Start With Backrest Contact Height
Assess office chairs with armrests and fixed-height backrests by first observing where the backrest meets each person's back. Because that vertical position cannot be reset, a mismatch cannot be addressed through a back height control. Ask the user to sit in their normal working position, then note where contact occurs and whether it remains useful during ordinary tasks. Do not treat a taller backrest as automatically more suitable. Its relationship to the individual matters more than its visual size, particularly when several colleagues will use the same chair during a normal working week.
Check Armrests Against The Desk
Armrests introduce another point of contact that needs to work with the workstation. Check whether the user can approach the desk without the arms meeting its edge prematurely. Observe the shoulders and elbows while the person types, pauses and reaches for the mouse. Establish which armrest settings, if any, are available before deciding how a clearance issue could be resolved. Office chairs should be compared at the same desk wherever possible, because changing the working surface between trials makes it harder to identify whether the chair or workstation explains a difference in fit.

