What are you stretching?
I have written previously about short versus tight muscles, using an example of short or tight hamstrings limiting the ability to bend and touch your toes. Think about the stretch feeling you get in the back of your thighs when attempting to bend and reach for your toes. That stretch feeling is coming from the elongation of your hamstrings as muscle fibers are being pulled to their limits, right? Maybe. We don’t exactly know what structure is generating that feeling. It may be muscle fibers, the tendons that attach the muscles to bones, or nerves under tension.
Unlike skin, fascia, muscle, tendons and ligaments, nerves do not have elastic properties. In other words, nerves don’t stretch well. Nerves like to glide. They run inside sleeve-like structures that allow them to slither and slide to accommodate movement. The sciatic nerve and its branches, receiving connections from the brain and spinal cord, reach from your low back all the way to your feet. This nerve moves and winds intricately through and around bones, muscles, tendons, and ligaments to allow for someone to bend. So, what happens when a movement such as bending tugs on a nerve? It is difficult to be precise, and symptoms are often vague, but any of the following are theoretically possible: feeling a stretch, numbness, tingling, pins and needles, burning, stiffness, or even pain. This has been labeled ‘adverse neural tension,’ although ‘adverse neurodynamics’ has been used most recently and is more indicative of the mechanism behind the symptoms written above.1
Any of the symptoms noted above (stretch, numbness, tingling, burning, stiffness, or even pain) can be NORMAL. These symptoms do NOT mean that something is wrong. I am confident I can put almost anyone in a position that tenses a nerve. Tension on a nerve can be a normal limitation. We can all feel these symptoms with specific movements and positions. However, it is only when normal, functional, every-day movements are limited AND reproduce neural tension symptoms that suggest adverse neurodynamics may be at play. How do we know? It is not always clear, but physical therapists have specific tests that can help determine if adverse neurodynamics are contributing to your pain or dysfunction. Tests involving the lower and upper extremities, including the sciatic, median, radial and ulnar nerves, are the most standard.
In my experience, when adverse neurodynamics are involved they are only part of the picture of what brings someone to physical therapy. There are typically other things that we need also need to work on. As far as why a person experiences adverse neurodynamics is usually unclear. I see it sometimes following surgeries, injuries, immobilization, and for reasons totally unknown. It is important to differentiate certain musculoskeletal diagnoses, as adverse neurodynamic involvement may mimic common diagnoses like carpal tunnel syndrome and tennis elbow.2 A physical therapist examination can help determine this involvement and provide interventions to improve nerve excursion, symptoms and restore function.
1 Ellis RF, Hing WA. Neural Mobilization: A systematic review of randomized controlled trials with an analysis of therapeutic efficacy. J Man Manip Ther. 2008: 16(1):8-22.
2 Coppieters MW, Butler DS. Do ‘sliders’ slide and ‘tensioners’ tension? An analysis of neurodynamic techniques and considerations regarding their application. Man Ther. 2008; 13:213-221.