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Caitlin: Do you dream of becoming an astronaut? How’s your handshake? Firm? Confident?

If you’re an astronaut, spacewalks are an important part of the job. But, it turns out, spacewalks have nothing to do with your legs at all. Pretty much everything you need is in the palm of your hands.

On March 18th, 1965, the cosmonaut Alexey Leonov went on the first ever spacewalk. His mission was just to survive, and try to take some pictures. Since then, spacewalks, also known as extravehicular activities, have become an important part of most space missions.

From repairs and modifications, to setting up science experiments there's a lot to keep astronauts busy on the outside of a spacecraft. But spacewalks are just one of many extreme situations that astronauts can go through: There’s living in weightlessness, touching down in the Pacific ocean, dealing with huge g-forces, or staying awake for a triple-shift of emergency repairs. Which means they have to be super fit to handle all that stress on their bodies.

Astronauts undergo lots of physical tests, from weight checks to eye exams. Not to mention military water survival training, which includes swimming 75 meters, and treading water for 10 minutes – all in a flight suit and tennis shoes. They spend hours practicing spacewalks in the pool, because it's a great way to simulate weightlessness. Rehearsing in water helps astronauts get used to equipment and practice repairs, but also helps strengthen important muscles. And the muscles that are most important for spacewalks aren’t in your legs – they're in your arms.

Spacewalks actually don’t involve “walking” at all. Your legs and feet mostly just get in the way – muscles in your hands and forearms let you maneuver around in space. So not having a good grip could be a nightmare. Astronauts are safe because they're always tethered to the spacecraft. But can you imagine spending 5 to 8 hours weightless in space, holding on to railings and juggling power tools? It isn't easy.

To make matters worse, spacesuits are designed to be pressurized and stiff, making the gloves naturally stretched out. Fighting against that stiffness to hold onto something can be exhausting and your hands also take a real beating. A 2005 study on 770 NASA spacewalk training tests found that around 47% of symptoms and injuries were in the hands – more than double the shoulders, which were 21% of the symptoms. Those injuries included everything from sprains and blisters, to completely detached nails. And yes, those detached nails can happen on a spacewalk.

When you're in a spacesuit and trying to grip something, your fingers tend to hit up against the walls of the glove. The inner layer is made of a rubbery balloon-like material, but when it’s pressurized it becomes rock solid. Circulation issues can also arise by the glove putting pressure on your finger joints, and all that can lead to infections in the exposed tissue. It can be such a problem that a few astronauts have been known to get their fingernails removed and nicely bandaged up before going to space.

Astronauts can even develop repetitive strain injury, or RSI – that's the same condition gamers can get in their hands from mashing buttons over and over again. So even if you’re lucky – you don't get RSI, and your fingernails hold it together – it's still hard to avoid those tired, achy muscles by the end of a spacewalk. But sometimes the most frustrating problems can bring about some of the coolest solutions.

NASA is working with General Motors to develop a Robo-Glove, which just sounds awesome. It responds to pressure from your hand movements, and could double or even triple astronauts' grip strength. In space, a similar technology has only been tested in a fully automated robot called Robonaut 2, which was sent to the ISS in 2011, and has been busy helping astronauts ever since.

But engineers are already working to find a way to integrate the Robo-Glove into a future spacesuit. So, if you dream of becoming an astronaut, the selection process and the job are both pretty grueling. For several reasons, you'd better practice your handshake. No limp wrists in space, people!

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