The present study examined the cardiovascular, metabolic, neuromuscular and perceptual effects of low-intensity jumping in simulated lunar gravity (∼20% bodyweight) with blood flow restriction (BFR). Fourteen healthy adults (24 ± 4 years; 1.81 ± 0.06 m; 75 ± 12 kg) completed an incremental jumping test in simulated lunar gravity (9.5° head-up tilt suspension) followed by a graded exercise test to determine maximal oxygen uptake ( V . O 2 peak ). Two exercise visits (with and without BFR) were completed on separate days comprising 6 × 2 min of low-intensity (40% V . O 2 peak ) continuous jumping at ∼20% bodyweight, with 1-min passive rest periods. Blood flow restriction was applied at 60% limb occlusion pressure to the lower limbs during the exercise periods and removed during the rest periods. Jumping in simulated lunar gravity with BFR, compared to without BFR, significantly decreased muscle tissue oxygenation within the vastus lateralis (∼20%) and gastrocnemius medialis (∼5%), and increased heart rate (10-23 beats min-1), carbon dioxide output (2-4 mL kg-1 min-1) and minute ventilation (7-16 L min-1). Oxygen consumption was either unaffected or slightly elevated up to 3 mL kg-1 min-1. Blood lactate concentration was significantly greater during BFR jumping by ∼1-2 mmol L-1. Pre-post exercise knee extension peak force declined in both conditions to similar extents. Perceived exertion, discomfort and body instability significantly increased with BFR. Jumping in simulated lunar gravity with BFR requires little equipment and elicits similar metabolic, cardiovascular and perceptual responses to BFR aerobic exercise in terrestrial settings (e.g., BFR walking/cycling), and therefore may have value as a musculoskeletal and cardiovascular exercise countermeasure during planetary exploration missions.

The ability to withstand impairments in key physiological variables during prolonged exercise, known as "durability," is emerging as an important factor in cycling performance. While females possess physiological characteristics that could confer enhanced durability relative to males, little is known about potential sex differences. Sixteen males (V̇O2peak 58 ± 6 mL·kg-1·min-1) and 16 females (V̇O2peak 51 ± 3 mL·kg-1·min-1) performed an incremental exercise test to exhaustion in visit 1. In visit 2 they performed 90 min of heavy-intensity cycling (HVY) at 110% of gas exchange threshold (GET), followed by another incremental test. During HVY, pulmonary gas exchange (V̇O2), heart rate (HR), rating of perceived exertion (RPE), near-infrared spectroscopy, and electromyography were recorded, and blood lactate (BLa) was collected. Before and after HVY, maximal voluntary contraction (MVIC), voluntary activation (VA), and potentiated twitches (100 Hz, 10 Hz, Qtw·pot) of the knee extensors were assessed. Power at GET (-16% ± 15% vs. -2% ± 13%) and respiratory compensation point (-13% ± 10% vs. -6% ± 9%) decreased more in males than females (p ≤ 0.049), whereas V̇O2peak and its associated power decreased similarly (p ≥ 0.073). All aspects of neuromuscular function decreased (all p < 0.001), without sex differences (p ≥ 0.096). During HVY, HR, V̇O2 (%peak), relative energy expenditure increased more in males (p ≤ 0.008), whereas respiratory exchange ratio decreased more in females (p = 0.001). BLa was higher in males than females (p ≤ 0.040). Muscle oxygen extraction was lower (p = 0.004) and tissue saturation index higher for females (p < 0.001). The smaller reductions exhibited by females in submaximal thresholds, associated with lesser derangements to oxidative efficiency, suggest considering sex-specific training prescription and pacing strategies.

The Moon's gravitational field strength (17% Earth's gravity) may facilitate the use of bodyweight jumping as an exercise countermeasure against musculoskeletal and cardiovascular deconditioning in reduced gravity settings. The present study characterised the acute physiological and kinetic responses to bodyweight jumping in simulated Lunar gravity. Nineteen healthy adults (age: 25 ± 7 years, weight: 73 ± 11 kg; height: 1.81 ± 0.05 m, : 50 ± 11 mL kg −1 min −1 ) performed an incremental jumping test in simulated Lunar gravity (9.5° head‐up tilt suspension) comprising 4‐min stages of jumping with 1‐min rests, beginning at 30 cm and increasing 5 cm per stage up to 70 cm. A graded exercise test (GXT) to volitional exhaustion was subsequently performed using upright cycle ergometry. Cardiorespiratory outcomes (, , , breathing frequency, respiratory exchange ratio and heart rate (HR)) and peak vertical ground reaction forces (vGRF) increased linearly ( R 2 = 0.77–0.97) and blood lactate concentrations increased exponentially with jump height ( R 2 = 0.98). Participants achieved HRs of 158 ± 17 beats min −1 (88 ± 9% HR max ), metabolic rates of 35 ± 6 mL kg −1 min −1 (71 ± 9% ), blood lactate concentrations of 5.8 ± 1.7 mmol L −1 and peak vGRFs of 119 ± 17% bodyweight. Jumping at ∼20% bodyweight requires no equipment, allows for submaximal cardiovascular exercise intensities with and without blood lactate accumulation, and may have value as an exercise countermeasure in Lunar/Martian surface habitats.

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.

AbstractBlood flow restriction (BFR) has been identified as a potential countermeasure to mitigate physiological deconditioning during spaceflight. Guidelines recommend that tourniquet pressure be prescribed relative to limb occlusion pressure (LOP); however, it is unclear whether body tilting or reduced gravity analogues influence LOP. We examined LOP at the leg and arm during supine bedrest and bodyweight suspension (BWS) at 6° head‐down tilt (HDT), horizontal (0°), and 9.5° head‐up tilt (HUT) positions. Twenty‐seven adults (age, 26 ± 5 years; height, 1.75 ± 0.08 m; body mass, 73 ± 12 kg) completed all tilts during bedrest. A subgroup (n = 15) additionally completed the tilts during BWS. In each position, LOP was measured twice in the leg and arm using the Delfi Personalized Tourniquet System after 5 min of rest and again after a further 5 min. The LOP at the leg increased significantly from 6° HDT to 9.5° HUT in bedrest and BWS by 9–15 mmHg (Cohen's d = 0.7–1.0). Leg LOP was significantly higher during BWS at horizontal and 9.5° HUT postures relative to the same angles during bedrest by 8 mmHg (Cohen's d = 0.6). Arm LOP remained unchanged between body tilts and analogues. Intraclass correlation coefficients for LOP measurements taken after an initial and subsequent 5 min rest period in all conditions ranged between 0.91–0.95 (leg) and 0.83–0.96 (arm). It is advised that LOP be measured before the application of a vascular occlusion in the same body tilt/setting to which it is applied to minimize discrepancies between the actual and prescribed tourniquet pressure.

Cardiorespiratory fitness is a key component of health-related fitness. It is a necessary focus of improvement, especially for those that have poor fitness and are classed as untrained. However, much research has shown individuals respond differentially to identical training programs, suggesting the involvement of a genetic component in individual exercise responses. Previous research has focused predominantly on a relatively low number of candidate genes and their overall influence on exercise responsiveness. However, examination of gene-specific alleles may provide a greater level of understanding. Accordingly, this study aimed to investigate the associations between cardiorespiratory fitness and an individual's genotype following a field-based endurance program within a previously untrained population. Participants (age: 29 ± 7 years, height: 175 ± 9 cm, mass: 79 ± 21 kg, body mass index: 26 ± 7 kg/m2) were randomly assigned to either a training (n = 21) or control group (n = 24). The training group completed a periodized running program for 8-weeks (duration: 20-30-minutes per session, intensity: 6-7 Borg Category-Ratio-10 scale rating, frequency: 3 sessions per week). Both groups completed a Cooper 12-minute run test to estimate cardiorespiratory fitness at baseline, mid-study, and post-study. One thousand single nucleotide polymorphisms (SNPs) were assessed via saliva sample collections. Cooper run distance showed a significant improvement (0.23 ± 0.17 km [11.51 ± 9.09%], p < 0.001, ES = 0.48 [95%CI: 0.16-0.32]), following the 8-week program, whilst controls displayed no significant changes (0.03 ± 0.15 km [1.55 ± 6.98%], p = 0.346, ES = 0.08, [95%CI: -0.35-0.95]). A significant portion of the inter-individual variation in Cooper scores could be explained by the number of positive alleles a participant possessed (r = 0.92, R2 = 0.85, p < 0.001). These findings demonstrate the relative influence of key allele variants on an individual's responsiveness to endurance training.

Data set relating to the publication 'COVID-19: Self-Reported Reductions in Physical Activity and Increases in Sedentary Behaviour During the First National Lockdown in the United Kingdom'.

Space agencies are planning to send humans back to the Lunar surface, in preparation for crewed exploration of Mars. However, the effect of hypogravity on human skeletal muscle is largely unknown. A recently established rodent partial weight-bearing model has been employed to mimic various levels of hypogravity loading and may provide valuable insights to better understanding how human muscle might respond to this environment. The aim of this study was to perform a systematic review regarding the effects of partial weight-bearing on the morphology and function of rodent skeletal muscle. Five online databases were searched with the following inclusion criteria: population (rodents), intervention (partial weight-bearing for ≥1 week), control (full weight-bearing), outcome(s) (skeletal muscle morphology/function), and study design (animal intervention). Of the 2,993 studies identified, eight were included. Partial weight-bearing at 20%, 40%, and 70% of full loading caused rapid deconditioning of skeletal muscle morphology and function within the first one to two weeks of exposure. Calf circumference, hindlimb wet muscle mass, myofiber cross-sectional area, front/rear paw grip force, and nerve-stimulated plantarflexion force were reduced typically by medium to very large effects. Higher levels of partial weight-bearing often attenuated deconditioning but failed to entirely prevent it. Species and sex mediated the deconditioning response. Risk of bias was low/unclear for most studies. These findings suggest that there is insufficient stimulus to mitigate muscular deconditioning in hypogravity settings highlighting the need to develop countermeasures for maintaining astronaut/cosmonaut muscular health on the Moon and Mars.

Introduction: The introduction of the COVID-19 lockdown and social distancing policy has the potential to restrict access to physical activity, change exercise behavior, and to increase sedentary behavior. This study was conducted with the support of British Blind Sport and evaluates the effect of the lockdown policy on adults with visual impairments in the United Kingdom (UK). Methods: An online survey based on the World Health Organization’s Global Physical Activity Questionnaire was completed by 73 participants (median age 35–44 years, 59% female) to gain information on how the implementation of the lockdown policy by the UK government has affected physical activity and sedentary behavior in adults that are visually impaired. Paired sample t-tests and Wilcoxon signed rank tests were used to analyze continuous and Likert scale data, respectively. Results: The majority of participants continued to exercise during lockdown, but the nature of this activity altered with a significant change to exercising in a private indoor space (+190% (always), z = −3.871, p < 0.001), and those exercising alone (+118% (always), z = −2.595, p = 0.009). The volume of activity reduced in all cases, between −11% and −52%, with significant changes in duration of vigorous day-to-day activity, moderate day-to-day activity, travel by foot or cycle, and vigorous recreational activity. Sedentary behavior increased on average by 21% ( t(59) = −2.050, p = 0.045), with a greater effect seen in females (+36%, t(35) = −2.525, p = 0.016). Discussion: Reductions in physical activity volume and increases in sedentary behavior are consequences of the UK lockdown for those with visual impairments. The health and well-being implications of these data to this specific population are of particular concern. Implications for Practitioners: Lockdown measures should be designed with consideration of the needs of people with disabilities. Innovative ways to engage these populations in physical activity are strongly encouraged.

Space agencies are preparing to send humans to the Moon (16% Earth's gravity) and Mars (38% Earth's gravity), however, there is limited evidence regarding the effects of hypogravity on the skeletal system. A novel rodent partial weight-bearing (PWB) model may provide insight into how human bone responds to hypogravity. The aim of this study was to perform a systematic review investigating the effect of PWB on the structure and function of rodent bone. Five online databases were searched with the following inclusion criteria: population (rodents), intervention (PWB for ≥1-week), control (full weight-bearing), outcomes (bone structure/function), and study design (animal intervention). Of the 2,993 studies identified, eight were included. The main findings were that partial weight-bearing exposure for 21-28 days at 20%, 40%, and 70% of full loading causes: (1) loss of bone mineral density, (2) loss of trabecular bone volume, thickness, number, and increased separation, (3) loss of cortical area and thickness, and 4) reduced bone stiffness and strength. These findings predominately relate the tibia/femur of young/mature female mice, however, their deconditioning response appeared similar, but not identical, to male rats. A dose-response trend was frequently observed between the magnitude of deconditioning and PWB level. The deconditioning patterns in PWB resembled those in rodents and humans exposed to microgravity and microgravity analogs. The present findings suggest that countermeasures against bone deconditioning may be required for humans exploring the Lunar and Martian surfaces.

BACKGROUND: The Aerospace Medicine Systematic Review Group was set up in 2016 to facilitate high quality and transparent synthesis of primary data to enable evidence-based practice. The group identified many research methods specific to space medicine that need consideration for systematic review methods. The group has developed space medicine specific methods to address this and trialed usage of these methods across seven published systematic reviews. This paper outlines evolution of space medicine synthesis methods and discussion of their initial application.METHODS: Space medicine systematic review guidance has been developed for protocol planning, quantitative and qualitative synthesis, sourcing gray data, and assessing quality and transferability of space medicine human spaceflight simulation study environments.RESULTS: Decision algorithms for guidance and tool usage were created based on usage. Six reviews used quantitative methods in which no meta-analyses were possible due to lack of controlled trials or reporting issues. All reviews scored the quality and transferability of space simulation environments. One review was qualitative. Several research gaps were identified.CONCLUSION: Successful use of the developed methods demonstrates usability and initial validity. The current space medicine evidence base resulting in no meta-analyses being possible shows the need for standardized guidance on how to synthesize data in this field. It also provides evidence to call for increasing use of controlled trials, standardizing outcome measures, and improving minimum reporting standards. Space medicine is a unique field of medical research that requires specific systematic review methods.Winnard A, Caplan N, Bruce-Martin C, Swain P, Velho R, Meroni R, Wotring V, Damann V, Weber T, Evetts S, Laws J. Developing, implementing, and applying novel techniques during systematic reviews of primary space medicine data. Aerosp Med Hum Perform. 2021; 92(8):681688.

Background: Exercise countermeasures are the main approach taken to protect astronauts from musculoskeletal deconditioning in microgravity (mu g). Future exploration class missions will require astronauts to live on the surface of the Moon (0.16g) and Mars (0.38g) in hypogravity where the level of protection is assumed to be insufficient. However, it is not well understood how much exercise is required to protect the musculoskeletal system against 'small planet deconditioning'. The purpose of this review was to systematically synthesize evidence regarding the effectiveness of exercise countermeasures for the prevention of musculoskeletal deconditioning in hypogravity. Method: Databases were searched for relevant literature using appropriate search terms: PubMed, Web of Science, EMBASE, The Cochrane Collaboration Library, SPORTDiscus, the National Aeronautics and Space Administration (NASA) Technical Reports Sever, the NASA Life Science Data Archive and the German Aerospace Centre Elibrary. Two independent reviewers screened hits for relevance in accordance with the a priori PICOS criteria. Studies that included Earth based hypogravity analogs (e.g. head up tilt bed rest), a healthy terrestrial population, an exercise countermeasure and non exercise control group (i.e. randomized/clinical control trial), measuring any musculoskeletal outcome, were eligible for inclusion. Space related research (e.g. Lunar mission data) were not eligible for inclusion. Results: No studies were identified that met the eligibility criteria established for this review. Of the n = 2805 articles identified, n = 124 were classified as potentially relevant, however all were excluded following full text examination. Conclusions: Assumptions regarding the effect of hypogravity on the human musculoskeletal system are yet to be confirmed with long duration data. Future research should aim to fill this gap by investigating the longitudinal effects of simulated hypogravity (and Lunar/Martian habitat environments) on the human musculoskeletal system, to establish whether any deconditioning is of a large enough magnitude to compromise health and performance. If so, thereafter investigating exercise countermeasure strategies to prevent deconditioning in simulated Lunar/Martian settings will help inform evidence-based medical guidelines for planetary exploration. The ecological validity and thus transferability of data from chronic hypogravity analogs are essential to providing accurate and high quality data. Therefore, Lunar/Martian data is extremely valuable to understand whether data collected in analogs can be accurately transferred.

BACKGROUNDSprint interval training is a popular workout modality. Studies have eluded to a positive effect on maximal oxygen uptake, however little is known about the mechanistic basis of this adaptation. Therefore, the purpose of this study was to determine the effects of a short-term high-intensity sprint interval training (SIT) intervention on V̇O2max through quantification of both the respiratory and hemodynamic responses.METHODSThirty-six physically active participants undertook 4 weeks of either cycling-based SIT (8×20 s at 170% P-V̇O2max with 10 s recovery) or continuous exercise training (CET) (30 min at 70% P-V̇O2max) 3 times per week. V̇O2max, blood-based markers and hemodynamic responses were assessed pre and post the intervention period. V̇O2max was assessed using breath-by-breath open circuit spirometry, while hemodynamic responses were monitored using thoracic impedance cardiography.RESULTSV̇O2max exhibited a non-significant 4.1% increase (ES=0.24) for SIT with 7.0% P=0.007 (ES=0.40) increase for CET. Hemodynamic responses (maximal cardiac output, maximal stroke volume) displayed non-significant responses for CET and SIT while a-vO2dif-max increased from 15.8±4.8 to 18.3±2.9 mL/100 mL) (P=0.02) (ES=0.63) in SIT.CONCLUSIONSV̇O2max is a function of maximal cardiac output and a-vO2dif-max, so for a meaningful change to occur in cardiorespiratory fitness, there must be a concomitant increase in O2 delivery. This study demonstrates that a low volume SIT intervention evokes peripherally mediated responses (a-vO2dif) and anaerobic substrate utilization rather than O2 delivery components. Future works should address the time course of the responses and when assessing V̇O2max-based responses that due attention be given to the hemodynamic responses as means of quantification of the response.

Abstract Even pacing within the marathon has been associated with faster marathon performance times, however, little literature has investigated the association between pacing ability during a marathon and a recreational marathoner’s training characteristics and previous experiences. N = 139 participants completed an online questionnaire concerning training history in relation to a 2017 marathon and previous long-distance running experiences. Online databases were used to collect split times of the participants after successfully completing a 2017 marathon, identifying the percentage slowdown in pace between the first half and second half of the marathon, used for correlational analyses. The strongest correlates for pacing ability were marathon finishing time and previous distance race personal best finishing times (i.e. marathon, half-marathon, 10 and 5 km). There were many weaker, however significant correlates for training history characteristics and previous long-distance running experience. The current findings demonstrate that greater accrued long-distance running experiences and higher weekly training volumes are strongly associated with smaller declines in pace during the second half of the marathon in comparison to the first half and less variability in pace during the marathon.

Previous works assessing the impact of high intensity interval training on VO2max have offered varying results PURPOSE: To determine the meaningful effects of a short-term high-intensity interval training (HIIT) or continuous training (CET) intervention on VO2max and the anaerobic capacity through quantification of both the respiratory and haemodynamic responses. METHOD: Following local institutional ethical approval, 37 physically active participants undertook 4-weeks of either cycling-based HIIT (age, 17.0 ± 0.5 yrs; height, 173.1 ± 9.2 cm; mass, 62.4 ± 6.9 kg). (8 x 20 s at 170% pO2max with 10 s recovery) or CET (age, 17.0 ± 0 yrs; height, 173.6 ± 8.7 cm; mass, 69.3 ± 17.0 kg) (30 min at 70% O2max) 3 times per week. VO2max, anaerobic capacity as determined through the maximally accumulated oxygen deficit (MAOD), blood-based markers and haemodynamic responses were assessed pre and post the intervention period. VO2max and MAOD were evaluated using breath-by-breath open circuit spirometry while haemodynamic responses were monitored using thoracic impedance cardiography. Analysis conducted using both inferential analysis as well as magnitude-based inferences (MBI) and effects sizes (ES). RESULTS: VO2max exhibited a non-significant 4.1% increase (P> 0.05) (ES= 0.24) for HIIT with 7.0% p= 0.007 (ES= 0.40, MBI= likely trivial) increase for CET. Haemodynamic responses (Qmax, SVmax) displayed non-significant responses for CET and HIIT (P> 0.05) while a-vO2dif-max increased from 15.8 ± 4.8 to 18.3 ± 2.9 ml 100 ml) (p= 0.02) (ES= 0.63, MBI= possibly beneficial) following HIIT. MAOD increased by 7.3 mlkg for HIIT (p= 0.001) (ES= 0.72, MBI= likely beneficial), with CET showing no change (p >0.05). CONCLUSIONS: VO2max is a function of Qmax and a-vO2dif-max, so for a meaningful change to occur in cardiorespiratory fitness there must be a concomitant increase in O2 delivery. This study demonstrates that a short-term HIIT intervention evokes peripherally mediated responses (a-vO2dif) and anaerobic substrate utilisation rather than O2 delivery components. The increase in VO2max for CET in the absence of haemodynamic responses lends further support to the need for valid quantification of VO2max.