By now, most people are familiar with the term “Ergonomics" and understand that ergonomic furniture is more healthy for the body because it helps to maintain more natural positions that reduce stress to the bones, muscles, and nerves throughout the body. But chair companies and ergonomists often throw around terms related to the designs and functions of ergonomic chairs that the common consumer may not understand. Here is a list of some terms you may need to know.
Lumbar Support: This is one of the most important features of an ergonomic chair. This device is intended to prevent, as much as possible, the flattening of the lumbar spine that occurs to most people when there are seated. Lumbar supports usually work as a gentle curve in the backrest shape, and allow user to be seated more comfortable for a longer period of time.
Backrest Height Adjustability: This function allows the user to change the height of the lumbar support area in the chair backrest, although this feature is often interpreted as the ability to change the height of the entire backrest. This function accommodates preference by different users regarding where and how the lumbar support curve contacts the back.
Lumbar Depth Adjustability: This feature affects the size and sometimes the firmness of the lumbar support curve in a chair's backrest. Like backrest height adjustability, it accommodates different body types and preferences by the user.
Height-adjustable Armrests: This function, as the name suggests, allows the user to adjust the height of the armrests to suit the body of the person, this helps people avoid using chairs with too high or too low of armrests, which could result in elevated shoulders and pressure on the undersides of the elbows and forearms, or would require the user to slump or lean over to one side to use the armrest, respectively. This feature also allows for the armrest to be moved out of the way during some activities that may require lots of arm movement.
Width-adjustable Armrests: This function allows the user to change the distance between the armrests, not the armrests themselves. For an ergonomic office experience, the user does not want a chair with armrest too close together as this will splay the elbows and cause the wrists to bend to the side during activities such as typing. This puts the user at wrist for Carpal Tunnel Syndrome.
Padded Armrests: This feature is advisable as it prevents uncomfortable pressure on the undersides of the forearms and elbows.
Backrest Angle Adjustability: This function allows the user to change the angle of the backrest relative to the angle of the seat. The most common way to adjust the backrest is through and adjustment mechanism, however, it can also be adjusted through flexing materials or springs in the shell of the chair. Backrest angle adjustability enables the chair to support different degrees of recline for the body, which in turn transfers some upper-body weight to the chair backrest and relieves the lower back's intervertebral discs. This function also increases the angle between the torso and the thighs, which causes the lower back to curve inward. This inward curve in the back also relieves pressure on the disc.
Chair Recline or Tilt: This is a similar function to the Backrest angle adjustors, but not the same. Chair recline or tilt changes the angle of the entire chair seat relative to the floor. There are a couple of ways that this function can work. One is a column tilt, which pivots the chair at the top of the base post and lifts the knees slightly while the back descends. The second is called a knee tilt, where the pivot point is forward of the post, closer to the knees. In a knee tilt chair, the knee lift is negligible, but the back descend more than in a column tilt chair.
Seat Height Adjustability: This function allows the user to adjust the height of the chair to allow one's feet to rest comfortably on the floor or footstool while still maintaining optimum distance from the desk and keyboard. Pneumatic adjustable features are easier to use than mechanical adjustable chairs.
Seat Depth Adjustability: Chairs with the function are able to change the front-to-back depth ratio of the seat by either a backrest in-out adjustability or a sliding seat pan. For smaller people, a shorter seat pan is preferred to allow the person to use the backrest, while a deeper one offers more stability to taller individuals.
Seat Pan Angle Adjustability: This function generally refers to the ability the user has to change the forward-back angle of the seat. It allows them the choice of a fixed angle, rather than a free-floating recline. This function commonly allows for a forward tilt, in which the thighs slope downward. The main purpose of forward tilt is to open the angle between the trunk and thighs, inducing lordosis and reducing disc pressure.
© 2007 Sit On This Ergonomics, LLC.
Author Bio: Amy Pedersen has worked in the Ergonomics and Office Furniture industry for over 10 years and is owner of Sit On This Ergonomics, operating a number of ergonomic websites dedicated to Office Chairs and the practice of good Workplace Ergonomics.
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