Lie down. Spin, squat, cycle. Breathe harder. Repeat.

Nestled in an Alpine valley in Slovenia, a group of 24 volunteers followed this routine for two months to explore how prolonged inactivity affects the human body. Participants were not allowed to stand up and performed all daily activities with their heads lower than their feet, including eating, showering and toilet breaks.

This strict protocol tricked their bodies into responding as if they were astronauts on the International Space Station for a long-duration mission. Scientists monitored everything from brain function to immune response, collecting data on muscles, bones and fluid shifts.

The second campaign of BRAVE – short for Bed Rest with Artificial gravity and resistive Vibration Exercise – brought complexity to previous bedrest studies by adding three more layers: artificial gravity and resistive vibration exercises, all under reduced oxygen levels simulating conditions at 4,000-metre altitude. BRAVE took place at Slovenia’s Planica Nordic Centre.

The 24 participants were divided into different groups. While some volunteers remained lying in bed for the entire two months, others followed exercise routines and went for a spin in artificial gravity using a short-arm human centrifuge.

As spinning encouraged blood to flow back towards the feet, participants followed a 30-minute daily exercise regime of squats, jumps, heel and toe raises. Artificial gravity has the potential to reduce many of the negative effects of weightlessness on the human body.

Each day was carefully structured: meals in bed, medical checkups, cognitive tests and biological sampling. The Planica facility has clinical research equipment that allows for comparison with other ESA bedrest studies.

The BRAVE campaign conducted a total of 13 experiments and allowed researchers to test techniques to counteract the negative impact of living in space. Many of these effects – osteoporosis, muscle loss and cardiovascular deconditioning – mirror those experienced by elderly or bedridden patients.

As the BRAVE study enters its final phase, European researchers are preparing to analyse a wealth of data that could improve care and treatments for patients on Earth.

This research also consolidates the cooperation with Slovenia, which became the 23rd ESA Member State in January 2025.