What happens to the muscles of astronauts who are in space for a extended period?

In space, astronauts experience muscle atrophy due to the microgravity environment, which reduces the mechanical load on their muscles. Without the need to support their body weight, muscles can weaken and shrink, leading to a decrease in strength and endurance. To combat this, astronauts engage in regular resistance and aerobic exercise while aboard the International Space Station to help maintain muscle mass and overall fitness. Despite these efforts, some muscle loss still occurs during extended missions.