Here's a good way to fight the sedentary lifestyle. Most of us sit down to work these days, and we keep getting told lately that sitting = smoking for badness. So, I've been doing this thing that seems to help not only keep the blood moving, but the time be more useful in general.
Get one of those old fashioned clicky egg timers. Set it for 25 minutes and put it down on the other side of the room so you're not looking at it. When it rings, get up immediately and set it for another five minutes.
In that five minutes, you'll be amazed at what you can do. Hang up a load of laundry. Feed the cat and put the kettle on. Do fifty jumping jacks and twenty crunches/sit-ups. Clean the bathroom sink. Do anything that does not involve sitting down. When it goes off, set the timer for another 25 minutes.
You'll be amazed at how much more you get done when you know the timer is ticking down. I had friends coming over for dinner a couple of weeks ago, and had to both work and get the house cleaned up and dinner on and I just did it all in five minute increments throughout the day. Worked like a charm.
What do you do?