Background The cardiovascular system is strongly dependent on the gravitational environment. Gravitational changes cause mechanical fluid shifts and, in turn, autonomic effectors influence systemic circulation and cardiac control. We implemented a tilt paradigm to (1) investigate the acute hemodynamic response across a range of directions of the gravitational vector, and (2) to generate specific dose‐response relationships of this gravitational dependency. Methods and Results Twelve male subjects were tilted from 45° head‐up tilt to 45° head‐down tilt in 15° increments, in both supine and prone postures. We measured the steady‐state hemodynamic response in a range of variables including heart rate, stroke volume, cardiac output, oxygen consumption, total peripheral resistance, blood pressure, and autonomic indices derived from heart rate variability analysis. There is a strong gravitational dependence in almost all variables considered, with the exception of oxygen consumption, whereas systolic blood pressure remained controlled to within ≈3% across the tilt range. Hemodynamic responses are primarily driven by differential loading on the baroreflex receptors, combined with differences in venous return to the heart. Thorax compression in the prone position leads to reduced venous return and increased sympathetic nervous activity, raising heart rate, and systemic vascular resistance while lowering cardiac output and stroke volume. Conclusions Gravitational dose‐response curves generated from these data provide a comprehensive baseline from which to assess the efficacy of potential spaceflight countermeasures. Results also assist clinical management of terrestrial surgery in prone posture or head‐down tilt positions.

https://www.ahajournals.org/doi/pdf/10.1161/JAHA.121.024175

Gravitational Dose‐Response Curves for Acute Cardiovascular Hemodynamics and Autonomic Responses in a Tilt Paradigm

Abstract Introduction Astronauts will encounter isolated, confined and extreme (ICE) conditions during future missions, and will have to be able to adapt. Until recently, however, few places on Earth could serve as acceptable space analogues (i.e., submarine and polar regions). The coronavirus disease-2019 (COVID-19)-related lockdowns around the globe provided a good opportunity to obtain more comprehensive datasets on the impact of prolonged isolation on human functioning in a very large sample. Methods Seven hundred forty-eight individuals (Belgium 442, Spain 183, Germany 50, Italy 50, US 23; Mean age ± SD: 41 ± 14 years, with an age range of 18–83 years; 66% women) filled out an online survey assessing the impact of the COVID-lockdown on psychological, exercise and general health variables a first time near the beginning of the initial lockdown (hereafter ‘T1’; 24 ± 13 days after the start of the first lockdown; i.e., 3 weeks after the start of the first lockdown) and a second time a couple of weeks thereafter (hereafter ‘T2’; 17 ± 5 days after the first online survey; i.e., 6 weeks after the start of the first lockdown). Results From T1 to T2 an improvement of subjective sleep quality was observed ( P = 0.003), that was related to an increase in subjective sleep efficiency and a decrease in sleep latency and disturbance ( P ≤ 0.013). Weekly sitting time decreased, and the weekly amount of moderate and vigorous physical activity increased from T1 to T2 ( P ≤ 0.049). No differences from T1 to T2 were observed in terms of mood, loneliness and state anxiety. A lower amount of sitting time was significantly correlated with improved subjective sleep quality ( r = 0.096, P = 0.035) and with an increased amount of moderate ( r = −0.126, P = 0.005) and vigorous ( r = −0.110, P = 0.015) physical activity. Conclusion Compared to 3 weeks into the first COVID-imposed lockdown, 6-weeks after the start of the first COVID-imposed lockdown, physical activity and subjective sleep scores were positively impacted. The present, large sample size study further confirms exercise as a worthwhile countermeasure to psycho-physiological deconditioning during confinement. 

The impact of the COVID-19 lockdown on human psychology and physical activity; a space analogue research perspective

http://manuscript.elsevier.com/S0094576522002211/pdf/S0094576522002211.pdf

The impact of digital scents on behavioral health in a restorative virtual reality environment

Long duration spaceflight missions will require novel exercise systems to protect astronaut crew from the detrimental effects of microgravity exposure. The SPRINT protocol is a novel and promising exercise prescription that combines aerobic and resistive training using a flywheel device, and it was successfully employed in a 70-day bed-rest study as well as onboard the International Space Station. Our team created a VR simulation to further augment the SPRINT protocol when using a flywheel ergometer training device (the Multi-Mode Exercise Device or M-MED). The simulation aspired to maximal realism in a virtual river setting while providing real-time biometric feedback on heart rate performance to subjects. In this pilot study, five healthy, male, physically-active subjects aged 35 ± 9.0 years old underwent 2 weeks of SPRINT protocol, either with or without the VR simulation. After a 1-month washout period, subjects returned for a subsequent 2 weeks in the opposite VR condition. We measured physiological and cognitive variables of stress, performance, and well-being. While physiological effects did not suggest much difference with the VR condition over 2 weeks, metrics of motivation, affect, and mood restoration showed detectable differences, or trended toward more positive outcomes than exercise without VR. These results provide evidence that a well-designed VR “exergaming” simulation with biometric feedback could be a beneficial addition to exercise prescriptions, especially if users are exposed to isolation and confinement.

Virtual Reality “exergames”: A promising countermeasure to improve motivation and restorative effects during long duration spaceflight missions

Virtual reality can be used to support computer graphics teaching, e.g. by offering the chance to illustrate 3D processes that are difficult to convey. This paper describes the development and first evaluations of RePiX VR a virtual reality tool for computer graphics education, which focuses on the teaching of fundamental concepts of the rendering pipeline and offers researchers the opportunity to study learning in VR by integrating learning analytics. For this, the tool itself is presented and the evaluation, which uses quantitative methods and learning analytics to show the effectiveness of the tool. The first evaluations show that even learners without prior knowledge can use the VR tool and learn the first basics of computer graphics.

RePiX VR - Learning environment for the Rendering Pipeline in Virtual Reality

The exploration of space will require ever-increasing exposure to microgravity environments. The human response to this exposure has been categorized and mitigated via countermeasures, principally exercise. However, additional constraints to future mission design minimizes the allotted space and modalities for exercise, creating a risk for psychological fatigue, a reduction in motivation, and a suite of other categorical factors that could, taken together, present a risk for reduced adherence to the countermeasures and/or mission performance. Thus, the current study will examine the effects of a virtual reality (VR) intervention on spaceflight-validated exercise protocols using a prototype rowing ergometer designed to operate within the constraints of future long-duration exploration missions (LDEM). The Integrated Resistance and Aerobic Training (dubbed “SPRINT”) protocol will be used in conjunction with a combination flywheel and resistance training device (M-MED) utilized in prior bedrest studies. The SPRINT protocol trades exercise duration for intensity, providing similar benefits to existing countermeasures while reducing time spent on exercise. The M - MED permits resistance training on the muscles most effected by microgravity exposure on the same device used to train cardiovascular function, thus reducing the volume and weight requirements of the exercise countermeasure. It is upon this framework that we will add the VR rowing simulation. VR has shown to be a lightweight, reliable, and enjoyable technology in numerous studies, while exergaming has been shown to improve measures of motivation and adherence. We will create a rowing simulation that can integrate with a rowing ergometer and any exercise protocol, and then implement it on the M-MED with SPRINT. The simulation will feature virtual teammates, virtual competitors, and other gaming mechanisms that encourage a user to maintain a prescribed heart rate intensity in a way that aims to maximize factors associated with enjoyment and adherence. We plan to conduct a within-subjects experiment on an astronaut-like population. Subjects will be randomly assigned to VR or non-VR in their initial experiment, complete the SPRINT protocol on the M-MED, break for a one-month minimum washout period, then return to complete the protocol again in the other group. As a pilot study, dependent variables have been selected broadly. Physical and psychological outcomes are to be measured alongside adherence to and motivation toward this very challenging protocol. Additional measures are to be made of virtual presence, preexisting bias toward or against VR, and personality traits, which may influence a preference for or against VR. Preliminary data on non-VR subjects shows increasing measures of state-trait anxiety, negative feelings toward the exercise, and amotivation from the start to the end of the protocol. It is hypothesized that overall attitudes toward the protocol will improve with the VR intervention as indicated by metrics of adherence, motivation, affect, and mood restoration. The results of this study will inform future designs of exercise combined with VR applications for implementation during LDEM.

Adam Johnston

Papers

Augmenting Exercise Protocols with Interactive Virtual Reality Environments

SpaceCRAFT VR: an Event-Driven, Modular Simulation Platform with Fully-Asynchronous Physics