The effects of going from lower to higher gravity

[Blackhawk748]

Simple question for a Sci Fi setting Im making. What are the general effects of going from a 0.9 or 0.8 Earth gravity to a 1.0 Earth gravity? Is there just some discomfort? Are there long term health issues? (bone issues, heart problems?) Are the issues minimal?

Rather curious.

[factotum]

For such a small difference I doubt you'd notice. You might find climbing stairs a bit harder, and your chap born and raised in 0.8g will be taller and more slender build than his regular counterpart, but it's certainly not going to be debilitating.

You could probably simulate this quite well by simply wearing a backpack containing about one-fifth of your bodyweight in ballast, I'd have thought.

[Kaptin Keen]

For such a small difference I doubt you'd notice. You might find climbing stairs a bit harder, and your chap born and raised in 0.8g will be taller and more slender build than his regular counterpart, but it's certainly not going to be debilitating.

You could probably simulate this quite well by simply wearing a backpack containing about one-fifth of your bodyweight in ballast, I'd have thought.

That's still 20% - in my case, like, 18 kilos. All the time. It wouldn't kill me, but I'd certainly notice =D

And carrying 18 kilos up all stairs all the time (until I'd adjusted) would make me take elevators - something I otherwise never do.

[Mastikator]

I guess the stress on your heart could potentially be severe, the heart would be acclimated to pump blood at a specific gravity and at higher gravity the heart would have to work harder or you risk death. If you step it up slowly tiny bit by bit then I think you could get used to it, not much different than regular exerciser. Going from 0.8g -> 1g might be bad for you and you but hopefully you can just lay down to rest with regular intervals.
Going from 1g -> 2g would probably make the average person pass out and put their health and life at risk.

[Blackhawk748]

For such a small difference I doubt you'd notice. You might find climbing stairs a bit harder, and your chap born and raised in 0.8g will be taller and more slender build than his regular counterpart, but it's certainly not going to be debilitating.

You could probably simulate this quite well by simply wearing a backpack containing about one-fifth of your bodyweight in ballast, I'd have thought.

So noticeable and rather uncomfortable and annoying.

I guess the stress on your heart could potentially be severe, the heart would be acclimated to pump blood at a specific gravity and at higher gravity the heart would have to work harder or you risk death. If you step it up slowly tiny bit by bit then I think you could get used to it, not much different than regular exerciser. Going from 0.8g -> 1g might be bad for you and you but hopefully you can just lay down to rest with regular intervals.
Going from 1g -> 2g would probably make the average person pass out and put their health and life at risk.

Or it could be rather problematic for your heart. I suppose it would depend on the heart in question?

[Fyraltari]

So noticeable and rather uncomfortable and annoying.



Or it could be rather problematic for your heart. I suppose it would depend on the heart in question?

Well human hearts are optimized for 1g so a human raised in a 0.8g environment would have a easier time adapting to 1g than an alien whose species is native to such an environment. But an adaptation period is going to be necessary. I am reminded of how people who climb the Everest are obligated to spend days at higher altitudes so that their body can adapt to the lesser amount of oxygen in the air.

[factotum]

Yeah, their heart is going to have to work a bit harder than it's used to, but hearts are actually pretty good at that--otherwise you'd keel over and die every time you went above walking pace, which would be slightly inconvenient. Unless they have a naturally weak heart, the worst I'd expect to happen is their life be shortened by a few years due to an early(ish) heart attack.

I recall that Larry Niven mentioned in one of his Known Space books that the inhabitants of Jinx (a world with a surface gravity around 1.5x Earth's) are short, wide and very strong, but they tend to die early of heart failure. I have no idea if he was basing that on actual medical projections or if he just made it up on the spot, though.

[Blackhawk748]

Well human hearts are optimized for 1g so a human raised in a 0.8g environment would have a easier time adapting to 1g than an alien whose species is native to such an environment. But an adaptation period is going to be necessary. I am reminded of how people who climb the Everest are obligated to spend days at higher altitudes so that their body can adapt to the lesser amount of oxygen in the air.

Yeah, their heart is going to have to work a bit harder than it's used to, but hearts are actually pretty good at that--otherwise you'd keel over and die every time you went above walking pace, which would be slightly inconvenient. Unless they have a naturally weak heart, the worst I'd expect to happen is their life be shortened by a few years due to an early(ish) heart attack.

I recall that Larry Niven mentioned in one of his Known Space books that the inhabitants of Jinx (a world with a surface gravity around 1.5x Earth's) are short, wide and very strong, but they tend to die early of heart failure. I have no idea if he was basing that on actual medical projections or if he just made it up on the spot, though.

So an alien from a low grave world would need an acclimation period (a month or so?) and to probably take some extra nutrition to encourage heart health, but would otherwise be fine?

[factotum]

So an alien from a low grave world would need an acclimation period (a month or so?) and to probably take some extra nutrition to encourage heart health, but would otherwise be fine?

I would say so, yes. As I said, their overall lifespan might be a bit shorter due to the extra strain on their heart, but I suspect that's not likely to make much difference to your story unless they've been on this planet for a LONG time.

[Radar]

So an alien from a low grave world would need an acclimation period (a month or so?) and to probably take some extra nutrition to encourage heart health, but would otherwise be fine?

The additional workload on the heart there is due to blood pressure distribution in the body (1 bar per meter in 1 G) - this will depend a lot on the heigth of a given individual. For humans the brain is on the top of the body about 40 cm above the heart, so going from 0.8 G to 1 G would mean 0.08 bar pressure difference (60 mmHg), which the heart needs to compensate and a jump by 60 mmHg is a serious ammount of work. When we go from idle to full-on physical excersises the difference in peak pressure is less then that. Basically the heart of a 0.8 G world inhabitant standing on Earth would need to work harder then it ever did assuming the same height and overal body proportions.

There is also the problem of varices. It is very common for people to develop them over time anyway, since the blood pressure in legs is significantly higher than around the heart. Since the pressure in the brain needs to remain roughly constant, then going from 0.8 G to 1 G would mean an additional 0.2 bar (150 mmHg) around the feet for a person 2 m tall. Without additional support the blood vessels in the legs would fail pretty quickly. Proper therapeutic high stockings might help significantly here.

Come to think of it a well tailored full-body suit could be made to compensate those pressure effects decreasing the strain on both the heart and the blood vessels. With that out of the way (maybe) the key remaining problems are mechanical (muscle and bone endurance) and overal physical condition, which can be trained over time.

[warty goblin]

Aside from heart problems, I suspect a low gravity person would find themselves alarmingly breakable in higher Gs. Given that astronauts lose appreciable bone mass from an adult from due to pretty limited time in zero G, I'd expect at least some effect due to growing up in lower G. Not only is walking going to be hard due to the extra weight, but tripping is going to be a lot worse for our low G visitor than it is for us.

[factotum]

Aside from heart problems, I suspect a low gravity person would find themselves alarmingly breakable in higher Gs. Given that astronauts lose appreciable bone mass from an adult from due to pretty limited time in zero G, I'd expect at least some effect due to growing up in lower G. Not only is walking going to be hard due to the extra weight, but tripping is going to be a lot worse for our low G visitor than it is for us.

I wouldn't call 0.8g really "low gravity" in that regard, though. A person born and raised in that environment will tend to be taller and more slender than a regular human, but I don't think it's enough of a difference that they'd be seriously risking breaking their legs as soon as they set foot in the higher gravity environment.

[Peelee]

For such a small difference I doubt you'd notice. You might find climbing stairs a bit harder, and your chap born and raised in 0.8g will be taller and more slender build than his regular counterpart, but it's certainly not going to be debilitating.

You could probably simulate this quite well by simply wearing a backpack containing about one-fifth of your bodyweight in ballast, I'd have thought.

I now choose to believe that my getting fat was based on experimenting with a simulation of a 0.8g environment person goi g to 1g.

... Well, maybe 0.9g origin would be more accurate.

Aside from heart problems, I suspect a low gravity person would find themselves alarmingly breakable in higher Gs. Given that astronauts lose appreciable bone mass from an adult from due to pretty limited time in zero G, I'd expect at least some effect due to growing up in lower G. Not only is walking going to be hard due to the extra weight, but tripping is going to be a lot worse for our low G visitor than it is for us.

There's a massive gap between low gravity and microgravity, though.

[Lvl 2 Expert]

So an alien from a low grave world would need an acclimation period (a month or so?) and to probably take some extra nutrition to encourage heart health, but would otherwise be fine?

Heart health is a tricky thing, at least in humans/Earth mammals (possibly all vertebrates? I don't really know how far this goes.)

When our heart needs to pump harder we don't actually make any new heart cells. The cells grow bigger, and so does the internal space of the heart, but this does not result in entirely the ideal healthy situation but upscaled. The hearth also doesn't really do shrinking down again. Had a medical condition that forced your heart to pump harder? It's now bigger fir the rest of your life, and that itself can cause complications. You even see this in Olympic athletes and the like, after they retire they sometimes just drop dead of heart failure at the age of 50 or so, partially because of their enlarged hearts, which they have because they lived super healthy and sportsy (PSA: this is still a better heart condition to have than the alternatives caused by not doing anything all day, don't be afraid of sports.) So assuming the alien is humanlike in this aspect but not actually a human evolved to deal with 1g they might develop a heart problem a bit like that.

[Blackhawk748]

Heart health is a tricky thing, at least in humans/Earth mammals (possibly all vertebrates? I don't really know how far this goes.)

When our heart needs to pump harder we don't actually make any new heart cells. The cells grow bigger, and so does the internal space of the heart, but this does not result in entirely the ideal healthy situation but upscaled. The hearth also doesn't really do shrinking down again. Had a medical condition that forced your heart to pump harder? It's now bigger fir the rest of your life, and that itself can cause complications. You even see this in Olympic athletes and the like, after they retire they sometimes just drop dead of heart failure at the age of 50 or so, partially because of their enlarged hearts, which they have because they lived super healthy and sportsy (PSA: this is still a better heart condition to have than the alternatives caused by not doing anything all day, don't be afraid of sports.) So assuming the alien is humanlike in this aspect but not actually a human evolved to deal with 1g they might develop a heart problem a bit like that.

So the Doctors would have to keep an eye out for heart failure then. Got it. I would presume they'd do a bit more intensive inspections during their normal physicals to make sure they're all right.