I've only just discovered this author but this atricle led me to many others, all excellent.
The gist is that even if you exercise regularly, if you then sit for the balance of the day, you are doing your body real damage. The author, Gretchen Reynolds says in the article; http://www.nytimes.com/2012/04/29/sunday-review/stand-up-for-fitness.html?ref=gretchenreynolds "So now every 20 minutes I rise" she spends as much time as possible moving, even just standing up yields results.