Why thoracic gliding?
As movement teachers we all know that it is so important to move all of our joints daily, ideally in all of the ways they are able to move. As Norman Doidge reiterates time and again in his book The Brain that Heals Itself, we have a "use it or lose it brain," and, by extension, we also have a "use it or lose it" body. Basically, the ability to move the body is based on our ability to receive & process sensory input, and then to create motor output based on that sensory input. The amount of space in the brain dedicated to processing sensory input for any particular region of the body, as well as to directing motor output from that region, is determined by how much we use it. Our sensory & motor brain maps diminish or become blurred--and at times can even disappear!--when we don't use a region often or expose it to sensation, and they expand, becoming more clear and detailed, with frequent sensory input and use.
So what does this all mean in relation to our thoracic spines and thoracic gliding?
Well, we live in a society that spend a lot of time with the thoracic spine frozen into a single position (flexion), and that thanks to all kinds of technology has eliminated a lot of the reasons we used to move the spine into other positions (one small example: back up cameras in cars replace the need to turn the head and t-spine in order to see what is behind you when you drive in reverse). What we don't use, we lose, and most people have very little mobility in their thoracic spine simply because they don't have very many reasons to move through that region of the spine on a daily basis.
Okay, but why are we talking just about glides here, rather than total spinal mobility?
Training glides specifically is so important because they are so often forgotten as a movement option in the spine. Yoga and Pilates and group fitness and personal training regularly get people to move their spines through flexion and extension, lateral flexion, and rotation, but rarely (if ever!) ask them to glide. In fact, the spine's gliding capabilities are only mentioned in passing in a single sentence in the 698 pages of the National Association of Sports Medicine's (NASM) personal training textbook!
So what is a glide, and how is it different from flexion/extension or lateral flexion?
Flexion is, to quote NASM, "a bending movement in which the relative angle between two adjacent segments decrease." You can think of it as a closing of the space between two body parts. Extension is the opposite: "a straightening movement in which the relative angle between two adjacent segments increases." Lateral flexion is the same as flexion in the sagittal plane, only now the angle between two body parts decreases through the frontal plane (that is, to one side or the other: think of making a "C" shape with your spine, drawing one shoulder down towards the same side hip in a side bend). These more commonly focused on movements of the spine are what we call "axial" movements.
Gliding, by contrast, is considered a "non-axial" movement, and consists of a translation in which the two adjacent segments move apart from each other by sliding either forward and back or side to side. For the spine to glide, then, we aren't looking at closing or opening the angle between two vertebra, but rather at stacking the vertebra on a diagonal (either on an anterior/posterior diagonal, or a lateral diagonal). (There is a third option for gliding in the spine, on a superior/inferior line of movement, that we more often talk about in terms of "fractioning" or "compressing" the spine.)
If this is all new to you, there is a lovely summary of the ways the spine can move with lots of visuals here (while the author focuses on the lumbar spine, the discussion of how the vertebra can move applies to the thoracic spine as well). (The image below is from the same post.)
In this video, I follow-up on Erin's tutorial about anterior/posterior thoracic glides by sharing: