Evidence of Health Risks Associated with Prolonged Standing at Work and Intervention Effectiveness

Basically the short of the long of it is that you should not sit or stand for longer than an hour without doing a few minutes of the opposite.

Otherwise you will start experiencing accelerating fatigue.

Places of work that require standing should prioritize letting workers sit for a couple of minutes once an hour at minimum. It retains 95% of productivity (if not boosts it when fatigue goes down), and reduces fatigue by at least half when compared to perpetual standing.