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Fascia and the lower back

This is an excerpt from Low Back Disorders 4th Edition With HKPropel Access by Stuart McGill.

FASCIA: HOW OUR UNDERSTANDING HAS CHANGED AND ITS LARGE INFLUENCE ON BIOMECHANICS, RESILIENCE, AND PERFORMANCE

It wasn’t until I retired and was motivated by podcasters’ questions to reflect on my career that I thought about how my concept of fascia had matured and expanded. Bill Parisi had invited me to speak to the Professional Football Strength & Conditioning Coaches Association. He mentioned he was writing a book on fascia and its role in potentiating athletes’ performance and asked if I had any thoughts. I replied I had never done specific fascia experiments, but I would give it some thought, and then it hit me—although we hadn’t realized it at the time, several of our experiments ended up revealing several fascia-related insights. Bill’s probing motivated me to unify these concepts.

I explained in chapter 1 how I created a highly detailed, anatomical model of spines in the computer, driven by an individual’s biological muscle and movement signals, for my PhD work—the “virtual spine.” As it turned out, the model was quite good at predicting tissue loads and advanced the general understanding of spine and injury mechanics. However, the model did not predict elite performance very well. The early renditions of the model assumed the muscles created force. However, muscles create both force and stiffness, and this was added to the model with Jacek Cholewicki’s pioneering PhD work (Cholewicki and McGill, 1995, 1996). Tissue stiffness and transmission of these forces through the fascia covering every muscle cell, binding the muscles together, and transmitting forces along so-called anatomy trains potentiates resilience and athletic performance.

This new knowledge created tremendous dissonance. I was teaching undergraduate biomechanics, and the syllabus included teaching students about muscles being agonists and antagonists to a specific movement. In a very early experiment, we measured people creating twisting torque during standing (McGill and Hoodless, 1990). All of the muscles were active. As we measured the contributions of each muscle, the agonist forces and torques cancelled out those of the antagonists. The test participants were generating close to 100 Nm of twisting torque, yet the virtual spine recognized the agonist–antagonist canceling, so where was the torque coming from? As it turned out, the majority of athletic power in skilled athletes was generated at the hips and transferred through a stiffened core that actually amplified the power with strategic pulses of elastic energy. The torso muscles were creating essential stiffness.

Unskilled athletic performance, on the other hand, was characterized by participants who tried to create power with spine muscles while stiffening their hips. In fact, we saw this in many examples, across all sport. The concept of muscles being agonists and antagonists works for some simple discussions of force, but the body uses stiffness to control motion and optimize elastic contributions. Any discussion of biomechanics and the optimization of performance and injury resilience must include force and stiffness. Thus, the quantum leap in my development occurred as it became overwhelmingly apparent that all muscles became agonists to the elite performance. I could no longer teach the undergraduate biomechanics syllabus in good conscience. The missing link was the material binding muscles together on all sides of joints and spanning many joints in the skeletal linkage. That material is fascia.

Further experiments investigated the role of fascia as a composite using rats (Brown and McGill, 2005, 2009). We directly measured how fascia enhances the force output of a group of muscles when bound together in the fascial network. We reexamined the role of different muscle groups that led to our concepts of performance and better training techniques. The abdominal muscles forming a composite will be discussed later in this chapter. The notion of elastic fascia potentiating performance is discussed in chapter 5. If I were not retired, I would dedicate substantial effort to more investigation of the role of fascia.

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