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Let's say that at an asteroid mining site, the workers live in a rotating wheel space station that can produce 1g. They use Earth's 24 hour day, and for 8 hours a day, people go to the asteroid to work, which means they experience 8 hours of microgravity. When they're not working, people live in the rotating station.

My question is, can the people in the space station stay healthy by just being in the space station, assuming their level of activity is about the same as most people on Earth? Or would they need special exercises like astronauts in the ISS?

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  • $\begingroup$ Would this be the equivalent of climbing up and down a very steep hill everyday? $\endgroup$ – nzaman Apr 25 '18 at 12:19
  • $\begingroup$ wouldn't the work be physical? I think the amount of necessary sport depends a lot about the work itself $\endgroup$ – Kepotx Apr 25 '18 at 12:34
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    $\begingroup$ Long term lack of "proper" gravity isn't the only threat to human health in space. For example, a space station in earth's orbit is still partially shielded from radiation by earth's magnetic field. Once you get far enough away from earth you are subject to potentially loads of radiation coming from all sorts of sources. $\endgroup$ – r41n Apr 25 '18 at 14:04
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    $\begingroup$ Adding to @r41n 's comment, are you only concerned about effects of the micro-gravity, or also from other effects of long durations of space exposure? Also, if you are interested in other effects, please provide more details on the work environment and gear the people use (so we can know how protected are they). $\endgroup$ – Rick M. Apr 25 '18 at 21:19
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    $\begingroup$ Consider that sleep time effectively adds to your 8 hours. While it's not the same in many ways, laying down has been used in several studies as proxies for weightlessness. $\endgroup$ – CircleSquared Apr 25 '18 at 23:04
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Short term, sure. Long term, unknown.

We have astronauts who have spent very long continuous periods in microgravity. The effects are known or at least hinted at. Modern science has no data whatever on rapidly alternating periods of normal and microgravity. The effects will probably take years to develop and can't be predicted in advance. Exercise in 1g would certainly help with mitigating the effects of time spent in microgravity.

However, there are many examples where science enables some new thing then discovers years or decades later that really bad things happen as a result. Examples include but are certainly not limited to cures for morning sickness, mosquito suppression, plastic liners in bottles, microbeads in lotion, burning coal for energy, fixes for engine knock.

This isn't all bad though since this gives the Author an opportunity to create a disease of their choosing to move the story forward. The disease will of necessity be subtle and not what the miners or the doctors are expecting. It should take a long time to develop because if the onset of the disease were fast, it would be easy to track down the source.

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Yes, we could stay healthy

To my understanding the reason behind the weakening of a mars colonists bone structure is that they are permanently experiencing low gravity and their body is "overequipped" for that. So over an extended period of time the body will build less bone support. (People born on Mars would never even have a bone structure as strong as ours)

In my opinion the bone structure would not decay as it is still required daily. They would severely struggle for 16 hours a day if the structure was weakened. There is still a need for that, just as there is on earth.

So there would be no or barely any decay in the structure and thus no impedance of ones health.

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    $\begingroup$ I'm not sure Mars gounts as micro gravity, you pretty much need to be in free fall or deep space for that $\endgroup$ – jk. Apr 25 '18 at 14:22
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    $\begingroup$ @jk.: Mars has much higher gravity than microgravity. I am aware of that. But even this slight difference in gravitational pull makes a huge difference regard bone strength. Obviously even lower gravity than mars has a bigger impact. So my explaination is not challenged. $\endgroup$ – ArtificialSoul Apr 25 '18 at 14:27
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    $\begingroup$ @jk.: The focus isn't on the degree of microgravity, but rather the frequency one is subjected to non-microgravity environments. The Mars colonist argument relies on a long-term uninterrupted exposure to a lower gravity. Their bodies would stop accounting for being able to handle "normal" gravity as they haven't experience "normal" gravity for an extended period. The miners, on the other hand, experience "normal" gravity daily, so they would immediately notice any change in their body that compromises their ability to handle "normal" gravity.Their bodies don't get enough time to adapt to MG. $\endgroup$ – Flater Apr 26 '18 at 9:51
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Your astronauts are going to be the healthiest and most jacked humans ever.

Why?

The body can adapt to nearly any stress, but it needs to cycle between high stress and low stress moments.

If there is only stress or only relax you see a decline in health and eventually shorter lifespan.

If your astronauts experience 16 hours of normal gravity and 8 hours of 0 gravity, it's fine and nothing would change much. But if they do any form of gymnastic activity 2-3 times a weak they will be automatically jacked and incredibly strong because their bodies have 8 hours of 0 muscular and bone stress every single day, they would probably be compared to steroid users in therms of strength and level of fitness while also retaining normal health.

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    $\begingroup$ Can you back up any of those statements? $\endgroup$ – Samuel Apr 25 '18 at 22:02
  • $\begingroup$ For me this is good schi-fi plot seasoning. I'd handwave arguments away just for the good story-telling opportunity :) $\endgroup$ – brett Apr 26 '18 at 9:54
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The weightlessness experienced by astronauts is fun, but it is not without consequence.

The human body was designed for lazyness. That is why it takes so little effort to be overweight, but it takes effort to stay slim. When you don't exercise, muscle is replaced with fat, and bones grow thinner.

A regular person living in 1g will at least put their legs' bones and muscles to work a little whenever walking around, and their arms muscles and bones when doing things like using forks, knives or hashi for eating. In space, the lack of weight makes these activities so much easier, so the muscles and bones get less stress. In response, they grow weaker. And it's not just the limbs. The heart and lungs start getting lazy too.

From the ESA site for kids, on bone loss:

Space research is helping scientists to understand what happens and to find a way to combat the problem.

One method is to use volunteers who stay in bed for many weeks. These bed rest studies show how bones change when no weight is being put on them.

I've been emailing them for years now, volunteering myself. I could to that in a home-office setting even.

Anyway, exercising in space helps the body stay in shape, and helps avoiding osteoporosis. If your miners do go under 1g for most of the day, then they should be getting more stress on their muscles and bones than an astronaut at ISS would. They should not need to exercise in order to avoid weightlessness related problems. They should exercise, anyway, because it takes more than just an apple a day to keep the doctor away.

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    $\begingroup$ Thanks, COLBERT! $\endgroup$ – corsiKa Apr 25 '18 at 22:32
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    $\begingroup$ Your logic is arbitrary and non-sequitur: "A human body that is not exercised grows weak" -> "Therefore, the human body was designed for lazyness [sic]." One could more sensibly conclude from the same data that the human body was designed for motion. $\endgroup$ – Wildcard Apr 26 '18 at 2:21
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    $\begingroup$ Try your logic on another subject: "A car that is not oiled will break down and cease to drive." -> "Therefore, cars were designed to sit still." $\endgroup$ – Wildcard Apr 26 '18 at 2:22
  • $\begingroup$ @wildcard a car engine's HP does not vary whether it is used once a week or everyday. Apples and oranges. $\endgroup$ – Renan Apr 26 '18 at 9:50
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    $\begingroup$ "That is why it takes so little effort to be overweight, but it takes effort to stay slim." Ehm... it takes little effort to stay slim (don't work, don't eat) and it takes a lot of effort to be overweight (food needs to be grown, collected, fed to animals, etc.). Regardless of exercise, excess food is turned into fat to survive times when there is less food. When you don't exercise and you eat little, no muscle is going to be replaced with fat. $\endgroup$ – David Mulder Apr 26 '18 at 14:27
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As far as I know there are no studies on this kind of regime, probably because sending people on a 8 hours commute to space is really expensive.

Nevertheless there are evidence that constant physical activity helps in reducing part of the collateral damages induced by microgravity.

Being in a normal gravity environment for 2/3 of a day is also a way of removing the body from microgravity. So I think in the worst case scenario it would simply spread the damage over a longer time span, but it would still be beneficial.

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