As with many things, the exercise problem gets a lot easier if you have plenty of space to work with. That is why the first virtual moon colony being made is something pretty developed, to really assess the potential. Two things are being put in for exercise that hopefully could make a big difference. One is a human-powered centrifuge, a variation on the kind used to test human tolerance to high g forces. One the German space agency has is shown below:
|You go in the box then it spins real fast|
In the low gravity of the Moon, two or three people could slowly spin up something much larger until the effect was like a full gravity pressing people against the outer wall of a connected wheel, like old-fashioned Rotor amusement park rides. As evidence it really doesn't take that much power to revolve such a structure fast enough, I recall two older boys once had some fun spinning a roundabout, which is similar, so fast that i was no longer strong enough to hold on and went flying off, and i was not the only squealing kid on the ride begging them to stop. Ah, childhood... This is how long-term memories are formed...
|Fun ride and torture device|
|The people in the middle spin the wheel|
|Just a schematic. My 3d model skills are still immature...|
To be really effective, those on the wheel would need to do exercises while under that force, stuff that loads there bones and muscles well. Squats, push-ups, sit-ups, chin-ups, lunges, stuff like that. Just being on the wheel though would also be helpful. The crew on the International Space Station have some difficulties because there is no gravity keeping fluids properly distributed in their bodies, and so it collects in their upper bodies and especially in their heads. Pressure on their eyeballs due to that is the leading explanation for the vision problems they often have. Their sinuses also often get clogged. Being on the wheel would provide relief from that. The wheel has a wide enough radius to limit the dizziness people feel on such structures when they move their heads around - in this model it is 12 m. Spending an hour or more on it shouldn't cause nausea, though it might take people a bit to adapt to the sensations.
It isn't until we contemplate a space large enough for such an innovation, with the infrastructure in place to create it right there on the Moon so the expense isn't exorbitant, that we can really get our juices flowing and imagine a future colony in detail. This is hopefully a good example of that process. In the next few days i'll post about another very useful exercise option - swimming pools. That implies a lot of infrastructure too, more than this does even. But that is the goal, right? The thing is to outline the path leading there better and better.