Recently there has been a trend online toward opinion pieces that are without nuance. It would seem the bolder opinion and the more controversial subject overrides the complexities of reality. This unfortunate circumstance has led to a lot of confusion for the fitness participant and yoga practitioner.

A recent online article came out by Michaelle Edwards entitled, ‘Stop Stretching Your Hamstrings!’ This article is riddled with confusing statements many of which are not based in facts. It was eloquently refuted in an online article by Greg Lehman called, ‘If you want to stretch your hamstrings please continue to do so.’

From her article the exercises that appeared to be most demonized by Edwards were “bending forward from standing or lying with the knees straight and ankles flexed creating a targeted stretch for the hamstring muscles.” Her rationale was they impose unnecessary and damaging force on ligaments at the pelvis. Like Lehman, I had noted she was confused by anatomical science such as, sacral nutation versus counternutation and the function of ligaments (or for that matter I would include her use of the term hamstring ligaments, as she may have meant to refer to hamstring tendons).

I can understand the concerns in being fooled to think that stretching hamstrings will solve lower back problems. The science on this can be found in Dr. Stuart McGill’s book, ‘Low Back Disorders,’ “’Tight’ hamstrings are often blamed for back troubles, but as is noted several times in this book, this blame is often misdirected. The bulk of evidence supports neither a link between shorter hamstrings as a predictor of back trouble nor the idea that stretching enhances strength output (e.g., Fowles et al., 2000; Avela et al., 2003) and offers no protective value against injury risk (eg., Black and Stevens, 2001).” (‘Low Back Disorders,’p.68-69)

I would like to note first that Dr. McGill stated that tight hamstrings are not a “predictor of back trouble,” and scientific evidence does not support “the idea that stretching enhances strength output.” Here we require some nuance. I propose that there is a need to investigate how the hamstrings are reacting in standing forward bends versus lying supine hamstring stretches. How are the hamstrings being affected? Edwards speaks about both “bending forward from standing or lying with the knees straight and ankles flexed creating a targeted stretch for the hamstring muscles.” The truth of the matter is standing forward bends have a radically different effect on hamstrings than do supine straight-leg stretches.

Hamstring flexibility is not improved by standing forward bends. In the book ‘The Stark Reality of Stretching,’ by Dr. Steven Stark, Dr. Stark offers research that indicates the hamstrings do not become more flexible when forward bending, since the action of hamstring musculature is an eccentric contraction that is activated in order to provide pelvic stability. “When a person is standing and bends forward from the pelvis, the hamstring muscles involuntarily contract (myotactic reflex) to stabilize the pelvis against gravity. The hamstrings will remain contracted, stabilizing the pelvis, as long as the person remains bent forward from the hips.” (‘The Stark Reality of Stretching,’ p.149)

This means when forward bending from standing while engaging the hip-hinge method that we practice in the BIM Yoga System, you are actually strengthening hamstrings similar to when performing Romanian dead-lifts. In her article Edwards states, “Keeping the back muscles and hamstrings strong and tight is good for your body.” With this in mind, I would like to invite yoga students to practice standing forward bends similar in form to Romanian dead-lifts, and thereby strengthen the back muscles and hamstrings. This is what happens when you practice forward bends in a hip hinge method with a neutral spine and a moderate bend in the knees.

Of course when the yoga practitioner folds forward with excessive spinal flexion from a standing position there is a severely compromised lumbar curve. Considering the mechanical forces on the spine, this would be a risk factor for someone who had inter-vertebral disc injury, and I would consider this a contraindicated form of the yoga pose. If, however, someone has a hyper-lordic spine, no history of disc injury, but instead facet joint pathology, an argument could be made that forward bending with slight spinal flexion could potentially offer some relief of compressive forces in the facet joints, and with the sacrum extending upward to prevent excessive spinal flexion gravity may help the process of decompression of facet joints through traction.

In ‘the Stark Reality of Stretching,’ it is Dr. Stark’s concern that when practicing standing forward bends mechanical forces on the spine can lead to back trouble. This point of view would be correct for anyone who is vulnerable to disc injury and certainly anyone who has sustained disc injury; but not all back problems are the same. An exercise prescription must be offered for each individual yoga practitioner based on their medical history. It is evident for individualized learning there is a need for nuance.

Dr. McGill recognizes that in many vocational activities the opportunity for maintaining a neutral spine when lifting is not possible. A partially flexed spine is designed to withstand shear forces; it is at near end point range of motion that the greatest risk for injury occurs. “A spine that is not fully flexed ensures that the pars lumborum fibers of the longissimus thoracis and iliocostalis lumborum are able to provide a supporting posterior shear force on the superior vertebra, while full flexion causes the interspinous ligament complex to strain, imposing an anterior shear force on the superior vertebra. For these reasons, avoiding full flexion not only ensures a lower shear load but also eliminates ligament damage.” (‘Low Back Disorders,’ p.136-137)

One of the main reasons I have chosen to have my students use the ‘hip-hinge’ when coming out of forward bends and not the ‘roll-up’ is to lower the risk of back injury. The ‘roll-up’ requires a maximal flexion part way through ascending to standing position, whereas the ‘hip-hinge’ maintains the neutral spine’s lordotic lumbar curve during ascent to standing. “Maintaining a more neutrally lordotic spine will maximize shear support, ensure a high tolerance of the joint to withstand compressive forces, eliminate the risk of ligamentous damage since the ligaments remain unstrained, eliminate the risk of disc herniation since this is associated with a fully flexed spine, and qualitatively emulate the spine postures that Olympic lifters adopt to avoid injury.” (‘Low Back Disorders,’ p.136)

The key to safety while performing standing forward bends is to minimize the amount of spinal flexion when in the ‘hang position.’ Ensure the coccyx is lifting higher toward the ceiling than are the lumbar vertebrae. No space should be visible between the torso and legs. Especially important is to recognize a ‘hang position’ is not possible for those with inflexible musculature and those who are vulnerable to disc injury, as those individuals should maintain a neutral spinal lordotic lumbar curve while ‘hip-hinging’ and scale back range of motion to accommodate this.  

So what about lying supine straight-leg stretches? When working the musculature involved in the lying supine leg stretch the pelvis is stabilized by the floor, and this opens the possibility of stretching hamstrings without the reaction of an eccentric contraction. There is opportunity for increased hamstring flexibility, and this is why you see trainers stretching professional athletes’ hamstrings while the athletes are lying in supine. After all these trainers are the top in their field having spent years studying kinesiology and athletic therapy; they know how hamstrings are stretched.

If Edwards’ article is to be taken to heart then we should stop stretching hamstrings all together; so why do trainers stretch their athlete’s hamstrings? The answer is emphatic in some of the best kinesiology literature available such as ‘Basic Biomechanics’ by Dr. Susan Hall, “Since most daily activities do not require simultaneous hip flexion and knee extension, the hamstrings are rarely stretched unless exercises are performed for that specific purpose. The resulting loss of extensibility makes the hamstrings particularly susceptible to strain.” (‘Basic Biomechanics,’ p.240)

The frequency of hamstring strains leads me to believe they are worthy of attention. The need for acquiring flexibility in hamstrings appears obvious. In ‘Fundamentals of Sports Injury Management’ by Dr. Marcia Anderson and Dr. Gail Parr the authors state, “The hamstrings are the most frequently strained muscles in the body and are typically caused by a rapid contraction of the muscle during a ballistic action or a violent stretch.” (‘Fundamentals of Sports Injury Management,’ p.253)

There is a possibility of harming the lower back while stretching hamstrings in supine. The lumbar curve can be compromised by the pulling action of the leg, and this is what Edwards is trying to suggest in her article. However, what if there was a lumbar support placed under the lower back while performing the lying supine leg stretch? This could leave the sacroiliac joints in neutral, as the lumbar support would resist the tendency toward sacral counternutation from pulling the leg toward the body and negate the subsequent flattening of the low back against the ground. Would it be a risk factor for someone to practice a supine hamstring stretch if they had hyper-lordosis? Probably not.

I do like that Edwards appears to support the idea of a slight knee bend in postures that are often considered ‘straight-legged.’ I have been an advocate of a slight knee bend I call a micro-bend for 2 decades. When practicing postures like the triangle pose, I would recommend that the lead leg be in a microbend since 70% of the body weight resides over the lead leg. With only 30% of the bodyweight over the rear leg, I recommend the leg be straight with a lifted kneecap engaged by front thigh musculature to enhance the strength of the vastus medialis oblique fibers, which most physiotherapist would like to see strengthened to improve knee stability. Again you see the need for nuance.

I would like to add to the conversation that in either lying supine leg stretches or standing forward bends there are many more muscles working in patterns of contraction and lengthening, and there are underlying factors involving skeletal arrangements and neuro-muscular connections. How does the structure of articulating connective tissue surfaces covering bones impact the conditions for forward bends or lying supine leg stretches? What about external hip rotators such as the piriformis muscle, which if pulled beyond its proprioceptive tissue limits, will be triggered into a flexion reflex action and cause sciatic nerve pain? Answers to these questions are essential for yoga teachers to maintain an appropriate standard of care. Research conducted by author Thomas Myers should be mandatory reading for any budding yoga teacher.

Thomas Myers in his book, ‘Anatomy Trains,’ describes the continuous arrangement of fascia tissue that envelopes muscle, organizing lines of pull moving bones at skeletal joint articulations. Yoga posturing is about bringing balance to the body in terms of fascia, and the relative muscular strength and length in the agonist, antagonist relationship. It may be necessary to stretch a line of fascia tissue that includes the hamstrings, such as the ‘Superficial Back Line’ Myers describes in his book, in order to bring balance with respect to the other anatomy trains. As Myers says, “Muscle cells are caught within the fascial web like fish within a net. Their movement pulls on the fascia, the fascia is attached to the periosteum, the periosteum pulls on the bone.” (‘Anatomy Trains,’ p.41)

Myers dedicates a portion of his book to the subject of tensegrity. This concept is an excellent way to understand the complexities of interwoven relationships between body tissues. Myers states, “’Tensegrity’ was coined from the phrase ‘tension integrity’ by the designer R. Buckminster Fuller (working from original structures developed by artist Kenneth Snelson). It refers to structures that maintain their integrity due primarily to a balance of woven tensile forces continual through the structure as opposed to relying on continuous compressive forces like any common wall or column… although every structure is ultimately held together by a balance between tension and compression, tensegrity structures, according to Fuller, are characterized by continuous tension around localized compression.” (‘Anatomy Trains,’ p.43)

The subject of tensegrity implies the need for balanced lines of pull within muscle and fascia that impose tensile forces on bones, which represent compressive force. From Myers’ ‘Anatomy Trains’ concept, the fascia connections Myers calls ‘trains,’ require a state of equilibrium for improved postural arrangement.  This may prove the need for hamstrings, and the associated fascia making up the ‘Superficial Back Line,’ to be lengthened.  

It is evident from the research sited above that things are more complex than the bold statement from Edwards, ‘Stop Stretching Your Hamstrings.’ Yoga is not about the bold opinions you may be reading online. Yoga is about subtlety. For me the research into how the body is affected by yoga practice has been a labor of love. As so much online opinion and conjecture has been diluting reality into misleading sound-bites, I would like to express the need for nuance.

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