Microgravity has a significant impact on muscle health and muscle physiology of astronauts during space missions. In a microgravity environment, muscles undergo atrophy, which is characterized by a decrease in muscle mass and volume. This atrophy occurs due to the reduced mechanical load normally exerted by gravity on Earth, resulting in decreased muscle strength and endurance. In addition, changes in muscle fiber and muscle tissue composition also occur, where there is a decrease in type I muscle fibers (which contract slowly and last long) and an increase in type II muscle fibers (which contract quickly but fatigue quickly) [1].

The mechanism supporting these changes involves muscle adaptation to the microgravity environment. Reduced physical activity under microgravity conditions reduces the mechanical stimulus required to maintain muscle mass. According to Barratt and Pool [2] in the book “Principles of clinical medicine for space flight”, muscle adaptation to this environment includes changes in gene expression and molecular signaling that regulate muscle growth and degradation.

Space radiation has different impacts on bone cells, especially osteoclasts and osteoblasts. Research shows that radiation can increase the activity of osteoclasts, the cells responsible for bone resorption, and reduce the activity of osteoblasts, the cells responsible for bone formation. Barratt and Pool [3] in the book “Principles of clinical medicine for space flight” also emphasize that this leads to an imbalance in bone remodeling, resulting in decreased bone mineral density and increased risk of osteoporosis.

Various studies have been conducted to understand the effects of microgravity on muscles and bones. For example, a study published in “Musculoskeletal research in human space flight” by Liphardt et al. [2] in 2023 stated that astronauts experience up to 20% decrease in muscle mass and 1%−2% loss of mineral bone density per month during Space missions. Other studies have shown that the use of physical exercise and resistive equipment can reduce this rate of muscle and bone loss, although not completely prevent it.

Key studies show that interventions such as intensive physical exercise using devices such as treadmills and resistive exercise devices (REDs) can help reduce the negative impact of microgravity on muscles and bones. Research by Liphardt et al. [3] in 2023 also emphasized the importance of proper nutrition and the use of supplements such as vitamin D and calcium to support bone health during and after space missions.

To prevent the negative effects of microgravity on muscles and bones, various preventive procedures and physical exercises have been recommended. Recommended exercises include resistive exercises, weight training and aerobic exercises designed to mimic the mechanical loads normally exerted by gravity on Earth [3]. These principles are outlined in the book “Principles of clinical medicine for space flight”.

Equipment and technologies used to support physical exercise in space include treadmills adapted for microgravity conditions, REDs (such as the Advanced Resistive Exercise Device [National Aeronautics and Space Administration, NASA]), and stationary bicycles in Liphardt et al. [3]. Nutrition and supplements, including vitamin D and calcium, also play an important role in supporting astronauts’ muscle and bone health.

Proper nutrition is essential for maintaining healthy muscles and bones during space missions. Supplements such as vitamin D and calcium help maintain bone mineral density and support muscle function. Pharmacological interventions, including the use of drugs that increase osteoblast activity or reduce osteoclast activity, are also being explored to prevent further bone degradation during spaceflight [2]. Especially when muscular changes occur kinetically as in Fig. 1 [3].

Post-mission rehabilitation is designed to restore astronauts’ muscle and bone health after returning to Earth. The rehabilitation program includes structured physical exercise, physical therapy and nutritional monitoring to ensure optimal recovery. Studies in the “Space Flight Rehabilitation Journal” emphasize the importance of an intensive and focused rehabilitation program to minimize the long-term impact of microgravity exposure on the musculoskeletal system [2].

By understanding the effects of microgravity and space radiation on muscle and bone health, and implementing appropriate prevention and intervention procedures, we can ensure the well-being of astronauts during and after space missions.

This research is of interest because it has significant health implications, especially given the impact of microgravity and space radiation on astronauts’ muscle and bone health. Understanding the physiological changes that occur and the mechanisms behind them is critical to developing effective mitigation strategies. In addition, this research encourages the development of new technologies and procedures to prevent and overcome the negative effects of microgravity, including innovations in exercise devices, nutritional supplements and pharmacological interventions. Findings from this research also have broad applications on Earth, such as for treating osteoporosis, muscle atrophy due to aging, and other immobility conditions. With planned missions to Mars and long-term stays on the moon, understanding and addressing the effects of microgravity is becoming increasingly crucial, and this research will provide a strong scientific basis to support the success of future space missions. In addition, this research will enrich scientific knowledge in the fields of space physiology and clinical medicine, and may lead to new insights into the human body’s adaptation to extreme environments.

This research is necessary because maintaining the health and well-being of astronauts is a top priority in space missions. This research will help identify and implement effective preventive measures to protect them from the negative effects of microgravity and radiation. Ensuring the success and long-term sustainability of space missions requires a deep understanding of how the human body adapts and how we can support this adaptation through medical interventions and preventative procedures. This research also provides important data that can be used to design better habitats and life support systems in space, as well as prepare astronauts for the physical challenges they face during and after a mission. The conditions astronauts experience in microgravity are similar to certain medical conditions on Earth, so the findings from this study could be used to develop new therapies and interventions for diseases such as osteoporosis and sarcopenia. In addition, this research is driving advances in biology, medicine and biomedical engineering technology, with the resulting innovations having far-reaching impacts in both the space context and everyday clinical practice. Therefore, research on the effects of microgravity on astronauts’ muscle and bone health as well as preventive procedures and medical interventions are essential to provide long-term benefits to human health, both on Earth and in space.

This research methodology was conducted using a literature review approach to analyze the effects of microgravity on muscle and bone health in astronauts during space missions. The first step in this methodology is the search and collection of data from various relevant scientific sources, including journals, books, research reports, and official documents from various freely available space agencies such as from NASA and European Space Agency. The search was conducted using reputable scientific databases such as PubMed, Google Scholar, and IEEE Xplore with specific keywords such as “microgravity effects on muscle health”, “bone density in astronauts”, “space mission medical interventions”, and other related terms.

After data collection, each study was evaluated based on strict inclusion criteria to ensure the quality and relevance of the information. Inclusion criteria included studies conducted within the last 20 years for papers and no year limit for books, studies with adequate samples, and peer-reviewed articles. The collected data was then systematically analyzed to identify common trends, significant findings, and gaps in the existing literature.

The analysis process included grouping study results based on topics such as physiological changes in muscle and bone, mechanisms underlying the effects of microgravity, and preventive procedures and medical interventions that have been implemented or proposed. Each group of results was further analyzed to assess the effectiveness of various interventions, such as specific physical exercises, nutrition, and the use of medications.

The results of this analysis were compiled in the form of a narrative describing the astronauts’ muscle and bone health conditions before, during and after the space mission, and discussing the most effective strategies for mitigating the negative effects of microgravity. With this approach, the study not only provides a comprehensive overview of the effects of microgravity but also provides evidence-based recommendations for optimal prevention procedures and medical interventions.

1. Study overview radiation effects

The study of the effects of space radiation on bone cells has been the focus of research in the field of space medicine. One of the key findings comes from research conducted by the NASA involving observations of astronauts who have spent significant time in space [4]. The study found that exposure to space radiation caused a decrease in bone mineral density in astronauts, indicating damage to bone tissue. Another study published in the journal “Bone” revealed that space radiation can induce genetic changes in bone cells, leading to decreased osteoblast function and increased osteoclast activity. Similar findings were also found in a study published in the journal “Radiation Research”, where exposure to space radiation caused deoxyribonucleic acid damage in bone cells, which is also illustrated in Fig. 2 [5].

1) Microgravity effect

The study of the effects of microgravity on muscle and bone has become an important research focus in understanding the health impacts of astronauts engaged in long-term space missions. Several key studies have provided deep insights into how the microgravity environment affects the human musculoskeletal system. One significant study, published in the journal “Journal of Applied Physiology”, highlighted that exposure to microgravity causes a decrease in muscle mass and physical strength in astronauts during space missions such as research by Bonanni et al. [6] in 2023. These findings are supported by another study published in the “Journal of Bone and Mineral Research”, which showed that microgravity accelerates bone mass loss and increases the risk of osteoporosis in astronauts. These studies also highlight that microgravity may interfere with the regeneration process of muscle and bone tissue, as well as affect the balance between bone formation and resorption given that astronauts’ postures vary and are demonstrated as in Fig. 3 [2].

Furthermore, research in the journal “Frontiers in Physiology” suggests that microgravity could trigger changes in the expression of genes involved in muscle and bone metabolism by 2024 [7], these studies provide strong evidence that microgravity has a significant impact on human muscle and bone health, and an in-depth understanding of the mechanisms involved is important for developing effective protection and intervention strategies for astronauts engaged in long-term space exploration.

2. Microgravity

Microgravity has a significant impact on astronauts’ muscle health, mainly causing adverse physiological changes in the musculature system [6]. One of the main effects is muscle atrophy, which is the shrinkage of muscle mass that occurs due to decreased physical activity in a microgravity environment. On Earth, gravity forces muscles to work against the pull of gravity when performing daily activities, so muscles maintain their strength and muscle mass. However, in space, the lack of gravity means muscles don’t have to work as hard, resulting in a significant decrease in muscle strength and endurance [8].

In addition to atrophy, there are also changes in muscle fibers and muscle tissue composition. Studies show that there is a shift from type I muscle fibers, which are known to have high endurance, to stronger but less durable type II muscle fibers [9] by 2022. These changes reflect muscle adaptation to a microgravity environment where endurance-demanding activities are reduced and faster, stronger activities become more dominant. Muscle tissue composition also undergoes changes, with a decrease in muscle mass and an increase in the proportion of fat tissue [10].

The mechanism underlying these changes involves several factors. First, reduced physical activity in a zero-gravity environment reduces the mechanical stimulus that normally maintains muscle mass and strength. Without the constant weight of gravity, muscles lose the stimulation necessary to maintain their function [6]. Second, muscle adaptation to the microgravity environment involves changes in metabolism and molecular signals that regulate muscle growth and maintenance. A decrease in anabolic signals, such as insulin-like growth factor 1, and an increase in catabolic signals, such as myostatin, contribute to muscle degradation in space.

3. Effects of space radiation

The effects of space radiation on bone cells and cells have significant implications especially in the context of the health of astronauts who are on long-term space missions [7]. Radiation outside the Earth’s atmosphere tends to be more intense and different in composition compared to radiation on the Earth’s surface. When this radiation comes into contact with an astronaut’s body, its impact on bone cells can vary. Osteoblasts and osteoclasts, which are the two main cell types responsible for bone growth and maintenance, can be affected differently by space radiation. Studies have shown that exposure to space radiation can increase the activity of osteoclasts, the cells responsible for bone resorption or absorption [5]. This can lead to decreased bone density or osteoporosis in astronauts. On the other hand, radiation can also inhibit the activity of osteoblasts, the cells responsible for new bone formation. This can disrupt the bone regeneration process and lead to a decrease in bone strength and density. Therefore, understanding how space radiation affects bone cells and cells is important for developing effective protection and treatment strategies for astronauts engaged in long-term space missions.

4. Preventive procedures

Preventive procedures and physical exercise are crucial components in maintaining astronaut health and performance during space missions. Based on the principles of clinical medicine for spaceflight in chapter 14, pages 299−304, a number of preventive measures and physical exercises have been recommended by Hart [11] in 2023. First, prevention of musculoskeletal damage, such as osteoporosis, is emphasized. This can be achieved through a specific exercise program involving resistance training, cardiovascular training, and balance and flexibility training. Resistance training may include the use of tools such as body weights or specialized equipment designed for microgravity environments. Cardiovascular exercises, such as running on a treadmill or stationary cycling, can help maintain a healthy heart and blood vessels. In addition, balance and flexibility exercises are important for maintaining coordination of movements and preventing injuries.

Other preventive measures include reducing the risk of injury and infection. Astronauts need to keep themselves and their environment clean, and adhere to strict hygiene protocols. [11]. Vaccination programs may also be put in place to protect astronauts from infectious diseases. In addition, it is important for astronauts to maintain their mental health during space missions. This can be achieved through psychological support programs, meditation and other relaxation techniques.

In addition to prevention, physical exercise is also an integral part of maintaining astronaut health. The principles of physical exercise for spaceflight emphasize the importance of consistency, variety and intensity of exercise. Astronauts need to follow a regular exercise schedule, which includes resistance, cardiovascular and flexibility exercises. Variation in the type of exercise helps prevent boredom and ensures all areas of the body are properly trained. Training intensity should also be tailored to individual needs, taking into account factors such as age, physical condition and training goals.

5. Equipment and technology used

The equipment and technologies used as well as nutrition and supplements play an important role in maintaining the health and performance of astronauts during space missions. Based on the principles of clinical medicine for spaceflight in chapter 14, pages 299−303, several equipment and technologies have been recommended for astronauts to use [7]. One of the key pieces of equipment is the treadmill, which is used to maintain the cardiovascular and muscular health of astronauts. Treadmills are specifically designed for microgravity environments, with the ability to adjust the speed and strength of gravity. In addition, resistance training equipment such as REDs are also essential for maintaining muscle strength and preventing muscle mass loss during space missions. REDs use a system of pistons or springs to provide resistance, allowing astronauts to perform weight training similar to that on Earth.

Apart from training equipment, nutrition and supplements are also very important in maintaining astronaut health. Astronauts need a diet rich in nutrients to meet their energy needs and prevent nutritional deficiencies. The astronaut diet usually consists of food packed in special packaging to maintain its freshness and nutritional quality during space missions. In addition, nutritional supplements are often given to astronauts to ensure they get all the necessary nutrients. Supplements such as vitamin D and calcium are given to support bone health, while protein supplements can help maintain muscle mass [12].

Other technologies used include health monitoring systems, such as electronic stethoscopes and automatic blood pressure monitors, which allow astronauts to monitor their physical condition regularly. Water and air filtration systems are also required to maintain a clean and safe environment inside the spacecraft. By using the right equipment and technology, and maintaining appropriate nutrition and supplementation, astronauts can maintain their health and performance during long space missions [12].

6. Post-mission rehabilitation

Post-mission rehabilitation is an important aspect of restoring astronaut health after returning from a space mission [13]. Specially designed rehabilitation programs aim to restore muscle and bone health that may have been impacted by exposure to microgravity in space as summarized in the illustration in Fig. 4 [6]. According to research published in the journal “Space Flight Rehabilitation”, post-mission rehabilitation programs often involve a series of physical exercises designed to strengthen muscles and increase bone density. These exercises may include resistance training using tools such as REDs or body weight exercises. The goal is to rebuild muscle mass that may have been reduced during the space mission and strengthen muscles that may have been weakened. In addition, the rehabilitation program may also include cardiovascular exercises to improve the strength of the heart and blood vessels, as well as balance and flexibility exercises to improve coordination of movements and prevent injuries [14].

Aside from the physical exercise aspect, a post-mission rehabilitation program may also include nutrition and supplements. Astronauts may require a specialized diet rich in nutrients to help speed up the recovery process and strengthen muscle and bone health. Supplements such as vitamin D and calcium may also be given to help increase bone density and prevent the risk of osteoporosis. In addition, the use of advanced technologies such as physical therapy utilizing signal processing and electrical stimulation may also be part of the post-mission rehabilitation program to accelerate the healing process and recovery of astronauts’ musculoskeletal health.

In conclusion, this detailed study of the effects of microgravity and space radiation on astronauts’ musculoskeletal health highlights the enormous challenges humans face in exploring space. Microgravity triggers muscle atrophy and changes in muscle tissue composition, while space radiation can affect bone cells by increasing osteoclast activity and inhibiting osteoblast activity. The importance of preventive procedures, post-mission rehabilitation and the use of appropriate equipment and technology in maintaining astronaut health is prominent. In addition, proper nutrition and the role of supplements such as vitamin D and calcium are important factors in maintaining bone density and muscle mass of astronauts. These studies provide an important foundation for the development of effective protection and intervention strategies for astronauts engaged in long-term space exploration, confirming that a deep understanding of the impact of the space environment on the human body is key to maintaining optimal health and performance in space.

No potential conflict of interest relevant to this article was reported.

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