Here's a link to a quick overview of 5/3/1: http://www.tmuscle.com/free_online_a..._pure_strength
I wouldn't just add more sprints in and expect to get the same benefit as easy walks a few times/week.
See this link
, 3rd block down on easy conditioning.
Intervals/sprints are more useful for most people, however there is a place for walking and other low intensity steady state activity. Take your lunch hour, walk for 30 minutes and then spend the other 30 eating and get back to work. Add in an hour on a weekend and you'll get 2.5-3 hours/week. Not bad when you add up the other movement.