Quick Facts

• Astronauts can lose 30% of lower-body muscle mass without exercise countermeasures in space
• Current ISS crew members exercise 2.5 hours daily, 6 days per week using specialized equipment
• Space exercise research helps develop treatments for muscle atrophy and bone loss on Earth

NASA astronaut Jessica Meir commands the International Space Station’s Crew-12 mission while maintaining a rigorous exercise routine that prevents severe muscle and bone loss. The Marine biologist turned space commander launched February 13, 2026, for an eight-month mission studying everything from bacteria to blood flow.

Meir exercises 2.5 hours daily using three specialized machines. The Advanced Resistive Exercise Device (ARED) simulates weightlifting with vacuum cylinders providing 11-272 kg of resistance. She also runs on the COLBERT treadmill and pedals the Cycle Ergometer with Vibration Isolation and Stabilization (CEVIS).

Without this daily routine, astronauts face devastating physical consequences. Research shows they lose approximately 15% overall muscle mass and up to 30% of lower-body muscle during long missions. Weight-bearing bones become 1% less dense each month without countermeasures.

‘Without daily exercise on the ISS, we would lose significant muscle mass and bone density, since we don’t have the daily loading on our bodies that Earth’s gravitational environment provides,’ Meir said from the space station. She added that starting exercise again felt natural: ‘Complete muscle memory! Really feels like I never left.’

The workout split shows ARED comprising 46% of exercise time, COLBERT treadmill 33%, and CEVIS bike 20%. The treadmill provides a unique experience in microgravity. ‘It’s pretty fun to run on T2. You get a little extra spring in your step,’ Meir noted.

NASA research indicates up to 17% of astronauts could still experience muscle performance loss, bone health decline, and reduced cardiovascular fitness despite current exercise protocols.

This marks Meir’s second space mission. She previously spent 205 days on the ISS during Expedition 61/62, where she completed the first three all-woman spacewalks with Christina Koch. Before becoming an astronaut, she worked for Lockheed Martin coordinating bone loss and muscle atrophy studies.

The space exercise research extends beyond astronaut health. Scientists study how microgravity affects human physiology to develop better treatments for aging, sedentary lifestyles, and illness-related muscle loss on Earth.

Future lunar and Mars missions face equipment constraints requiring smaller, more efficient exercise devices. NASA researchers are developing combination aerobic and resistance machines while exploring virtual reality integration to make workouts more engaging.

Crew-12 will conduct experiments on pneumonia-causing bacteria, automated plant monitoring, and blood flow research during their mission. The four-person crew includes NASA pilot Jack Hathaway, European Space Agency astronaut Sophie Adenot, and Russian cosmonaut Andrey Fedyaev.

Read more: NASA Astronaut Workout: How Jessica Meir Builds Muscle and Bone Strength in Space