Stretching in yoga

From Dr. Günter Niessen

A lot is written, claimed and argued about what stretching actually is, how to do it most intelligently and whether it is useful at all. I believe this is because there are many different ways of looking at stretching and its effects. Not only can stretching be defined in different ways, but the mechanism of stretching can also be investigated in different parts of the body and in individual tissues.

In this article, I would like to propose a useful, understandable definition that makes sense for us as yoga teachers and therapists and incorporate the latest findings as well as the physical, emotional and cognitive effects of stretching into our presentation. As always, a seemingly simple term is much more complex than we think and in the end, I believe, much simpler than we thought. I have listed a small selection of literature below this article.

In relation to yoga and the human body (many studies refer to tests on animals or materials), we define stretching as increasing the distance between two fixed landmarks on the body. At the same time, it is necessary for corresponding areas on the opposite side to approach each other. These areas are, as it were, pushed into each other or compressed. I would like to discuss the significance of this rarely noticed fact later.

For us humans, stretching is a very complex and individual experience and depends on numerous internal and external influencing factors. For example, if we raise our right arm sideways and then bring it back to shoulder height, the distances between all the structures between the sternum and the hand move away. The feeling of stretching on the front chest wall, at the front of the shoulder and further down the arm becomes increasingly clear as the range of movement increases and the distance increases. The feeling of stretching is easier to perceive the further apart the two measuring points are. Where the stretching sensation is perceived depends, among other things, on the mobility of the individual areas, any pre-existing injuries, shortenings, scars and the functional application of this movement in the everyday life of the person stretching. Whether the stretching sensation also originates from the affected tendons, ligaments, muscles, nerves, fascia or previous, still stored experiences of an injury varies greatly.

At the end of this increase in distance, i.e. at the end of the full range of motion (ROM), the stretching sensation turns into stretching pain. Our body recognizes the danger and reports it, appealing to our awareness with the aim of averting injury. Whether and when someone then experiences the feeling of stretching as pleasantly painful or pulling or clearly painful is again highly individual. The following applies to all forms of stretching: injuries occur at the end of a stretch into pain. Depending on the intensity, speed, load, gravity, muscle strength, resilience of the various tissues or training condition, slight strains, partial tears or complete ruptures of the bone-tendon junction, the tendon or the muscle or even an avulsion of the bone can result. I have been able to treat all of these injuries in my medical practice often enough and some of you can tell me about your experiences.

Before an injury occurs, the various tissues mentioned react by adapting to the stimulus acting on them. The intensity of the stimulus, its frequency and duration are just as decisive for the adaptive response as, for example, genetic predisposition, training status, eating habits, time of day and temperature, our mood, hormone status, etc., precisely because we are complex beings and a myriad of variables are constantly influencing us. When we're angry or fired up, our entire musculoskeletal system is more efficient and resilient under the influence of more cortisol, adrenaline and other hormones than when we're relaxed, exhausted or tired. If our diet is of moderate quality, how can our tissues be of good quality? If we use a movement day in, day out, it is easy and supple for our body and, conversely, unfamiliar and demanding.

The feeling of stretching and stretching pain are not the same thing. At the transition from a stretching sensation to a more painful feeling, our nervous system sends a different type of signal at precisely this point. Instead of remaining at ease, all impulses that indicate an impending injury are now activated and our attention is directed there. Special receptors in the area of the insertion of the tendon into the bone, in the course of the tendon and in the muscles work together with complex control circuits of our organ systems, temperature and time of day perception, digestive, immune and cardiovascular systems to create an integrating breeding ground in our central nervous system for our movements as a whole and also the amplitudes of movement ("range of motion"). You have all experienced that stretching after a meal feels different from relaxing on the mat in the afternoon in late summer or in the morning in the cold in spring or when you were irritated or flooded with gratitude, or after sport in the sauna or two hours after intensive running training. At the point in the range of motion where the stretching sensation turns into stretching pain, our mind, our cognitive instance, decides what to do next. Some act according to the principle of "more is better" or develop ambition, impatience, compare themselves with others or imaginary target states, while others remain mindful and linger in a sense of well-being or surrender, of allowing. The former willingness to act very often leads to injuries and the latter ... well, to a sustainably enlarged ROM and pleasant experiences. The prerequisite for a meaningful reaction, however, is that we can feel what is happening inside us and why we are doing something. To do this, we need to slow down, pause and be able to perform an appropriate action. Impulses, what we hear from other people, learned behaviors, etc. are often misleading and do not apply to us at all. Does my personal "more", "further", "otherwise it's no use", my "haste" come from impatience, too little information, lack of experience, comparisons with others or am I fully awake, alert and make decisions according to the situation? Why some people react this way and others differently is the field of study of psychology.

In Kriya Yoga, as described by Patañjali, an important element is the exploration of the self. In Sanskrit, this process is described as Svadhyāya and is not just an intellectual endeavor, but above all a way of practicing yoga. If you have ever found yourself in painful states, you will know that not only Āsanaand Prānāyāma practice, but also meditation are much more difficult. The yoga path empowers us to find out for ourselves how we can best deal with our body and its possibilities. Again, this does not mean that we should not consult others, read specialist literature and listen to experts, but only that we are the final and decisive authority to take care of our own well-being and pain. It is therefore also useful to find out why we want to maintain or increase mobility, experience emotional changes, prefer self-punishment or reward, want to feel ourselves better or feel at all, who we want to show or prove what to and also to be clear whether we want to stretch a specific tissue or body region (this is how it is scientifically considered and described) or whether we, as complex beings, want to perform a movement in a certain way and change the movement possibilities. It is not the fascia or the tendon, the muscle or the shoulder or the ankle joint mobility that is being stretched or increased. It is always the whole person who performs a certain movement with a certain goal in a defined way (smooth, gentle, painful, violent, halting, pulling, ...).

This way of looking at things characterizes the fundamental difference between the yogic and the scientific view.

A person performs a movement at a certain time with the thoughts, feelings and conditions that arise at that time in a very specific way; not the person's arm, not the soft tissue or bones and muscles. The range of movement of my hip joint is not independent of what I have experienced, eaten, experienced from birth or done before.

It is also important to find out when I - unlike you - have time, what kind of stretching suits me and what the goal of my efforts is. We are by no means spared from feeling into ourselves and experiencing what stretching does in us, whether it is motivated by ambition or longing, held by devotion or arises from obedience, to name just a few examples. If we think about this wisely and exchange ideas and train our mindfulness when practising on the mat and in everyday life, we will soon find the best individual answers within ourselves. It is not for nothing that the suggestions in the ancient yogic texts point in unison to the repeatedly used terms: compassionate, joyful, alive, kind, gentle, without desire or ambition, content and serene... - all qualities that prevent injury in every way and support healing. In addition, large parts of science are currently discovering that it is precisely these qualities that make us more resilient not only physically, but also emotionally and mentally, and promote our regeneration.

Uncertainty in feeling when stretching, on the other hand, does not come from reading old scriptures, which are rather unambiguous, but from information and half-knowledge from hearsay and comparison with other people. Facebook and master classes are just as unsuitable for getting to the bottom of my real needs and possibilities as blind obedience or ambition. The fear of hurting ourselves can easily dissolve when we take responsibility for ourselves. By the end of this article, you will be as competent and equipped with as much knowledge as you need to follow your own path to safe, injury-free mobility.

Scientific studies try to measure how the individual tissues react to the process of stretching in order to give us advice or clues as to how we can most effectively increase our ROM, for example. We look at visual or fascial tissue, muscle, nerve or capsule tissue to measure how they react to a specific increase in distance. It is also investigated whether the distance or tissue reaction can be achieved more easily, more quickly, more sustainably or to a greater extent with certain stimuli. There are no studies that could even begin to take into account the extensive factors described above. The stretching protocols defined for the individual studies define the time, frequency or type of stretching and to name techniques such as static versus dynamic stretching, slow or fast (springy, ballistic) stretching, loaded or unloaded stretching with or without additional weights and apparatus or also by utilizing the reflex arcs via the nervous system. There are proponents and emotionally charged counter-arguments for all types of stretching. Certain protocols of stretching in humans have been investigated, especially in the ankle joint and the complex movement of hip flexion over a period of 6-12 weeks with different intensities. These are generalized and advertised as protocols to exercisers, often without further explanation. Often the purpose or goals of the exercisers are not inquired about, the state of health, the overall mobility of the examined person, and in some articles conclusions are generalized on the basis of microscopic changes in the tissues involved and only short examination periods are included. It is also difficult to include other effects of stretching, such as the improvement of explosive or jumping power, smoothness of movement or the feelings and experiences experienced.

We and our students should be aware of the most important influencing factors in order to make good decisions. Not everyone can learn to do the splits or sit in a lotus position. The body's warning signals should be taken seriously from a therapeutic point of view and not ignored. With certain warm-up techniques, increasing the outside temperature, medical support, rubbing, rubbing or swinging movements, our ROM increases and the body's warning signals are reduced. Whether this is a good thing or not may only become apparent after a strain or partial rupture or rupture of the tendon insertion or bone avulsion. There are no long-term studies on the effect of stretching protocols, nor are there any studies on how many injury-related breaks or regressions in mobility are recorded.

Among other things, ambition, obedience and disregarding proprioceptive cues from the body lead to exceeding the tissue load capacity and thus to injuries. Too much stretching and a lack of strength and coordination in the newly acquired range of motion lead to prolonged pain in the stretched area, more frequent injuries and not to a sustainable increase in ROM.

Many people find it difficult to feel themselves. Stretching is an intense stimulus that can make it easier to feel yourself in a pleasant way. Here, too, you need to pay careful attention to whether the feeling and stretching are well balanced. It is generally advisable to really take your time - years or at least months rather than days.

At the level of our central nervous system, stretching is associated with an increase in the tolerance of the corresponding signaling units to the stretching stimulus. This already leads to an increase in ROM without structural changes to the tissues involved. Letting go, release, relaxation and a soothing flow are excellent alternatives to ambitious and more intensive stretching methods. Incidentally, these only help as long as you stretch regularly and use the mobility gained in everyday life, and it has been shown that increasing the ROM through strength exercises up to the limit of movement that is considered comfortable is just as effective as active or passive stretching protocols, but significantly safer in terms of the injury rate.

If, as is unfortunately so often advised, injured tissue is stretched, this tends to stand in the way of healing and leads to re-traumatization, chronification and undesirable tissue transformation processes, e.g. from tendon to bone tissue.

An important note for all those who perform or instruct stretching exercises. In contrast to the region to be stretched, for example stretching the gluteal muscles or the hamstrings on the back of the body, tissue is compressed and pushed into each other at the front, in this example at the groin. This is where we should always focus our attention and not be distracted by the feeling of stretching. The smooth sliding together of the tissue at the front should never be accompanied by a feeling of strong pressure or painful compression. If these indications from the body are ignored, this will not lead to the injuries to the stretched tissues described, but to sometimes irreversible changes in the compressed area. In the example of the hip region, I am increasingly seeing yoga teachers and dedicated practitioners developing so-called impingement syndromes (femoropatellar impingement) and even degenerative changes in the hip joint itself (coxarthrosis).

So how can we stretch? Up to a certain point, our body becomes more and more flexible by gently moving to the limits of movement. At some point, and contrary to the promises of many so-called experts, we all reach an individual, anatomical limit for every movement. In this context, "individual" refers not only to the personal factors of body physiognomy/anatomy and physiology, but also to the respective eating habits, mental and emotional mood, time of day, age, fitness, season and many other influencing factors mentioned above. The new mobility gained in the process and with a lot of time is a result of the training of the body, its tissue resilience, the nervous system and the practitioner as a whole. The gently gained flexibility can be used in everyday life and thus remains sustainable. In order to avoid the frequent injuries in yoga that occur during the various attempts at stretching, this process requires four supporting qualities:

  • Time, i.e. patience, because short-term improvements in mobility often lead to injuries. The newly gained ROM must be backed up by movement experience, coordination and strength.
  • Regularity - so that after the initial, rapid successes of stretching, a lasting improvement in mobility can be achieved through the increase in central nervous tolerance to the warning signals that occur during stretching. The application and use of the mobility gained in everyday life requires persistence, otherwise the tissues will adapt to the previous ROM again within a few minutes (6-90 minutes, depending on the study).
  • Strength and coordination - in order to secure the range of movement gained neuromuscularly. We should therefore make sure that we and our students go into a movement slowly and actively, linger as an option and come out just as mindfully and actively. The longer we linger, the more important it is to pay attention to the quality of the stretch and the slowness with which we end the stretch.
  • Awareness is needed above all to sense the limits of our own anatomical possibilities. The body's gentle cues through our proprioceptors, nociceptors and interoceptors cannot be heard if we are accompanied by ambition, imitation, compliance and comparison in movements or if the movements are performed too quickly. Especially with passive stretches and over longer periods of time, we must first learn to interpret these signals. Any stretch that leads to a feeling of "I look forward to the end of the stretching exercise" or to pain and is "endured" does not correspond to yogic principles and does not lead to improved flexibility or greater suppleness of movement. Recent studies on low-intensity stretching with terms such as "low-intensity stretching" or "micro-stretching" are encouraging. The stretches performed in this way lead to equivalent or better and in any case more sustainable results and correspond to the yogic approach and underlying ethical ideas of non-injury and a positive inner state of mind

In our experience - and this procedure is now referred to in the literature as "micro-stretching" - it is perfectly sufficient if we perform the respective movement regularly to a very fine, gentle stretching sensation; 30-50% of the intensity is perfectly adequate. To classify: 100% marks the beginning of stretching pain, even if this can be perceived as pleasant. If you go into the often quoted and repeatedly cited "pain of well-being", this is less effective when it comes to increasing mobility. However, the effect on suppressing the perception of pain from other causes, injuries or chronic pain is greater if you stretch more intensively. The pain from stretching then exceeds the original sensation of pain for the duration of the stretch and often for 30 to 90 minutes afterwards. In the medium and long term, however, this is not a solution to the pain or injury problem, because the effect fizzles out, the dependency on the stretch to experience something "nice" increases and the actual injury region is further destabilized, which in turn tends to trigger the pain and other alarm signals from the body. In the end, gentle, loving and sustained attention and common sense are decisive for the success of the stretch, the suppleness of the movement and the transformation of our inner space into a positive state of mind.

I wish you lots of fun and a spirit of research - Günter

 

 

 

 

 

 

 

References from Pubmed - unfortunately only in English - can be found on the following pages!

I have selected a few from hundreds of studies on the subject:

Strength Training versus Stretching for Improving Range of Motion: A Systematic Review and Meta-Analysis

https://pubmed.ncbi.nlm.nih.gov/33917036/

Abstract: Background: Stretching is known to improve range of motion (ROM), and evidence has suggested that strength training (ST) is effective too. However, it is unclear whether its efficacy is comparable to stretching. The goal was to systematically review and meta-analyze randomized controlled trials (RCTs) assessing the effects of ST and stretching on ROM (INPLASY 10.37766/inplasy2020.9.0098). (2) Methods: Cochrane Library, EBSCO, PubMed, Scielo, Scopus, and Web of Science were consulted in October 2020 and updated in March 2021, followed by search within reference lists and expert suggestions (no constraints on language or year). Eligibility criteria: (P) Humans of any condition; (I) ST interventions; (C) stretching (O) ROM; (S) supervised RCTs. (3) Results: Eleven articles(n = 452 participants) were included. Pooled data showed no differences between ST and stretching on ROM (ES = -0.22; 95% CI = -0.55 to 0.12; p = 0.206). Sub-group analyses based on risk of bias, active vs. passive ROM, and movement-per-joint analyses showed no between-protocol differences in ROM gains. (4) Conclusions: ST and stretching were not different in their effects on ROM, but the studies were highly heterogeneous in terms of design, protocols and populations, and so further research is warranted . However, the qualitative effects of all the studies were quite homogeneous.

Stretching and injury prevention: an obscure relationship

https://pubmed.ncbi.nlm.nih.gov/15233597/

Abstract: It is generally accepted that increasing the flexibility of a muscle-tendon unit promotes better performances and decreases the number of injuries. Stretching exercises are regularly included in warm-up and cooling-down exercises; however, contradictory findings have been reported in the literature. Several authors have suggested that stretching has a beneficial effect on injury prevention. In contrast, clinical evidence suggesting that stretching before exercise does not prevent injuries has also been reported. Apparently, no scientifically based prescription for stretching exercises exists and no conclusive statements can be made about the relationship of stretching and athletic injuries. Stretching recommendations are clouded by misconceptions and conflicting research reports. We believe that part of these contradictions can be explained by considering the type of sports activity in which an individual is participating. Sports involving bouncing and jumping activities with a high intensity of stretch-shortening cycles (SSCs) [e.g. soccer and football] require a muscle-tendon unit that is compliant enough to store and release the high amount of elastic energy that benefits performance in such sports. If the participants of these sports have an insufficient compliant muscle-tendon unit, the demands in energy absorption and release may rapidly exceed the capacity of the muscle-tendon unit. This may lead to an increased risk for injury of this structure. Consequently, the rationale for injury prevention in these sports is to increase the compliance of the muscle-tendon unit. Recent studies have shown that stretching programs can significantly influence the viscosity of the tendon and make it significantly more compliant, and when a sport demands SSCs of high intensity, stretching may be important for injury prevention. This conjecture is in agreement with the available scientific clinical evidence from these types of sports activities. In contrast, when the type of sports activity contains low-intensity, or limited SSCs (e.g. jogging, cycling and swimming) there is no need for a very compliant muscle-tendon unit since most of its power generation is a consequence of active (contractile) muscle work that needs to be directly transferred (by the tendon) to the articular system to generate motion. Therefore, stretching (and thus making the tendon more compliant) may not be advantageous. This conjecture is supported by the literature, where strong evidence exists that stretching has no beneficial effect on injury prevention in these sports. If this point of view is used when examining research findings concerning stretching and injuries, the reasons for the contrasting findings in the literature are in many instances resolved.

A systematic review into the efficacy of static stretching as part of a warm-up for the prevention of exercise-related injury
https://pubmed.ncbi.nlm.nih.gov/18785063/

Abstract: A systematic review of the literature was undertaken to assess the efficacy of static stretching as part of the warm-up for the prevention of exercise-related injuries. Computer-aided literature search for articles post-1990 and pre-January 2008 related to static stretching and injury prevention using MEDLINE, SPORT Discus, PubMed, and ScienceDirect databases. All relevant randomized clinical trials (RCTs) and controlled clinical trials (CCTs) satisfying inclusion/exclusion criteria were evaluated by methodological assessment to score the studies using accredited criteria. Seven out of 364 studies met the inclusion/exclusion criteria. All four RCTs concluded that static stretching was ineffective in reducing the incidence of exercise-related injury, and only one of the three CCTs concluded that static stretching did reduce the incidence of exercise-related injury. Three out of the seven studies noted significant reductions in musculotendinous and ligament injuries following a static stretching protocol despite nonsignificant reductions in the all-injury risk. All RCTs scored over 50 points (maximum possible score = 100), whereas all CCTs scored under 45 points. There is moderate to strong evidence that routine application of static stretching does not reduce overall injury rates. There is preliminary evidence, however, that static stretching may reduce musculotendinous injuries.

A Comparison of Two Stretching Modalities on Lower-Limb Range of Motion Measurements in Recreational Dancers
https://journals.lww.com/nsca-jscr/Fulltext/2009/10000/A_Comparison_of_Two_Stretching_Modalities_on.34.aspx

Abstract: Wyon, M, Felton, L, and Galloway, S. A comparison of two stretching modalities on lower-limb range of motion measurements in recreational dancers. J Strength Cond Res 23(7): 2144-2148, 2009-Most stretching techniques are designed to place a “stress” on the musculoskeletal unit that will increase its resting length and range of motion (ROM). Twenty-four adolescent dancers participated in a 6-week intervention program that compared low-intensity stretching (Microstretching) with moderate-intensity static stretching on active and passive ranges of motion. Microstretching is a new modality that reduces the possibility of the parasympathetic system being activated. Repeated measures analysis indicated changes in ROM over the intervention period (p < 0.05), with the Microstretching group demonstrating greater increases in passive and active ROM than the static stretch group (p < 0.01); there was no noted bilateral differences in ROM. The results from this study agree with past studies that have found that stretching increases the compliance of any given muscle and therefore increases the range of motion. One main finding of the present study was that throughout a 6-week training program very-low-intensity stretching had a greater positive effect on lower-limb ROM than moderate-intensity static stretching. The most interesting aspect of the study was the greater increase in active ROM compared to passive ROM by the Microstretching group. This suggests that adaptation has occurred within the muscle itself to a greater extent than in structures of the hip joint. Practical application for this technique suggests it is beneficial as a postexercise modality that potentially has a restorative component.

Stretching to prevent or reduce muscle soreness after exercise
https://pubmed.ncbi.nlm.nih.gov/21735398/

Abstract: Background: Many people stretch before or after engaging in athletic activity. Usually the purpose is to reduce risk of injury, reduce soreness after exercise, or enhance athletic performance. This is an update of a Cochrane review first published in 2007.

Objectives: The aim of this review was to determine effects of stretching before or after exercise on the development of delayed-onset muscle soreness.

Search strategy: We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to 10 August 2009), the Cochrane Central Register of Controlled Trials (2010, Issue 1), MEDLINE (1966 to 8th February 2010), EMBASE (1988 to 8th February 2010), CINAHL (1982 to 23rd February 2010), SPORTDiscus (1949 to 8th February 2010), PEDro (to 15th February 2010) and reference lists of articles.

Selection criteria: Eligible studies were randomized or quasi-randomized studies of any pre-exercise or post-exercise stretching technique designed to prevent or treat delayed-onset muscle soreness (DOMS). For the studies to be included, the stretching had to be conducted soon before or soon after exercise and muscle soreness had to be assessed.

Data collection and analysis: Risk of bias was assessed using The Cochrane Collaboration's 'Risk of bias' tool and quality of evidence was assessed using GRADE. Estimates of effects of stretching were converted to a common 100-point scale. Outcomes were pooled in fixed-effect meta-analyses.

Main results: Twelve studies were included in the review. This update incorporated two new studies. One of the new trials was a large field-based trial that included 2377 participants, 1220 of whom were allocated stretching. All other 11 studies were small, with between 10 and 30 participants receiving the stretch condition. Ten studies were laboratory-based and other two were field-based. All studies were exposed to either a moderate or high risk of bias. The quality of evidence was low to moderate. There was a high degree of consistency of results across studies. The pooled estimate showed that pre-exercise stretching reduced soreness at one day after exercise by, on average, half a point on a 100-point scale (mean difference -0.52, 95% CI -11.30 to 10.26; 3 studies). Post-exercise stretching reduced soreness at one day after exercise by, on average, one point on a 100-point scale (mean difference -1.04, 95% CI -6.88 to 4.79; 4 studies). Similar effects were evident between half a day and three days after exercise. One large study showed that stretching before and after exercise reduced peak soreness over a one week period by, on average, four points on a 100-point scale (mean difference -3.80, 95% CI -5.17 to -2.43). This effect, though statistically significant, is very small.

Authors' conclusions: The evidence from randomized studies suggests that muscle stretching, whether conducted before, after, or before and after exercise, does not produce clinically important reductions in delayed-onset muscle soreness in healthy adults.

The Effectiveness of Post-exercise Stretching in Short-Term and Delayed Recovery of Strength, Range of Motion and Delayed Onset Muscle Soreness: A Systematic Review and Meta-Analysis of Randomized Controlled Trials https://pubmed.ncbi.nlm.nih.gov/34025459/

Conclusion: There wasn't sufficient statistical evidence to reject the null hypothesis that stretching and passive recovery have equivalent influence on recovery. Data is scarce, heterogeneous, and confidence in cumulative evidence is very low. Future research should address the limitations highlighted in our review, to allow for more informed recommendations. For now, evidence-based recommendations on whether post-exercise stretching should be applied for the purposes of recovery should be avoided, as the (insufficient) data that is available does not support related claims.

Acute Effects of Dynamic Stretching on Muscle Flexibility and Performance: An Analysis of the Current Literature
https://pubmed.ncbi.nlm.nih.gov/29063454/

Conclusion: In this review, we highlight the need for future studies reporting homogeneous, clearly described stretching protocols, and propose a clarified stretching terminology and methodology.


CURRENT CONCEPTS IN MUSCLE STRETCHING FOR EXERCISE AND REHABILITATION
Phil Page, PT, PhD, ATC, CSCS, FACSM
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3273886/

A nice overview of stretching methods

Abstract: Stretching is a common activity used by athletes, older adults, rehabilitation patients, and anyone participating in a fitness program. While the benefits of stretching are known, controversy remains about the best type of stretching for a particular goal or outcome. The purpose of this clinical commentary is to discuss the current concepts of muscle stretching interventions and summarize the evidence related to stretching as used in both exercise and rehabilitation.

The impact of stretching on sports injury risk: a systematic review of the literature https://pubmed.ncbi.nlm.nih.gov/15076777/

Abstract: Purpose: We conducted a systematic review to assess the evidence for the effectiveness of stretching as a tool to prevent injuries in sports and to make recommendations for research and prevention.

Methods: Without language limitations, we searched electronic data bases, including MEDLINE (1966-2002), Current Contents (1997-2002), Biomedical Collection (1993-1999), the Cochrane Library, and SPORTDiscus, and then identified citations from papers retrieved and contacted experts in the field. Meta-analysis was limited to randomized trials or cohort studies for interventions that included stretching. Studies were excluded that lacked controls, in which stretching could not be assessed independently, or where studies did not include subjects in sporting or fitness activities. All articles were screened initially by one author. Six of 361 identified articles compared stretching with other methods to prevent injury. Data were abstracted by one author and then reviewed independently by three others. Data quality was assessed independently by three authors using a previously standardized instrument, and reviewers met to reconcile substantive differences in interpretation. We calculated weighted pooled odds ratios based on an intention-to-treat analysis as well as subgroup analyses by quality score and study design.

Results: Stretching was not significantly associated with a reduction in total injuries (OR = 0.93, CI 0.78-1.11) and similar findings were seen in the subgroup analyses.

Conclusion: There is not sufficient evidence to endorse or discontinue routine stretching before or after exercise to prevent injury among competitive or recreational athletes. Further research, especially well-conducted randomized controlled trials, is urgently needed to determine the proper role of stretching in sports.

Stretching Effects: High-intensity & Moderate-duration vs. Low-intensity & Long-duration
https://pubmed.ncbi.nlm.nih.gov/26701828/

Abstract: This study examined whether a high-intensity, moderate-duration bout of stretching would produce the same acute effects as a low-intensity, long-duration bout of stretching. 17 volunteers performed 2 knee-flexor stretching protocols: a high-intensity stretch (i. e., 100% of maximum tolerable passive torque) with a moderate duration (243.5 ± 69.5-s); and a low-intensity stretch (50% of tolerable passive torque) with a long duration (900-s). Passive torque at a given sub-maximal angle, peak passive torque, maximal range of motion (ROM), and muscle activity were assessed before and after each stretching protocol (at intervals of 1, 30 and 60 min). The maximal ROM and tolerable passive torque increased for all time points following the high-intensity stretching (p<0.05), but not after the low-intensity protocol (p>0.05). 1 min post-stretching, the passive torque decreased in both protocols, but to a greater extent in the low-intensity protocol. 30 min post-test, torque returned to baseline for the low-intensity protocol and had increased above the baseline for the high-intensity stretches. The following can be concluded: 1) High-intensity stretching increases the maximal ROM and peak passive torque compared to low-intensity stretching; 2) low-intensity, long-duration stretching is the best way to acutely decrease passive torque; and 3) high-intensity, moderate-duration stretching increases passive torque above the baseline 30 min after stretching.

Potential Effects of Dynamic Stretching on Injury Incidence of Athletes: A Narrative Review of Risk Factors
https://pubmed.ncbi.nlm.nih.gov/37162736/

Abstract: The use of dynamic stretching as a replacement for static stretching in the warm-up is widespread based on the reports of static stretching-induced performance impairments. While acute and chronic static stretching has been reported to reduce musculotendinous injuries, especially with explosive and change of direction actions, the influence of dynamic stretching on injury incidence lacks a similar volume of literature for acute and chronic responses. It was the objective of this narrative review to examine the acute and training effects of dynamic stretching on injury incidence and possible moderating variables such as dynamic stretching effects on range of motion, strength, balance, proprioception, muscle morphology, and psycho-physiological responses. One study demonstrated no significant difference regarding injury incidence when comparing a dynamic stretching-only group versus a combined dynamic stretching plus static stretching group. The only other study examined functional dynamic stretching training with injured dancers and reported improved ankle joint stability. However, several studies have shown that dynamic activity with some dynamic stretching exercises within a warm-up consistently demonstrates positive effects on injury incidence. Regarding moderating variables, while there is evidence that an acute bout of dynamic stretching can enhance range of motion, the acute and training effects of dynamic stretching on strength, balance, proprioception, and musculotendinous stiffness/compliance are less clear. The acute effects of dynamic stretching on thixotropic effects and psycho-physiological responses could be beneficial for injury reduction. However, the overall conflicting studies and a lack of substantial literature compared with SS effects points to a need for more extensive studies in this area.

Comparison Between High- and Low-Intensity Static Stretching Training Program on Active and Passive Properties of Plantar Flexors
https://pubmed.ncbi.nlm.nih.gov/34975544/

Abstract: The purpose of this study was to compare two static stretching (SS) training programs at high-intensity (HI-SS) and low-intensity (LI-SS) on passive and active properties of the plantar flexor muscles. Forty healthy young men were randomly allocated into three groups: HI-SS intervention group(n = 14), LI-SS intervention group(n = 13), and non-intervention control group(n = 13). An 11-point numerical scale (0-10; none to very painful stretching) was used to determine SS intensity. HI-SS and LI-SS stretched at 6-7 and 0-1 intensities, respectively, both in 3 sets of 60 s, 3×/week, for 4 weeks. Dorsiflexion range of motion (ROM), gastrocnemius muscle stiffness, muscle strength, drop jump height, and muscle architecture were assessed before and after SS training program. The HI-SS group improved more than LI-SS in ROM (40 vs. 15%) and decreased muscle stiffness (-57 vs. -24%), while no significant change was observed for muscle strength, drop jump height, and muscle architecture in both groups. The control group presented no significant change in any variable. Performing HI-SS is more effective than LI-SS for increasing ROM and decreasing muscle stiffness of plantar flexor muscles following a 4-week training period in young men. However, SS may not increase muscle strength or hypertrophy, regardless of the stretching discomfort intensity.


Acute Effects of Different Intensity and Duration of Static Stretching on the Muscle-Tendon Unit Stiffness of the Hamstrings
https://pubmed.ncbi.nlm.nih.gov/36523898/

Abstract: The effects of static stretching are influenced by prescribed and applied loads of stretching. The prescribed load is calculated from the stretching duration and intensity, whereas the applied load is assessed from the force of static stretching exerted on the targeted muscle. No previous study has investigated the prescribed and applied loads of static stretching on the muscle-tendon unit stiffness simultaneously. Therefore, the purpose of the present study was to examine the acute effects of the prescribed and applied load of static stretching on the change in the muscle-tendon unit stiffness of the hamstrings by using different intensities and durations of static stretching. Twenty-three participants underwent static stretching at the intensity of high (50 seconds, 3 sets), moderate (60 seconds, 3 sets), and low (75 seconds, 3 sets), in random order. The parameters were the range of motion, passive torque, and muscle-tendon unit stiffness. These parameters were measured before stretching, between sets, and immediately after stretching by using a dynamometer machine. The static stretching load was calculated from the passive torque during static stretching. The muscle-tendon unit stiffness decreased in high- and moderate-intensity after 50 (p < 0.01, d = -0.73) and 180 seconds (p < 0.01, d = -1.10) of stretching respectively, but there was no change in low-intensity stretching for 225 seconds (p = 0.48, d = -0.18). There were significant correlations between the static stretching load and relative change in the muscle-tendon unit stiffness in moderate- (r = -0.64, p < 0.01) and low-intensity (r = -0.54, p < 0.01), but not in high-intensity (r = -0.16, p = 0.18). High-intensity static stretching was effective for a decrease in the muscle-tendon unit stiffness even when the prescribed load of static stretching was unified. The applied load of static stretching was an important factor in decreasing the muscle-tendon unit stiffness in low- and moderate-intensity static stretching, but not in high-intensity stretching.

Static Stretching Intensity Does Not Influence Acute Range of Motion, Passive Torque, and Muscle Architecture
https://pubmed.ncbi.nlm.nih.gov/30300070/

Abstract: Context: Although stretching exercises are commonly used in clinical and athletic practice, there is a lack of evidence regarding the methodological variables that guide the prescription of stretching programs, such as intensity.

Objective: To investigate the acute effects of different stretching intensities on the range of motion (ROM), passive torque, and muscle architecture.

Design: Two-group pretest-posttest design.

Setting: Laboratory.

Participants: Twenty untrained men were allocated into the low- or high-intensity group.

Main outcome measures: Subjects were evaluated for initial (ROMinitial) and maximum (ROMmax) discomfort angle, stiffness, viscoelastic stress relaxation, muscle fascicle length, and pennation angle.

Results: The ROM assessments showed significant changes, in both groups, in the preintervention and postintervention measures both for the ROMinitial (P < .01) and ROMmax angle (P = .02). There were no significant differences for stiffness and viscoelastic stress relaxation variables. The pennation angle and muscle fascicle length were different between the groups, but there was no significant interaction.

Conclusion: Performing stretching exercises at high or low intensity acutely promotes similar gains in flexibility, that is, there are short-term/immediate gains in ROM but does not modify passive torque and muscle architecture.

The Impact of Stretching Intensities on Neural and Autonomic Responses: Implications for Relaxation
https://pubmed.ncbi.nlm.nih.gov/37571672/

Abstract: Stretching is an effective exercise for increasing body flexibility and pain relief. This study investigates the relationship between stretching intensity and relaxation effects, focusing on brainwaves and autonomic nervous system (ANS) activity. We used a crossover design with low- and high-intensity conditions to elucidate the impact of varying stretching intensities on neural activity associated with relaxation in 19 healthy young adults. Participants completed mood questionnaires. Electroencephalography (EEG) and plethysmography measurements were also obtained before, during, and after stretching sessions. The hamstring muscle was targeted for stretching, with intensity conditions based on the Point of Discomfort. Data analysis included wavelet analysis for EEG, plethysmography data, and repeated-measures ANOVA to differentiate mood, ANS activity, and brain activity related to stretching intensity. Results demonstrated no significant differences between ANS and brain activity based on stretching intensity. However, sympathetic nervous activity showed higher activity during the rest phases than in the stretch phases. Regarding brain activity, alpha and beta waves showed higher activity during the rest phases than in the stretch phases. A negative correlation between alpha waves and sympathetic nervous activities was observed in high-intensity conditions. However, a positive correlation between beta waves and parasympathetic nervous activities was found in low-intensity conditions. Our findings suggest that stretching can induce interactions between the ANS and brain activity.

And something else interesting to listen to or read through:

Podcast by Prof. Andrew Hubermann on the subject of stretching and the studies cited therein:
https://www.youtube.com/watch?v=tkH2-_jMCSk

Articles Force enhancement after stretch of isolated myofibrils is increased by sarcomere length non-uniformities: https://go.nature.com/3tyUfxT

A Comparison of Two Stretching Modalities on Lower-Limb Range of Motion Measurements in Recreational Dancers: https://bit.ly/3Hkpy5q

Microfluidic perfusion shows intersarcomere dynamics within single skeletal muscle myofibrils: https://bit.ly/3MLJWNV

The Effect of Time and Frequency of Static Stretching on Flexibility of the Hamstring Muscles: https://bit.ly/3aKIDRN

The Relation Between Stretching Typology and Stretching Duration: The Effects on Range of Motion: https://bit.ly/3aXtpcw

Stretching Reduces Tumor Growth in a Mouse Breast Cancer Model: https://go.nature.com/3xLQY0U Insular Cortex Mediates Increased Pain Tolerance in Yoga Practitioners: https://bit.ly/39pLIXd

And still easy to read:

https://australianballet.com.au/blog/strength-beats-stretch

https://www.researchgate.net/publication/281097991_Microstretching-A_practical_approach_for_recovery_and_regeneration/link/55d491f608ae0a34172482af/download?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6InB1YmxpY2F0aW9uIiwicGFnZSI6InB1YmxpY2F0aW9uIn19

And at the end a few things in German:

https://circuit-training-dehnen-dr-klee.de/dokumente/Marschall_Verletzungsprophylaxe.pdf

And there are countless detailed studies on all aspects of stretching. In my opinion, personal experience is the greatest treasure and mindfulness is the best basis for decision-making.

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