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The basic requirements are to have a workstation and job tasks designed to allow a person to remain in a balanced position or neutral posture, regardless of the work being done. The CSA Standard Z412-17 Office ergonomics – An application standard for workplace ergonomics recommends that alternating between sitting and standing, or variations on sitting and standing postures (e.g., reclining, forward tilting, and semi-standing) are encouraged in order to avoid the negative effects of prolonged sitting or standing in one posture. CSA also states that there is no uniquely correct working posture that fits a user for an extended period of time.
This document covers working in a sitting position. Please see other OSH Answers, including Sit/Stand Desk, Working in a Sitting Position, and Working in a Standing Position, for more information.
A workstation should allow the worker to sit in a balanced body position.
A job design should allow the worker to work in a variety of balanced positions.
Gravity constantly exerts a downward force on our bodies. Parts of our body in contact with a supporting structure (the seat of chairs, armrests, floors, etc.) will feel pressure from the structure to balance this force. Parts of our bodies that are not in contact with a supporting structure will use muscles, tendons, and ligaments to balance the force of gravity with an upward force of their own.
The body position that has the highest strength to handle the pressure felt by the supporting structure, while causing the least amount of strain on the muscles, tendons, and ligaments, is called the neutral or balanced body position.
The following recommendations outline how to maintain a neutral body position while sitting:
Note: No one seating position can remain comfortable over a long period of time. For this reason, multiple positions in which the body can be in the neutral position are recommended. As mentioned above, the workstation should allow the worker to adjust and move between these positions.
Seated manual tasks should be designed to maintain vertical alignment of the spine, and avoid constant stress on the shoulder region. This alignment can be done by: