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It's my perception that discussions of the use of artificial gravity for manned deep-space travel missions are primarily centered on avoiding bone loss. Am I right so far? Microgravity seems to be fairly agreeable to most of the popular reports and YouTube videos, except possibly for issues of sleep difficulty, loss of some sensation of taste of food, and potential eyesight degradation.

I think the idea is that bones that do not experience "normal" regiments of strain will start to loose calcium. Is the idea behind the discussions of artificial gravity for long missions that it will help reproduce this type of strain to the bones?

Does each bone need to experience strain separately - is it localized, or is it more systemic. Put bluntly, will straining my tibia reduce decalcification of my ulna?

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Just a partial answer, limited to this part of the question:

Does each bone need to experience strain separately - is it localized, or is it more systemic.

Bone growth is definitely controlled locally, in response to the stress applied to each part of the bone.

Humeral hypertrophy in response to exercise (Jones 1977) described thickened bone in the dominant arms of tennis players.

Also a more modern paper with a more modern looking density plot (Taylor et al 2008) describes bone density in the arms of one tennis player as well as attempts to match these with a simplified mechanical analysis.

The X-ray images revealed a significant increase of bone density in the right upper arm. The bone mass density index of the humeral shaft was found to be 24% higher in the dominant right arm as compared to non-dominant left arm. These values represent the average bone mass density of the entire humerus shaft. Since bone adaptation is an extremely local phenomenon that primarily affects selected regions of bone, we conclude that the local density increase is significantly higher than just one fourth.

(Taylor et al, "The phenomenon of twisted growth: humeral torsion in dominant arms of high performance tennis players")

Bear in mind these high bone densities have built up over many years as these are long-term players. So these should probably be seen as relatively extreme examples, but they prove the principle.

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  • $\begingroup$ Looks good. Have to be careful of even the most common-sense assumptions with biology and medicine. Bone growth and densification due to extended, enhanced exercise may not be the same mechanism as rapid decalcification in due to lack of strain in microgravity. Most biological systems have multiple feedback loops in different pathways. most systems have both up-regulators and down-regulators. While I would guess that in this case one does imply the other, in biology you never know until you really know. $\endgroup$
    – uhoh
    Jun 6, 2016 at 18:15
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    $\begingroup$ Sorry, I've no idea what research is being done into artificial gravity conditions. I only happened to know of the bit about local bone growth in response to stress. $\endgroup$
    – Andy
    Jun 8, 2016 at 14:04
  • $\begingroup$ Partial, but the most important part! $\endgroup$
    – uhoh
    Jun 8, 2016 at 14:13
  • $\begingroup$ Do we know how microgravity induced loss is distributed? I assume that leg strain is reduced more than arm strain - astronauts still have to reach for things, operate equipment, grab hold of things, and so on. $\endgroup$
    – Russell Borogove
    Jun 9, 2016 at 3:00
  • $\begingroup$ @RussellBorogove - well if they do a few hours exercise a day including treadmill running, that might put some impact stresses on the leg bones and partially reduce losses there. I didn't find anything published though. $\endgroup$
    – Andy
    Jun 9, 2016 at 7:07

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