The experiment lasted 138 days: 15 days of baseline observation and pre-adaptation, 90 days at a six-degree head-down tilt, and 33 days of recovery after the participants returned to an upright position. Radial pulse graphs were recorded at baseline, on days 7, 15, 30, 45, 60, 75, and 90 of bed rest, and on recovery days 7, 15, and 30. Cardiovascular ultrasound data were collected at corresponding stages. This repeated schedule allowed the investigators to compare not only pre- and post-bed-rest averages, but also the timing of physiological changes during the prolonged exposure and their course after normal gravity resumed.

The study was a controlled simulation, not a spaceflight, and it cannot reproduce the combined effects of radiation, isolation, confinement, disrupted circadian rhythms, and microgravity. Its participants were all healthy men aged 32.0 ± 2.6 years, and each experimental group contained only seven or eight people. The researchers randomly allocated them according to age, height, weight, peak oxygen consumption, maximum squat strength, and femoral-neck bone mineral density. Eight men formed a control group without a countermeasure. The remaining groups received aerobic exercise, resistance exercise, combined aerobic and lower-load resistance training, or combined aerobic and high-load resistance training. Because the study was conducted in healthy young men, its findings cannot automatically be generalized to women, older adults, people with cardiovascular disease, or astronauts in orbit.

Pulse waves were acquired with a digital instrument at the left radial artery, with the forearm relaxed, the palm facing upward, the elbow flexed to about 120 degrees, and breathing kept steady. After the waveform stabilized, its amplitude was maximized and a 30-second pulse graph was recorded. The investigators extracted time-domain features using a combination of an energy envelope and the Hilbert transform. Principal amplitude measures included h1, the main wave associated with large-artery compliance and left-ventricular ejection; h3, a pre-dicrotic wave linked to arterial elasticity and peripheral resistance; h4, the dicrotic notch associated with peripheral resistance and aortic-valve closure; and h5, a dicrotic wave related to large-artery compliance and aortic-valve function. Timing features described one cardiac cycle and the rapid-ejection, systolic, and diastolic phases, while ratios expressed relationships among wave heights and durations.

Most pulse characteristics changed across the baseline, bed-rest, and recovery stages. The main wave h1 rose from an average of 17.41 at baseline to 20.68 during bed rest before falling to 19.40 during recovery. The pre-dicrotic wave h3 increased from 12.02 to 13.52 and then returned toward baseline at 11.52, while the dicrotic notch h4 rose from 6.79 to 8.60 before declining to 6.51. The total cardiac-cycle duration t rose from 0.79 to 0.94 during bed rest and remained somewhat elevated at 0.90 during recovery. In contrast, h3/h1 and w/t declined, and h4/h1 rose during bed rest before falling below its baseline value during recovery. These are group-level patterns and measured differences, not evidence that every individual responded in the same way.

Ultrasound measurements showed that the clearest changes involved vascular structure, arterial wave propagation, blood flow, and resistance rather than conventional cardiac structure or function. Carotid intima-media thickness increased from 0.45 ± 0.08 mm at baseline to 0.50 ± 0.07 mm during bed rest and 0.51 ± 0.07 mm during recovery. Density-calibrated pulse-wave velocity rose from 5.20 ± 0.59 to 5.82 ± 0.83 m/s, while common-carotid pulse-wave velocity increased from 7.40 ± 1.03 to 8.14 ± 1.37 m/s. The maximum velocities measured in the left internal carotid and femoral arteries initially decreased and then rose again during recovery. Resistance indices in the internal carotid, vertebral, and femoral beds generally declined. By contrast, ejection fraction and other cardiac structural and functional measures did not differ significantly across the three broad stages, although repeated-measures analysis detected changes in some ventricular dimensions.

Canonical correlation analysis tested whether the pulse-feature set and ultrasound-indicator set moved together as two broader systems. The two reported canonical correlations were 0.741 and 0.674, both statistically significant at P < 0.05. The ultrasound variables contributing most strongly included carotid and femoral resistance indices and carotid-femoral pulse-wave velocity. Pulse features with higher contributions included h3, h4, t5, As, h3/h1, h5/h1, and w/t. Separate bivariate analyses identified recurring relationships over at least four time points, with coefficients above 0.3, between individual pulse parameters and measures such as carotid-femoral pulse-wave velocity, density-calibrated pulse-wave velocity, internal carotid resistance, and femoral resistance. These are statistical associations, not proof that pulse morphology directly causes a cardiovascular change or can diagnose a specific condition on its own.

The intervention groups followed broadly similar physiological trajectories, but their timing and fluctuations differed. The peak in h1 occurred earlier in all four exercise groups than in the control group—for example, on day 7 in the resistance-exercise group compared with day 15 in controls. Carotid intima-media thickness continued to rise in controls during early bed rest, whereas it stabilized after an initial increase in the intervention groups and subsequently declined after day 30. The combined aerobic and high-load resistance group showed the smallest intima-media fluctuations, while the resistance-only group showed the largest. The control group also had greater fluctuations across most ultrasound indicators. Because these intergroup findings were based largely on time-point trends in small groups, they indicate a possible advantage of combined training rather than establishing a causal or definitive superiority of one exercise protocol.

Taken together, the results support radial pulse-wave parameters as possible dynamic indicators of cardiovascular adaptation during prolonged head-down bed rest. The authors interpret the shared patterns as evidence that changes in vascular elasticity and local hemodynamics can be reflected in outwardly detectable pulse characteristics. The approach is technically promising because it could support repeated, noninvasive monitoring where direct cardiovascular assessment is difficult, but the current evidence comes from a simulated environment and does not establish clinical performance in space. The authors also note that recovery was not uniform: some pulse ratios remained different from baseline even after 30 upright days, indicating that cardiovascular readaptation may proceed in phases. Further studies with larger and more diverse populations, longer follow-up, and more complex environmental simulations will be needed before pulse-based monitoring can be considered a validated space-medicine tool.

Subject of Research: Assessment of cardiovascular adaptation to prolonged head-down bed rest using radial pulse-wave features and ultrasound.

Article Title: Application of radial artery signal characteristics in long-term head-down bed rest experimental cardiovascular status assessment

Article References: Ha, K., Hu, X., Liu, D., Zhang, G., Zhang, S., Zhao, S., Tu, L., Jiang, T., Ma, X., Fan, Q., Liu, J., Zhang, C., Shi, H., Xu, J., & Cui, J. (2026). Application of radial artery signal characteristics in long-term head-down bed rest experimental cardiovascular status assessment. Frontiers in Physiology, 17, Article 1961052. https://doi.org/10.3389/fphys.2026.1961052

Image Credits: AI Generated

DOI: 10.3389/fphys.2026.1961052

Keywords: head-down bed rest, simulated weightlessness, radial pulse waves, cardiovascular monitoring, arterial elasticity, exercise intervention, space medicine, vascular resistance, pulse-wave analysis, Application, radial, artery

The central question the researchers set out to answer was deceptively simple but enormously consequential for mission planners. When astronauts spend months floating in microgravity, the heart no longer has to pump blood uphill against the pull of Earth’s gravity, and the body begins to shed the capacity it no longer uses. Muscle mass and cardiac mass both decline in orbit because the cardiovascular system is working far less than it does on the ground. The worry has always been what happens at the other end of the journey: Mars has a surface gravity only about one-third as strong as Earth’s, and a crew arriving after months of weightlessness would need to stand, walk and work almost immediately after landing. If their hearts could not maintain blood pressure and blood flow to the brain in that transition, the mission concept itself would be in jeopardy.

Historically, that worry was well founded. Many astronauts returning from earlier space missions struggled with dizziness and lightheadedness when they stood up after landing, a phenomenon known as orthostatic hypotension. The sudden shift back into a gravitational environment causes blood to pool in the lower body, producing a drop in blood pressure that can leave people faint or unsteady. It is one of the classic hazards of re-entry into gravity, and it has shaped decades of thinking about how long a crew could safely remain in space before losing the ability to function on a planetary surface.

What distinguished the astronauts in this study was their exercise regimen. Following a NASA program called Exercise Countermeasures, the crew members worked out for up to two hours every day while in orbit. That routine included 30 to 45 minutes of endurance exercise and 60 to 75 minutes of resistance training, a combination designed to preserve both the aerobic capacity of the heart and the strength of the skeletal and cardiac muscle that gravity normally maintains. The payoff was clear in the data: the astronauts largely tolerated the transition back into a gravitational environment without the severe orthostatic problems seen in earlier eras of spaceflight.

Senior author Dr. James Thomas, professor of medicine in the division of cardiology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine cardiologist, explained the underlying physiology in plain terms. You lose muscle mass and cardiac mass in a weightless environment because you are working less up there, he noted, describing how astronauts float through the cabin and can sail across the module with a light tap of the foot. To counter that loss, he said, exercise is crucial when you are in space. The study’s message, in his view, is optimistic: with these findings, there is now reason to think that crews would be able to traverse to Mars, get there and actually work on the surface of Mars.

The technical backbone of the study was a remarkable series of echocardiograms, ultrasound scans of the heart, collected before, during and after each mission. Rather than relying solely on ground-based measurements taken before launch and after landing, the researchers captured cardiac structure and function continuously in flight. The astronauts were trained to perform echocardiographic scans on one another every few weeks aboard the station, and the images were transmitted to Earth for analysis. Thomas, working with collaborators Dr. Benjamin Levine of UT Southwestern Medical Center and Dr. Michael Bungo of McGovern Medical School at UTHealth Houston, reviewed the recordings as they arrived. Because the space station runs on Greenwich Mean Time, that often meant monitoring live scans around 3 a.m., coaching the astronauts in real time to adjust their technique and improve image quality. The result is an unusually rich longitudinal dataset on how the human heart behaves in prolonged weightlessness.

That dataset revealed a clear pattern of adaptation. During the first two weeks of spaceflight, the astronauts experienced reductions in cardiac filling, stroke volume and other measures of cardiac performance. In practical terms, their hearts were filling with less blood between beats and pumping less blood with each contraction, reflecting the reduced circulatory demands of weightlessness. But this early dip proved temporary. As the missions progressed, cardiac filling and stroke volume gradually moved back toward preflight levels, indicating that the heart stabilized rather than continuing to deteriorate over the months in orbit. For mission designers, that trajectory matters enormously: it suggests the cardiovascular system reaches a workable equilibrium in microgravity rather than entering an open-ended decline.

The most novel part of the study came after the astronauts returned to Earth. To simulate the moment of arrival on Mars, the research team tilted the astronauts 22 degrees upward from a lying-down position. This head-up tilt shifts blood toward the lower body, mimicking the hydrostatic effects of Martian gravity, which pulls with roughly one-third of Earth’s force. The scientists then assessed how the astronauts’ hearts responded to this simulated Martian environment. The verdict was striking: the astronauts’ hearts handled the simulated Martian conditions as well as they had handled simply standing upright on Earth before launch. In other words, after six months in space, their cardiovascular performance under Mars-like loading was indistinguishable from their preflight baseline on Earth.

The study, titled Impact of Prolonged Spaceflight on Cardiac Structure and Function: An Exploratory Longitudinal Observational Study, is the first to examine how the heart responds to simulated Martian gravity after prolonged exposure to microgravity. That combination, long-duration flight data plus a Mars-gravity simulation, is what gives the findings their weight for future exploration planning. A Mars transit is expected to take far longer than a typical six-month station increment, so questions remain about even longer exposures, but the demonstration that daily exercise can preserve cardiac function through half a year of weightlessness and a gravity transition removes one of the major physiological roadblocks from the mission architecture.

For the growing community of scientists and engineers working toward human exploration of deep space, the study is a reminder that the body is not a fixed liability but a adaptable system that responds to the demands placed on it. The astronauts in this study did not avoid the cardiovascular deconditioning of weightlessness entirely; their hearts initially shrank in output just as predicted. What they did was counter that loss with disciplined, hours-long daily training, and their hearts repaid the effort by performing under simulated Martian gravity as though the months in orbit had barely happened. As NASA refines its plans to send astronauts to the Red Planet, the message from Circulation is clear: the heart, given the right workout every day, appears ready to make the trip.

Subject of Research: Effects of prolonged spaceflight and exercise countermeasures on astronaut cardiac function and adaptation to simulated Martian gravity

Article Title: Exercise helps astronauts’ hearts handle months in space, boosting prospects for Mars

Article References: Exercise helps astronauts’ hearts handle months in space, boosting prospects for Mars. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: astronauts, cardiac function, microgravity, Mars, International Space Station, echocardiography, exercise countermeasures, orthostatic hypotension, stroke volume, space medicine, Circulation, Northwestern University

The choice of the specific parameters measured in this study reflects both practical constraints and the priorities of space medicine. Body weight, core body temperature, blood pressure, heart rate, and peripheral oxygen saturation are inexpensive, quick, and reliable to obtain in a confined habitat without specialized equipment, making them feasible for repeated measurement by crew members themselves. Each parameter also serves as a proxy for a distinct physiological system. Body weight integrates fluid balance, energy intake, and expenditure, and shifts in weight during confinement can signal changes in dietary habits, hydration, or activity levels. Blood pressure and heart rate reflect cardiovascular regulation and, indirectly, autonomic nervous system tone, which is sensitive to stress, sleep quality, and physical activity. Core body temperature relates to thermoregulation and circadian rhythmicity, both of which can be disrupted when natural light cycles and environmental variability are removed. Peripheral oxygen saturation, while generally stable in healthy individuals at sea level, provides a safety margin check that can detect respiratory or environmental problems. Together, these five measures form a minimal but informative panel for monitoring crew health in resource-limited settings.

The pronounced inter-individual variability observed, particularly for body weight and cardiovascular measures, deserves careful attention because it mirrors one of the most consistent findings across analog and spaceflight literature. Individual responses to identical environmental stressors can diverge substantially, influenced by baseline fitness, habitual diet, sleep chronotype, stress coping styles, and prior experience with confined or expeditionary settings. In the Mars500 experiment, for example, crew members showed markedly different patterns of sleep-wake disruption and activity over the 520-day simulated mission, and similar heterogeneity has been documented in Antarctic overwintering personnel. This variability has practical consequences: group-level averages can mask clinically meaningful changes in individual crew members, which argues for personalized monitoring approaches in which each individual serves as their own control. It also complicates the design of analog studies, since small cohorts drawn from a variable population may not represent the range of responses expected in larger, more diverse astronaut corps.

The methodological decision to rely on descriptive statistics rather than inferential testing reflects a common and often underappreciated challenge in analog research. With 40 participants measured at three time points, the dataset is respectable by the standards of analog missions, which frequently involve crews of four to six individuals. Even so, the authors found that several variables deviated from normal distributions, as assessed with Q-Q plots, which undermines the assumptions underlying parametric tests such as repeated-measures analysis of variance. Non-normal distributions of physiological parameters in small samples can arise from genuine biological heterogeneity, from measurement variability, or from the bounded nature of some measures such as oxygen saturation, which clusters near its physiological ceiling. When distributional assumptions fail, inferential tests lose their interpretability, and presenting medians, ranges, and distribution shapes becomes more honest than reporting p-values that may be unstable or misleading. This approach also guards against overinterpreting random fluctuation as meaningful adaptation, a pitfall that has affected some smaller analog studies.

The measurement schedule itself, with assessments on Days 1, 7, and 14, represents a compromise between scientific resolution and operational feasibility. Weekly sampling can capture broad trends and identify whether parameters drift over the mission, but it cannot resolve day-to-day fluctuations that may carry their own information. Heart rate and blood pressure, for instance, are influenced by acute factors such as sleep quality, caffeine intake, exercise timing, and even the stress of being measured, and single daily readings may not distinguish between transient variation and genuine directional change. The authors’ call for higher-frequency monitoring in future studies aligns with a broader trend in space health research toward continuous or near-continuous ambulatory monitoring using wearable sensors. Such devices can capture heart rate variability, activity levels, and sleep patterns around the clock, providing a far richer picture of autonomic adaptation than episodic spot checks. However, wearables introduce their own challenges in confined habitats, including sensor drift, skin irritation, data management, and the psychological effect of constant observation on crew behavior.

The LunAres Research Station itself is worth situating within the broader landscape of analog facilities. Located in Piła, Poland, it operates as an isolated habitat in which crews live and work without access to the external environment for the duration of a mission, simulating key characteristics of what researchers term ICE environments: isolated, confined, and extreme. Unlike facilities that simulate specific planetary surfaces, such as HI-SEAS on Hawaiian volcanic terrain or stations designed around Martian regolith scenarios, LunAres emphasizes the human factors dimension of isolation, with modular living quarters, laboratory space, a gym, and a kitchen arranged around a central research area. This design makes it particularly suitable for studies of behavioral health, crew dynamics, and physiological monitoring under confinement, complementing facilities whose primary value lies in geological or operational realism. The diversity of analog platforms is itself an asset, since different facilities isolate different subsets of the stressors experienced in spaceflight, allowing researchers to attribute effects more precisely.

It is important to recognize what this study deliberately does not model. Microgravity, space radiation, and the specific hazards of launch and landing are absent by definition in a terrestrial habitat, and the authors are explicit that their aim was not to replicate spaceflight physiology. This transparency matters because analog findings are sometimes overextended in popular reporting, with confinement effects conflated with the cardiovascular deconditioning or bone loss caused by weightlessness. What analogs like LunAres isolate is the psychological and behavioral component of spaceflight: the loss of environmental variety, the enforced proximity to a small group, the structured routines, and the separation from family and normal social life. These stressors are genuinely relevant to long-duration missions, and their physiological correlates, such as altered sleep, changed activity patterns, and stress-mediated cardiovascular adjustments, can be studied without the enormous cost and rarity of orbital research. The finding that short-term confinement alone did not perturb basic physiological parameters suggests that, for healthy adults, the psychological stress of a two-week isolation is within the adaptive capacity of normal homeostatic mechanisms.

The emphasis on standardized measurement protocols in the authors’ conclusions points to a persistent weakness in the analog literature. Because analog studies are conducted by many independent groups with different instruments, timing conventions, and definitions of baseline, results are difficult to compare or pool. Blood pressure measured after rest versus after activity, body temperature measured orally versus tympanically, and weight measured at different times of day relative to meals can all yield systematically different values. Establishing community standards for measurement timing, posture, instrumentation, and data reporting would allow individual studies to contribute to a cumulative evidence base rather than existing as isolated snapshots. The authors’ observation that routine parameters are often interpreted without adequate consideration of confounders such as hydration status, circadian phase, and recent physical activity is a pointed reminder that even simple measurements require careful protocol design to be interpretable.

The prospective observational design, in which measurements were planned before the mission and collected at fixed time points, strengthens the study relative to retrospective analyses of mission records, though it remains observational in the strict sense. Without a control group experiencing the same schedule outside confinement, the study cannot attribute any observed change specifically to isolation, and indeed the absence of temporal trends means there is little to attribute. This limitation is inherent to analog research, where the practical and ethical difficulty of isolating a matched control group for two weeks is considerable. Some studies address this by comparing mission data with pre-mission baseline periods or with crew members’ habitual routines, and future LunAres studies could incorporate such baseline extensions to sharpen inference.

Finally, the study’s framing of physiological stability as a finding in its own right, rather than as a failure to detect effects, is a useful corrective to publication norms that favor dramatic results. Demonstrating that a well-controlled two-week confinement does not destabilize basic cardiovascular, thermal, and metabolic markers in healthy adults provides a reassuring data point for short-duration mission planning and establishes a baseline against which longer missions can be compared. The authors’ recommendation to add psychological markers alongside physiological ones acknowledges that the most consequential effects of isolation may be behavioral rather than vital-sign-based, and that integrated monitoring of mood, cognition, sleep, and interpersonal dynamics will be essential as mission durations extend toward the months and years required for lunar surface operations and eventual journeys to Mars.

Subject of Research: Physiological monitoring of healthy adults during a 14-day isolated analog space mission

Article Title: Analytical comparison of physiological parameters in participants during an analog space mission

Article References: Kijak, K., Lubkowska, A., Skomro, P., Ardan, R., Budkowska, M., Gronwald, B., Gronwald, H., Stachowska, E., Kijak, K., Orzechowski, L., Mintus, A., & Lietz-Kijak, D. (2026). Analytical comparison of physiological parameters in participants during an analog space mission. Frontiers in Space Technologies, 7, Article 1752453. https://doi.org/10.3389/frspt.2026.1752453

Image Credits: AI Generated

DOI: 10.3389/frspt.2026.1752453

Keywords: space analog mission, isolation, LunAres Research Station, physiology, blood pressure, heart rate, body temperature, oxygen saturation, space medicine, confinement, inter-individual variability, Analytical

The reasoning behind the project is straightforward yet profound. A transit to Mars can require almost a year, and returning to Earth for a vision-limiting cataract, an injury, or another surgical eye problem may simply not be realistic. Dr Micheletti told the congress that he believes someone will need cataract surgery on Mars within his lifetime, and that treatment will ultimately need to happen where the patient is. Astronaut candidates, he noted, do not need perfect uncorrected vision, and refractive correction or certain prior refractive surgeries are compatible with selection. More importantly, good vision at launch does not prevent aging, radiation exposure, injury or disease later in the mission. As human spaceflight expands beyond career astronauts, the travelling population will become more diverse, and the medical systems that support it must be designed and validated long before the first patient needs them. In his words, we cannot wait until someone is on Mars to ask whether the lens, equipment and sterile supplies survived the trip.

To begin answering that question, Dr Micheletti launched the Joint Assessment Of Material Exposure In Space, or JAMES, project. The experiment flew 135 unpackaged intraocular lenses to the International Space Station, where they were mounted in special carriers positioned at three different exterior locations. The carriers, named CLAIRE, short for Carrier for Lens Analysis in Interstellar Research Expeditions, held lenses at three distinct test sites: Ram, where the lenses were exposed to high levels of atomic oxygen; Zenith, where they received substantial ultraviolet radiation from the Sun; and Underdeck, where they were partially shielded from direct atomic oxygen and solar ultraviolet by being mounted beneath the exposure platform. This placement strategy allowed the researchers to observe how different combinations of space-environment stressors affect lens materials.

Dr Micheletti was careful to explain that the study was not intended to recreate how a packaged intraocular lens would normally be shipped to Mars. Instead, the purpose was to identify potential failure modes under harsh exposure so that better packaging, shielding, storage and material selection strategies can be designed. Testing the lenses inside the station would not answer the same question, because the interior is controlled and pressurised. The team wanted to minimise packaging and, ideally, determine whether these products can be shipped without climate-controlled crew-cabin storage, because mass and volume carry significant costs in spaceflight. Every kilogram launched toward deep space demands fuel, money and payload capacity, so medical supplies that can survive the journey without elaborate protective enclosures would represent a meaningful engineering advantage.

On Earth, 45 intraocular lenses were removed from their original packaging and placed in a control carrier called WILLIAM, the Worldly Interface for Lens Logistics and Integrated Astronomical Monitoring. These control lenses remained at room temperature and atmospheric pressure for the duration of the experiment. After approximately six months in orbit, the 135 flight lenses returned to Earth for laboratory analysis. The current analysis included 61 of the space-flown lenses and 20 of the 45 terrestrial controls, a total of 81 lenses. Dr Liliana Werner and her team at the Intermountain Ocular Research Center at the University of Utah examined each lens for overall clarity, how well the lens materials remained intact, and whether any deposits or surface changes had developed during the mission.

The results revealed a spectrum of responses to the space environment. Most of the lenses, 42 of the 61 analysed, showed no notable exposure-associated findings when examined. The remaining 19 lenses displayed three principal patterns of change. In the most directly exposed Ram tray, eight of the nine lenses showed cracks and localised surface roughening consistent with early atomic oxygen erosion. All eight were acrylic lenses, including five hydrophobic and three hydrophilic designs, while the ninth lens, made of silicone, showed yellow discoloration instead. Atomic oxygen, the highly reactive form of oxygen that predominates in low-Earth orbit, is a well-known hazard for spacecraft surfaces, and these findings suggest it can degrade certain ophthalmic materials even over a relatively short orbital stay.

The second pattern involved yellow discoloration in five space-exposed lenses, including two hydrophobic acrylic and three silicone lenses. Four of these were located in the Zenith tray and one in the Ram tray. Spectrophotometry measurements showed lower light transmission in the affected lenses, particularly between 400 and 500 nanometres, the blue region of the visible spectrum that is essential for colour perception and contrast. This finding is especially relevant for a device whose entire purpose is to transmit light clearly to the retina. A yellowed lens inside an eye would act somewhat like a permanent filter, subtly altering the colour and quality of the vision it delivers, which could matter for pilots, scientists or anyone performing precision tasks in space.

The third and perhaps most puzzling pattern emerged among the light-adjustable lenses. All six of these space-exposed lenses, located across all three positions on the station’s exterior, developed a similar cobblestone or bubble-wrap appearance on both surfaces and along the optic edge. Neither of the two corresponding terrestrial controls showed this appearance. The mechanism behind the change remains unknown, and the researchers note that an explanation unrelated to direct space exposure cannot yet be excluded. Light-adjustable lenses are a sophisticated class of intraocular lenses whose optical power can be fine-tuned after implantation using ultraviolet light, making any unexplained surface alteration on their polymers particularly worthy of investigation before such devices are trusted on a mission where no replacement is available.

Dr Micheletti stressed that this was an exploratory, descriptive study, not designed to compare different makes or types of lenses or to test a formal hypothesis. The analysis covered a selected subset of the payload, sample sizes were small and uneven, and in some carrier positions there was only one lens of a given model. The lenses were deliberately unpackaged, so handling or environmental contamination could not be fully excluded, and the control lenses did not undergo launch, return or flight handling, which limits attribution of the observed changes specifically to external exposure. Beyond transmission spectrophotometry, image-quality, mechanical and clinical-performance testing has not yet been completed. The findings, he cautioned, should not be used to rank manufacturers or lens models and do not imply any safety concern for routine cataract surgery on Earth. What they do suggest is that lens material and exposure location may influence the changes observed, and that packaging, shielding and storage are the next protective strategies to test. The engineering challenge, he said, will be providing enough protection without adding unnecessary mass, because every kilogram sent into space carries a cost.

The significance of the work was underlined by Dr Joaquín Fernández, ESCRS Secretary, CEO of Qvision and Medical Director of the Andalusian Ophthalmology Institute at Vithas Hospitals in Almería, Spain, who was not involved in the research. He observed that as more people travel into space and for longer periods, eye surgery will likely be required at some point, making it imperative to understand how lenses and other surgical materials behave beyond Earth’s atmosphere, and he described the research as forward-thinking and certain to play an important role in preparations for deep space exploration. The JAMES study is, to the investigators’ knowledge, the first controlled experiment to expose multiple modern intraocular lens materials directly to the external low-Earth-orbit environment and return them for laboratory analysis. While published clinical reports have described astronauts who flew with implanted lens devices, those devices were protected inside the eye and body, so preimplantation exposure had never been studied. Dr Micheletti now hopes to investigate how a phacoemulsification system, the ultrasound and fluidics platform at the heart of modern cataract surgery, performs during the brief microgravity of parabolic flights, with the longer-term path leading to sustained microgravity testing and eventually an in-orbit surgical experiment. His guiding philosophy is deliberate: first the materials, then the equipment, then the procedure, and ultimately the surgery, in the hope of helping make the first eye operation beyond Earth a reality.

Subject of Research: Exposure of intraocular lenses to the low-Earth-orbit environment outside the International Space Station to assess their suitability for space-based cataract surgery.

Article Title: ‘Space: The final frontier’ for cataract surgery!

Article References: ‘Space: The final frontier’ for cataract surgery!. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: intraocular lenses, cataract surgery, International Space Station, space medicine, atomic oxygen, ultraviolet radiation, light-adjustable lenses, Mars missions, ophthalmology, JAMES project, low-Earth orbit, ESCRS

Researchers led by Janez Urevc of the University of Ljubljana, working with colleagues at the Medical University of Graz and supported by the European Space Agency, have built what they call a force–area digital twin of the internal jugular vein. The idea is to record, simultaneously and quantitatively, the force the probe exerts on the neck and the cross-sectional area of the vein visible in the B-mode ultrasound image. The resulting force–area curve is not merely a picture of collapse; it is a mechanical fingerprint of the vein–tissue system, one whose slope and shape change systematically depending on what is inside the vessel. By pairing real measurements with a physics-based computational model, the team has shown, in silico, that healthy veins, partially obstructed veins and fully occluded veins each leave distinct signatures in this curve.

The experimental half of the work relied on a custom-built force-sensing attachment mounted on a standard linear ultrasound transducer. Three load cells inside a rigid housing stream force data at roughly 100 hertz while the Philips CX50 system acquires images at 30 frames per second. Nine healthy adults underwent supine imaging of the internal jugular vein, with an experienced cardiovascular physician performing three slow compressions per recording, from minimal contact through full lumen closure and back. After rigorous quality control, which excluded six of seventeen recordings due to load-cell artefacts, alignment failures or unusable cycles, the team retained 34 compression cycles from eight subjects. Manual segmentation of the vein lumen in every frame, smoothed with a Savitzky–Golay filter, yielded the area trace that was paired with the force signal.

The measured response had a characteristic concave shape: at large vein areas the probe force stayed low, but as the vein approached collapse the force rose steeply. Fitting a straight line over the active compression regime, defined as forces above 0.2 newtons, gave a cohort reference slope of 0.148 plus or minus 0.113 newtons per square millimetre. That large spread, with a standard deviation equal to 76 percent of the mean, underscores how much inter-subject variability even healthy necks contain, and it foreshadows one of the study’s central challenges: how to compare a single representative computer model against a scattered population of real anatomies.

The digital twin itself is a finite-element model built in Abaqus, representing the principal load-bearing structures between the probe and the vertebral body: the internal jugular vein and carotid artery as thin pressurised shells, the sternocleidomastoid muscle and surrounding connective tissue as continuum blocks, and the probe as a rigid body pressing from above. Geometry came from cohort mean anatomical landmarks, including wall depths, vein diameter and the artery–vein centre distance, while the stress-free collapsed reference configuration was extrapolated from head-up tilt recordings in which progressively reducing venous pressure drives the vein toward collapse. Three unknown material parameters, the vein wall modulus and the effective stiffnesses of muscle and subvenous tissue, were identified by an inverse procedure that jointly matched the cohort mean closure force, indentation depth and anatomical landmarks, reproducing every target within roughly fifteen percent.

With the healthy model validated against experiment, the team turned to the question that motivates the whole framework: what does a thrombus do to the compression curve? Clots were modelled as isotropic linear-elastic bodies inserted into the already pressurised vein, ensuring that all simulated cases started from an identical pre-stressed baseline so that differences arose purely from the thrombus itself. Fully occlusive configurations spanned three lengths of two, four and eight centimetres and three stiffness levels of five, thirty and one hundred kilopascals, reflecting the reported mechanical range of venous thrombi. Partial, non-occlusive clots occupying about ten or fifty percent of the lumen were attached to either the lateral or the inferior wall, yielding seventeen thrombotic configurations in total.

The results were striking. Fully occlusive thrombi produced force–area slopes between roughly 2.5 and 14.7 times steeper than the healthy reference of 0.038 newtons per square millimetre, with thrombus stiffness, not length, acting as the dominant driver. Partial occlusions produced intermediate responses, with fifty percent obstructions approaching the fully thrombotic regime and ten percent obstructions shifting measurably toward greater mechanical resistance even though such veins would still appear compressible under conventional binary assessment. Crucially, the dimensionless version of the slope, which normalises both force and area and thereby removes the influence of anatomy and absolute scale, agreed closely between simulation and experiment: minus 0.81 for the model versus minus 0.86 plus or minus 0.33 for the cohort. That agreement indicates the digital twin captures the underlying shape of the compression response, even though the dimensional slope differed by a factor of about four, a gap the authors attribute to population variability, model simplifications and the intrinsically nonlinear experimental data.

The study also introduced a second, complementary indicator derived from the geometry of collapse. By computing the eigenvalues of the covariance matrix of the vein contour at each simulation step, the researchers defined an aspect ratio change that quantifies how strongly the lumen departs from its initial shape toward a flattened, slit-like geometry. Healthy veins produced large aspect ratio changes as they collapsed, while fully occlusive thrombi confined the response to a narrow low-deformation regime. Partial thrombi generated intermediate and asymmetric patterns, and, notably, the simulations distinguished between clots attached to the inferior wall and those on the lateral wall, information the slope alone could not provide. In one soft, small lateral configuration the slope stayed near the healthy value while the deformation trajectory remained clearly distinct, demonstrating exactly why the two indicators work best together: the slope measures how strongly the vein resists compression, the aspect ratio change measures how the lumen deforms as it yields.

The authors are careful to frame the work as a mechanistic proof of concept rather than a validated diagnostic tool. No patients with confirmed thrombosis were scanned, the reported indicator values are configuration-specific rather than diagnostic thresholds, and the thrombus model, while appropriate for quasi-static loading given published loss tangents of only 0.02 to 0.1, deliberately ignores viscoelasticity and nonlinear behaviour that emerges at strains near seventy percent. Intraluminal pressure was prescribed rather than measured, force and ultrasound streams were synchronised post hoc, and the cohort of nine subjects cannot establish population-level reference distributions. Clinical translation, the team writes, will require tissue-mimicking phantom studies followed by prospective trials in patients, ideally exploiting the natural within-subject control offered by unilateral jugular thrombosis.

Even so, the implications reach well beyond the laboratory. In space medicine, where microgravity distends the internal jugular vein, promotes blood stasis and has already produced one confirmed in-flight thrombosis in 2019, autonomous and objective diagnostics are essential because real-time teleguidance is unavailable on deep-space missions. A sensorised probe that reports continuous biomechanical indicators, potentially accelerated by reduced-order surrogates of the digital twin for near-real-time inference, could flag abnormal compression behaviour before complete occlusion develops. The framework is also not vein-specific: adapting it to the femoral or popliteal veins for standard deep vein thrombosis screening would require site-specific geometry and tissue representation but no change to the underlying method. By transforming a subjective visual judgement into a physics-informed biomechanical measurement, this work moves quantitative compression ultrasound from empirical observation toward a genuinely mechanistic biomarker, one in which learned image features can eventually be constrained by known biomechanics rather than treated as opaque outputs of a black box.

Subject of Research: Quantitative compression ultrasound using a force–area digital twin to assess venous thrombosis biomechanics

Article Title: Quantitative Compression Ultrasound via a Force–Area Digital Twin for Mechanistic Assessment of Venous Thrombosis

Article References: Urevc, J., Kovšca, D., Maček, A., Halilovič, M., Goswami, N., & Bergauer, A. (2026). Quantitative Compression Ultrasound via a Force–Area Digital Twin for Mechanistic Assessment of Venous Thrombosis. Annals of Biomedical Engineering. https://doi.org/10.1007/s10439-026-04362-9

Image Credits: AI Generated

DOI: 10.1007/s10439-026-04362-9

Keywords: compression ultrasound, venous thrombosis, internal jugular vein, digital twin, finite-element modelling, biomechanics, deep vein thrombosis, force sensing, space medicine, computational biomechanics, ultrasonography, biomedical engineering

The timing of the study is significant. NASA is currently planning multiple missions with durations exceeding six months in space, spanning commercial activity in low Earth orbit, the Artemis IV mission that will carry the first crewed flight to the lunar south pole in 2028, and the development of sustainable surface capabilities on the moon in preparation for eventual human journeys to Mars. Each of these endeavors will demand more human participation and more cumulative time spent in extraterrestrial environments, and each will draw on crews selected precisely because of their exceptional physical fitness and optimal health. The paradox highlighted by the new research is that the very individuals best equipped to endure the rigors of spaceflight may nonetheless carry forward hidden skeletal vulnerabilities that standard post-flight assessments do not fully capture.

The underlying physiology is well established, even if its long-term consequences have been harder to quantify. Muscle and bone loss in the microgravity environment of space is a common physiologic phenomenon among astronauts, and it is understood as an adaptive response to disuse. In the absence of gravitational loading, the skeleton receives far less mechanical stimulation than it does on Earth, and the body responds by reducing bone formation while resorption continues, gradually eroding bone mass and altering the internal architecture of load-bearing structures such as the hip. What makes this process insidious, as lead investigator Jean D. Sibonga, PhD, of NASA’s Johnson Space Center has noted, is that humans do not feel the effects of bone loss. An astronaut can return from space, feel stable, and even believe themselves fully recovered, then resume physically demanding activities despite underlying skeletal changes caused by prolonged disuse.

That disconnect between how astronauts feel and what their bones can actually withstand is central to why the new findings matter. A better understanding of bone health after spaceflight, the researchers argue, could help astronauts, patients, and clinicians assess long-term health concerns, determine appropriate care, and reduce the risk of injury. The hip is a particularly consequential site in this regard. Hip fractures are among the most serious fragility fractures in any population, associated with substantial morbidity, long recovery periods, and elevated mortality risk, especially when they occur at ages earlier than typical. A fracture rate that rises after long-duration flight, and that emerges at younger ages than would be expected in the general terrestrial population, therefore represents a warning signal that extends well beyond the immediate post-mission period.

One of the persistent obstacles in spaceflight medicine has been the sheer difficulty of gathering statistically robust data. Matthew T. Drake, MD, PhD, of the Endocrinology and Metabolic Bone Disease Service at the Hospital for Special Surgery in New York, and co-author of an accompanying editorial in the same journal, observed that while data to date on bone loss associated with spaceflight are consistent, a major limitation is accuracy, because astronaut cohort sample sizes are small and spaceflights are rare. With only a few hundred people having ever flown in space, and only a subset of those undertaking missions longer than 90 days, conventional epidemiological comparisons often lack the statistical power to detect meaningful differences in fracture outcomes. Small cohorts and rare events make it easy for real effects to hide within the noise.

To overcome this statistical limitation, the investigators took a different analytical approach. They surveyed a cohort of US-based astronauts for all fractures reported during annual clinical exams, assembling a longitudinal record of skeletal outcomes across careers that spanned missions of varying lengths. They then analyzed these data using Bayesian probabilistic modeling, a framework that allows researchers to draw more stable inferences from small samples by incorporating prior knowledge and quantifying uncertainty explicitly. The results were striking in their specificity. While the study did not find a higher incidence rate for fractures in general, the incidence rate for hip fractures in astronauts was increased after a long-duration spaceflight of more than 90 days. The effect was not a diffuse elevation of injury risk across the skeleton, but a concentrated signal at one of the body’s most mechanically critical sites.

Two features of that signal stand out. First, the increased hip fracture rate occurred at a younger age than would be expected in a non-astronaut terrestrial population, meaning astronauts were experiencing these injuries earlier in life than standard fracture epidemiology would predict. Second, the rate was greater than the rate observed before a long-duration mission, or with no spaceflight exposure at all, which points to the spaceflight itself, rather than age or occupational hazards alone, as the differentiating factor. Moshe Gertzulin, MD, also of the Endocrinology and Metabolic Bone Disease Service at the Hospital for Special Surgery and co-author of the accompanying editorial, summarized the implication: taken together, the finding of hip fracture occurrence at an age earlier than expected after long-duration spaceflight is clinical evidence that spaceflight-induced bone loss can lead to real long-term fracture consequences, which should be addressed accordingly.

The study’s authors argue that these conclusions carry direct implications for how space agencies monitor skeletal health. Dr. Sibonga emphasized the need to expand NASA’s current bone surveillance program beyond dual-energy X-ray absorptiometry, or DXA, measurements of bone mineral density, the long-standing standard for assessing skeletal status. DXA provides a two-dimensional summary of density but offers limited insight into the three-dimensional structure of bone, which is increasingly recognized as a critical determinant of fracture resistance. NASA has recently begun ordering quantitative computed tomography scans before and after spaceflight, a modality that can provide more detailed information about different areas of the bone and about whether astronauts have truly fully recovered. Without that finer-grained insight, astronauts could risk placing too much strain on bones that have not yet regained their preflight condition, precisely the scenario in which a fragility fracture is most likely to occur.

Beyond surveillance, the investigators advocate for prophylactic countermeasures designed to preserve the baseline, pre-flight skeletal health of the astronaut, rather than attempting to reverse damage after the fact. A fuller characterization of spaceflight-induced changes to bone mass, density, structure, and microarchitecture will determine which interventions, whether pharmaceutical agents, exercise regimens, or dietary adjustments, are most beneficial for long-term skeletal health. Current in-flight countermeasures centered on resistive exercise have slowed but not fully prevented bone deterioration on long missions, and the new fracture data suggest that residual deficits matter over timescales of years, not weeks. Identifying the right combination of countermeasures before crews embark on months-long lunar surface stays and multi-year Mars transits could mean the difference between a mission that ends with healthy crews and one that seeds decades of orthopedic problems.

The broader significance of the study extends beyond the astronaut corps. The disuse-related bone loss that astronauts experience is, in essence, an accelerated model of the immobilization and unloading that affects patients on Earth, from those confined to bed rest to individuals with spinal cord injuries or age-related osteoporosis. Insights gained from studying spaceflight-induced skeletal changes, and from the advanced imaging and modeling techniques being deployed to study them, may inform how clinicians on Earth assess and manage fragility in their own patients. For now, the message from Mayo Clinic Proceedings is unambiguous: the skeleton keeps a record of every day spent in microgravity, and for missions longer than 90 days, that record includes a heightened risk of hip fracture that surfaces earlier in life than anyone would want. As humanity prepares to spend longer stretches of time on the moon and beyond, safeguarding the bones that carry astronauts home has become a scientific challenge worthy of the ambition of the missions themselves.

Subject of Research: Long-duration spaceflight-induced bone loss and hip fracture risk in astronauts

Article Title: Study links 90+-day spaceflights to higher rates of hip fractures in astronauts

Article References: Study links 90+-day spaceflights to higher rates of hip fractures in astronauts. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: astronauts, hip fracture, bone loss, microgravity, spaceflight, NASA, Mayo Clinic Proceedings, bone mineral density, quantitative computed tomography, osteoporosis, Artemis, space medicine

The study matters because future missions are expected to last longer and travel farther, increasing the likelihood of injuries and illnesses in orbit. Ultrasound can be helpful, but it demands substantial operator training and depends on sound-wave transmission through appropriate tissue. In contrast, X-rays are fast and provide high-value anatomical information when image quality is sufficient.

Traditional X-ray units are typically bulky, radiation-intensive, and prone to motion blur—problems intensified by the constant movement of microgravity. The research team therefore tested whether a portable system, designed for everyday use on Earth, could survive spacecraft prelaunch conditions and deliver interpretable images in space.

Prior to the Fram2 flight, the crew received four hours of training on the portable radiography workflow. Preflight imaging included hands, forearms, abdomen, pelvis, and chest X-rays, establishing baselines for comparison. The onboard setup also used an ultraportable wireless digital generator, enabling imaging with minimal medical expertise.

Fram2 launched on March 31, 2025, on a SpaceX Falcon 9 rocket into a 90-degree orbit roughly 425 to 450 kilometers above sea level. Over 3 days and 14 hours, the team acquired in-flight images of both a calibration phantom and several human anatomical regions, transmitting results to an onboard computer for immediate review by the crew.

After landing and recovery, the researchers captured postflight images designed to replicate the in-orbit protocol. Although the generator sustained superficial structural damage during touchdown, internal components and X-ray output remained functional, allowing the team to complete comparable imaging.

Three independent radiologists assessed image quality, spatial and contrast resolution, and positioning. Overall diagnostic performance was maintained between preflight and inflight acquisitions, with the main weakness appearing in the positioning scores for certain central-body images such as the chest, pelvis, and abdomen. Still, the inflight scans reached a diagnostic level for all examined regions.

Importantly, crew members reported that the system was easy to use and the protocol straightforward to follow. Estimated radiation exposure for the crew was no higher than standard clinical imaging on Earth, supporting the potential for routine onboard implementation.

Beyond human health, the study suggests X-rays could support mission-critical nonmedical tasks, from inspecting electronics and spacesuits to imaging malfunctioning satellites and analyzing lunar rover targets. The researchers argue that smaller, more rugged autonomous radiography systems could transform both space operations and broader global health logistics.

Subject of Research: People
Article Title: SpaceXray: Feasibility and Diagnostic Capabilities of On-Orbit Medical Radiography
News Publication Date: 14-Jul-2026
Web References: https://pubs.rsna.org/journal/radiology
References: Radiological Society of North America (RSNA) / Radiology
Image Credits: Radiological Society of North America (RSNA)

Keywords: Space flight; Medical imaging; Radiography; Astronauts