Case Study Definition Yin Yoga

What is a case study?

A case study is a research approach that is used to generate an in-depth, multi-faceted understanding of a complex issue in its real-life context. It is an established research design that is used extensively in a wide variety of disciplines, particularly in the social sciences. A case study can be defined in a variety of ways (Table ​5), the central tenet being the need to explore an event or phenomenon in depth and in its natural context. It is for this reason sometimes referred to as a "naturalistic" design; this is in contrast to an "experimental" design (such as a randomised controlled trial) in which the investigator seeks to exert control over and manipulate the variable(s) of interest.

Stake's work has been particularly influential in defining the case study approach to scientific enquiry. He has helpfully characterised three main types of case study: intrinsic, instrumental and collective[8]. An intrinsic case study is typically undertaken to learn about a unique phenomenon. The researcher should define the uniqueness of the phenomenon, which distinguishes it from all others. In contrast, the instrumental case study uses a particular case (some of which may be better than others) to gain a broader appreciation of an issue or phenomenon. The collective case study involves studying multiple cases simultaneously or sequentially in an attempt to generate a still broader appreciation of a particular issue.

These are however not necessarily mutually exclusive categories. In the first of our examples (Table ​1), we undertook an intrinsic case study to investigate the issue of recruitment of minority ethnic people into the specific context of asthma research studies, but it developed into a instrumental case study through seeking to understand the issue of recruitment of these marginalised populations more generally, generating a number of the findings that are potentially transferable to other disease contexts[3]. In contrast, the other three examples (see Tables ​2, ​3 and ​4) employed collective case study designs to study the introduction of workforce reconfiguration in primary care, the implementation of electronic health records into hospitals, and to understand the ways in which healthcare students learn about patient safety considerations[4-6]. Although our study focusing on the introduction of General Practitioners with Specialist Interests (Table ​2) was explicitly collective in design (four contrasting primary care organisations were studied), is was also instrumental in that this particular professional group was studied as an exemplar of the more general phenomenon of workforce redesign[4].

What are case studies used for?

According to Yin, case studies can be used to explain, describe or explore events or phenomena in the everyday contexts in which they occur[1]. These can, for example, help to understand and explain causal links and pathways resulting from a new policy initiative or service development (see Tables ​2 and ​3, for example)[1]. In contrast to experimental designs, which seek to test a specific hypothesis through deliberately manipulating the environment (like, for example, in a randomised controlled trial giving a new drug to randomly selected individuals and then comparing outcomes with controls),[9] the case study approach lends itself well to capturing information on more explanatory 'how', 'what' and 'why' questions, such as 'how is the intervention being implemented and received on the ground?'. The case study approach can offer additional insights into what gaps exist in its delivery or why one implementation strategy might be chosen over another. This in turn can help develop or refine theory, as shown in our study of the teaching of patient safety in undergraduate curricula (Table ​4)[6,10]. Key questions to consider when selecting the most appropriate study design are whether it is desirable or indeed possible to undertake a formal experimental investigation in which individuals and/or organisations are allocated to an intervention or control arm? Or whether the wish is to obtain a more naturalistic understanding of an issue? The former is ideally studied using a controlled experimental design, whereas the latter is more appropriately studied using a case study design.

Case studies may be approached in different ways depending on the epistemological standpoint of the researcher, that is, whether they take a critical (questioning one's own and others' assumptions), interpretivist (trying to understand individual and shared social meanings) or positivist approach (orientating towards the criteria of natural sciences, such as focusing on generalisability considerations) (Table ​6). Whilst such a schema can be conceptually helpful, it may be appropriate to draw on more than one approach in any case study, particularly in the context of conducting health services research. Doolin has, for example, noted that in the context of undertaking interpretative case studies, researchers can usefully draw on a critical, reflective perspective which seeks to take into account the wider social and political environment that has shaped the case[11].

Table 6

Example of epistemological approaches that may be used in case study research

How are case studies conducted?

Here, we focus on the main stages of research activity when planning and undertaking a case study; the crucial stages are: defining the case; selecting the case(s); collecting and analysing the data; interpreting data; and reporting the findings.

Defining the case

Carefully formulated research question(s), informed by the existing literature and a prior appreciation of the theoretical issues and setting(s), are all important in appropriately and succinctly defining the case[8,12]. Crucially, each case should have a pre-defined boundary which clarifies the nature and time period covered by the case study (i.e. its scope, beginning and end), the relevant social group, organisation or geographical area of interest to the investigator, the types of evidence to be collected, and the priorities for data collection and analysis (see Table ​7)[1]. A theory driven approach to defining the case may help generate knowledge that is potentially transferable to a range of clinical contexts and behaviours; using theory is also likely to result in a more informed appreciation of, for example, how and why interventions have succeeded or failed[13].

Table 7

Example of a checklist for rating a case study proposal[8]

For example, in our evaluation of the introduction of electronic health records in English hospitals (Table ​3), we defined our cases as the NHS Trusts that were receiving the new technology[5]. Our focus was on how the technology was being implemented. However, if the primary research interest had been on the social and organisational dimensions of implementation, we might have defined our case differently as a grouping of healthcare professionals (e.g. doctors and/or nurses). The precise beginning and end of the case may however prove difficult to define. Pursuing this same example, when does the process of implementation and adoption of an electronic health record system really begin or end? Such judgements will inevitably be influenced by a range of factors, including the research question, theory of interest, the scope and richness of the gathered data and the resources available to the research team.

Selecting the case(s)

The decision on how to select the case(s) to study is a very important one that merits some reflection. In an intrinsic case study, the case is selected on its own merits[8]. The case is selected not because it is representative of other cases, but because of its uniqueness, which is of genuine interest to the researchers. This was, for example, the case in our study of the recruitment of minority ethnic participants into asthma research (Table ​1) as our earlier work had demonstrated the marginalisation of minority ethnic people with asthma, despite evidence of disproportionate asthma morbidity[14,15]. In another example of an intrinsic case study, Hellstrom et al.[16] studied an elderly married couple living with dementia to explore how dementia had impacted on their understanding of home, their everyday life and their relationships.

For an instrumental case study, selecting a "typical" case can work well[8]. In contrast to the intrinsic case study, the particular case which is chosen is of less importance than selecting a case that allows the researcher to investigate an issue or phenomenon. For example, in order to gain an understanding of doctors' responses to health policy initiatives, Som undertook an instrumental case study interviewing clinicians who had a range of responsibilities for clinical governance in one NHS acute hospital trust[17]. Sampling a "deviant" or "atypical" case may however prove even more informative, potentially enabling the researcher to identify causal processes, generate hypotheses and develop theory.

In collective or multiple case studies, a number of cases are carefully selected. This offers the advantage of allowing comparisons to be made across several cases and/or replication. Choosing a "typical" case may enable the findings to be generalised to theory (i.e. analytical generalisation) or to test theory by replicating the findings in a second or even a third case (i.e. replication logic)[1]. Yin suggests two or three literal replications (i.e. predicting similar results) if the theory is straightforward and five or more if the theory is more subtle. However, critics might argue that selecting 'cases' in this way is insufficiently reflexive and ill-suited to the complexities of contemporary healthcare organisations.

The selected case study site(s) should allow the research team access to the group of individuals, the organisation, the processes or whatever else constitutes the chosen unit of analysis for the study. Access is therefore a central consideration; the researcher needs to come to know the case study site(s) well and to work cooperatively with them. Selected cases need to be not only interesting but also hospitable to the inquiry [8] if they are to be informative and answer the research question(s). Case study sites may also be pre-selected for the researcher, with decisions being influenced by key stakeholders. For example, our selection of case study sites in the evaluation of the implementation and adoption of electronic health record systems (see Table ​3) was heavily influenced by NHS Connecting for Health, the government agency that was responsible for overseeing the National Programme for Information Technology (NPfIT)[5]. This prominent stakeholder had already selected the NHS sites (through a competitive bidding process) to be early adopters of the electronic health record systems and had negotiated contracts that detailed the deployment timelines.

It is also important to consider in advance the likely burden and risks associated with participation for those who (or the site(s) which) comprise the case study. Of particular importance is the obligation for the researcher to think through the ethical implications of the study (e.g. the risk of inadvertently breaching anonymity or confidentiality) and to ensure that potential participants/participating sites are provided with sufficient information to make an informed choice about joining the study. The outcome of providing this information might be that the emotive burden associated with participation, or the organisational disruption associated with supporting the fieldwork, is considered so high that the individuals or sites decide against participation.

In our example of evaluating implementations of electronic health record systems, given the restricted number of early adopter sites available to us, we sought purposively to select a diverse range of implementation cases among those that were available[5]. We chose a mixture of teaching, non-teaching and Foundation Trust hospitals, and examples of each of the three electronic health record systems procured centrally by the NPfIT. At one recruited site, it quickly became apparent that access was problematic because of competing demands on that organisation. Recognising the importance of full access and co-operative working for generating rich data, the research team decided not to pursue work at that site and instead to focus on other recruited sites.

Collecting the data

In order to develop a thorough understanding of the case, the case study approach usually involves the collection of multiple sources of evidence, using a range of quantitative (e.g. questionnaires, audits and analysis of routinely collected healthcare data) and more commonly qualitative techniques (e.g. interviews, focus groups and observations). The use of multiple sources of data (data triangulation) has been advocated as a way of increasing the internal validity of a study (i.e. the extent to which the method is appropriate to answer the research question)[8,18-21]. An underlying assumption is that data collected in different ways should lead to similar conclusions, and approaching the same issue from different angles can help develop a holistic picture of the phenomenon (Table ​2)[4].

Brazier and colleagues used a mixed-methods case study approach to investigate the impact of a cancer care programme[22]. Here, quantitative measures were collected with questionnaires before, and five months after, the start of the intervention which did not yield any statistically significant results. Qualitative interviews with patients however helped provide an insight into potentially beneficial process-related aspects of the programme, such as greater, perceived patient involvement in care. The authors reported how this case study approach provided a number of contextual factors likely to influence the effectiveness of the intervention and which were not likely to have been obtained from quantitative methods alone.

In collective or multiple case studies, data collection needs to be flexible enough to allow a detailed description of each individual case to be developed (e.g. the nature of different cancer care programmes), before considering the emerging similarities and differences in cross-case comparisons (e.g. to explore why one programme is more effective than another). It is important that data sources from different cases are, where possible, broadly comparable for this purpose even though they may vary in nature and depth.

Analysing, interpreting and reporting case studies

Making sense and offering a coherent interpretation of the typically disparate sources of data (whether qualitative alone or together with quantitative) is far from straightforward. Repeated reviewing and sorting of the voluminous and detail-rich data are integral to the process of analysis. In collective case studies, it is helpful to analyse data relating to the individual component cases first, before making comparisons across cases. Attention needs to be paid to variations within each case and, where relevant, the relationship between different causes, effects and outcomes[23]. Data will need to be organised and coded to allow the key issues, both derived from the literature and emerging from the dataset, to be easily retrieved at a later stage. An initial coding frame can help capture these issues and can be applied systematically to the whole dataset with the aid of a qualitative data analysis software package.

The Framework approach is a practical approach, comprising of five stages (familiarisation; identifying a thematic framework; indexing; charting; mapping and interpretation), to managing and analysing large datasets particularly if time is limited, as was the case in our study of recruitment of South Asians into asthma research (Table ​1)[3,24]. Theoretical frameworks may also play an important role in integrating different sources of data and examining emerging themes. For example, we drew on a socio-technical framework to help explain the connections between different elements - technology; people; and the organisational settings within which they worked - in our study of the introduction of electronic health record systems (Table ​3)[5]. Our study of patient safety in undergraduate curricula drew on an evaluation-based approach to design and analysis, which emphasised the importance of the academic, organisational and practice contexts through which students learn (Table ​4)[6].

Case study findings can have implications both for theory development and theory testing. They may establish, strengthen or weaken historical explanations of a case and, in certain circumstances, allow theoretical (as opposed to statistical) generalisation beyond the particular cases studied[12]. These theoretical lenses should not, however, constitute a strait-jacket and the cases should not be "forced to fit" the particular theoretical framework that is being employed.

When reporting findings, it is important to provide the reader with enough contextual information to understand the processes that were followed and how the conclusions were reached. In a collective case study, researchers may choose to present the findings from individual cases separately before amalgamating across cases. Care must be taken to ensure the anonymity of both case sites and individual participants (if agreed in advance) by allocating appropriate codes or withholding descriptors. In the example given in Table ​3, we decided against providing detailed information on the NHS sites and individual participants in order to avoid the risk of inadvertent disclosure of identities[5,25].

What are the potential pitfalls and how can these be avoided?

The case study approach is, as with all research, not without its limitations. When investigating the formal and informal ways undergraduate students learn about patient safety (Table ​4), for example, we rapidly accumulated a large quantity of data. The volume of data, together with the time restrictions in place, impacted on the depth of analysis that was possible within the available resources. This highlights a more general point of the importance of avoiding the temptation to collect as much data as possible; adequate time also needs to be set aside for data analysis and interpretation of what are often highly complex datasets.

Case study research has sometimes been criticised for lacking scientific rigour and providing little basis for generalisation (i.e. producing findings that may be transferable to other settings)[1]. There are several ways to address these concerns, including: the use of theoretical sampling (i.e. drawing on a particular conceptual framework); respondent validation (i.e. participants checking emerging findings and the researcher's interpretation, and providing an opinion as to whether they feel these are accurate); and transparency throughout the research process (see Table ​8)[8,18-21,23,26]. Transparency can be achieved by describing in detail the steps involved in case selection, data collection, the reasons for the particular methods chosen, and the researcher's background and level of involvement (i.e. being explicit about how the researcher has influenced data collection and interpretation). Seeking potential, alternative explanations, and being explicit about how interpretations and conclusions were reached, help readers to judge the trustworthiness of the case study report. Stake provides a critique checklist for a case study report (Table ​9)[8].

Table 8

Potential pitfalls and mitigating actions when undertaking case study research

Table 9

Stake's checklist for assessing the quality of a case study report[8]

The desire for yin yoga classes seems to be growing louder than the groans of students coming out of the poses. But, while more and more people resonate with this wonderful style of practice there has come some cautions, some quite vocal. My intention in this article is to start a discussion on the merits of such critiques and to explain some flaws in the logic being presented. To further this conversation, I invite comments via the Forum at

Here are a few of the concerns about yin yoga that I have heard:
  • Yin yoga is dangerous for students who are pregnant, hypermobile, have osteoporosis, etc.;
  • There is no proof yin yoga works; it does not increase flexibility;
  • It doesn't build strength or stability in the joints;
  • It destabilizes the joints;
  • Ligaments (or connective tissues) shouldn't be stretched
  • I know someone who was hurt doing yin yoga.
This is not an exhaustive list but it is a good place to start.

What is Yin Yoga?

Since I wish to respond to criticisms of yin yoga, the onus is on me to define what I mean by the term, which admittedly may not be what others mean. Unfortunately, there are many misunderstandings of what yin yoga is, and how it is best taught. This has arisen because there is no standardized form of yin yoga. No one owns it. No one created it. Anyone is free to call what they teach "yin yoga". My definition of yin yoga is the particular style of yoga I learned from Paul Grilley and Sarah Powers, who have been teaching it since the 1990's. They coined this practice "yin yoga" to differentiate what they were teaching from Paulie Zink's Taoist yoga. (For a history of yin yoga, see Who owns Yin Yoga.) This is the practice I mean when I use the term yin yoga and it is the style I have described in my books and on the web site.

The Intentions of Yin Yoga

When the criticism is leveled at yin yoga that it is inappropriate for some students, we have to first acknowledge that this is true! There is no form of yoga that is appropriate for all people. The reality of human variation is so vast that there is no medical intervention or therapy that works for every body (even aspirin is harmful to some people). This applies to yin yoga, but also to all forms of yoga: Ashtanga yoga can be dangerous to some people; Bikram's also; but even restorative yoga may be harmful to some people. Life is inherently dangerous: people have died just getting out of bed in the morning, but this does not mean that people should not get out of bed. It means that everything can be a problem for some people, and that includes yin yoga.

Having acknowledged that yin yoga may not be appropriate for some, I do not mean it is inappropriate, as an a priori-rule, for people with hypermobility, pregnant women, students with osteoporosis, osteoarthritis, bad backs, or a host of other ailments. These conditions by themselves do not preclude the practice. I have written elsewhere on why hypermobile students may benefit from adopting a yin yoga practice and I won't repeat all those points again here, but I will point out one very important fact: the repertoire of yin yoga postures are nowhere near as deep or intense as other yoga styles and do not take a hypermobile student anywhere close to the limits of her range of movement. There is little chance of these students going too far in a yin yoga class, because yin yoga does not offer postures that take the body as far as a hypermobile student could go. There is no Supta Kurmasana or Urdvadhanurasana, no Ekapadasirsasana or Tittibhasana B in Yin Yoga. Hypermobile students should not be afraid of yin yoga making them more flexible.

"Ligaments must never be stretched" is simply not true

One commonly heard critique of Yin Yoga is that it's intention is to stretch connective tissues. This is usually followed by a dogmatic statement that ligaments should not be stretched. I am not sure where this dogmatic belief arose: there are many ligament in our body that do stretch and should stress. The nuchal ligament, along the back of the neck is very stretchy and its elasticity helps us to bring our head upright after flexion. The ligamentum flavum which runs between vertebrae along the spine is the most elastic ligament in the human body: it is made up of mostly elastin fibers (80%). Again, it is very stretchy. The facet joint capsules of the spine are also elastic. Even the stiff iliotibial band (IT band) is somewhat elastic and this little elasticity helps us save energy when we walk or run. So, to say that "ligaments must never be stretched" is simply not true. It depends up which ligament or connective tissue you are refering to. But, in any case our intention in Yin Yoga is not to stretch connective tissues (even though that would be okay) but rather to stress our connective tissues. And here, an important distinction must be made: Stress is not stretch!

Let's define a few terms to make this clear: Stress is the force we apply to our tissues and stretch is the resulting elongation, if any, that results from the force. (Technically we could also call stretch strain, although here too some confusion can arise as "strain" could also be used as a verb to indicate stress.) Lots of tissues can stretch: our muscles, tendons, fascia, ligaments, and joint capsules can all elongate--some only a little, others a lot. But for many yoga students, the intention is not to stretch but to strengthen: they need more stability in their joints, not less. To build this stability they still need to stress the tissues, but not to the point of stretching. Stress is not the same as stretch. (It may be more appropriate for yoga teachers, especially yin yoga teachers, to use the verb "stress" when they habitually use the term "stretch.")

Every tissue in our body needs exercise to remain or regain health. In our yang forms of exercise, we engage our muscles to reduce the dynamic, potentially destabilizing stress on the joints. But, if we are not stressing the joints in our active yoga practice, when can we safely stress these tissues? During yin yoga! During the long held, static stress on our connective tissue, biochemical changes occur at a cellular level: the fibroblasts, chondrocytes and osteoblasts that rebuild our fascia, ligaments, cartilage and bones respond to the mechanical strains that they experience. The fear expressed by those criticizing yin yoga arises due to this misunderstanding: we are not trying to stretch connective tissues. We are trying to stress them.

Even a little stress can be too much, for some students

For some students, the stress of a yin yoga posture on the connective tissues may be too much. They may already have a weakened joint, ligament or fascial connection, and it would be easy for them to go too far now. These students need to pay close attention to the signals the body is giving them, to discover how much stress their body can tolerate and for how long. But this warning applies regardless of what style of yoga they choose to practice: they need to practice with both attention and intention. But this does not necessarily preclude a yin yoga practice for these students. There are many benefits available through yin yoga: developing mindfulness, relaxing the nervous system (turning off the sympathetic response), enhancing energy flow, etc.

Even students with damaged joints or weak bones need to stress these tissues! All tissues need stress, but when the tissues are damaged, it is easy to go too far. This doesn't mean no stress at all is the healthiest option: the optimal level of stress is to be sought. (See the article Are yoga teachers making us fragile?) Perhaps this is the time for a restorative yoga class, rather than a yin yoga class. Remember, yin yoga is not for everyone, but this certainly does not mean that it is not for anyone, or many "ones". Even some students with problematic joints may find yin yoga beneficial, as long as they don't try to do too much.

Pregnant Yin

Just as hypermobile students can benefit from a yin yoga practice, so can pregnant students. Again, the intention is not to enhance flexibility but to optimize health. A pregnant yoga student attending a yin yoga class is advised not to seek greater range of motion (ROM); whatever ROM she had before becoming pregnant should be her limit now; but she can benefit energetically, mentally and even physiologically from a yin yoga practice. Many yin yoga teachers are also prenatal teachers who have borne babies and found yin yoga helpful. The concerns raised against yin yoga from a prenatal perspective are all focused on going too far physically. That need not be an intention or a concern if the student pays attention and accepts her previous range of motion as her current limit.

Time is more important than intensity

         The Goldilocks' Position:
         Not too much, and not too little!

One of the reasons people misunderstand yin yoga is because they believe the practice focuses on taking joints to their ultimate range of motion: this is not what is suggested. In yin yoga we try to find the Goldilocks' position - not too much, and not too little. We do need to feel something, stress is necessary, but it is not necessary to go to a maximum limit. We come to an edge where we feel a stress, then we wait. We linger. We marinate in the juiciness of the posture. We do not seek the maximum edge. Time is more important than intensity. Studies by Helen Langevin and her coworkers have shown that sometimes we need to let a stress soak in for 30 minutes before "fibroblasts change shape in response to sustained stretching". [1] While we do not hold a single posture for 30 minutes in yin yoga, we may stress a targeted area for that long, through multiple postures. [2] Thomas Myers, whom I will quote again later, also says sustained stretches are required to allow muscles to relax so that the fascia starts to stretch and release.

Since we are not seeking maximum intensity and we do not take joints to their extreme ranges of motion, there is no reason for most hyperflexible students or pregnant women to avoid yin yoga out of fear of becoming more flexible. (Again, I refer you to the article on Yin Yoga and Hypermobility for more details: certainly there are some hyperflexible students who due to a connective tissue disorder will have to be very careful of doing any form of yoga.)

Yin yoga and osteoporosis

One particular teacher, Margaret Martin, created a blog and video describing her first experience with yin yoga and how frightened she was for the students in that class. Her fear: osteoporosis. Margaret is very experienced in teaching students with osteoporosis. In her view, these students must not allow their spines to flex at all: all flexion must come from the hips. This is an over-reaction and an over-simplification. Outside the yoga studio, people with osteoporosis flex their spine through simply daily living. Leaning over the bathroom sink to brush teeth, bending over to tie shoes, reaching for the kale in the fridge, or for the salt on the table all cause some flexion in the spine. Yes, they can go too far: but, again, to never stress the spine will lead to atrophy of the tissues you are trying to protect. (There a term for this: disuse osteoporosis[3]!) For people with mild osteoporosis some flexion is necessary to maintain back health; for people with severe osteoporosis - caution is reasonable. These students should tell their yoga teachers before class starts about this condition, or seek a restorative class! Students: do not abdicate your health responsibility to a teacher. It is your spine, not hers. Learn what your limits are and respect them.

Blaming the practice instead of the teacher

In fairness to Margaret, she does state in her blog, "So if you chose to do a yin class, you really have to be meticulous about your alignment. You have to take it upon yourself to ensure that your alignment is correct". But then she goes on to say, "Otherwise I suggest you look for a different type of yoga". I would point out that it is not yin yoga that is inherently dangerous, but how the teacher leads the class and how much responsibility the student gives up to the teacher. Someone with severe osteoporosis is well-advised to learn what will be appropriate for her, regardless of what style of yoga she is doing or what the teacher is asking her to do. It is not yin yoga per se that Margaret found dangerous but how it was presented. I am sure she would have had the same comments if she saw flexion of the spine occurring in any yoga class. Regardless, it is also not reasonable to blame the teacher in every situation.

Unreasonable expectations of a yoga teacher

It is unreasonable to expect a yoga teacher to know about all possible pathologies or injuries that a human body is subject to. Some yoga teachers are medical doctors and physical therapists, but even they don't know everything, and even if they did, there is not enough time in one class to run through an exhaustive list of every possible malady that students might have and what to do about them. We can try to focus on the important ones, but which ones are they? One teacher well educated in osteoporosis will talk about how to be careful of postures that might cause harm in students suffering porous bones. Another teacher knowledgeable about osteoarthritis will spend time offering contraindications for problem joints. Another teacher will caution students who are pregnant, or suffer high blood pressure, or diabetes, or .... the list can go on and on. It is unreasonable to expect that any teacher can be knowledgeable in all areas or can offer contraindications for all conditions. The failure to do so is not a judgment of the teacher's qualities or personality; it is just a fact of life. We cannot protect every student from every problem.

What a teacher can do, however, which is far more reasonable and powerful than reciting a cascade of contraindications, is teach the student how to be her own doctor, therapist, and yoga teacher. Teachers can give cues and guidance to the student on how to listen to her own body, to determine which sensations are acceptable or to be avoided, to notice how her body responds to her practice, to take reasonability for her own life.

Where is the proof that yin yoga works?

While scientific studies have been conducted over the years on the benefits of yoga, there are not many, and many are not conclusive. This is not just a problem with yin yoga! It is hard to find clinical studies that verify many of yoga's health claims. This is slowly changing[4], but I am aware of no studies specifically about yin yoga. It just hasn't been studied yet (although, I am aware of a few pending studies, and look forward to their conclusions.)

The absence of proof is not proof of absence. Just because yin yoga has not been proven to work does not mean that it does not work. I could share with you many anecdotes from people who told me that yin yoga has helped them. However, it is not possible for me to say what it was about yin yoga that was efficacious: was it the physical stress, the calming environment, the mindfulness practice, getting out of the house, the presences of a community? We don't know why, but we do know people felt better after yin yoga.

Certainly mindfulness, which there is a lot of opportunity to practice in a yin yoga class, has been studied and found helpful to many.[5] Long held static stresses have also been found to be beneficial in pain management and reorganizes the connective tissue (again, see Helen Langevin's work.[6]) We can verify that many parts of yin yoga work therapeutically, and we can report on anecdotes that show it to be effective, but we cannot point to any specific studies, not yet, that prove it works. But this is not proof that yin yoga is not beneficial.

Other practices do not include long-held stretches, so why does yin yoga?

I have heard this claim or ones similar: "There are no sustained stretches in the dance world". Or, I am told, in Tai Chi or Ki Gong or other Eastern practices. It is a strange critique because it is a form of "guilt-by-dissociation". It is like saying, "If no one else is doing something, then it must be wrong." Imagine if this attitude was applied to the first antibiotics: "No one else is using penicillin, therefore it must not work: don't take penicillin!" Clearly this is flawed reasoning, but this comment is problematic for another reason: long-held stretches have been used for centuries! Yin yoga is not new, nor is sustained stretching unique to yin yoga. Dancers have used this practice, despite what some ex-dancer yoga teachers may claim.[7] For a long time gymnasts have also employed static stretches. Yin-like postures have been described in both ancient texts and in B.K.S. Iyengar's Light on Yoga (written in the 1960's). This critique is problematic and wrong.

A friend of mine got hurt while doing yin yoga

I am truly sorry to hear of anyone being injured while doing any form of yoga, but the fault is not always the practice. There is a logical flaw called the last straw fallacy which highlights the inappropriateness of assigning blame to an event simply because it was the closest event in time to the occurrence of a problem. Recall that it is the last straw that is blamed for breaking the proverbial camel's back, which ignores the great weight of all the other straws already loaded onto the poor camel. The same situation arises in yoga; a student may have a dangerously weakened joint from years of repetitive stress from sports, from work, from lifestyle ... and yet, when she comes to a yoga class and does the one posture which is the last straw, she will blame that posture for the pain and problem. She may also extrapolate and blame the style of yoga, the teacher and the studio. This can happen in any style of yoga. Pigeon is a great posture to blame for hurting knees, but often the problem arises because of the predisposition to injury already existed, developed over years, but was ignored.

If a predisposition for an injury or fragility in a joint exists, then there is a real danger of a precipitating event occurring while doing yin yoga, or another yoga style. In these cases, the injury is unfortunate, but blaming any particular style of yoga for causing the injury is inappropriate. A more useful investigation should be to look into what caused the predisposition, how to avoid making matters worse, and how to recover health. It may likely be true that people with certain joint problems should avoid a yin yoga practice: remember - yin yoga is not for everybody. But to criticize the practice and imply that yin yoga is not appropriate for any body is not reasonable.

Science has shown that yin yoga does not increase range of motion

I have to boldly refute this claim: Science has not shown that yin yoga does not increase ROM. One reason I can state this so boldly is the fact that no-one has yet studied yin yoga! The other reason is that I have seen it increase my ROM and that of my students. It is one thing to say we don't know how yin yoga increases ROM, but to state it doesn't increase ROM is to deny evidence that is very plain to see. The genesis of this criticism of yin yoga seems to come from recent studies that have looked at short-held, cyclical stresses and the effect they have on the range of motion of a muscle.[8] These studies used 20-second to 1-minute applications of stress, and concluded that increased range of motion are due to nervous system responses, not because of a permanent lengthening of the muscle. There are many problems with this conclusion and these studies: first--they were not studying yoga; they were studying stretching. Yoga is far more than just stretching: it is breath work, mindfulness, stress and recovery, practiced over years. Secondly, these studies were not using yin-like stresses, which are held much longer. Finally, these studies do not take into account the reality of many yoga students' experience. Yoga does make us more flexible. To deny this obvious fact because some studies don't know why it happens is ludicrous. Let's make the science fit the facts, not ignore the facts because our theories are, so far, inadequate to explain them.

I was sent an email with a critique of yin yoga, claiming that fascia experts have found "passive stretching doesn't actually change anything". To rebut that statement, I will return to Thomas Myers, who ironically was cited as one of the fascia experts. He recently said,

...generally, the sustained stretches of yoga where you hold a posture for several minutes ... give the muscles a chance to calm down. The muscles have to relax first, and then the fascia starts to stretch and release. And that can facilitate the kind of repatterning that leads to lasting release of chronic holdings and, in many cases, a profound change of mind and body...

General exercise won't [work]. They will not change the pattern of the fascia. You need long, slow stretches.... One of the wonderful things about yoga is that because of the sustained stretch held in many yoga poses, you actually do change the connective tissue. So you change the pattern of that fascia and thus you can get down to the chronic tension patterns lodged in the tissues.
[Emphasis added]

It is a challenge for anatomists, clinicians and scientist to explain the reality that so many students have experienced: yin yoga has increased their range of motion. The question to be considered is not "does it?" but "how does it do it?"[9]


There are many criticisms that have been leveled against yin yoga, but most of them misrepresent what yin yoga is and how it is practiced. The criticisms are aimed at a straw man caricature, not the actual practice of yin yoga. Yin yoga does not seek maximum ranges of motion, it does not try to stretch our joints, and it does not destabilize the joints. It does seek to stress the connective tissues, which is not the same as stretch. Through this stress, it can strengthen the connective tissues around a joint to make the joint stronger. Yin yoga can be a safe, healing practice for most students, even pregnant women or hypermobile people, as long as they practice with intention and attention. However, like any yoga practice, there are a few people who probably would be better advised to do a different practice, but not because yin yoga is inherently dangerous, but because every body is unique and what they need in their practice may be very different than what works for someone else.


1) "Ongoing studies in my lab are addressing why the fibroblasts change shape in response to sustained stretching. So far we have found that the changes are associated with a large-scale relaxation of the connective tissue. We also saw that the fibroblasts initiated a specific Rho-dependent cytoskeletal reorganization that was required for the tissue to fully relax. Rho is an intracellular signaling molecule known to play a role in cell motility and the remodeling of cell-surface proteins that connect the fibroblast to its surrounding matrix. The molecule's involvement in fibroblast shape change suggested that the cells are able to reduce the tissue tension by adjusting how strongly and where they are gripping the surrounding connective tissue or muscle. In addition, we found that the shape change is also associated with a sustained release of ATP from the fibroblast. Within the cell, ATP acts as fuel, but outside of the membrane, ATP can function as a signaling molecule. Extracellular ATP can be converted to other purines such as adenosine, which can act as a local analgesic, thus providing a possible cellular and physiological mechanism to explain the pain relief experienced by some acupuncture patients." From The Science of Stretch, Helene M. Langevin, May 1, 2013, The Scientist.
2) We may perform in sequence Butterfly, Half-butterfly, Saddle and Caterpillar, which together will stress the fascia along the back of the body for 30 minutes or more.
3) See NASA's explanation of disuse osteoporosis.
4) See 50 scientific studies of yoga
5) See "What are the benefits of mindfulness" at
6) Check this article for a representative example.
7) Not only have many dancers used long held stresses to increase their range of motion, there are styles of dance which require long held stillness as part of the dance (for example, Butoh dance.)
8) "Holding stretches for 20 to 30 seconds is a good standard because most of the stress relaxation in passive stretches occurs in the first 20 seconds." See The Biomechanics of Stretching by Duane Knudson in the Journal of Exercise Science & Physiotherapy, Vol. 2: 3-12, 2006
9) For more on how yin yoga may work, see my article A Scientific Basis for Yin Yoga.

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