In November, we ran a story about a NASA study that was paying Andrew Iwanicki $18,000 to lie in bed for three months. This is how the remainder of the study went.

I woke up on December 2, and for the first time in 70 days, I stood up. Or at least I tried to. The nurses wheeled me over to a hospital bed that would be tilted vertically, with blood pressure cuffs hugging my arm and my finger, an ultrasound machine pointing at my heart. Then they told me, with the encouragement that you'd give a toddler learning to walk, to try standing for 15 minutes.

As soon as the bed was tilted to the vertical position, my legs felt heavier than ever before. My heart started to beat at 150 BPMs. My skin became itchy; I was covered in sweat. Blood rushed into my legs, expanding the veins that had become increasingly elastic throughout the past several months of bed rest. I felt like I was going to faint. I was fighting to remain standing from the start, and it only became more difficult. Around the eight-minute mark, my pulse dropped from 150 down to 70. My body was about to collapse. As my vision started to go black, the staff saw my numbers drop on the machines and promptly returned the bed to the horizontal position. It was only later that they told me that none of the NASA bed-rest subjects have lasted the full 15 minutes.

Related: "Taxi to Mars"

It was no surprise my body acted this way, of course. After spending 70 days tilted at a negative-six-degree angle, I had lost about 20 percent of my total blood volume. The standing test simulated the effects on astronauts' cardiovascular systems during spacecraft reentry to Earth or Mars. But it was easy to forget all that because most of the NASA bed-rest study had been, despite my expectations, kind of boring.

When I last wrote about my experiences in the study, I was still in the honeymoon phase—there was a parade of researchers poking and prodding me, sure, but it was also one of the most relaxing times of my adult life. For years, I had continually been in a rush: cramming for tests in college, staying ahead in the workplace, and fulfilling social obligations during whatever gaps I could find. All of that was suddenly gone. Beyond following the program protocol, I had no real responsibilities. I was free to do as I pleased—as long as it didn't involve leaving my bed, or eating a snack, or taking a nap. Some days, I read from morning until night. On others, I spent several hours on the phone with friends and family. I spent an ungodly amount of time fiddling with my fantasy football teams and playing StarCraft 2. Sometimes, I would simply lie peacefully, reflecting on the past, planning for the future, or basking in a quiet moment. I was truly appreciative of these opportunities afforded by my state of isolation. But eventually, the novelty wore off.

The following eight weeks in bed were a drastic departure from that early period. While the days were punctuated by regular meals, exercise, vital-sign readings, and intermittent testing, the bulk of my time was empty. Even the testing became increasingly monotonous: I was often asked to lie completely still while data was collected. An MRI machine measured the growth and decay of my muscles. An X-ray checked my bone density. A plastic bubble captured my air intake. I was left alone for extended periods of time with only my thoughts and a view of foam-tile ceiling.

By the fourth week, I could feel a significant psychological shift. I became accustomed to my isolated antisocial state. I wrote fewer emails to friends. Conversations with the staff became shorter, more practical. I made phone calls to family less often. I often felt I had nothing to share.

"Hey, Drew! What have you been up to?"

"Not much. Still in bed..."

That's not to say my days were completely blithe. I was still shitting in a bedpan, after all. I still experienced moments of fear and anxiety. I was certain that I was one bad day away from a mental breakdown—how could I possibly just drift through ten weeks in bed?

The most intense anxiety during this time actually stemmed from my girlfriend's upcoming visit. I was fully aware of my odd mental state, and I was certain I looked pretty foul, though I hadn't glanced in a mirror in more than a month. What would our visit be like when I couldn't even stand up to properly greet her? Was I even capable of extended conversation after so many hours of solitude? How would she react when she saw me in shambles: detached, vulnerable, and dependent? Tears were inevitable, and I wouldn't even be able to comfort her the way I should.

As soon as she came into the hospital wing, she jumped on the bed to hug and kiss me. A rush of euphoric release was immediately interrupted as a nurse rushed in to inform her that she could not be on the bed at any time. In fact, she wasn't allowed to even touch the bed "for safety reasons." We had been waiting for more than two months to see each other, and this was how it had to be.

She sat in a chair by my side as we talked for three days. Physical contact was limited. We couldn't explore the town together. We couldn't even share a meal, since guests weren't allowed to bring outside food into the unit. When lights out came around, she drove back to her hotel to sleep alone. It was a cruel tease that reminded us both of what we were missing. It shook me from my meditative state and reawakened a desire for my former life outside the hospital walls.

That was the last truly personal interaction I had for another two months.

An average meal in the research unit

The following weeks held few details of note. The days blurred together. I tried to avoid counting down my time left; rather, I measured my stay by my increasing sensitivity to the small, daily frustrations that were slowly chipping away at my mind. Why did I have to drink water out of an open glass, even though at the angle of my bed, it inevitably spilled all over my table and chest? Why did they serve soup in shallow bowls? Why were they serving soup to people in bed anyway? Did any of the staff have any idea what it was like to be stuck in bed?

After the fifth time I ate a soggy, microwaved filet of fish, I finally asked if I could be served something else—anything else. During orientation, the staff had assured us that they would do their best to cater to individuals' tastes, but the dietitian's response was simply a friendly apology and explanation that they must keep all participants' diets consistent. I asked if I might be able to substitute dry cereal for the oatmeal we were often served for breakfast. Again, the answer was no. My biggest win was the addition of one packet of black pepper to each meal.

Around week seven, the other two participants in CFT 70 finished their part of the study. I congratulated them as they left, but considering how isolated we all were, I hardly noticed a difference when they were gone. Without them, I was the last man lying and the only subject on the hospital wing.

In the home stretch, I forced myself to think about all that I had gained from the past 70 days. I had read hundreds of pages. I was meditating regularly. I was rediscovering my love of video games and kicking ass in fantasy football. And I was putting some serious money in the bank—almost $18,000, when all was said and done.

And so I found myself at the end of the ten weeks in good sprits and feeling healthy—until the last day of the study, when they tilted me upright and asked me to stand.

I remained horizontal until the following day. That morning, I was strapped to a stretcher and put in the back of a van to head to Johnson Space Center for the first of four rounds of marathon testing. As I was wheeled through the sliding glass doors of the hospital, sunlight touched my skin for the first time in more than two months. This was the first time I had a good look at the sky or anything that wasn't the stark white walls of the hospital, and I couldn't wipe the smile off my face. My deprivation renewed my appreciation for the simple pleasures of the world.

I performed the same slew of testing that I did pre-bed rest: running through mazes, jumping off of platforms, standing on force plates, executing hand-eye coordination tasks, testing my balance, measuring my leg and arm strength. And yes, the muscle-twitch test, a.k.a. the blast-your-fucking-leg-full-of-electricity test. But the anxiety I felt in pre-bed-rest tests was replaced with anticipation. The finish line was in sight, and each electrical shock brought me one measurement closer to my freedom. I was a mere two weeks away from completing my 108-day stay.

The author's fond farewell to urinating into a "pee jug" rather than the toilet

As I was wheeled into the testing facility, I was greeted by many familiar and unfamiliar faces. A number of the research staff had decided to come to watch the final participant of the CFT 70 project take his first steps. I was certainly excited, but I imagine many of them were even more thrilled than me. While this project had consumed my life for the last three months, it had been the primary focus of their work for four years. It was an important moment for all of us.

With a staff member on each side and an audience on hand, I sat up on the stretcher and stepped down onto the ground. My feet tingled like they were asleep. My legs felt strong, but my balance was weak. My first steps were sluggish and short as I dragged my feet across the ground and kicked my ankles. I lacked all the fine coordination skills that I hadn't used for months. I felt sharp pains in my ankles and feet as I pivoted through the obstacle course, and I certainly couldn't walk a straight line well, but I completed all the tests without any real troubles.

Within a few days of casual strolling and formal reconditioning exercise, my balance returned and my endurance began to recover. By the end of the two-week post-bed-rest period, I felt 95 percent physically normal. I was ready to go.

On the 108th day, I packed my bags as I fantasized about everything that awaited me outside the hospital walls: On the way to the airport, I would have a breakfast burrito, maybe even a Bloody Mary. I was moments away from delicious food, bountiful liquor, the sun, and my girlfriend.

I said a round of farewells to the staff and thanked them profusely. Despite any of my complaints, the team was full of good-hearted people who had intelligently designed and executed a remarkable feat. I was truly appreciative of their focus, hard work, and support.

With $18,000 added to my bank account, an open calendar, and freedom from any protocol beyond state and federal law, I felt better than I had in years. I had no regrets. And so, as I sipped an overpriced Bloody Mary in the airport terminal, I found myself looking into new research studies. There was one infecting participants with a new flu strain, which paid $4,000 for ten days... Who says I couldn't do it all over again?