Try the pomodoro technique! You do focused work for 25 minutes and then take a 5 minute break. After two hours you take a longer break and have a snack or lunch or go for a short walk. During the short breaks you can fit in some working out, crunches, squats, whatever. I've looked up short workouts that are maximum five minutes of length that I do. When on break you should get up from your desk, go grab a coffee, walk around the room, do some stretches or whatever.
I know it sounds like it's a lot of breaks but in 25 minutes of complete focus you get HUGE amounts of work done. When I use the pomodoro technique I get more work done in one day than I usually do in two days or even more of working several hours in a row without breaks. Look it up on the Internet. There are pomodoro timer apps for Google Chrome that you can use.
Gud luck rechardo n.
Tin@ h.. great :) nd gud luck