, not from stretching [30]. Another big cause of joint replacement surgery is trauma – whether from sudden acute injuries or repetitive stress that harms the joint. When done correctly, stretching doesn't cause this kind of joint damage. In my experience, after over 36 years of practicing martial arts and 26 years of teaching, I’ve seen far more people end up injured with joint problems because they don’t stretch. You don’t have to do the splits to kick high, but you need to get close to the splits if you want to kick high. Ultimately, the flexibility you gain from static passive stretching lets you move with ease and agility in dynamic active movements.

McGuff’s view on martial artists needing joint replacements because of stretching is one I’ve faced too many times. People often mistake correlation for causation. I know the reality of joint replacements. Both of my hips were replaced in 2015. Before that, I had spent nearly three decades practising martial arts. It’s easy for some to assume that the years of stretching or kicking brought about my need for new hips. But it wasn’t that. It was the result of injuries I got from a roadside bomb in Iraq over ten years before, back when I was in the army. At the time, the doctors said hip replacements were unavoidable. Yet, static passive stretching became my best remedy. It helped me in three ways: 1) reducing the muscle and joint pain from that old injury, 2) bringing back my flexibility to its former state, and 3) postponing the need for hip replacements. What’s more, that same stretching got me back to doing the splits in under nine months after I finally had the surgery:

Static passive stretching held off the need for new hips by nearly a decade. Now, almost ten years after the surgery, the new hips are doing fine. If you're curious about life and flexibility after joint replacement, there's a video that might interest you. In it, I talk with my lifelong coach and mentor, Bill "Superfoot" Wallace. We discuss his hip replacements and his views on stretching and kicking. Bill is pushing eighty, yet he can still do the splits and kick a man in the head, even after having both hips replaced twice. Like me, Bill’s initial hip replacements were due to injuries and accidents, not stretching. It’s the stretching that has allowed him to continue doing the splits and high kicks, even with his replaced hips, at his age.

Contrary to what McGuff wrote (which Lakhiani parroted), stretching is not useless.

Claim 5: Stretching does not affect muscles; it only affects the nervous system.

Reality: The nervous system regulates flexibility, but other structures and mechanisms, apart from the neural, also shape the outcomes of stretching.

One such non-neural factor is passive stiffness, an inherent resistance to being stretched that exists in all muscles and tissues. Earlier, I spoke of how muscle is encased in layers of connective tissue – epimysium, perimysium, and endomysium – providing both support and aiding in force transmission. Collagen fibres within this connective tissue grant muscles their elastic nature. When a muscle stretches, these fibres align before resisting further stretching. The stiffness of a muscle depends on the density and arrangement of these fibres. Notably, this stiffness operates independently of the nervous system – it persists whether we are awake or under anaesthetic.

On a microscopic level, the protein titin within muscle fibres functions as a molecular spring, contributing to passive elasticity. Titin connects myosin filaments to the Z-disc in the sarcomere, adding to passive tension. Changes in titin's elasticity also influence passive stiffness. Like collagen fibres in fascia, titin's stiffness remains intact regardless of our level of consciousness. The notion that a leg could be bent behind the head under general anaesthetic, as Kotler suggests, is a fallacy – it overlooks the non-neural limits that remain even when the brain is silenced by sedation. While a sedated patient can have their limbs stretched further compared to when they are awake, the notion that they can be pushed to their absolute anatomical limits without resistance or causing injury is false. Furthermore, even if stretching were purely a matter of the nervous system, this wouldn’t render stretching meaningless, nor would it condemn long-duration stretching.

Key Takeaways

Yoga has always been seen as a safe and beneficial form of exercise. Yet, it has come under fire in recent years for different reasons, often tied to how people practice and perceive it. The common complaints include poor teaching from instructors who lack the proper training, pushing too hard in stretches because of a competitive mindset, and failing to adjust poses to fit the individual – whether out of inability or unwillingness from the teacher. There’s also the issue of doing yoga while dealing with existing health problems that might worsen with certain poses. But it’s crucial to note that these problems are not widespread, nor are they unique to yoga.

The truth is that much of the criticism aimed at yoga comes from those who don't understand it or have never stepped onto a mat themselves. This is particularly evident in fitness circles focused on strength and muscle, like powerlifting and bodybuilding. Some members of these communities– not all, but some – have a narrow view that leaves little room for open discussion. Often, the problems stem from a mix of ego and a lack of awareness of the scientific studies on yoga. Unfortunately, even people outside these circles have started to join the chorus of criticism. However, when experienced and knowledgeable instructors teach yoga and safety is taken seriously, it remains a very safe practice, offering numerous benefits to anyone who engages with it.

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