In practice it would mean taking periodic breaks to walk around a bit, and trying to arrange things such that you could walk some of your commute, or walk to the store, etc
Obviously harder for people in suburbia.
True, takes some adjustments... When I drive somewhere, I try to park at the back of the parking lot for a bit of a walk (bonus: keeps your car dent free too).
When I go check my mail, I walk to the end of the block first and get it on my way back (bonus: get to keep an eye on my neighborhood and say hi to some neighbors).
When I drop my daughter at school we park a block away and walk in (bonus: get to spend more time with my daughter and meet some other parents).
These changes all sound trivial, but from my fitness tracker I can attest that they make a quantifiable difference, especially when you look at it over a month. Additionally, those other little bonuses contribute to overall happiness.
Here's another: when I'm in a multi story building, I almost never take the elevator down. If the building is less than five stories I'll generally take the stairs up too, often at a light run.
One more: stairs instead of escalator. At minimum, walking on an escalator.