Ergonomic office chairs

In the previous post, Ergonomics in the Office, we talked about the meaning of ergonomics and the benefits that an ergonomic office can offer.In this post, we will instead talk about ergonomic office chairs and how to choose one.

An office chair must offer a set of adjustments that allow most users to find a comfortable seating position.The fact that a chair is comfortable is a subjective evaluation, related to several physical parameters, such as our height, the shape of our back, etc.

However, in general, an office chair can be defined as ergonomic if a scientific study has been conducted proving its comfort for 90% of possible users, or if it meets the requirements of a reference standard.In fact, chair manufacturers and the scientific community have promoted studies that have led to the concept of a reference standard (normative).

The EN1335 Standard for Office Chairs

A standard (normative) is a set of rules that define when an office chair can be considered ergonomic and suitable for professional, continuous use in the office (8 hours a day).

For office chairs in the European market, the EN1335 Standard provides a series of dimensional requirements to guarantee the ergonomics of the chair. By respecting these dimensions and adjustments, it is as if the chair had been subjected to the scientific studies mentioned above.

For example, the standard specifies that the lumbar support must have an adjustable height ranging from 6.7'' to 8.66'' (17-22 cm) relative to the seat. This means that, in 90% of cases, users from the shortest to the tallest will be able to adjust the support to a comfortable position.

The same applies to the seat, the mechanism, and the armrests: specific adjustment ranges are defined by the standard.

The standard also includes load and fatigue tests to ensure that the chair is robust and durable, making it suitable for continuous use.

There are several accredited laboratories that certify product compliance with the standard.For example, in Italy, CATAS of which SbS is a member verifies the compliance of seats with the EN1335 Standard.

SbS seat kits are almost entirely tested according to this standard, both through internal lab tests (especially during the product design phase) and at CATAS for official certification.

Ergonomic Chair and Video Terminal Workstation: Recommendations

An ergonomic chair allows you to work in the recommended static position:

The checklist for correct posture is:

• Feet resting firmly on the ground (possibly with the use of a footrest)

• Thighs horizontal and calves vertical (approximately a 90° angle between them)

• Arms well supported by the armrests and bent at about 90°

• Back well supported by the chair’s lumbar support

• Shoulders and neck relaxed, head straight

• Distance from eyes to screen approximately 18–24'' (45-60 cm), with the top edge of the screen at eye level

(This posture, called static, is the one in which muscle effort is minimized.However, it is clear that maintaining the same posture for 8 hours is impossible.

In fact, the most recent ergonomic research (1) recommends alternating this posture with a dynamic seating position, in which the chair allows the pelvis to perform small movements, promoting better blood circulation.

Another suggestion from these studies (1) is to alternate sitting work phases with standing ones, possibly using adjustable workstations or simply taking short walks at regular intervals.

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(1) GOOD WORKING POSITIONS – OSHA