Software engineers aren’t the only ones who spend much of the day sitting. But we certainly do a lot of it. This is just one case, but I can certainly attest to this: Being physically fit absolutely helps with focus and productivity at work.
Scientific American: Workout at Work May Up Productivity
Exercise Boosts Work Productivity
UCLA Health: How nutrition and exercise can increase productivity and lower health care costs
Exercise promotes productivity in business says Bobby Kerr
Time Management Ninja: 5 Ways That Exercise Increases Your Productivity
McPherson Sentinel: Exercise aids productivity
This list of articles on this subject goes on and on.