I found the below link which is in the spirit of Lifestyle interventions to increase longevity:
3 Short Walking Breaks Can Reverse Harm From 3 Hours of Sitting"
The /.-summary:
> Medical researchers have been steadily building evidence that prolonged sitting is awful for your health. One major problem is that blood can pool in the legs of a seated person, causing arteries to start losing their ability to control the rate of blood flow. A new experimental study (abstract) has discovered it's quite easy to negate these detrimental health effects: all you need to do is take a leisurely, 5-minute walk for every hour you sit. "The researchers were able to demonstrate that during a three-hour period, the flow-mediated dilation, or the expansion of the arteries as a result of increased blood flow, of the main artery in the legs was impaired by as much as 50 percent after just one hour. The study participants who walked for five minutes for each hour of sitting saw their arterial function stay the same — it did not drop throughout the three-hour period. Thosar says it is likely that the increase in muscle activity and blood flow accounts for this."
I'm reasonably sure it depends on the sort of interrupt. This is based on introspection, so it's not very reliable, but an interrupt that involves thinking about something different-but-similar is murder, while e.g. switching tracks entirely to reading a book doesn't seem to be nearly as much of a problem.
Getting up to take a walk is something else again; it doesn't actually break my concentration at all, I'll still be thinking about the same problems while walking.