The study's finding, reported online Monday in the Proceedings of the National Academy of Sciences, was that the crew suffered from hypokinesis, meaning "they simply moved less," Dinges says. The volunteers moved less while awake and asleep, and spent more waking hours each day engaged in restful activities-playing video games, reading books, or watching movies. The crewmembers' wristwatches, which were equipped with light sensors, showed that the more lethargic they became, the more they shunned the lighted parts of the ship. By the final few months of the mission, three of the crewmembers slept about an hour more per day than they had at the beginning of the simulation.
The beds were small, recalls French crew member and flight engineer Romain Charles, and so narrow that he often had to sleep with his arm across his face. "I just had to learn to sleep like that," he says. But even though he adapted to the sleeping arrangements, it became difficult to take on intellectually laborious tasks, like improving his Russian language skills, in the final few months of the mission. Instead, he spent his spare time playing the video game Counter-Strike. "It really helped me get through that," Charles remembers.
It wasn't until the final 20 days of the mission that the crew, excited for their seclusion to finally end, became nearly as energetic as they were when the mission began.
These findings are important because a crew in space needs to be at peak performance to work competently and act quickly should an emergency strike, says psychologist Gloria Leon of the University of Minnesota, Twin Cities, who was not involved with the study. "What they're showing is that NASA and other organizations need to pay close attention to developing some measures that will prevent hypokinesis."