Being an astronaut takes not only high mental acuity, but also a high level of physical fitness, especially for those who spend a long amount of time away from Earth, such as the astronauts serving on the International Space Station. Without the constant pull of Earth's gravity on the body, space travelers quickly lose bone density and muscle mass. See how well your middle schoolers or high schoolers understand the concept through a drawing and writing activity. Learners draw and label the bones and muscles of an arm that has been in space versus one that has been on Earth, then devise a diet and exercise plan to combat the bone and muscle atrophy of microgravity.