Bad posture can certainly restrict veins and increase the pressure causing them to swell. Sitting in a wheelchair for example hardly speeds up recovery does it? I believe wheelchair posture makes sure people stay in wheelchairs, and that sitting in an inclined posture, rather than the bucket seat type posture found in most cars and closely resembling the poor wheelchair posture with knees higher than the seat is compromising not only the circulation in the arteries and veins but also the cerebrospinal fluid circulation, the lymphatic circulation and the peripheral nerve circulation.

Furthermore, sitting for too long on a firm chair will undoubtedly increase blood pressure.

Having the hands at the keyboard for example with them raised slightly higher than the elbows will induce numbness in fingers, tingling, and even some loss of function in healthy people. I have experienced this and experimented with posture.

So according to my own research at least, your seat should be at least level with your knees. A foam wedge cushion can be purchased to take the dip out of the bucket type sitting position and used in cars. I am sitting on one right now typing this.

Andrew