Ergonomics, the false prophet

 

We have all seen articles about the ergonomics of standing desks and sit-stand desks. The scientific-looking drawings convey a strong feeling of authority and demand assent. But what is their real values?

We are specifically interested in the matter of height adjustment with a focus on “elbow angle”.

OSHA, the federal government Occupational Safety and Health Administration, which is mandated by the US Congress to “assure safe and healthful working conditions for working men and women” does not have much to say on Sit-Stand desks to begin with as follows:

“A height adjustable surface is desireable (sic) as it accommodates many almost (sic) all users when partnered with a height adjustable chair and provides for regular changes in work postures.”

In another article on “Working safely with Video Display Terminals”, OSHA offers a drawing of an employee sitting in front of a computer and is, as height adjustment is concerned, focusing on the chair, not the table:

“The chair height is correct when the entire sole of the foot can rest on the floor or footrest and the back of the knee is slightly higher than the seat of the chair…”

In other words, no mention of the elbow in sitting position, nor was any in the standing position as we saw first.

However, vendors of standing desks and sit-stand desks do not hesitate to be more specific. Thus, a webpage from a major such vendor, Varidesk, states:

“A good rule to follow for standing desk posture and height is to keep your elbows at no less than a 90-degree angle ..”

However, as all rules, this one seems to have ossified and turned into Gospel truth. Visiting the drawings offered for “standing desk ergonomics” on the web we will notice that ALL the drawings show the human subject standing with a 90-degree elbow angle with example above.

Now to study how much beyond a 90-degree angle this angle can be while still allowing for proper posture, the Canadian Center for Occupational Health and Safety declares”

“elbows stay close to the body and are bent between 90 and 120 degrees”

Now with a little bit of trigonometry, and a reasonable estimate of the length of a forearm, 120 degrees mean that we still have correct height with adjustment within 5 inches. Therefore, an ultimate height adjustment for a perfect 90-degree elbow angle is not mandated.

Now foregoing ultimate adjustment but allowing adjustment within one inch, as the DeskPup does, permits several important construction benefits. First the non-use of metal is made possible, with the related problems of cost, weight and rust. Second the need to a mechanism, such as screw stop to stop height adjustment at a specific point is also not critical. Such stopping mechanism creates a tremendous stress on these parts of the desk and therefore both a limit to the weight the desk can hold and increases its fragility. Eventually with a lighter desk, a desk that does not requires metal in its construction, it can be easily moved off the table or moved back on the table and allow a real flat surface to work on while most sit-stand desk in the sitting position offer an awkward surface to work on. Finally, the light construction of a nonmetal sit stand desk allow it to be foldable and portable.

 

 

  1. https://www.osha.gov/SLTC/etools/computerworkstations/checklist_purchasing_guide.html
  2. https://www.osha.gov/Publications/videoDisplay/videoDisplay.html
  3. https://www.varidesk.com/active-office-resources/top-standing-desk-mistakes
  4. https://www.ccohs.ca/oshanswers/ergonomics/office/sit_stand_desk.html

 

 

 

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