Stretching Redefined

Jules Mitchell delves into the science behind stretching in her book Yoga Biomechanics: Stretching Redefined .  Artfully woven throughout the book is a sub-text that improves the reader’s research literacy while making an impassioned plea for the role of research in the evolution of how teachers teach, and how practitioners practice. Yoga teachers and yoga practitioners alike will discern yoga asana for its role in one’s musculoskeletal health. This article is an excerpt from Yoga Biomechanics: Stretching Redefined by Jules Mitchell, copyright of Handspring publishing (2019).

Some time ago, when I was developing the narrative for this book, I took an informal survey of everyone on my mailing list and asked them “what is stretching?” I intention- ally made the question open-ended, hoping to get answers that weren’t led by my own words. The responses varied, of course, but three distinct themes came up: ROM, tissue lengthening, and sensation. When we look at conventional stretching as it is described and studied in the research, these themes are absolutely central to the conversations of flexibility, muscle architecture, and tolerance. It seems we can all agree on some basic concepts, but where we get lost is in the details.

In my informal survey, some answers described stretching as a function of muscle relaxation with an insinuation that a stretch is the opposite of a contraction.

Others described stretching as an activity designed to bring “strength,”  “suppleness,”  and “elongation” to the muscle. I’m hoping you are, at this point, asking what type of stretching would develop strength and how it is measured, while also wondering what exactly “suppleness” might mean. A clear definition for “elongation” is also needed (is it deformation, tolerance, or sarcomerogenesis?) before determining the accuracy of  that perspective. Some responders separated muscle from connective tissue, implying they can be stretched separately and alluding to the notion that different approaches to yoga target different tissues. In our review of conventional stretching thus far, we have discussed very little about connective tissue outside of the fascial layers providing the structure for the muscle organ. In order to establish how stretching might affect tendons and ligaments, we would first need to define the properties of the tissue, and then the type of stretching, the load parameters, etc. In other words, the details.

I highlight these varied and sometimes contradicting perspectives for you here to explain the importance of coming together to agree on terminology. As the reader, you don’t have to agree with my definitions or interpretations of the literature; however, we must at least agree on the words we use so that we can form our opinions knowing we are talking about the same thing. If you are talking about how muscle tissue behaves during a stretch and I’m talking about how the collagen in connective tissue behaves, we will always be tuned to different channels. This reminds me of the John Godfrey Saxe poem of the six blind men and the elephant. Each blind man’s position near the elephant influenced how they perceived the animal. One man likened the elephant to a tree stump (feeling the leg). Another argued that the elephant is like rope (being near the tail). While yet another likened to elephant to a spear (feeling the tusk). And so on.

While all the men were partially right, they were all wrong. This quote serves to highlight the importance of continuing to define our terms.

In order for us to discuss stretching in terms of connective tissue, it is important that we re-establish the definition of stretching as load; a tensile load. This will keep us within a framework of biomechanics while including forces that may not fit into any conventional type of stretching. For example, a concentric muscle contraction applies a tensile load to the tendon (because the force produced by a muscle pulls on the tendon, in turn pulling on the bone to create, or prevent, movement across a joint). Most would not consider a concentric contraction to be a tendon stretch, but in fact, it is. A passive stretch also applies a tensile load to a tendon, albeit a lesser load due to less muscle force. An isometric contraction at end range, which we have established is a type of conventional stretch, might apply a great tensile load to a tendon, depending on degree of muscle contraction. If we want to ascertain how a tendon responds to a stretch, we have to include all types of tensile loading, not just passive stretching. If you recall the conversation I had with my colleague about stretching tendons, these were some of the concepts we had to go over to move forward in our discussion. At the conclusion of this book, when in a conversation about stretching, it is my goal for you not to be bound by the limitations of the blind men discussing the elephant.

Incidentally, my favourite response to my stretching survey was from a medical writer who flatly declared “I have no idea how to describe stretching.” It takes a vast amount of education to be willing to say, “I don’t know.” It also creates a perfect starting point to a discussion on the finer points of loading, stretching, and tissue adaptation. Admittedly, my “what is stretching?” probe was somewhat of a trick question.

This article is an excerpt from Yoga Biomechanics: Stretching Redefined by Jules Mitchell, copyright of Handspring publishing (2019).