The reason you sit up straight, and avoid slouching are because it helps you keep your spine and pelvis straight. When you slouch you are putting the pressure on your low back, your tailbone, which will in turn put a lot of pressure on your spinal cord. This can eventually lead to back pain, fatigue, and even damage to the discs that cushion your vertebrae. Not only does sitting up straight help keep your spine aligned but it also helps keep your buttocks strong.
Many people spend a long time working in front of a computer which involves sitting for long periods. I’m sure you can guess what happens when one sits in chairs for too long. A sub-standard chair will start to lean back, which puts the weight directly on the back of the neck and shoulders, not the abs. The extended angle of the lower back often puts unnatural pressure on the tailbone, which in turn puts additional pressure on the spinal cord. For quality Reception Chairs, go to Best Buy Office Chairs
Now, it is true that if you have to sit down for a long time it’s extremely important not to slump into the chair. You don’t want to end up with poor posture, that is how you start to get back and neck problems. However, that doesn’t mean you should never sit down for more than two minutes. I think that it’s fine to occasionally sit for 30 minutes at a time but you should aim to stretch and move around at least once every hour.