Introduce small, basic workout areas in the airports with just a couple of showers and fitting rooms.
You have 2-3 or more hours of waiting time. You cannot do much other than sit around. Why not get some exercise?
There is only one real gym in an airport worldwide (Baltimore/Washington), yoga rooms are a bit more common. The reason is airport space is very expensive and it is hard to make a profit from a gym. However, small, basic rooms would be enough for people to get some exercise.
By exercising before or between flights you:
Compensate for the health impact of long sitting hours during the flights.
Spend your time while waiting for your flight, without further sitting.
Similar to airport yoga rooms only that visitors can do heavier exercise (and make more noise).
Rooms big enough to fit 3-4 people (depending on the demand and the available space).
Basic (mats, small weights) or no equipment. People can do body weight exercises (Calisthenics style).
A couple of changing rooms (travelers bring a change of clothes in their backpack or carry-on, no shoes while working out).
A couple of showers and ideally towels.
If need be, the entrance will have a small fee.
What do you think? Would you workout in these areas?