So... what if you built a sphere, filled it with water, and then used a dynamo and spin it. It really wouldn't take much; a system spending that long in space is going to need water for shielding and drinking anyway.... with a hydrolisis machine you can recycle the O2.. anyway.. you put a bunch of water in a sphere, give someone a breathing mask, and let them walk around the edge like a hamster. I can see the devastation if the O2 mask fails... where are you going to put the H20 and how are you going to do it fast enough; but... as long as it's spinning you can simulate gravity and wield density to create an artificial weight lift. You could adjust the rotation for just walking; walking uphill, running uphill... hell you could get magnetic gloves and boots; put magnets on the outside of the glass and do push ups and tricep curls at the same time.

Would you even need to spin anything? Exercise is just resistance against force like gravity, so it would be much simpler to just get a few elastics or wear some weights or something, right?

Wear some weights. In space....
But the elastics is a good idea though

inertia is also a resistance

yeah, you spin it so you aren't just floating there...

But the weights thing... remember that in aeronautics that every bit matters. Weights could make it more expensive

I didn't even think of that lol

of course it would make it more expensive. I'm not considering cost.... I'm thinking about something that works. Running on treadmills delays it, but it doesn't come close to doing the job of helping the human body take care of itself on long voyages... plus, doing it for 4 hrs a day is just inefficient.

and I mean spinning faster = more resistance, you don't even have to bring a weight with you.