Among the many functions performed by skeletal muscles, an important one is maintaining our posture. If it weren't for these muscles, Earth's gravitational pull may make it difficult for us to stand and walk around. The group of muscles—mostly present in our limbs, back, and neck—which are responsible for maintaining our posture and allowing us to move against the force of gravity are rightly called "anti-gravity" muscles.

But what happens to these muscles when there is no gravity (or an "unloading" of gravitational force) for them to work against? The question might sound ridiculous to some, but not to an astronaut aboard the International Space Station (ISS). In outer space, where gravity is minimal, our muscles (especially the anti-gravitational ones) are not used as much, which might result in their atrophy and changes to their structure and properties. In fact, human calf muscles are known to reduce in volume during a flight in space.

Living and working in space for extended periods of time presents a number of challenges. These include radiation, as locations beyond Earth's protective magnetosphere are exposed to greater levels of solar and cosmic rays. There's also the need for self-sufficiency since lunar or Martian bases are too far to rely on regular resupply missions like the International Space Station (ISS). Last, there's the issue of low gravity, which is especially pressing for long-term missions and habitats beyond Earth. If humanity's future truly lies in space, we must devise solutions to this issue in advance.

A popular idea is to create rotating habitats in space that simulate artificial gravity, like the Pinwheel Station or the O'Neill Cylinder. Another proposal by a team of Japanese researchers calls for something bolder: a rotating habitat on the moon. On July 5, representatives from Kyoto University and the Kajima Corporation (one of the oldest and largest construction companies in Japan) announced that they would be partnering to conduct a study on this concept and how it could make humanity's plans for living on the moon and Mars a reality.