International Space Station, United States module.
Steven had just completed a fitness workout on the combined weighted external resistance treadmill. He had persisted in running for an hour, and he also did some other resistance training.
In a microgravity environment, muscle atrophy and bone calcium loss can easily occur. If a certain level of physical exercise isn't maintained, these symptoms will get worse.
Upon returning to Earth, due to muscle atrophy, an astronaut could be unable to walk, and due to osteoporosis, the bones could easily fracture.
Steven dried his sweat, moved his lithe body back to the living module, where all sorts of equipment were hanging on the wall.
He checked the pressure inside the module and found nothing abnormal. Not long ago, there was a leak in the Russian module, losing 220g of air per day. The amazing Russians took a month to finally find the leak, a hole of only 1mm. They used tape to seal it and then proclaimed themselves out of danger.
