To nail her role as an astronaut in the film "Gravity," Sandra Bullock turned to astronaut Catherine "Cady" Coleman, who spent 180 days in outer space, for advice. A retired US Air Force colonel and 21-year NASA veteran, Coleman e-mailed and chatted with Bullock while on her third space mission, where she served as a flight engineer aboard the Russian Soyuz TMA-20 spacecraft and spent 159 days aboard the International Space Station (ISS) as the lead robotics and science officer.

While Bullock spent all 91 stressful minutes of "Gravity" trying to get home in one piece, we were curious to know what else astronauts are up to on the ISS when they're not being separated from George Clooney and losing all connection with ground control. We chatted with Coleman to get an inside glimpse into what everyday activities we do down on earth are like up in space. Click ahead to see why you should never take your pillow or clipping your toenails for granted.

"We are all basically living breathing, experiments" in space, Coleman says. Astronauts are healthy, fit people with fairly normal medical histories, which makes them the perfect lab rats, er, subjects for testing new drugs. During her time aboard the ISS, Coleman volunteered to test a new osteoporosis medication because, in space, humans lose bone mass 10 times faster. "The amount of bone mass a 70-year-old woman with full-blown osteoporosis loses in one year, we can lose in one month," Coleman says.

Because osteoporosis settles in so quickly in space, researchers were able to test the drug's abilities and study the effects of going on a low salt, low animal fat diet, and zero in on how exercise maintains muscle and bone mass. While research is still being conducted on the different regions of bone where mass is lost and regained, we're happy to report that Coleman came back to our planet with the same amount of bone she left with.

Oh, sure, they're doing important scientific research and, you know, floating around and pushing blinking buttons, but Coleman admits that 22 hours a day, astronauts are "resting." And when they're not resting or eating, they're working out. "You really feel it if you don't exercise," says Coleman, and she's not referring to that sluggish feeling you get after spending a week on the couch. Spending days, weeks and months in a weightless environment causes astronauts to lose a significant amount of bone mineral density -- the same accelerated osteoporosis described earlier -- and according to Coleman, a few days without exercise actually hurts. "It's debilitating," she says. Exercising is one way to keep the pain at bay and maintain healthy bones.

If that's not motivation enough, having 100 scientists, engineers and doctors on earth monitoring your every move helps. That, and the fact that your gym is rigged with space Nautilus and it's approximately 17 inches away from where you eat, sleep and work. "Let's just say your motivation is through the roof," Coleman adds. "We're exercising up there at least five days a week and it's not hard at all."

What does the ISS gym look like? There's a weightlifting machine that simulates gravity through cylinders within cylinders (in zero g, astronauts can adjust the weight from six to 600 lbs.), a treadmill (hovering in the air, just like the astronauts) and a mechanical bicycle strapped to the floor. "We also do squats, dead lifts, heel raises, bench presses, sit-ups ... anything you can do with a bar for leverage," says Coleman. We aim for one and a half hours a day, because the other 22 and a half hours of the day, you're resting."

"It's a very, very dry environment. We do have certain moisturizers that are approved, just to not be so flaky ... [but] there are always flakes of dead skin floating around -- on the vents, on the screens," says Coleman. The biggest culprit? Feet. Because they're floating around 24/7, calluses disapppear. "We come back with super soft, baby feet," she says. On the flipside, the tops of their feet take a beating. "We're always using our feet on handrails to stay in place and kind of 'perch' when we're watching TV," says Coleman.

"We're allowed to bring makeup, and I've brought it on every [mission] ... but I rarely use it," says Coleman. Plus, the process of finding products that are compatible with the environmental system -- the one responsible for cleaning the air and removing carbon dioxide -- is enough of a hassle. "We have a sort of 'girl's club' in the program and we leave things for each other [on ISS] -- things that are nicer to have: a nice comb, a belt, makeup, a moisturizer we really loved that didn't throw off the environment. It's so hard getting something up into space, it's not really worth it to bring your own."

Floating in the ISS gives your hair super strength that puts Biotin to shame. Coleman recalls being able to use a floating, single strand of hair to propel herself off a wall. Coleman didn't notice any difference in growth rate, but purposefully grew her hair out for her mission. "I really wanted to have my hair be a little bit long, because I wanted it to be clear that I was a woman in space -- not just an astronaut in a picture taken on the ground," says Coleman, who let her big, curly head of hair loose in space. "It was nice letting it have a little life of its own."

Also, pulling her hair back into a ponytail -- Coleman's preferred and practical style -- is a big no-no. In a weightless environment, hair elastics crank those annoying dents up 10 levels. "Your hair will be perpetually bent in one place," she says.