The Importance of Posture Part 2 – Ergonomics
October 17th, 2008 Posted in posture
Today, there are more seated workers than standing workers worldwide. This presents a significant challenge to the body, because our bodies are simply not designed to sit! The chair is said to have entered into our life style thousands of years ago through Egyptian heritage. The chair, in Egyptian times, was a symbol of power; only the King was allowed to use a chair. As time passed, the King sat in the largest chair at the head of the table, the Queen in a slightly smaller and less intimidating chair at the opposite end of the table, and finally the underclassmen in smaller chairs around the table.
As you are aware, this same “power structure” can be found in households and boardrooms all over the world today. Interestingly, two things have not changed since the advent of the chair, and one thing has; we still apply the persona of power to the “size of ones chair”, the human body has not changed at all since the chair was put into use, and finally, we are more sedentary than ever and WE HAVE MORE BACK PAIN THAN EVER
The therapist treating a patient today must look carefully at the patient’s ergonomics and fully educate the patient so they can control their environment. The patient wanting full recovery from musculoskeletal injury and/or prevention of postural strain and repetitive stress disorders leading to chronic musculoskeletal disorder must seek assistance with ergonomic education.
It is critical to remember that we function in a field of gravity, relentless gravity, twenty-four hours a day. Some of you may say, “you don’t have to worry about gravity when you are sleeping though”. If you ever have a cervical spine injury, you will quickly learn that you may even have to take your ergonomics training to bed!
Sitting in a chair for hours at a time, bending over the hood of a car, or working over a work bench for hours at a time can be very taxing to the postural muscles of the body. When the postural muscles are chronically over worked, they tend to tighten and shorten, altering our natural spinal curvatures
As the body begins to deteriorate from poor posture and an unrelenting ergonomic environment, it becomes less and less able to handle the stresses of life, often leading to unwanted and unexpected injury. For the patient seeking help from a professional medical practitioner, their failure to educate you as to ideal ergonomics will only serve to progressively drain your finances, time and patience, often leading to unnecessary use of non steroidal anti-inflammatory drugs and other pain masking medications. Eventually, the whole system begins to deteriorate, leaving you, the patient a bewildered, frustrated and confused mess
Chair height
When your chair is too high, the space behind your knee (the popliteal fossae) becomes compressed. This frequently causes numbness in the lower leg and slows circulation to and from the lower leg, resulting in swollen feet.When your chair is too low, the large nerve structure called the “sciatic” nerve often gets compressed. This leads to pain in the low back and legs and can result in numbness in one or both legs.
When your chair fits correctly, there is a 90° angle at the knee and there is no discomfort behind the knee or in the butt region. The feet should always rest flat on the floor unless you are using a footrest.
If you are short, and your working surface is high enough that you can’t keep your feet on the ground without excessive pressure on the backs of your legs (Left), it will be necessary to use a footrest.
To determine the height of your footrest, adjust your chair height until your arms are comfortably placed on the table and your elbow is bent to 90°. Once your arms are at the correct height, measure how high your footrest will have to be and then either have a carpenter custom build one for you or purchase an adjustable footrest form an office supply store.
How to Fit a Lumbar Support
When using a chair with an adjustable lumbar support, it is important to position it correctly. The apex of your lumbar curve is directly behind your belly button. Adjust your lumbar support so that the most convex point of the lumbar support is directly behind your belly button
Arm Rest Adjustment
For those of you who must perform data entry tasks for extended periods of time, arm rests are suggested. An armrest, when adjusted to support your arms so they are parallel to the floor and level with your keyboard, will save you from muscle soreness in the upper back, shoulders and neck. A good chair has adjustable arm supports.
Keyboard Height
Because the keyboard height is fixed in most desks, it is critical that you adjust your chair to allow your forearms to be parallel to the floor when you hands are in a comfortable typing position and you are sitting in good upright posture
Keyboard Set-up
After you have determined the correct keyboard height, it is very important to set your body up correctly with respect to the distance from the keyboard and hand placement on the keyboard itself. If your keyboard is positioned such that your wrist flexor tendons touch the edge of your desk or keyboard tray, you are much more likely to inflame your wrist flexor tendons. This is often a partial contributor to carpal tunnel syndrome. To prevent unwanted repetitive stress injuries, use a protective wrist pad. They can be purchased at most any computer or office supply store
Don’t sit too far away from your keyboard
When setting yourself up at a keyboard or to do any work task, be it at a counter top in the garage, to cook in the kitchen, it is always best to minimize how much shoulder flexion you must maintain. As seen to the left, holding your arms in a position of shoulder flexion with your hand only five centimetres above the working surface produced severe pain in young men in only twenty minutes!
When positioning yourself at a desk or keyboard, it is best to try and keep the upper arm as vertical as possible when sitting with good upright posture. The same principle applies to work environments that require prolonged standing at counter tops.
Selecting the correct height and distance for your video display unit
Once you have set your chair height so that you are properly set-up to your keyboard and you have chosen a footrest if needed, it is time to set your video display (VDU) height. To find the optimal height for your VDU, sit at your ergonomically correct workstation. Have a friend or co-worker measure the distance from the outside corner of your eye to the floor. Use this measurement to determine how high the centre of your VDU screen should be from the floor (see diagram).
By setting your VDU height so that you are looking directly into the centre of the screen, you are more likely to maintain optimal posture throughout the day because your eyes dictate posture. If your eyes are focused below the centre point most of the day, the tendency is to be drawn into flexion or forward. When you VDU is set-up correctly, your eyes will wonder above and below the mid-point, which will encourage better postural alignment, improve blood flow to the head and improve productivity.
Selecting the correct work station:
Writing tables are generally 5-8 centimetres higher than is recommended for data entry . To prevent unwanted repetitive stress injury, it is always best to invest in a table or desk designed to suit the primary need of the workstation.
If your work requires a combination of both handwriting and data entry, a combination desk is highly recommended. These desks are readily available and inexpensive today. In fact, for the price of one visit to an orthopedic surgeon to find out what is wrong with your neck, you could probably pay for a combination desk at most office supply stores
Hopefully now you have a better understanding of the importance of ergonomics and how to set up your desk and control your environment.
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