Astronaut Mark Vande Hei recently set the American record for the longest spaceflight—355 days to be exact. Now, there are enough movies about sad men in space (Interstellar! Ad Astra! The Martian!) to drive home that this experience doesn’t exactly sound like a walk in the park. There’s repetitive food, isolation from friends and family, plus all sorts of weird changes that zero gravity does to your body, including major bone density loss.

So how did Vande Hei stay in top physical and mental shape while orbiting the planet in the International Space Station? He filled GQ in on his routine from the NASA headquarters in Houston.

GQ: First off, how do you prepare yourself to go up in space? Is there a special regimen for acclimating your body?

Mark Vande Hei: Each astronaut has their own preferences. Some people like running, some people like lifting weights. For me, personally, I did Crossfit type stuff. A big part of the preparation is training you how to use the equipment. We've got the ARED—the Advanced Resisted Exercise Device—that we use up there that requires some training on the ground before you use it in space. You can't replicate everything about that zero G environment on the ground. There's some tweaks you have to do that you can only get while you're in space

So what was your daily fitness routine up there?

I woke up at 5:00 AM every day. Our first meeting of the day was at 7:30 in the morning. Between then, I’d be lifting weights, which sounds like a lot, but the time would go by pretty quick.

Then the morning meeting would be done by 7:45. Then, ideally, my next event would be some cardiovascular training from 7:45 to 8:45. Three days of the week, I would use that to do high intensity interval training on either the bike or the treadmill. It eventually worked up to being 30 seconds of high intensity with 15 seconds of rest over the course of 20 minutes. Once a week I would take off completely.

What’s lifting weights in zero gravity like?

It's a very interesting system. The way I like to describe it is if you imagine a seesaw and your job is to lift up your end of the seesaw. You can do it in such a way that you can do a bench press to lift up your end of the seesaw, or you can do a shoulder press or a squat or a deadlift. But instead of another person sitting down on the seesaw, imagine someone else pulling up on the seesaw—that's shoving your end down while they're pulling up.

That person always applies the same amount of force, so that's not really very useful with the wide variety of exercises you want to do. But what you do is you shift where the fulcrum is. So you change the lever arm so you can give more or less mechanical advantage to you versus the resistive force. That's how we can adjust for anywhere between 20 pounds of force to 600 pounds of force.

I think we all have an idea of what astronaut food is and I’m curious how much that differs from reality. What did a typical day of eating look like?

We didn't have any dehydrated ice cream up there at all. We do get a lot of what I would call camping food, though. At one end of the spectrum is thermal stabilized food. Basically, the main entree in a meal ready-to-eat from a military ration. There are rehydratables and the rehydratables are actually pretty, really good. And we had a little ovens, kind of an Easy-bake oven, just a hot plate.

There's common off-the-shelf items like brand name protein bars, snack packets of almonds. A wide variety of coffee—but everything has to be sipped through a straw, otherwise it just makes a mess and floats all over the place.

Did you follow any specific diet—either high protein, or plant-based?

For me, there was an experiment that I volunteered to do. "We want you to eat a certain amount of fish. We want you to eat a certain amount of foods that have lycopene.” They were tracking how much potassium I got. I signed up for it right away, because I really do like eating a lot of fish. So much so that they told me, "Wait, you're eating too much fish. You have to cut back on the fish." I do like eating more protein than is commonly recommended.

And I read you were growing some chili peppers too?

Yeah, hatch chili peppers. The experiment was to try to get them to grow. That one was nice because we got to eat the chilis. We had to send some back to the ground too, but we got to eat quite a few.

I imagine being up in space for so long has its mental challenges. How do you work to stay sane?

If you're spending a lot of time in space, the internal conversations you have with yourself become extremely important. If you're the type of person that's always screaming at yourself and beating yourself up, if you got your own internal drill sergeant, that could be a really tough year. I can say that because my first flight was six months long and my internal voice was very much a drill sergeant. If I made a little mistake, I beat myself up.

This time, I really dedicated a lot of effort to focusing on what that was doing and kind of just being more aware of what that was and noticing it. That helped because, for example, let's say you feel like you're doing your schedule and you're doing it more slowly than most people would. If you're not hearing from the ground how they perceive you're doing, you can fill that gap in by saying, "Oh, they must think I'm doing a terrible job. I can't believe it's taking me this long." When you recognize it, [you can say], “Wait a minute, you just don't know what they think.” If you’re more focused on beating yourself up, you're less focused on doing things correctly. So, when you can divorce yourself from those negative attitudes and try to think of something more positively, it's really, really helpful in performing better too.

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It also sounds as if some pretty gnarly stuff can happen to your body up there, like extreme bone density loss. What was your experience?

It did take away 8 percent of my bone density. It's more bone density loss for me than most people. My last flight, I lost 7 percent. The good news is I didn't lose twice as much of my bone density in twice as much time. I got it all back after my last flight so I'm pretty confident I'll get it all back again. I’m expecting it to be more than a yearlong process.

I’m not sure how many discomforts I'm experiencing now are associated with returning from a long space flight versus being a 55-year-old human being. My lower back is bothering me a little more. If I'm doing a lot of pushups and then jump up quickly, my body still hasn't adapted quickly to shoving the blood rapidly to the right places.

How do you get yourself adapted back to Earth?

Right now, every part of my work day is two hours of physical therapy. For example, one of my glutes, it kind of shut down and so they're trying to do an exercise to get that to activate again. I suspect that might have been shut down before the space flight.

It’s really nice when you get three highly trained professionals watching everything you do to try to figure out the right thing to do the next day. After 30 minutes of mobility work, today I was doing agility drills. They had me doing some circuit training, pull ups. It varies a lot and it's very much geared for what issues you have. For me, I felt pretty comfortable walking around after 48 hours. There's some people that can still feel quite nauseous just by walking around still.

It sounds like while you were up there, you had a pretty structured fitness routine and could develop good habits because you didn’t have anywhere else to go. Is there anything you picked up in space that you think you’ll continue?

When I was doing the high intensity interval training, that can get pretty repetitive. You barely pulled it off on your previous workout and then you start in the next workout and you feel like, "I just don't want to do this right now." But what I realized was recognizing that I can do more if I focus on the gain versus the lack. So, if I'm focused on, "Oh my gosh, this hurts so bad right now. And, I still have eight more repetitions of this, eight more cycles to go through,”can get you to say "Stop."

Human beings are really good at planning, but because we're so good at planning, our brain is going to try to make sure you survive this. If you're trying to go all out on every single one of those repetitions, then the best thing to do is not pay any attention to the next thing. Sometimes I was successful because I would almost have an out of body experience where I would be focused so much on just how I felt. I would imagine myself observing somebody else and somehow that let me keep going. Just focusing on the present seemed to help my performance and motivation a lot.

You said you didn’t have any astronaut ice cream … but did you have any cheat meals?

Oh gosh, yes. We have these containers called BOBs. I don't know what the acronym is, but there was one that was desserts and snacks. There was cherry cobbler and there were brownies. The consumption rate of that container varied a lot with the crew. A favorite of mine was popsicles. On transportation spacecraft we would get kind of a special delivery treat of these frozen food items. So, being able to take something out of the freezer that was really cold, just seemed so refreshing. I could have eaten three popsicles in one sitting.

This interview has been edited and condensed.

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Gabriella Paiella is a senior staff writer at GQ, where she covers culture in the form of features, profiles, and Q&As. She’s profiled Nicolas Cage, Jeremy Strong, and Zoë Kravitz for the cover of the magazine, explored why men are so obsessed with the 2003 nautical drama Master and Commander,... Read moreSenior Staff WriterXInstagram