The spine is a complex structure. It is composed of 24 distinct vertebrae, which are separated by discs consisting of an outer fibrous layer and inner gelatinous core, which allows for a mobile, but stable, trunk. The thoracic spine is uniquely distinct from the cervical and lumbar spine. It has a kyphotic curve and is convex in shape, versus the cervical and lumbar spines which are concave. These curves are highly interdependent; the movement of one spinal segment can change the movement along other segments within the chain. Consequently, the thoracic spine is the central portion of the spine, which helps and supports the proper motion of both the head/neck and lower trunk.
To understand this relationship, it helps to have an idea of how the bones change throughout the spine and how it allows for movement. The neck (cervical spine) joints are oriented in the frontal plane at a 45 degree angle, allowing for a significant amount of motion in all directions and aiding healthy individuals to having a rotational view of 360 degrees (90 degrees of rotation each direction, plus 90 degrees of peripheral vision from our eyes to each direction). This frontal plane angle gradually increases (on average 60 degrees) in the upper thoracic spine (from approximately T1-T8), which promotes more rotation, less flexion/extension, and even less side-bending secondary to rib attachments on the thoracic spine. When the head moves on the neck, its mobility is augmented by the continued movement through the upper thoracic spine. Ergonomically, this is important because slouching increases the rounding of the mid-back, making these joints less mobile for movements into side-bending and rotation. Our body is remarkable at compensating and will create greater movement through less stable segments (i.e. the lower cervical spine) to try and make up for the motion lost through the upper back. Over time, if these poor biomechanics continue to occur, it can create increased joint irritation that can cause pain in the lower neck and upper back regions.
Similar movement relationships occur with the thoracic and lumbar spine. The lower thoracic spine has joints which lie closer to the sagittal plane, gradually increasing the amount of flexion, extension and side-bending occurring in that area, while limiting rotation. This sagittal plane trend continues to increase through the lumbar spine towards the tailbone (sacrum). The lumbar spine joints are distinctive in that the orientation limits the majority of rotation. If you slouch excessively, it increases the curvature of the thoracic spine and decreases the curvature of the lumbar spine, which increases the strain on the lumbar spine. The thoracic spine can become stiff, limiting rotation and extension. Once again, this lower thoracic stiffness can be problematic for other areas, typically demanding excessive lumbar spine extension and rotation and increasing its vulnerability for potential injury.
As one can see, the spine is a complex area and the thoracic spine plays an important role linking the other regions together. It is important to keep this area of the spine healthy with proper posture, as well as mobile with activity and stretches. A couple stretches which help promote movement in both the upper and lower thoracic spines include:
– The Seated Rotation Stretch: in sitting, keep your belly button forward and rotate through the upper back while reaching back behind you in your chair to produce a stretch. Hold for 10 seconds and perform towards the other side. Repeat periodically throughout the day.
– The Standing Side-Bending Stretch: in standing, reach your hands upwards towards the ceiling, elongating your body. Gently reach towards one side while jutting your hips in the opposite direction, producing a stretch through the opposite side of the body. Then perform towards the opposite side. Hold for 10 seconds and repeat periodically throughout the day.
The body (and therefore the spine!) was built to move – promote it! If you are having any difficulties with these motions or would like to know more information, talk with your physical therapist today.