I am also fortunate in that I do not have a desk job.  I spend time walking at work about half of the time.

Back in my youth, I use to run track and got a scholarship offer to be on a track team. 

I started the run after the bike ride about 11 months ago.  It took me three months to be able to run the whole thing.  I am still getting faster at it.  The run has added quite a bit to how I feel.  I also have much more energy than a year ago.