Thursday, April 14, 2011
Thursday, April 7, 2011
By reading part 1 of The Desk Warriors Guide to Building a Healthy Back, we know that sitting for prolonged periods is something to be avoided. But what are we to do when sitting can't be avoided? After all, our jobs, our livelihoods are now spent hunched over computers. We can't all earn a living on our feet like pro-athletes, dancers or even bartenders for that matter. We have to sit at a desk and work.
I will first address the myth about "proper" posture. When we sit with "proper" posture, our feet flat on the floor, our knees and hips at 90', the spine long and upright; the head and chest up and our lumbar curve maintained we are actually damaging our lumbar spines. This may be aesthetic sitting posture or proper school boy/girl posture, but according to my man Stuart McGill it is only tolerable for 10 minutes max and should not be attempted further.
You would be correct. However, a back angle of anything less than 135* can't really be considered sitting since you are closer to laying down. Assuming we have to be at a desk/work station in a seated position, the ideal posture is one in which muscle activation is lowest via support (back of chair or lumbar support), maintenance of the normal lumbar curve and one in which we can change position easily.
The reason we need to change positions easily and regularly is to not overload any one tissue. Tissue loads need to be migrated from tissue to tissue in order to minimize the accumulated microtrauma of any one tissue. Think about it, you fidget for a reason. You are spreading the microtraua from tissue to tissue. McGill recommends changing postures very often. Atleast every ten minutes.
The chair is not helping the situation. Chairs are designed by architects, not biomechanists. Ideally, you would want a chair with a great deal of lumbar support. The Nottingham chair is one that supports the lumbar spine and aims to keep a posture more congruent with standing, thus sparing the spine. Standing desk stations are also a great way to preserve the spine. But yes, the Nottingham chair is expensive and unstylish and standing desk stations have their problems as well.
So when forced to sit for long periods of time. We want a chair that supports the entire back, rather than doing all the work ourselves via the core musculature and contributing to spinal compression in a flexed posture (contributing to discogenic pain). We want to be able to mimic normal standing posture as best as possible so a chair that supports the normal lumbar curvature is essential. If your work chair does not do this, simply buy a lumbar support. Arm rests also alleviate spinal compression, so use them when you get the chance. Most importantly, we want a chair with the ability to recline. The more the better. The optimal seated position would be in a lazy boy, but as most desk warriors aren't afforded this luxury, we must aim to achieve this recumbent position via lumbar support and reclining our chairs. Again, I reiterate that any position must be changed eventually to promote circulation and to spread the microtrauma to various tissues, thus our reclined lumbar supported position must to be changed regularly.
The least compressive the posture, the longer it can be tolerated. So Desk Warriors, arm yourselves with an arsenal of appropriate desk postures. Change the angle of your back via more or less lumbar support or varying degrees of reclination. Shift your weight to your right, then your left. Sit with your legs crossed, left and right. Cross your legs with your lean on. Essentially be mindful of maintaining your neutral lumbar spine while shifting into a variety of comfortable positions.
This stance on postural shifting can also be applied to sleep. No one sleeps in any one position and they shift subconsciously. They do this because it's our way of our body spreading the stresses to different tissues as we should do when we sit, stand, lie etc…
In conclusion, the ideal posture for prolonged sitting is a reclined ~135 back angle posture where our natural lumbar, thoracic and cervical curves are preserved. However, we learned that after a certain exposure, no position is safe and that we must find a variety of Desk Warrior poses to serve our productivity needs.
Callaghan, J.P., and McGill S.M. (2001) Low back joint loading and kinematics during standing and unsupported sitting. Ergonomics, 44 (4): 373-381
And of course the books cited in Step 1: Sit Less
Saturday, April 2, 2011
The Desk Warriors Guide to Building a Healthy Back! 1/10
The International Journal of Obesity found in 2001 that Australian men working full-time on average spent 9.8 hours sitting in a chair daily. Since we Americans work more than most any other country, I'd estimate we sit perhaps 10 hours per day on average. This may seem like a lot at first but think about ones typical day. We wake up and may sit down for breakfast, if not we sit in the car as we drive to work. Most of us spend the majority of time seated at work. We sit down for lunch and dinner. The drive home is spent sitting in traffic and finally we crash on the couch to watch some night time television or to check our Facebooks. So now 10 hours per day doesn't seem so outrageous. 10 hours per day is 3,650 hours per year, or 42% of our day!
This “trend” of sitting for such long hours on a daily basis is surely not in line with our evolution. Accountants and I.T. Professionals are rather recent vocations. Sitting through rush-hour traffic and sitcoms are also new endeavors. We are evolving from hunter-gatherers who spent very little time sitting and when they did, they sat like this to amorphis blobs that vegetate in front of computer screens. (see below)
So why is all this sitting a problem for our backs? Why does it contribute to pain? To understand this we must understand a little anatomy.
When we stand with ideal posture, the curve in the small of our backs (lumbar curve) enables us to stand with a minimum of core muscle activity. Small amounts of core muscle activity while at rest (lying, sitting, standing, walking) is a good thing, because all core muscle activity compresses the spine. Too much compression of the spine will require a large percentage of your backs daily tolerance to loading.(which we'll talk about later)
You see, a muscle can only contract, or shorten. The muscles that support the spine go from your ribs to your hips or from the vertebrae of the spine itself to your hips and femur. Thus when these muscles contract, they shorten effectively compressing the spine. This is all fine and dandy when we are doing athletic moves and need a stable spine, but when we are simply sitting and resting, we want minimal spinal compression thus we want our normal lumbar curve.
When we sit, our lumber curve is attenuated, even in the best of chairs. Thus, we lose our lumbar curve and contribute to spinal column compression via excess muscular activation. Excessive core activation overtime via sitting or poor posture will... as my man Dr. Stuart McGill, the leading spine researcher in the English speaking world states A.) Decrease our work capacity B.) Degenerate the spine more rapidly C.) Exacerbate pain and disc problems. D.) Increase in intradiscal pressure when compared to standing postures.E.) Increase in posterior annulus strain. (Thats your disc trying to herniate or bulge backward)F.) Creep in posterior passive tissues which decreases anterior/posterior stiffness and increases sheering movement. (less stabile/more painful)G.) Posterior migration of the mechanical fulcrum which reduces the mechanical advantage of the extensor musculature (resulting in compressive loading).
In Layman's terms, prolonged sitting forces the spine to bend forward. See the spine above, picture it bent forward. The front of the vertebrates compressed together, pushing the center (nucleus) of the disks backwards. This is how we get bulging and herniated discs without traumatic injury. Also, the ligaments that support the vertebrae on the back side are elongated. They adapt to this elongated position. This is referred to as ligamentous creep. The ligaments are stretched out and your spine is now less stable. We want a stable lumbar spine and good movement in the thoracic or mid-spine and the cervical or neck regions.
When we sit, our quads (muscles in front of our legs) and our hip flexors (deep muscles connecting spine-hip-femur) are in a shortened state. Since we are very adaptive organisms, our bodies adapt to this shortened position as the new norm. The end result is short, tight muscles. These short tight muscles then pull our hips into an anterior-tilt (forward). (IMAGE) This is a problem because our lower backs compensate.
Our lower backs also will compensate for the anterior, or forward head position as seen below. This problematic posture loads the neck muscles much more, resulting in increased compression and thus neck pain, cervical disk herniations, arthritis, pinched nerves, shoulder pain and other problems related to nerve impingement that will manifest elsewhere in the body. Now this forward head position throws off our spinal equilibrium. The neck is flexed forward, the mid-spine is stable due to the articulations with the ribs. The mid-spine is less mobile and therefore our lower backs will again pick up the slack and take on the extra flexion. This is PRECISELY WHY YOU SHOULD NOT LOOK UPWARDS WHEN SQUATTING!
Hopefully we understand better why sitting is awful for us. It makes us shorter, weaker, less attractive and more prone to injury and pain. But how can we expect to sit less? Our livelihoods now depend on our ability to sit for extended periods of time. This 10 part series on spine health will cover the best ways to sit all the way to strengthening and rehabilitating your jacked-up spine.
O yes, and my references...