The one thing I recall most about sitting for hours at an office desk is the agony to be put through by one’s back.  In fact mine got so bad that I ended up having to be referred to a occupational health therapist, who promptly decided my osteo artheritis had been made much worse by the state of the standard civil service issue desk chair, that I was to be supplied with a fantastic state of the art mobility assist jobbie.   This took some time to arrange, the cost was immense and there had to be negotiations with the bean counters in the finance HQ of the Ministry I was attached to.   Eventually the funding was made available, some two weeks before my knee replacement surgery which was also considered an urgent feature by the same OHT officer.   The desks were all at uniform height and if one had a shorter back or a longer back, then our chairs had to be manoeverable enough to accommodate these diferences.  One thing about being prescribed a specific type of remedy chair is that any colleagues found using could be caught for misconduct.  It did make the atomosphere a tad challenging sometimes.