A partial answer: according to Garret Erin Reisman, professor of astronautical engineering and former SpaceX human spaceflight developer, the current state of knowledge is that you can get around a loss of bone mass almost entirely by proper exercise.
The key to this is that bone loss is basically an issue of a lack of stimulation, and not a lack of ...
How will Starship ... accommodate micro-gravity?
As of today, it won't.
Making non-micro gravity by spinning about its long axis is impractical
because the ship's radius is only 15 feet.
have made detailed calculations for spinning about other axes.
This is the kind of thing that helps SpaceX
cultivate its bonkers-but-works reputation, but SpaceX ...
The technical term for them is "handrail".
Image source: http://www.hunchdesign.com/uploads/2/2/0/9/22093000/restraint_and_mobility_aids.pdf
IVA (IntraVehicular Activity) Handrail if you want to be formal.
Table source: https://snebulos.mit.edu/projects/reference/International-Space-Station/SSP50008RC.pdf
Seems unlikely astronauts would spend much time bare foot in the ISS, for example. There are blue handrails on different surfaces, in all four orientations, where astronauts secure themselves by sliding their feet underneath. You can see the handrails at the bottom left, top right (two on the "ceiling" and more on the right "wall"), and especially at the ...