Nice study that explains why sitting for long periods is so unhealthy - it reduces blood flow to the brain (cerebral blood flow) . The results from a study conducted in the United Kingdom (UK) found that prolonged, uninterrupted sitting (4 hours in the study) in healthy office workers reduced cerebral blood flow. However this was offset when frequent, short-duration walking breaks were taken - about 2 minutes of walking every 30 minutes. However, taking a 8 minute walking break every 2 hours did not have the same positive effect - even though that was the same amount of walking over the 4 hour period.
Maintaining good blood flow to the brain is a great reason to stretch your legs and walk a few minutes whenever possible, preferably at least every 30 minutes - whether at work or at home. From Medical Xpress:
A team of researchers with Liverpool John Moores University in the U.K. has found evidence of reduced blood flow to the brain in people who sit for long periods of time. In their paper published in the Journal of Applied Physiology, the group outlines the experiments they carried out with volunteers and what they found.
Suspecting that sitting for a long time could cause circulation problems to the brain, the researchers enlisted the assistance of 15 adult volunteers—each of them had a day job that required long hours of sitting. Each of the volunteers participated in three exercises over a period of time—each came to the lab on three separate occasions and sat for four hours. On each visit, they were fitted with a headband that measured blood flow to the brain using ultrasound. Each subject also wore a face mask that captured and measured carbon dioxide levels.
During the first exercise, the volunteers were asked to sit at a desk for four straight hours, leaving their chairs only to use the restroom. For the second exercise, each rose from their chair every 30 minutes and walked on a treadmill for two minutes. In the third exercise, each subject remained in their chair for two hours and then walked on the treadmill for eight minutes, then returned to the chair.
The researchers found evidence of reduced blood flow in all of the volunteers during all of the exercises. However, they also found that normal blood flow was restored by walking breaks. They report that the best outcome was when the volunteers took frequent two-minute walking breaks.