Astronauts Boost Muscle Health, Upgrade Space Station Vital Systems

Expedition 73 Crew Tackles Physiology Research and Critical Hardware Maintenance

Research into maintaining astronaut muscle mass and overall health took center stage aboard the International Space Station this week. The Expedition 73 crew also executed essential life support system upgrades and serviced diverse scientific equipment.

Battling Space-Caused Atrophy

The absence of Earth’s gravity significantly reduces the effort required for movement in space, leading to muscle loss. To counter this, spaceflight crews dedicate two hours daily to rigorous exercise, aiming to mitigate muscle and bone density decline and prepare for their return to Earth’s gravity.

Scientists are exploring electrical muscle stimulation in conjunction with exercise to enhance muscle function, potentially shorten workout durations, and enable the development of lighter exercise apparatus. NASA Flight Engineers Nichole Ayers and Jonny Kim collaborated within the Columbus laboratory module for this muscle study. The findings could benefit future long-duration space missions and aid individuals with mobility challenges on Earth.

Ayers wore electrodes that delivered electrical signals to her legs while Kim operated biomedical equipment to record her muscles’ responses. She later transitioned to a sensor-equipped headband and vest to gather her heart and breathing rates while exercising on the advanced resistive exercise device and an exercise cycle. This collected health data will allow researchers to continually refine crew exercise regimens and improve cardiovascular conditioning in microgravity.

Essential Life Support Overhaul

Later, Ayers and Kim assisted NASA Flight Engineer Anne McClain in replacing a critical catalytic reactor within the Tranquility module. This component is vital for introducing oxygen into the station’s water processing system, effectively oxidizing organic materials in wastewater. Station Commander Takuya Onishi of JAXA (Japan Aerospace Exploration Agency) finalized the maintenance by reinstalling hardware that had been removed to allow access to the advanced life support components.

Earlier, Onishi worked in the Kibo laboratory module, troubleshooting and inspecting combustion research hardware. He subsequently replaced the Microgravity Measurement Apparatus, a device that monitors vibrations within Kibo, which can be influenced by astronaut activities and spacecraft dockings, potentially impacting sensitive experiments.

Global Crew Fitness and Maintenance

Roscosmos cosmonauts Sergey Ryzhikov and Kirill Peskov also participated in an exercise study, using the Zvezda service module’s treadmill for a fitness assessment. The data will help doctors determine individual energy requirements for maintaining fitness in space and readiness for demanding tasks like spacewalks and re-entry. Meanwhile, Roscosmos Flight Engineer Alexey Zubritskiy began his shift by cleaning ventilation systems and smoke detectors. He also underwent training for various in-flight medical procedures, including eye examinations and injections.

The Progress 91 cargo craft, docked to the Zvezda service module, performed an engine burn lasting nearly 12 minutes on Wednesday. This maneuver adjusted the space station’s orbit, ensuring the correct altitude for the upcoming September docking of the Progress 93 cargo craft.

As of 2023, astronauts on the ISS conduct an average of two hours of exercise daily to combat the effects of microgravity on bone and muscle density, similar to the rigorous regimen astronaut Nichole Ayers is undergoing (NASA).

Onboard the @Space_Station, @NASA astronauts @Astro_Nichole and @Astro_JonnyKim are studying the effects of electrical muscle stimulation to help maintain astronaut health in space. #ISS #SpaceResearch pic.twitter.com/WfB70Q2sHw

— NASA (@NASA) July 16, 2025

The research conducted by the Expedition 73 crew highlights the ongoing commitment to astronaut well-being and the advancement of space exploration technologies.