How bedrest and cycling in artificial gravity is being tested to aid human spaceflight

by Bella Richards

For two months, 12 people from France will be put into a “compulsory reclined lifestyle” to study the impacts that microgravity has on astronauts and whether cycling in artificial gravity could combat the negative effects human spaceflight has on the body. The Bedrest with Artificial Gravity and Cycling Exercise (BRACE) is led by the European Space Agency (ESA) and the French Space Agency (CNES) and will mark the first bedrest study involving cycling in Europe.

The project racked up 3,000 expressions of interest from volunteers in France, but after an extensive selection process, 12 people were selected and are currently gearing up for 60 days in bed, with one shoulder always touching the mattress, tilted six degrees below the horizontal line with their feet up, in the name of science.

NSF sat down with Dr. Angelique Van Ombergen, ESA’s lead for life sciences at human and robotic exploration, to discuss what BRACE is and how it could benefit human spaceflight.

What is BRACE?

With the number of human spaceflight missions growing every year, studying microgravity’s physiological effects on the human body has become paramount to keeping astronauts healthy in space.

“By putting them in the bed for so long and by tilting them six degrees downwards, you induce processes in the human body that are similar to what astronauts are showing in space,” Dr. Angelique Van Ombergen said.

The volunteers will participate in one of three categories: remaining in bed the entire time, remaining in bed other than 30 minutes a day of cycling, or remaining in bed other than 30 minutes a day of cycling in the artificial gravity centrifuge. Everything from eating meals, toilet breaks, and showers will be done lying down.

Bedrest studies are not new but have garnered more attention over the past few years. In fact, in November 2021, NASA awarded Deutsches Zentrum fur Luft-und Raumfahrt (DLR) in Germany $49.9 million to support further bedrest studies.

This latest project follows a similar project conducted in 2019, where ESA, NASA, and Germany completed the first-ever bedrest study with artificial gravity to test whether it had an impact on the deterioration of the human body in space. Like BRACE, the previous study placed participants in a spinning artificial gravity centrifuge for 30 minutes a day to determine whether spinning could countermeasure the negative effects of microgravity. Dr. Van Ombergen said the preliminary results of the project were not as beneficial as hoped but believes BRACE might produce a better outcome.

“This BRACE study is basically a follow-up in the sense that we are looking at a combination of artificial gravity and cycling exercise in comparison to only cycling, to see whether there is a supplemental effect of artificial gravity, and to better understand whether there can be a potential extra advantage or benefit to save [astronauts] from the unwanted changes we see in bedrest that mimic some of the physiological changes in spaceflight,” Dr. Van Ombergen said.

Volunteer placed in wall-mounted bike category. (Credit: ESA)

The participants who have been assigned to use the bicycle without the artificial gravity centrifuge will be taken out of their bed once a day and cycle for 30 minutes on a wall-mounted device. The participants assigned to the artificial gravity will be taken out of bed to lie down in the centrifuge and cycle for 30 minutes, while being spun around to drive the blood toward their feet, doubling the force of gravity.

“We encourage volunteers to reach their maximum effort on the bike, and then compare the impact with those who are not biking at all,” explains Rebecca Billette, head of clinical research at MEDES, the Institute for Space Medicine and Physiology in Toulouse, France.

The study involves 14 different European scientific teams and is taking place at the MEDES Space Clinic in France.

“We will compare the impact of a daily exercise routine on a variety of physiological factors,” Billette added.

BRACE study begins in France. (Credit: ESA)

Bedrest and Human Spaceflight

Long-term bedrest has been touted as an effective way of mimicking the body’s response to weightlessness. Several bodily changes during bedrest are similar in space, such as blood flowing to the head, fluid shifts, and bone and muscle loss. According to NASA, without gravity pulling blood flow to the legs, astronauts’ heads are filled with fluids, causing puffy-head bird-legs syndrome.

“We hope to understand the added value of artificial gravity to the fitness routine astronauts follow on the International Space Station (ISS). The crew exercises two hours per day in orbit. It [artificial gravity] could become an effective solution for a healthier body during long-duration space missions, if the technological challenges can be overcome,” said Dr. Van Ombergen.

The primary benefit of performing these bedrest tests on Earth is that there are far fewer costs.

“We have much less constraints and logistics, and we don’t need to think about upload or download or anything like that. We don’t need to think about mass, we can test more subjects in a shorter amount of time, which of course, in biomedical research is really important. We can test or validate countermeasures that we can then later test in space. So, I think there’s a lot of advantage to doing these grounds studies to inform actual space missions,” Dr. Van Ombergen said.

However, although bedrest provides a good representation of the human body in space, its effectiveness is limited.

“When we put subjects on Earth in a bed for so long, there’s the disuse of their bones and muscles, and that’s why they deteriorate, but the gravity is still there,” she said. “Whereas in space, the astronauts are actually quite active, but still their muscles and bones deteriorate because there’s no gravity that’s working in against the muscles or impacting their bones metabolism.”

In a 2016 study published by the American Physiological Society called ‘Long-Duration bed rest as an analog to microgravity,’ the authors noted that more of the body’s surface area is compressed in bedrest compared to in space.

Volunteer undergoes rigorous testing during the 60-day bedrest. (Credit: MEDES)

“In actual microgravity, external compression of all body surface areas is minimal, whereas bed rest generates more compression of tissues over a greater surface area of the body area. This greater compression increases tissue pressures and probably dehydrates areas of weight bearing because of greater interstitial flow into the microcirculation,” the paper explained.

Despite these caveats, Dr. Van Ombergen said bedrest remains a strong model to validate technology that could benefit human spaceflight.

The Ups and Downs of 60 Days in Bed

The 12 volunteers will be treated as human guinea pigs for two months and will be poked and prodded all day long, Dr. Van Ombergen said. ESA and CNES went through a vigorous process to find their participants, filtering out those who may have certain neurological, bone, or muscle diseases.

The main criteria for selection were that the volunteers had to be male, aged between 20 to 45, in good physical shape with a BMI between 20 and 27, and a non-smoker.

Once they begin the 60 days, each participant will be placed into their category: cycling, cycling with artificial gravity, or bed rest. While the participants are given detailed information about what they will undergo, the category they are placed in will be completely randomized, which Dr. Van Ombergen said can be psychologically difficult.

Artificial gravity centrifuge at DLR in 2019 study. (Credit: DLR)

The participants will follow a very standardized routine, Dr. Van Ombergen said. “They will be woken up every day at the same time. They will take their meals at the same time. Their meals will be very standardized, [and] they will be measured in terms of the nutrients that are in there. They need to eat a specific portion of that food to make sure they get enough nutrients,” she said.

Even when they finish their food, the teams will calculate what is left on the plate to analyze the most accurate representation of what went into their body, which will impact their results.

Other than the 30 minutes of exercise for the two groups, their days will be filled with undergoing tests, such as muscle biopsies, urine samples, scans to check body composition, data collection to check blood pressure, heart rate, nutrient absorption, energy expenditure, bone mass, and mood.

The participants will get their own time, but Dr. Van Ombergen asserts that it will be difficult. Participants are encouraged to set goals, such as learning a new language or taking a class online, to help with boredom.

Volunteer placed in bedrest tilted six degrees to mimic the feeling of weightlessness. (Credit: DLR)

“From a physical perspective, you’re deteriorating to a certain extent by lying in bed for so long and you might get some nuisance or some things that are uncomfortable, maybe even some pain. At the same time, you’re being asked to participate in all the investigations, which sometimes are quite invasive or might be a little bit painful,” Dr. Van Ombergen says.

In early 2024, ESA and CNES will conduct a second part of the same study with another 12 participants. The agencies will then have a total of 24 people to analyze. The next project will be another 60-day study in Slovenia focusing on the combination of vibration exercise and artificial gravity, ESA explained.

After 60 days, the participants will undergo 14 days of post-bedrest recovery and monitoring. The study began on April 4 and will end in Early July.

(Lead image: BRACE bedrest volunteer placed in artificial gravity centrifuge. Credit: ESA)

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