Jeff,
I'm trying to determine why this study might be contradicting earlier studies. It suggests just 40 minutes of vigorous exercise can counteract 10 hours of sitting a day. It seems that earlier studies suggested that if you don't break up the sitting more often, there's no way of doing that damage of even 4 hours of sitting, at least not in such a short time frame.
https://bjsm.bmj.com/content/54/24/1499
Thanks,
Doug