Dr. Mercola addresses the negative side affects from sitting for too long. He even points out that vigorously working out for an hour or two and then sitting for most of the day may even cancel out the health benefits of the workout.
Marcelo came up with 5 health tips for those who have jobs that require them to sit for long periods of time while at work. One philosophy to go by is standing is better than sitting, and walking is better than standing. Check out the article above to find out more about the correlation between sitting and health.