A Cascade of Biomechanical Repercussions from Sitting

• Sitting is static stretching for the back

• What gets stretched? All the soft tissue from the center of the discs to the back of the body. This means all of the muscle, fascia, tendons, ligaments, and disc material/cartilage that lies posterior to the center of the lumbar discs

• This leads to joint laxity and ligamentous instability of the lumbar spine as the ligaments are no longer taut enough to correctly perform their job

• This also causes the posterior wall (annulus) of the disc to stretch, thin, and weaken, in addition to causing the disc nuclei to migrate posteriorly and exert pressure upon the weakened annulus, which creates disc bulges and herniations that protrude into the spinal column and can ultimately lead to extreme levels of pain. Tears and herniations are almost always posterior-ipsilateral in nature

• Pain leads to muscular inhibition and altered motor programming

• Sitting can force the body’s natural posture to exhibit lumbar flexion and posterior pelvic tilt, which is akin to a constant flexion moment on the lumbar discs and constant strain on the soft-tissue at the back of the spinal column

• This posterior pelvic tilt is the number one cause of mechanical dysfunction in the lumbar spine

• What else shortens? The hip flexor and hamstring muscles. This is known as“Adaptive Shortening.” Shortened muscles become dominant muscles

• An overactive psoas creates strong compressive forces upon the lumbar spine every time it contracts

• A tight psoas leads to decreased hip extension range of motion and therefore decreased glute activation from a mechanical perspective

• A tight psoas leads to what’s known as “Reciprocal Inhibition” which leads to decreased glute activation from a neural perspective, which is pronounced by the inhibition due to low back pain

• Compression of the glutes incurred while sitting also inhibits the glutes

• Decreased glute activation leads to what’s been coined, “Gluteal Amnesia”

• Gluteal Amnesia leads to flat (atrophied) and weak buttocks

• Weak glutes lead to what’s known as “Synergistic Dominance.” Synergists are “helpers” of the glutes which include the erector spinae, hamstrings, quads, and adductors depending on the movement

• Since the glutes aren’t functioning optimally and the hips “lock up” due to tight muscles, movement patters erode – more forward knee bend and lumbar rounding and less hip extension during squatting and standing from a chair, less hip extension and glute “pushing” and more hamstring “pulling” during gait, more lumbar extension and less hip extension when picking something up from off the ground, doing yard work, and deadlifting, etc. The erector spinae become prime movers rather than stabilizers in most movement patterns

• Synergistic Dominance leads to “Pattern Overload” which creates more pain

• Pattern Overload leads to tissue trauma, inflammation, spasm, trigger points, adhesions, altered motor patterns, and more muscular imbalance

• Spasms, trigger points, and adhesions lead to less movement and more sitting

• More sitting and less activity leads to detrimental postural adaptations in the form of flattened lumbar curve, kyphosis, posterior pelvic tilt, forward head posture, diminished mobility at the ankles, hips, thoracic spine, and shoulders, inflexibility of the hamstrings, hip flexors, and hip rotators, and weak glutes and core musculature

• Any attempts to exercise with considerable intensity or duration in this state leads to pain and possibly injury, especially at the hamstrings, groin, low back, knees, and shoulders

• Problems in one area of the body lead to problems in other areas of the body. If a misalignment exists in one segment of the kinetic chain, predictable patterns of dysfunction known as “Serial Distortion Patterns” throughout the entire kinetic chain will ensue, which compromise the body’s structural integrity both above and below the misaligned segment. For example weak upper glutes cause knee pain due to their inability to control the femur from being pulled into valgus (inward) when squatting, climbing, and jumping

• Dormant and weak muscles atrophy, which decreases the metabolic rate

• Decreases in metabolism leads to increases in body weight and body fat, which puts more stress on the joints and leads to increased pain and muscular inhibition

• The cycle repeats itself and the individual’s physique, movement patterns, posture, and performance capabilities enter into a continuous downward spiral

• In short, sitting changes the way we move and changes the way our bodies function


The Lumbar Spine – The Ultimate Compensator

As alluded to earlier, the lumbar spine is an amazing segment. It can and will compensate for lack of mobility found in many of the body’s major joints including the ankles, hips, thoracic spine, scapulae, and shoulders.

Let’s look at the hip. If your hip flexors are too tight and you can’t extend your hips (think of gait, hip thrusts, or back extensions), don’t worry; the lumbar spine will extend to pick up the slack. If your hamstrings are too tight and you can’t flex the hips (think of bending over in a deadlift or back extension), don’t worry; the lumbar spine will flex to make up the difference. In fact, the lumbar spine will compensate for any of the six actions of the hip; extension, flexion, external rotation, internal rotation, abduction, and adduction. If you have poor hip rotation and you play golf, where do you think you’ll get the extra range of motion when you swing the club and your hip mobility “runs out”? You’ll get it from the lumbar spine!

At the ankle joint, inadequate ankle dorsiflexion (toe to shin mobility) causes excessive forward lean and low back rounding in a squat. At the thoracic spine, inadequate thoracic extension can force the low back to extend during any exercise where you have to “keep the chest up,” including bent over rows, deadlifts, good mornings, squats, front squats, and overhead squats. Poor upward rotation of the scapulae will cause the low back to extend during overhead pressing. Insufficient external rotation at the shoulder joint will cause the low back to extend while holding onto the bar during a squat. These are just some of the movements that are performed by the lumbar spine that should be performed by other joints. If you lack mobility in key joints, the lumbar spine will contort to get you from point A to point B.

It should be mentioned that the low back musculature including the erector spinae, quadratus lumborum, multifidi, as well as the lats, glutes, rectus abdominis, external and internal obliques, transverse abdominis, diaphragm, and pelvic floor muscles should contract to keep the core tight, produce intra-abdominal pressure (IAP), efficiently transfer energy from one half of the body to the other, and prevent energy leaks during strength training and high-velocity sporting movement. However, the core should usually be braced isometrically and should not move much concentrically or eccentrically in any direction (flexion, extension, lateral flexion, rotation, etc.). While a standard “arch” is a good thing during heavy compressive loading, there’s a fine line between arching and hyperextending the lumbar spine. Contracting the erector spinae is wise, but overarching is unwise as it places the posterior elements of the spine under too much stress and will likely lead to damage and injury over time.

So we know that inflexible muscles (which can be either short or stiff due to excessive tone) can cause the low back to come into play as a “substitute.” But weak muscles can also cause the low back to move, even in the presence of perfect flexibility and mobility. Weak glutes will force an individual to lift with their low back, run with their hamstrings, and squat with their quads. A weak core will cause the low back to collapse and “leak” energy.

What’s the big deal, you might say? Who cares how someone gets from point A to point B as long as they make it? Due to their larger structure and the fact that they support much of the body’s weight, they take a serious beating when they move around at high velocities, under high load, or for sustained periods of time. So you need substantial flexibility, mobility, stability, and strength at the hips in addition to adequate core stability in order to spare your lumbar spine.

In summary, healthy, mobile, and stabile joints spare the lumbar spine. But it takes more than just mechanical efficiency. You also need neural efficiency. Sometimes sparing the spine is a simple matter of motor reprogramming. Many individuals possess adequate joint mobility and stability, yet they still move too much in their lumbar spines and too little in their hips and thoracic spines. These folks need to be taught proper movement mechanics and exercise form.

After working with beginners for an entire session many times they can learn how to stabilize their spine through bracing and move solely at the hips during various exercises and movement patterns such as hip abduction and external rotation movements, quadruped hip extension movements, supine bridging movements, squatting movements, deadlifting movements, lunging movements, and back extension movements. Upon learning proper form many of these individuals will remark that they “finally feel the exercise working the right muscles.” The body wants to take the path of least resistance. It is more cost effective physiologically to stoop rather than squat (Garg and Herrin 1979). You must override your brain’s default signals and teach it to automatically resort to proper motor programs.

For the full article click on the link below.

http://bretcontreras.com/puppies-in-vices/