The human body is capable of functioning in very diverse environments , for which, in principle, it has not been selected by evolution. We are capable of diving tens of meters deep into the sea and we are capable of reaching the top of the highest mountains . With enough training, we can push our bodies to the limit in many different ways. One of the most extreme ways to put our body to the limit is without a doubt weightlessness. Although staying in zero gravity is not a great effort, nor is it painful, uncomfortable or, in itself, deadly, it has very important effects on our body , as well attested by decades of research with astronauts and a recent study by the University of Calgary.
Specifically, they have studied how long-term stays affect bone loss and whether this loss can be remedied on land after the return of the astronauts. This study was initiated by Dr Steven Boyd in 2015 and has followed the evolution of 17 astronauts before, during and after their stay on the international space station during the last seven years. These results not only help us understand how weightlessness affects the human body, but also the functioning of the skeleton in general, regardless of its condition.
Bone loss not only affects astronauts, but also other humans, especially when we get older or when we develop any injury or condition that prevents us from moving normally . These studies with astronauts are especially important and interesting because they allow us to observe considerable changes in bone tissue in very short intervals of time . Normally it would be necessary to observe a person for more than a decade to accumulate the same loss that is measured in stays in the space of 6 months or more.
The research worked in collaboration with NASA’s Johnson Space Center in Texas, studying the wrists and ankles of astronauts before liftoff, after they returned to the Earth’s surface and both 6 and 12 months after landing. Apparently the bones used to bear weight (such as those of the legs or the torso) were more affected by weightlessness than those that have a more supportive function, such as those of the arms. Bone loss was only partially recovered one year after return to land. Of course these processes, like anything that has to do with health and the human body, do not affect everyone in the same way . The researchers describe how they have encountered astronauts who could barely stand as a result of weakness and loss of balance after their time in space, such as other astronauts who had greeted them comfortably by bicycle on arrival at the space facility. The NASA.
The answer is very varied and also requires certain rhythms and adaptation. The rector of the University of Calgary and astronaut Robert Thirsk mentioned as a result of the study that in the same way that it takes time to adapt to weightlessness at the beginning of a mission, a period of adaptation to Earth’s gravity is also required on the way back. . After all, an astronaut can spend a year functioning in a zero-gravity environment, where all your tasks, from moving through space to eating, brushing your teeth or relieving yourself, are completely different from what they were with gravity. After such a long period one would expect the need for such a period of reconditioning time .
Thirsk also comments that fatigue, dizziness and loss of balance affected him after his return to Earth, although after a few hours he regained normality . However, the muscles and bones require more time to readjust.
The study also found that those astronauts who spent short periods of time in space , less than 6 months at a time, regained lost bone mass more quickly than those who had spent longer on the International Space Station.
These lessons are very important if we want to develop a successful space exploration , with astronauts in good health. Currently, no human being has spent long periods of time in the reduced gravity of bodies smaller than Earth, such as the Moon or Mars , but without a doubt these environments will have effects on our physiognomy . Hopefully not as serious as those caused by total weightlessness. When establishing permanent colonies in these bodies, we must not only consider the technological development necessary to make them possible, but also how these experiences will affect those who embark on them . It would be useless to have the best technology if the astronauts who inhabit the Moon or Mars in the future cannot do so in conditions of health and well-being . Especially if we intend to make the space accessible to more and more people.
Referencia:
L. Gabel et al, 2022, Incomplete recovery of bone strength and trabecular microarchitecture at the distal tibia 1 year after return from long duration spaceflight, Scientific Reports, 12 (1) DOI: 10.1038/s41598-022-13461-1
