My approach is to drink a lot on the flight (both water and... "other") so that I have to pee a lot. The walking to/from the lav accomplishes the walking about goal
We do a lot of walking and exercise before/after flights...and maybe not as much during (especially on flights like LAX-LHR) as we should.
Cheers.
We follow the same approach.
I also try to walk at the airport before boarding and I hardly ever use moving walkways or trains unless there is no choice or I'm late for a connection.
Even at SFO, when I exit BART I walk. They keep trying to isolate T2 with nearby construction, but there is always some way to get there.