Different working postures need both the support to rest, and the freedom to move.
Because there is often a mix of forward and reclined tasks, adjustment of the chair is critical to keep good posture
Sustaining that posture is easier with both chair and work surface support
Attention to the job may require an active, forward posture, as shown on the left, or possibly a more relaxed, reclined posture shown on the right.
Forward postures are more active, using more postural muscle than reclined postures.
The spine is in a good position, and there is more freedom to move forward, but more effort is needed to stay upright.
Reclined postures are more stable and more relaxed, but because the chair is reclined, forward movement is limited, and the body may collapse into slump.
It is important to recognize how the work can be done with the best spine posture—either using a forward or reclined chair, and adjust the chair accordingly.