The Shenzhou XII astronauts returned triumphantly. What effects will the three-month space environment have on the human body?

On the afternoon of September 17, the three astronauts of Shenzhou XII returned to the ground successfully. What kind of impact will three months of space life have on the astronauts' bodies? How long will it take to recover later? Let's take a look at the details.

Written by reporter Li Peng, Photo and text editor Chen Yongjie

New Media Editor/Fang Yongzhen

Interview experts

Yue Maoxing (former director of the General Surgery Department of the 306th Hospital of the People's Liberation Army, director of the Special Medical Center, and leader of the manned space emergency rescue expert group)

Jiao Weixin (Professor, School of Earth and Space Sciences, Peking University)

Xiao Long (Professor at the Institute of Planetary Sciences, China University of Geosciences (Wuhan))

At 13:34 on September 17, the Shenzhou XII manned spacecraft carrying astronauts Nie Haisheng, Liu Boming and Tang Hongbo successfully landed at the Dongfeng Landing Site of the Jiuquan Satellite Launch Center. The three astronauts left the spacecraft safely and smoothly and were in good health. The first manned flight mission in the space station phase was a complete success. This was the first time that the Dongfeng Landing Site carried out a manned spacecraft search and recovery mission.

During the Shenzhou XII mission, three astronauts entered the Chinese space station for the first time and lived and worked in the space station complex for 90 days, breaking the record for the length of time Chinese astronauts have stayed in space on a single mission. What effects will the three-month space environment have on the astronauts' bodies?

▲At 13:34 on September 17, the return capsule of the Shenzhou XII manned spacecraft landed successfully. Astronauts Nie Haisheng (center), Liu Boming (right), and Tang Hongbo (left) exited the capsule safely and smoothly, and are in good health (Photo source/Xinhua News Agency)

The distribution of blood and body fluids in the body has changed significantly. The distribution of blood and body fluids in our body is adapted to the gravity environment on Earth. In the weightless environment of space, blood and body fluids will change. Yue Maoxing, former director of the General Surgery Department of the 306th Hospital of the People's Liberation Army, director of the Special Medical Center, and leader of the manned space emergency rescue expert group, said in an interview with reporters that the distribution of blood and body fluids in the body is different in different states of the space environment, and it will be distributed according to the effect of gravity. Astronauts start adjusting their blood and body fluids from the moment they get on the rocket.

Jiao Weixin, a professor at the School of Earth and Space Sciences at Peking University, said that when the rocket ignites and takes off, astronauts will experience an unusual feeling of overweight, just like a person sitting in an elevator, as if being pulled down, and this feeling will be much stronger when the rocket is launched. In this process, the blood and body fluids of the human body will be transferred to the lower limbs. After the separation of the rocket and the ship, the astronauts will experience the process from overweight to weightlessness. When weightlessness occurs, gravity will disappear completely, and the blood in the whole body will rush to the head at once. At this time, the human body will experience strong discomfort, just like the feeling of motion sickness and seasickness on the ground.

Yue Maoxing explained that when astronauts go into space, blood redistribution will occur throughout the body. Because after the spacecraft is in space, in a state of weightlessness, the blood will rush to the brain and upper body, and the viscosity of the blood will also change, causing facial swelling and even swelling of the head.

On September 1, when Nie Haisheng, Liu Boming and Tang Hongbo gave science lessons to primary and secondary school students across the country, many people noticed that the faces of the three astronauts were slightly swollen. Yue Maoxing said that this was also a reaction to congestion in the head. However, judging from the status of the three astronauts, their bodies are still in normal condition. In fact, if too much blood accumulates in the head, it can sometimes cause changes in the astronauts' sense of smell and taste, and even headaches and abnormal blood pressure. However, as long as there are countermeasures in advance, there will not be particularly serious situations.

▲On September 3, the "Times Spirit Shines in Hong Kong" event of "Looking Up at the Stars and Talking about the Tiangong" was held in Beijing and Hong Kong. The three astronauts and nearly 300 Hong Kong science and technology workers, teachers and college and high school students had a unique interaction between heaven and earth (Photo source: Visual China)

In the live broadcast of China Central Radio and Television, many viewers noticed that after the three astronauts returned to the ground from space, they rested in the cabin of the spacecraft for dozens of minutes before being carried out. Their faces were slightly paler than before, and they remained in a sitting position on the spacecraft to accept media interviews. Yue Maoxing explained that such an operation was taken to maximize the safety of the astronauts. Because when the astronauts return to the ground, their heads will be ischemic and their lower limbs will swell. They need time to adjust and recover so that the body's physiological functions can gradually adapt to life on the ground again.

Bone loss is a huge challenge. In a weightless environment, the pressure on the load-bearing bones of the human body, such as the lower limbs, pelvis, and spine, is reduced. At the same time, muscle movement is reduced, and the stimulation to the bones is weakened, causing the calcium stored in the bones to separate from the bone matrix. The clinical manifestations are reduced bone mass and decreased bone density, which lead to symptoms such as osteoporosis in astronauts. This is the so-called bone loss in space.

Yue Maoxing said that there is a big difference between astronauts staying in the space station for three months and for just a few days. When astronauts stay in space for a long time, the accelerated loss of bone calcium is a huge challenge that they must face.

Astronauts who lived on the International Space Station for six months did show a decrease in bone density after returning, with spine bone density decreasing by an average of 0.9% per month, hip bone density decreasing by 1.4%-1.5% per month, and calcaneal bone density decreasing by 0.4% per month.

▲The impact of the space environment on astronauts’ bodies (Image by Zhang Lin)

Many evidences show that the amount of bone loss in one month of space travel by astronauts is equivalent to the amount of bone loss in one year by an elderly woman with osteoporosis on Earth. Once osteoporosis is formed, it is difficult to reverse even after returning to the gravity environment on Earth. Therefore, bone calcium loss in space is listed as the first of the various risk factors faced by long-term space flight.

Yue Maoxing said that in space, astronauts are not carrying any weight, so bone calcium loss is inevitable, and severe cases may even lead to osteoporosis. However, with the support and intervention of diet, medical treatment, exercise, etc., the situation is much better. Many people have seen that in addition to completing their work tasks, astronauts in the space station must also perform a variety of physical exercises under the guidance of doctors on the ground. Yue Maoxing said that an important purpose of exercise is to avoid the accelerated loss of bone calcium.

Yue Maoxing told reporters that my country's astronauts' health management is relatively comprehensive. After the astronauts returned in the past, examinations showed that the loss of bone calcium was not particularly severe, and nothing particularly serious has occurred so far.

In order to fully protect the astronauts' bodies, they have to undergo very strict examinations and recuperation within a period of time after returning to Earth, and receive various functional recovery training to completely adapt to the Earth's environment and live a normal life. During the recovery period, some consequences of bone calcium loss must also be prevented. For example, strenuous exercise and weight bearing are prohibited.

However, Yue Maoxing also said that less serious bone calcium loss problems can be greatly alleviated through diet, exercise and some treatments of Chinese and Western medicine.

In 2019, the research team of the China Astronaut Research and Training Center and the Institute of Molecular Medicine of Peking University published a research paper on bone loss in space. The study established a clear relationship between changes in calcium signals in osteoblasts and bone formation, revealing a new mechanism of action for the regulation of bone formation. This study provides a new approach to the protection against bone loss in space and the treatment of osteoporosis. We also hope that the subsequent research results will provide further protection for the health of our astronauts during the space station period.

Muscle atrophy occurs in the space environment. Years of observation and research have shown that astronauts will suffer from muscle atrophy after spending a long time in space. This condition is mainly caused by factors such as weightlessness and lack of habitual muscle strength. The main manifestations are reduced muscle mass, thinner muscle fibers, reduced leg circumference, and decreased muscle (especially extensor) contraction strength. The degree of atrophy is generally greater in the lower limbs than in the upper limbs, and anti-gravity muscles are greater than non-anti-gravity muscles. The longer the stay in space, the more severe the muscle atrophy.

▲ In order to reduce the symptoms of muscle atrophy, European Space Agency astronaut Luca Parmitano exercises on the treadmill of the International Space Station (Photo source/NASA website)

A research team from the Massachusetts Institute of Technology compared the physical condition of 17 astronauts before and after working in the space station. They found that all astronauts who stayed in the space station for a period of time, such as an average stay of half a year, had some back muscle atrophy.

The consequence of muscle atrophy is a decrease in muscle strength, endurance, tension and coordination. When working under heavy load, astronauts feel general weakness and muscle pain. After returning to the ground, they generally feel weak, fatigued, have difficulty standing and walking, and have muscle pain. Fortunately, this process of muscle atrophy is reversible, and it can return to normal after more than a year of life and exercise on the ground.

Olga Maniko, head of the scientific team at the Institute of Biomedical Problems of the Russian Academy of Sciences and an ophthalmologist, said that in the case of long-term space flight (more than 3 months), 30% of astronauts experience fundus changes, which belong to the space neuro-ocular syndrome, including optic nerve edema, retinal structural changes, eyeball shape changes, hyperopia and other visual changes. The most common space neuro-ocular syndrome is optic nerve edema, which varies in severity, from mild to very obvious.

Foreign studies have shown that astronauts who have spent a long time in space may suffer from visual impairment and intracranial hypertension syndrome after returning to Earth. MRI examinations have found that the eyeballs of astronauts who have returned to Earth have become flatter and the optic nerves have become swollen, which is the result of cerebral fluid accumulation caused by the microgravity environment.

Medical observations have found that most astronauts who have just returned from space will have a slight decrease in vision, but scientists still do not know the exact cause. Some studies have also found that astronauts' decreased vision may be caused by a lack of vitamin B13 or folic acid. In addition, the radiation environment also increases the risk of astronauts developing cataracts, and no definite and reliable conclusion has yet been drawn.

Astronauts working on the International Space Station have reported that they felt a decrease in brain alertness and a slowdown in thinking when they were working on the space station. To find out why, scientists exposed mice to low doses of high-energy charged particles, and six weeks later, the mice underwent a series of learning and memory tests. The results showed that mice exposed to charged particles performed worse and were more likely to develop mental disorders. In addition, the number of dendritic cells in the brains of these mice was significantly reduced. Scientists speculate that astronauts on long-term space missions may have their brain nerve cells changed by cosmic ray radiation.

The vestibular system is a group of devices in the inner ear that are responsible for the balance movement of the head. It is mainly composed of the utricle, the saccule and three semicircular canals. It is also a special system for the human body to orient and balance in space. When astronauts enter space, this core component of the human body will also be disordered. When astronauts return to Earth, they often walk unsteadily, misplace things or knock things over. This is mainly because the operation of the vestibular system is related to the gravity and horizon of the earth. In space, the gravity and horizon of the earth lose their function on the human body, and the vestibular system must adapt to the new external conditions. After returning to Earth, it must be adjusted again. In this repeated adjustment process, the human body is often misled by wrong signals. Therefore, it takes a long time to recover.

Psychological problems may occur. Whether in the process of going to space or returning, astronauts have to accept extreme challenges psychologically. The normal biological clock of the human body is disrupted in the space station, and a long period of different life will also bring some changes to the psychology. Will astronauts have serious psychological problems after returning to the ground?

Yue Maoxing told reporters that the process of astronauts entering space and some of their experiences working and living in space will indeed have a great impact on people's psychology. It is understood that in order to avoid serious psychological problems, both foreign and Chinese astronauts must go through a very strict psychological test phase when selecting astronauts. Those who fail the psychological test will be eliminated. This can also avoid and alleviate the occurrence of serious psychological problems among astronauts.

NASA stipulates that if the astronauts' mission time exceeds one month, they need to communicate with the psychologists on the ground regularly through remote equipment. If an astronaut attempts to sabotage, other members can use violence to subdue him, including tying his hands and feet with ropes or forcibly injecting sedatives.

▲A psychological counselor at the China Astronaut Research and Training Center trains astronaut Liu Yang (Photo source: Visual China)

In addition, in order to effectively deal with the psychological problems of astronauts, the space station is also equipped with sedatives, antidepressants, antianxiety drugs and other drugs for treating mental illness. The response plan stipulates that astronauts who lose control of their emotions can be injected with sedatives. If they encounter resistance, the injection can be forcibly injected into the patient. Although no one has used these drugs yet, some experts believe that it is very necessary for astronauts to be equipped with psychotropic drugs for special missions. Because there have been cases in the past where astronauts have developed serious psychological conditions in the space station. Just in case, Chinese astronauts now also carry sedatives, antidepressants, antianxiety drugs and other drugs when they go to space.

In addition, adjusting the environment through facilities is also an effective way. For example, astronauts can adjust the cabin lighting environment, sleep mode, work mode, exercise mode, etc. through the App according to their personal needs. Different cabin lights can adjust the astronauts' mood and avoid the discomfort caused by being in a monotonous environment for a long time.

However, Xiao Long, a professor at the Institute of Planetary Sciences of China University of Geosciences (Wuhan), said that the psychological problems of astronauts vary from person to person. According to what he has learned, the psychological problems of foreign astronauts are not as serious as rumored by the outside world. There is no doubt that space flight will inevitably experience various fears and dangers, and those who go will also make various preparations. Yue Maoxing said that due to the adequate protection, Chinese astronauts did not have serious psychological problems after returning to Earth.

Paying attention to the psychology of astronauts has always been a cutting-edge topic, which requires continuous attention, exploration and follow-up research, so that in the future we can provide more adequate guarantees for Chinese astronauts to land on the moon and Mars.

Further reading >>>

Space medicine begins to serve ordinary people

"Our country has made some breakthroughs in the civilian transformation of aerospace medicine and in solving some medical problems such as ALS." Yue Maoxing told reporters that an important manifestation of ALS is muscle atrophy, and muscle atrophy can also occur in space. Through some scientific prevention and treatment methods, some serious situations can now be avoided in astronauts, and this coping strategy has also brought great inspiration to the treatment of ALS.

Yue Maoxing explored the integration of traditional Chinese and Western medicine and invented a new treatment for motor neuron injury, using a new treatment method of "recovering from the body's enzyme metabolism and promoting the repair of damaged nerve cells" to treat patients. In response to the different conditions, degree of injury, and underlying diseases of patients, he led the team to develop "Thaw No. 1" to "Thaw No. 6", as well as the traditional Chinese medicine "Ziwei Paste" and "Ziwei Pills".

The methods used in aerospace medicine can also be used to prevent bone calcium loss in the elderly. According to statistics, there are 8.9 million fracture cases in the world every year, and there are about 90 million osteoporosis patients in my country. Through some intervention measures, these patients have also received good news.

"Space medicine must be used by the people to play a greater role," said Yue Maoxing.

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