[tveita]

Spending too much time sitting down is believed to increase mortality even if you exercise regularly.

E.g. http://www.health.harvard.edu/blog/too-much-sitting-linked-t...:

“Even if you are doing the recommended amount of moderate to vigorous exercise, you will still have a higher risk of mortality if you’re spending too many hours sitting,” says Dr. JoAnn Manson, one of the study’s authors, and chief of preventive medicine at Harvard-affiliated Brigham and Women’s Hospital.

[fidz]

What is "too much"? So what should we do? In school, we studied in class by sitting on the school chair. That habit continue in campus. Also, some worker are forced to do their job by sitting (e.g. taxi driver, pilot).

Btw, The article said that 8+ hours and it applies to woman.