NASA Gives Space Biology a Workout: Astronauts Track Blood Flow and Muscle Strain in Space

Insider Brief

• NASA astronauts aboard the International Space Station are testing new tools to study how spaceflight affects circulation and muscle health in preparation for long-duration missions to the Moon and Mars.
• One study, Drain Brain 2.0, uses a neck-worn sensor to monitor how blood flows from the brain in microgravity, aiming to improve cardiovascular monitoring in space and inform treatments on Earth.
• Another study, ARED Kinematics, uses motion capture to analyze how astronauts perform resistance exercises in orbit, helping refine in-flight training programs and offering potential benefits for physical therapy on Earth.
• Image: NASA astronaut and Expedition 72 Flight Engineer Nichole Ayers works inside the International Space Station’s Kibo laboratory module loading software onto an Astrobee robotic free-flyer for a technology demonstration. (NASA)

NASA astronauts aboard the International Space Station are testing new tools to monitor how space travel affects circulation and muscle health, part of a broader effort to prepare crews for long-duration missions to the Moon and Mars, NASA said in a statement.

“Astronauts are living in space for months at a time and scientists have been continuously studying how their bodies adapt to weightlessness,” the NASA team writes. “Results are especially important as NASA and its international partners plan long-duration crewed missions to the Moon, Mars, and beyond that are less dependent on Earth.”

The latest round of studies focused on two key risks astronauts face in orbit: how blood drains from the brain without gravity and how the body responds to resistance exercise in microgravity. Both affect crew safety and long-term health, with potential benefits for medicine on Earth.

Drain Brain

NASA Flight Engineer Nichole Ayers began work on a study called Drain Brain 2.0, using a collar outfitted with sensors to track changes in blood volume in her neck. The experiment aims to measure how blood returns from the brain to the heart in weightless conditions.

“Doctors want more insight into how the lack of gravity impacts cardiac function from the brain to the heart to improve health screening for crews in space and promote new treatments for heart conditions on Earth,” NASA said in the post.

On Earth, gravity helps blood drain downward from the brain. In space, that pull is absent, leading to fluid shifts toward the head. These shifts are linked to vision changes, pressure behind the eyes, and possibly even blood clots. NASA says better data on blood flow patterns is needed to monitor astronaut health and develop effective countermeasures.

The experiment uses an upgraded plethysmography device, which includes solid-state strain gauges and ECG electrodes to detect changes in the jugular venous pulse, or JVP. The JVP waveform is a known marker of cardiac function and has been studied as a potential signal for diagnosing heart failure.

According to NASA, “results may help researchers design effective exercise programs to counteract the effects of weightlessness including bone loss and muscle atrophy.”

The hardware, developed as part of a previous Drain Brain study, is compact, non-invasive and designed for use in orbit. It works by detecting volume changes in the jugular vein using electrical sensors wrapped around the neck, according to the NASA project brief. The waveform data it generates provides information about how well the blood is draining from the brain and whether there are signs of backflow or blockages.

Research coordinator Angelo Taibi, in the project brief, noted the growing interest in jugular venous pulse monitoring and non-invasive diagnostic tools for both space and clinical medicine. The study is being maintained by NASA’s ISS Research Integration Office.

ARED Kinematics

Meanwhile, Takuya Onishi, a flight engineer representing the Japan Aerospace Exploration Agency, worked on a separate study called ARED Kinematics, which investigates how the body responds to strength training in orbit. He installed a motion capture system in the station’s Tranquility module and performed a recorded workout using NASA’s Advanced Resistive Exercise Device, or ARED.

ARED simulates free-weight exercises like squats and deadlifts, which astronauts use to prevent muscle and bone loss during missions. But it remains unclear exactly how much strain these exercises place on joints and muscles without gravity to provide natural loading.

“The ARED Kinematics investigation assesses the current exercise programs to allow for the improvement of exercise prescriptions by conducting a biomechanical analysis of exercise on the ARED onboard the space station,” according to NASA.

One goal is to quantify internal joint torques, muscle forces and bone stresses — key metrics that can’t be directly measured without motion tracking tools. This helps researchers adjust in-flight exercise plans to ensure astronauts are not under- or over-training.

Another aim is to determine how much body weight replacement (BWR) is needed. Because microgravity removes body weight, resistive loads on ARED must be increased to replicate Earth-like strain—but the optimal level of replacement remains uncertain.

This study, also supported by the ISS Research Integration Office, may guide improvements in space exercise protocols and equipment, especially for long-term missions or lunar surface work.

Applications on Earth

NASA says the methods developed through ARED Kinematics could have applications on Earth in sports training and rehabilitation. The same motion capture and biomechanical modeling tools may help design safer, more personalized workout routines for athletes and patients recovering from injury or managing chronic joint conditions.

The implications of Drain Brain 2.0 also extend to clinical care. On Earth, JVP is usually assessed visually or with ultrasound, and its quantification often requires invasive catheterization. NASA’s strain gauge-based plethysmograph offers an alternative — if validated.

“Since the variation over time of these blood volumes is closely related to cardiac oscillations in general, and to the JVP in particular, plethysmography is an excellent method to be performed in parallel with ultrasound scanning,” NASA said in a technical description.

Future exploration missions, including those to Mars, will involve extended periods in microgravity and low-gravity environments. NASA notes that stagnant or reversed blood flow in the jugular vein has been reported in space and could lead to deep vein thrombosis, making real-time monitoring tools like the plethysmograph essential.

Eye Checks

NASA Flight Engineers Anne McClain and Don Pettit also participated in regular eye checks as part of an ongoing study on vision changes in space. McClain served as crew medical officer, examining Pettit’s eyes using standard imaging gear while doctors on Earth monitored the session in real time.

The agency continues to study how headward fluid shifts affect the optic nerve, with past data showing that some astronauts experience changes in visual acuity and eye structure.

The experiments are part of a more than 24 year legacy in the space station where astronauts have continuously lived and worked, testing technologies, performing science and developing skills needed to explore farther from Earth, NASA reports.

For more information on space biology and a comprehensive breakdown of the space biotech industry, check out Charting the Space Biotech Landscape: A Look at the Industry’s Key Players and Emerging Trends.