Which of the following describes an effect of microgravity on astronauts?

Microgravity has significant impacts on the human body, particularly for astronauts who spend extended periods in space. One of the well-documented effects is bone loss. In the microgravity environment of space, the mechanical stress that normally stimulates bone maintenance and growth is greatly reduced. This results in a decrease in bone density, making bones weaker and more susceptible to fractures upon return to Earth.

During their time in space, astronauts can experience a loss of up to 1-2% of bone mass per month, especially in weight-bearing bones such as the spine and pelvis. This phenomenon is a direct consequence of the lack of gravitational pull that we experience on Earth, which normally helps maintain bone health. To counteract this issue, astronauts engage in regular exercise using specialized equipment designed for functioning in a microgravity environment, aiming to mitigate bone loss during their missions.