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Human movement has evolved within Earth's gravitational environment (1  g ; −9.81 m s −2 ). Future human exploration of terrestrial bodies, including the Moon (0.17  g ; −1.62 m s −2 ) and Mars (0.38  g ; −3.71 m s −2 ), will require astronauts to live and work within reduced gravitational environments (hypogravity). Progressing understanding of the physiological and biomechanical implications of movement in hypogravity will play a key role in supporting the expansion of humanity to terrestrial bodies beyond Earth, within our solar system. Ground‐based hypogravity analogues that enable the study of human movement are pivotal to developing knowledge in this field. Whole‐body suspension can serve as a resource‐efficient and accessible hypogravity analogue, yet only a limited number of such analogues exist globally. This technical report introduces a new hypogravity analogue facility: the Variable Gravity Suspension System (VGSS). The report introduces the VGSS and its theoretical framework, which enables simulation of both micro‐ and hypo‐gravity, presents proof‐of‐concept data regarding its ability to simulate hypogravity, and demonstrates the ability of the VGSS to facilitate locomotive and jumping activities in simulated hypogravity. What is the central question of this study? This study introduces and demonstrates proof‐of‐concept for the Variable Gravity Suspension System (VGSS), a newly developed analogue for simulating hypogravity using head‐up tilt whole body suspension What is the main finding and its importance? Hypogravity between 0 and 0.2  g can be accurately simulated using the VGSS and allows users to perform movement in the sagittal plane, including locomotive and jumping activities.

Long-lasting exposure to low gravity, such as in lunar settlements planned by the ongoing Artemis Program, elicits muscle hypotrophy, bone demineralization, cardio-respiratory and neuro-control deconditioning, against which optimal countermeasures are still to be designed. Rather than training selected muscle groups only, ‘whole-body’ activities such as locomotion seem better candidates, but at Moon gravity both ‘pendular’ walking and bouncing gaits like running exhibit abnormal dynamics at faster speeds. We theoretically and experimentally show that much greater self-generated artificial gravities can be experienced on the Moon by running horizontally inside a static 4.7 m radius cylinder (motorcyclists’ ‘Wall of Death’ of amusement parks) at speeds preventing downward skidding. To emulate lunar gravity, 83% of body weight was unloaded by pre-tensed (36 m) bungee jumping bands. Participants unprecedentedly maintained horizontal fast running (5.4–6.5 m s −1 ) for a few circular laps, with intense metabolism (estimated as 54–74 mlO 2  kg −1  min −1 ) and peak forces during foot contact, inferred by motion analysis, of 2–3 Earth body weight (corresponding to terrestrial running at 3–4 m s −1 ), high enough to prevent bone calcium resorption. A training regime of a few laps a day promises to be a viable countermeasure for astronauts to quickly combat whole-body deconditioning, for further missions and home return.

Modeling of weightlessness in rodents by hind limb unloading (HU) results in the development of musculoskeletal disorders, similar to hypogravity motor syndrome (HMS) that occurs in astronauts during orbital flight. To confirm our hypothesis about the presence of a neurogenic component in the pathogenesis of HMS, a genome-wide study of spinal cord (SC) lumbar enlargement cells of the mice was performed after 30-day HU and a subsequent 7-day recovery period. The changes in the transcriptome of mouse SC cells under HU condition correlate with changes in gene expression in mouse SC cells during space flight, suggesting the involvement of a neurogenic factor in the development of HMS in both modeling hypogravity condition on Earth and conditions of weightlessness. At the same time, after 7 days of rehabilitation, the transcriptome of SC cells did not differ from that in mice after 30 days of HU, which suggests that the negative changes in the SC persisted during the recovery period.

Prolonged exposure to reduced gravity in space leads to bone demineralization and muscle atrophy, which current countermeasures of simple body loading can partially address. To address this aetiology, a resistive hypogravity exosuit (R‐HEXsuit) is proposed for dynamic body loading in low gravity. R‐HEXsuit is a lightweight (1.4 kg) soft wearable exosuit that uses pneumatic artificial muscles to provide programmed bilateral resistance during walking, stimulating primary leg muscles. Tests on healthy subjects in Earth gravity and simulated Moon gravity reveal that the suit increases metabolic cost by 29.3% in Moon gravity, aligning it with Earth‐like metabolic cost. Muscle activation in key knee joint muscles also increases, matching or exceeding Earth levels, without altering natural gait patterns. These results highlight the R‐HEXsuit as a promising tool for replicating Earth‐like physical demands during low‐gravity missions, offering a potential solution for mitigating musculoskeletal degradation in space. The resistive hypogravity exosuit is a lightweight wearable robotic exosuit that uses pneumatic artificial muscles to restore Earth‐like metabolic and muscular demands during locomotion in low gravity. Tested on healthy subjects in Earth and simulated Moon gravity, the suit restores energy expenditure and muscle activation without altering gait, offering a potential additional countermeasure against musculoskeletal decline in space.

High quality cardiopulmonary resuscitation (CPR) increases survival outcomes. Smaller rescuers have been found to be at risk of providing inadequate CPR, particularly relating to chest compression depth, especially in novice rescuers. This study aims to look at the quality of CPR provided by smaller rescuers, and to investigate any potential compensation techniques used such as elbow flexion and extension, to maintain adequate quality CPR. Healthy adult participants performed three five-minute sequences of CPR on a mannequin with springs of 3 different strengths, in a randomized order. An electrogoniometer attached to the elbow measured the flexion and extension throughout. The results suggest that chest compressions were maintained at recommended depth and rate levels despite the increase in spring stiffness by using elbow flexion and extension, especially in participants with lower BMI and increased spring stiffness. These findings suggest potential compensatory mechanisms that can be used to maintain good CPR in situations of the rescuer being significantly smaller than the patient, similarly to as has been suggested when delivering CPR in hypogravity, thus transferring knowledge from these environments to Earth. Using elbow flexion and extension should be taken into consideration when revising the internationally recognized CPR guidelines.

Juggling is a complex motor skill that requires multiple sub-skills and cannot be mastered without extensive practice. Although prior studies have quantified performance differences between novice and expert jugglers, none have attempted to quantitatively decompose these components or model their contribution to juggling performance. This longitudinal study presents a multimodal evaluation system that integrates computer vision, motion capture, and biosensing to quantify three key elements of juggling ability: Sequencing, Prediction, and Accuracy. Twenty beginners completed a 10-day, three-ball juggling experiment combining visuo-haptic virtual reality (VR) and real-world practice, with half training in reduced gravity, previously shown to enhance early-stage motor learning. The fitted Gamma-Log generalized linear model (GLM) indicated that Sequencing is the dominant factor of early skill acquisition, followed by Prediction and Accuracy. This study provides the first computational decomposition of juggling, demonstrates how multiple elements jointly contribute to performance, and results in a principled approach to characterizing motor learning in complex real-world tasks.

Quasi-stiffness characterizes the dynamics of a joint in specific sections of stance-phase and is used in the design of wearable devices to assist walking. We sought to investigate the effect of simulated reduced gravity and walking speed on quasi-stiffness of the hip, knee, and ankle in overground walking. 12 participants walked at 0.4, 0.8, 1.2, and 1.6 m/s in 1, 0.76, 0.54, and 0.31 gravity. We defined 11 delimiting points in stance phase (4 each for the ankle and hip, 3 for the knee) and calculated the quasi-stiffness for 4 phases for both the hip and ankle, and 2 phases for the knee. The R 2 value quantified the suitability of the quasi-stiffness models. We found gravity level had a significant effect on 6 phases of quasi-stiffness, while speed significantly affected the quasi-stiffness in 5 phases. We concluded that the intrinsic muscle-tendon unit stiffness was the biggest determinant of quasi-stiffness. Speed had a significant effect on the R 2 of all phases of quasi-stiffness. Slow walking (0.4 m/s) was the least accurately modelled walking speed. Our findings showed adaptions in gait strategy when relative power and strength of the joints were increased in low gravity, which has implications for prosthesis and exoskeleton design.

Microgravity exposure is associated with loss of muscle mass and strength. The E3 ubiquitin ligase MuRF1 plays an integral role in degrading the contractile apparatus of skeletal muscle; MuRF1 null (KO) mice have shown protection in ground-based models of muscle atrophy. In contrast, MuRF1 KO mice subjected to 21 days of microgravity on the International Space Station (ISS) were not protected from muscle atrophy. In a time course experiment microgravity-induced muscle loss on the ISS showed MuRF1 gene expression was not upregulated. A comparison of the soleus transcriptome profiles between spaceflight and a publicly available data set for hindlimb suspension, a claimed surrogate model of microgravity, showed only marginal commonalities between the models. These findings demonstrate spaceflight induced atrophy is unique, and that understanding of effects of space requires study situated beyond the Earth’s mesosphere.

Exposure to prolonged periods in microgravity is associated with deconditioning of the musculoskeletal system due to chronic changes in mechanical stimulation. Given astronauts will operate on the Lunar surface for extended periods of time, it is critical to quantify both external (e.g., ground reaction forces) and internal (e.g., joint reaction forces) loads of relevant movements performed during Lunar missions. Such knowledge is key to predict musculoskeletal deconditioning and determine appropriate exercise countermeasures associated with extended exposure to hypogravity. The aim of this paper is to define an experimental protocol and methodology suitable to estimate in high-fidelity hypogravity conditions the lower limb internal joint reaction forces. State-of-the-art movement kinetics, kinematics, muscle activation and muscle-tendon unit behaviour during locomotor and plyometric movements will be collected and used as inputs (Objective 1), with musculoskeletal modelling and an optimisation framework used to estimate lower limb internal joint loading (Objective 2). Twenty-six healthy participants will be recruited for this cross-sectional study. Participants will walk, skip and run, at speeds ranging between 0.56-3.6 m/s, and perform plyometric movement trials at each gravity level (1, 0.7, 0.5, 0.38, 0.27 and 0.16g) in a randomized order. Through the collection of state-of-the-art kinetics, kinematics, muscle activation and muscle-tendon behaviour, a musculoskeletal modelling framework will be used to estimate lower limb joint reaction forces via tracking simulations. The results of this study will provide first estimations of internal musculoskeletal loads associated with human movement performed in a range of hypogravity levels. Thus, our unique data will be a key step towards modelling the musculoskeletal deconditioning associated with long term habitation on the Lunar surface, and thereby aiding the design of Lunar exercise countermeasures and mitigation strategies.

The response of plants to the spaceflight environment and microgravity is still not well understood, although research has increased in this area. Even less is known about plants’ response to partial or reduced gravity levels. In the absence of the directional cues provided by the gravity vector, the plant is especially perceptive to other cues such as light. Here, we investigate the response of Arabidopsis thaliana 6-day-old seedlings to microgravity and the Mars partial gravity level during spaceflight, as well as the effects of red-light photostimulation by determining meristematic cell growth and proliferation. These experiments involve microscopic techniques together with transcriptomic studies. We demonstrate that microgravity and partial gravity trigger differential responses. The microgravity environment activates hormonal routes responsible for proliferation/growth and upregulates plastid/mitochondrial-encoded transcripts, even in the dark. In contrast, the Mars gravity level inhibits these routes and activates responses to stress factors to restore cell growth parameters only when red photostimulation is provided. This response is accompanied by upregulation of numerous transcription factors such as the environmental acclimation-related WRKY-domain family. In the long term, these discoveries can be applied in the design of bioregenerative life support systems and space farming.