A new study from Australia involving over 83,000 participants found that prolonged standing may not improve heart health and could even increase the risk of certain circulatory problems.
Researchers discovered that standing for extended periods did not reduce the risk of heart disease and stroke. In fact, spending too much time either sitting or standing was linked to a higher risk of problems such as varicose veins and feeling dizzy or lightheaded when you stand up.
I’m pretty sure that any position is bad if you are not moving for a prolonged period of time. AFAIK the clue is to change positions as much as possible and standing desk can help with that because well, there are only so many ways you can sit.