"The human musculoskeletal system evolved under Earth's gravity," explains Professor Farina. "In microgravity, anti‑gravity muscles like the soleus and quadriceps rapidly atrophy, and weight‑bearing bones lose density at 1–2% per month. Even with two hours of daily exercise on the ISS, astronauts can lose up to 16% of muscle mass on short missions, and full bone recovery takes two to three years after return." The problem is compounded by radiation exposure (50–100 mSv during a six‑month mission, compared to 6.2 mSv annually on Earth) and psychosocial stressors such as isolation and confinement, which elevate cortisol and further accelerate muscle and bone degradation.
Current countermeasures, including the Advanced Resistive Exercise Device (ARED) and treadmills like COLBERT, have helped but remain resource‑intensive. They weigh hundreds of kilograms, require dedicated space, and have even caused injuries—such as shoulder and back strains—during use. More critically, they are impractical for future habitats where every kilogram of payload costs over $1,700 to launch. "We need a paradigm shift," says Professor Burdet. "Instead of a separate gym, imagine a wearable 'second skin' that provides continuous, adaptive loading during an astronaut's daily activities—turning every movement into a therapeutic exercise."
The authors highlight several emerging wearable technologies. Passive suits like the Gravity Loading Countermeasure Skinsuit (GLCS) and its predecessor Pingvin use elastic weaves to simulate gravitational pull, reducing spinal elongation and back pain. However, they are restrictive and uncomfortable for long‑term wear. Newer active systems, such as the Variable Vector Countermeasure Suit (V2Suit), incorporate inertial measurement units and control moment gyroscopes to deliver dynamic resistance. NASA's X1 exoskeleton and Robo‑Glove, developed with GM, represent early steps toward powered assistance, while soft exosuits made from textiles and driven by cables or pneumatic artificial muscles offer a low‑profile, highly wearable alternative.
"Soft exoskeletons are particularly promising for space because they are lightweight, transparent, and energy‑efficient," notes Dr. Kassanos. "In microgravity, actuators no longer have to fight gravity, so even modest forces can provide meaningful resistance. This breaks the vicious cycle of heavy actuators requiring large batteries, which add more weight." The review compares actuation principles—from DC motors and series elastic actuators to shape memory alloys, dielectric elastomers, and HASEL actuators—evaluating their suitability for space environments where radiation, temperature extremes, and vacuum impose strict reliability requirements.
Equally critical are wearable sensors. The authors describe textile‑integrated strain sensors (using liquid metal or carbon‑based composites), high‑density electromyography sleeves, and even flexible transistor arrays that can monitor suit‑body interaction forces, muscle fatigue, skin hydration, and early signs of injury. "A smart suit could detect that a shoulder joint is experiencing abnormal pressure from the space suit hard upper torso, then adjust its own stiffness or warn the astronaut before an injury develops," explains Khan. Combined with brain‑computer interfaces and eye‑tracking for intent detection, such systems could enable intuitive, closed‑loop control of exoskeleton assistance.
Nevertheless, formidable challenges remain. Radiation can degrade electronics and sensors, requiring radiation‑hardened components that are not yet miniaturized for wearables. Microgravity alters how inertial sensors estimate orientation, necessitating novel drift‑resilient algorithms. And, as the GLCS experience showed, any wearable must be comfortable, easy to don and doff, and psychologically acceptable—otherwise astronauts will reject it. "User‑centered design is not an afterthought; it is a core requirement," stresses Varghese.
The authors call for an integrated, multidisciplinary approach combining advanced materials (e.g., boron nitride nanotubes for radiation shielding, ultrathin radiative cooling interfaces for thermal management), neuromusculoskeletal digital twins, and AI‑driven adaptive controllers. "We envision a future where an astronaut's daily movements—reaching, walking, even sleeping—are continuously optimized to preserve muscle and bone," says Professor Farina. "And the same technologies that enable deep‑space missions will also transform rehabilitation for ageing populations and individuals with musculoskeletal disorders here on Earth.".
Authors of the paper include Shamas U.E. Khan, Rejin J. Varghese, Panagiotis Kassanos, Dario Farina, and Etienne Burdet.
This work was supported by the UK EPSRC with the FAIR-SPACE (EP/R026092/1) and NISNEM (EP/T020970/1) projects, as well as by the European Union with the Horizon 2020 ICT 871803 CONBOTS project.
The paper, "Space Physiology and Technology: Adaptations, Countermeasures, and Opportunities for Wearable Systems" was published in the journal Cyborg and Bionic Systems on Apr. 3, 2026, at DOI: 10.34133/cbsystems.0477.
