11
$\begingroup$

If suddenly put in a low gravity as on the Moon or on Mars, humans should feel very strong, easily breaking some olympic records for example. Apollo astronauts have said that they did not get tired from walking, carrying and working all day on the Moon. They just got tired in their fingers because of the bending resistance of the pressurized gloves (the excitement might have affected their perception, it is anecdotal afaik).

Would the muscle volume adapt to the lower gravity within a few months, making humans as relatively weak as we are on Earth? Are there reasons to believe that weight lifting exercises in low gravity can be efficient enough to retain the human Earth adapted strength?

$\endgroup$
  • 1
    $\begingroup$ I think this is a great question except for one completely wrong word - superpowers. Because they aren't super in any way. I am pretty certain we do have some duplicates here though: space.stackexchange.com/questions/132 is probably the nearest $\endgroup$ – Rory Alsop Jun 7 '15 at 9:42
  • $\begingroup$ @RoryAlsop I put it in quotes. It is certainly perceived as superpowers as in superman. I am more specifically, than the other question about heavy clothes, asking about the practical strength after some months in low or mid gravity. If the masses then will feel as heavy as on Earth because of muscle loss. $\endgroup$ – LocalFluff Jun 7 '15 at 9:55
  • $\begingroup$ Local - have an upvote from me then :-) $\endgroup$ – Rory Alsop Jun 7 '15 at 10:20
  • 2
    $\begingroup$ Do you have a source for the claim that Apollo astronauts weren't fatigued? The EVA suit plus life-support backpack massed 91kg, which still had to be moved by muscle power even if the lifting aspect was only 1/6 as difficult as usual. At various points in lunar EVA, Neil Armstrong's heart rate ranged from 120 to 160 bpm, and rest periods were required during the single 2 and a half hour operation. $\endgroup$ – Russell Borogove Jun 7 '15 at 17:19
  • 1
    $\begingroup$ @LocalFluff - I used to work out daily and know that if you take a break longer than one week, the effects are very noticeable. I also know that lifting plateaus are common and unless the workout regimen is altered, they will result in a loss of strength as well. So though this is anecdotal, I am quite certain that weight lifting alone would not prevent the eventual demise of your "super" strength. It takes a tremendous amount of effort, diet discipline, and variations of workouts to maintain strength on Earth, so under lower gravity it must be more difficult... $\endgroup$ – honeste_vivere Jan 26 '16 at 14:09
1
$\begingroup$

The rate of "normalization" would vary person to person. Hence why ISS personnel have mandatory exercise in space so they won't be essentially crippled when they return to earth. The exact statistics are unknown but it is reasonable to assume without countermeasures eventually moon gravity would feel similar to earth gravity eventually. IMHO

*(Citation added per request. New to Stack exchange and most of the cites I have visited are more casual and don't request citations. Thank you for informing me of that this is not the case here. Greatly appreciated. Supporting evidence with citations provided below.)

IMHO is related to no one being in space for an extremely extended period of time and very few people for any extended period. This leaves too small a pool of data to draw anything other than cursory data. The longest time by anyone was Valeri Polyakov at 14.5 months (almost 438 days). I am a retired RN and do have extensive knowledge of A & P. This bone loss begins within the first few days in space.

The most severe loss (of bone) occurs between the second and fifth months in space, although the process continues throughout the entire time spent in microgravity. Extended stays on Mir have resulted in losses of bone mass of as much as 20% (indicating there is a range). Astronauts regain most of their bone mass in the months following their return from space,but not all...

Ref

Calf muscles biopsies before flight and after a six months mission on the ISS show that even when crew members did aerobic exercise five hours a week and resistance exercise three to six days per week, muscle volume and peak power both still decrease significantly.

(Actually posts study on webpage as well.) In the study they measure muscle strength pre- and post flight in conjunction with biopsies of the soleus and gastrocnemius muscles to measure cell size and the structural changes of fast and slow muscle fibers. Chemical analysis measures muscle fiber structural changes involving myosin, (drives muscle contractions and cell divisions, enzymes, and substrates.) Electron microscopy "determines the relationship between thick and thin filament, the amount of myofilament loss, and changes in membrane-associated protein complexes found in skeletal muscle fibers and connective tissue that help the muscle resist stretch-induced damage."

MRI studies are done as well. These tests are run at multiple intervals both before and after space flight. It goes into further detail but shows significant variance in muscular atrophy, especially with a small sample set. A short synopsis reports

overall calf muscle volume significantly decreased by 13¬+2%, peak power decreased significantly by 32%, force-velocity characteristics were reduced significantly to -20 to -29% across the velocity spectrum, and there was a 12-17% shift in myosin

(As the atrophy progresses, strength will most likely continuously decline to the point where moon gravity would "feel" like earth gravity. (This would be the reason for the IMHO part of my conjecture. Almost all the data collected, and all data in this study, is over a period of 6 months. There is no data for a long enough period of time nor is there any data with the relative gravity of the moon. This data is for micro-gravity and we can only theorize as to how the data would change with the low gravity of the moon).

It should also be noted these are all individuals not only with the exemplary physical conditioning required to be accepted into a space program, but that this also indicates there is most likely relatively minimal variance among them in their level of physical conditioning. This is a small data set of individuals that are all in good health, meeting a high standard for their physical fitness and with relatively low age variance and yet has a statistically significant variance in muscle breakdown over the same time period in the same environment. If in only 6 months peak power decreases by 32%, muscle volume decreases by approximately 13% and force velocity decreases by 20-29%, I don't find it unreasonable to predict the eventual loss of "superpowers".

Hopefully that data helps answer your question. HAGD

$\endgroup$
  • 1
    $\begingroup$ You should note that completely opinion based answers here are not generally well received. If you have more to back up your answer with, it might increase chances of acceptance. $\endgroup$ – called2voyage Jan 19 '17 at 21:47
  • $\begingroup$ @RTachoir I have attempted to improve formatting a bit. Please feel free to undo/change what I have done if it does not match you intent. $\endgroup$ – OrangePeel52 Jul 13 '17 at 13:34
  • $\begingroup$ Just realized this thread is more than a year old.... oops $\endgroup$ – OrangePeel52 Jul 13 '17 at 13:35

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.