Introduction: Loss in bone mineral density and muscle strength in astronauts following long-duration spaceflight have been well documented, but the altered force and movement environments in microgravity which may contribute to these changes have not been well characterized. This paper describes the instrumentation, software, and data collection procedures developed for the “Foot” experiment that was conducted on the International Space Station (ISS) to provide insight into the biomechanics of daily activity in a microgravity environment. Methods: The instrumentation used for data collection included the Ambulatory Data Acquisition System (ADAS), ADAS electromyography (EMG) modules, the Joint Excursion System, and the Total Force-Foot Ground Interface system, which were all integrated into a specially designed Lower Extremity Monitoring Suit. There were 14 total channels of data that were collected at sampling rates between 8 Hz and 1024 Hz, including 7 channels of EMG, 4 channels of joint angle data, 2 channels of in-shoe ground reaction force, and a marker channel for event recording. Data were typically collected for between 6.5 and 11.8 h of activity during 4 d on Earth and 4–7 d in flight. Results: Exemplar data sets collected preflight on astronauts in 1 g to validate the instrumentation are presented. Discussion: We conclude that the system provides valid and useful biomechanical information on long-term activity. The analysis of data collected on-orbit using the system described here will be presented in a series of future papers characterizing the biomechanics of astronaut activity during complete working days on the Earth and on the ISS.
Research Containing: Human Research
Background Back pain and intervertbral disc (IVD) damage are common problems experienced by astronauts. We hypothesize this is from paraspinal muscle deconditioning, ∼5 cm body lengthening from spinal swelling and straightening, and biochemical tissue changes.Objective Examine morphological changes in the lumbar spine induced by spaceflight.Design Prospective, case series clinical study.Setting We studied crewmembers from the National Aeronautics and Space Administration (NASA).Participants Recruitment from International Space Station NASA/European Space Agency/Canadian Space Agency crewmembers, starting 2011. We enrolled 8 NASA crewmembers. One crewmember completed the study. The others are in various stages of testing.Risk factors Assessment Crew members were studied before and after a ∼180 day mission in the International Space Station.Main outcome measurements In pre-flight and post-flight studies of the lumbar spine, evaluate: 1) degenerative changes using MRI, 2) compressibility using an upright MRI backpack loading protocol, 3) spinal kinematics with X-ray videography, 4) visual analog scale pain.Results Comparing pre-flight and post- flight data, there were 1) increased lumbar IVD heights in the supine position, 2) increased lumbar IVD compressibility in the upright position, 3) decreased flexibility, and 4) increased low back pain post-flight.⇓Spinal kinematics (angles in degrees) during flexion/extension. Pre-flight degenerate disks had less motion. Post-flight, all disks had less motion.Conclusions The data support the idea that decreased gravitational forces on the IVDs, during prolonged microgravity, increases their water content but decreases proteoglycan. This increases disk degeneration risk on Earth. We have a sample size of one for complete Pre- and Post-Flight testing. It's difficult to make conclusions with this preliminary data. However, the acquired images are very high quality and provide confidence for future tests. The next crewmember returns to Earth for final testing November, 2013. Testing of 4 crewmembers and ongoing recruitment are underway.
Effect of gravity on human spontaneous 10-Hz electroencephalographic oscillations during the arrest reaction
Electroencephalographic oscillations at 10 Hz (alpha and mu rhythms) are the most prominent rhythms observed in awake, relaxed (eye-closed) subjects. These oscillations may be considered as a marker of cortical inactivity or an index of the active inhibition of the sensory information. Different cortical sources may participate in the 10-Hz oscillation and appear to be modulated by the sensory context and functional demands. In microgravity, the marked reduction in multimodal graviceptive inputs to cortical networks participating in the representation of space could be expected to affect the 10-Hz activity. The effect of microgravity on this basic oscillation has heretofore not been studied quantitatively. Because the alpha rhythm has a functional role in the regulation of network properties of the visual areas, we hypothesised that the absence of gravity would affect its strength. Here, we report the results of an experiment conducted over the course of 3 space flights, in which we quantified the power of the 10-Hz activity in relation to the arrest reaction (i.e., in 2 distinct physiological states: eyes open and eyes closed). We observed that the power of the spontaneous 10-Hz oscillation recorded in the eyes-closed state in the parieto-occipital (alpha rhythm) and sensorimotor areas (mu rhythm) increased in the absence of gravity. The suppression coefficient during the arrest reaction and the related spectral perturbations produced by eye-opening/closure state transition also increased in on orbit. These results are discussed in terms of current theories on the source and the importance of the alpha rhythm for cognitive function.
After spaceflight, astronauts sometimes suffer a variable degree of reduced orthostatic tolerance. Although many studies have addressed this problem, many aspects remain unclear. Also, it is unknown how long the cardiovascular system needs to recover from short duration spaceflights. The scope of the present study was to determine a long-term follow-up of cardiovascular control up to 25 days after spaceflight under control conditions in five astronauts using heart rate variability, blood pressure variability and baroreflex sensitivity (BRS) indices. In standing position heart rate after spaceflight was significantly higher compared with pre-flight (R+1: 99 (SD 9) BPM vs L-30: 77 (SD 3) BPM; p<0.001). At the same time high frequency modulation of heart rate was extremely depressed (R+1: 70 (SD 334) ms2 vs L-30: 271 (SD 68) ms2; p<0.01), as was BRS: (R+1: 5 (SD 1) vs L-30: 10 (SD 2) ms/mmHg, p<0.05). These changes had largely recovered after 4 days upon return to Earth. Orthostatic blood pressure control was well maintained from the first day after landing. The decrease in BRS and in vagal heart rate modulation following short-duration spaceflight appear to constitute an adequate autonomic neural response to restored gravity. After 4 days upon return to Earth, vagal heart rate modulation is almost completely recovered to the pre-flight level. The findings of the present study demonstrate that the decrease in vagal heart rate modulation in standing position should not be characterised as some kind of cardiovascular deconditioning, but rather as the normal response to orthostatic stress after spaceflight.
Impairment of cerebral blood flow regulation in astronauts with orthostatic intolerance after flight
BACKGROUND AND PURPOSE: We investigated cerebral blood flow regulation in astronauts before and after flights. We hypothesized that autoregulation would be different before flight and after flight between nonfinishers and the finishers of a stand test. METHODS: Twenty-seven astronauts from shuttle missions lasting 8 to 16 days underwent a 10-minute stand test: 10 days before flight, 1 to 2 hours and 3 days after landing. Mean blood flow velocity of the middle cerebral artery (MCA) was measured using transcranial Doppler; Mean arterial pressure was measured using a Finapres (Ohmeda, Englewood, CO) and was adjusted to the level of the MCA (BP(MCA)). Cross-spectral power, gain, phase, and coherence were determined for the relation between BP(MCA) and the cerebrovascular resistance index mean blood flow velocity/BP(MCA). RESULTS: BP(MCA) was reduced with stand (P<0.001). Differences between finishers and nonfinishers (P=0.011) and over test days (P=0.004) were observed. Cerebrovascular conductance was affected by stand (P<0.001), by group (P<0.001) with a group by stand, and test day interaction (P<0.01). Preflight data suggest that the nonfinishers were operating at a higher cerebral vasodilation than finishers for a given BP(MCA), and on landing day the nonfinishers had a greater decrease in mean blood flow velocity as a function of BP(MCA) with standing compared to finishers and preflight. There was a significant interaction effect of gender over the test days and from supine to stand (P=0.035). CONCLUSIONS: Our results indicate that the cause of presyncope in astronauts may be related to a mismatch of cerebral blood flow with blood pressure. Astronaut gender may also play a role in susceptibility to orthostatic intolerance after flight.
Cognitive demand of human sensorimotor performance during an extended space mission: a dual-task study
INTRODUCTION: Two previous single-case studies found that the dual-task costs of manual tracking plus memory search increased during a space mission, and concluded that sensorimotor deficits during spaceflight may be related to cognitive overload. Since dual-task costs were insensitive to the difficulty of memory search, the authors argued that the overload may reflect stress-related problems of multitasking, rather than a scarcity of specific cognitive resources. Here we expand the available database and compare different types of concurrent task. METHODS: Three subjects were repeatedly tested before, during, and after an extended mission on the International Space Station (ISS). They performed an unstable tracking task and four reaction-time tasks, both separately and concurrently. Inflight data could only be obtained during later parts of the mission. RESULTS: The tracking error increased from pre- to in flight by a factor of about 2, both under single- and dual-task conditions. The dual-task costs with a reaction-time task requiring rhythm production was 2.4 times higher than with a reaction-time task requiring visuo-spatial transformations, and 8 times higher than with a regular choice reaction-time task. CONCLUSIONS: Long-term sensorimotor deficits during spaceflight may reflect not only stress, but also a scarcity of resources related to complex motor programming; possibly those resources are tied up by sensorimotor adaptation to the space environment.
Introduction: The medical community of the International Space Station (ISS) has developed joint medical standards and evaluation requirements for Space Flight Participants (“space tourists”) which are used by the ISS medical certification board to determine medical eligibility of individuals other than professional astronauts (cosmonauts) for short-duration space flight to the ISS. These individuals are generally fare-paying passengers without operational responsibilities. Material and Context : By means of this publication, the medical standards and evaluation requirements for the ISS Space Flight Participants are offered to the aerospace medicine and commercial spaceflight communities for reference purposes. It is emphasized that the criteria applied to the ISS spaceflight participant candidates are substantially less stringent than those for professional astronauts and/or crewmembers of visiting and long-duration missions to the ISS. Conclusions: These medical standards are released by the government space agencies to facilitate the development of robust medical screening and medical risk assessment approaches in the context of the evolving commercial human spaceflight industry.
The Russian experience in medical care and health maintenance of the International Space Station crews
The main purpose of the medical support system aboard International Space Station (ISS) is crew health maintenance and high level of work capability assurance prior to during and after in space flights. In the present communication the Russian point of view dealing with the problems and achievements in this branch is presented. An overview on medical operations during flight and after finalization of the space missions based on Russian data of crew health and environment state monitoring, as well as data on the inflight countermeasures (prophylaxis) jointly with data on operational problems that are specific to ISS is presented. The report summarizes results of the medical examination of Russian members of the ISS and taxi crews during and after visits to the ISS.
Established with the personal participation of O.G. Gazenko, the Russian system of medical care for cosmonauts' health has been largely preserved till this day. The system was fully functional on board the orbital complex MIR and, with appropriate modifications, has been adopted as a core of the medical care for Russian members of the ISS crews. In the period of 2000-2008, 22 cosmonauts were members of 17 ISS increments from 140 to 216 days in duration. The main functions of the medical care system were to control health, physical and mental performance, and to support implementation of space researches. The flow of readaptation to the normal gravity was, in most cases similar to what has been typical on return from the Russian orbital stations; some deviations are accounted for by application of the in-flight countermeasures. The paper familiarizes reader with some aspects of the theoretical work of academician O.G. Gazenko in the field of medical care in space flight. It outlines the principles of ISS medical management. The integrated medical support system combines medical equipment and items available on the Russian and US segments; the integrated medical group consists of flight surgeons, medical experts and biomedical engineers of the international partners and coordinates planning and implementation of medical operations. Also, challenges of health care on the phase of ISS utilization are defined.
INTRODUCTION: Cultural differences among crewmembers and mission control personnel can affect long-duration space missions. We examine three cultural contrasts: national (American vs. Russian); occupational (crewmembers vs. mission control personnel); and organizational [Mir space station vs. International Space Station (ISS)]. METHODS: The Mir sample included 5 American astronauts, 8 Russian cosmonauts, and 42 American and 16 Russian mission control personnel. The ISS sample included 8 astronauts, 9 cosmonauts, and 108 American and 20 Russian mission control personnel. Subjects responded to mood and group climate questions on a weekly basis. The ISS sample also completed a culture and language questionnaire. RESULTS: Crewmembers had higher scores on cultural sophistication than mission control personnel, especially American mission control. Cultural sophistication was not related to mood or social climate. Russian subjects reported greater language flexibility than Americans. Crewmembers reported better mood states than mission control, but both were in the healthy range. There were several Russian-American differences in social climate, with the most robust being higher work pressure among Americans. Russian-American social climate differences were also found in analyses of crew only. Analyses showed Mir-ISS differences in social climate among crew but not in the full sample. DISCUSSION: We found evidence for national, occupational, and organizational cultural differences. The findings from the Mir space station were essentially replicated on the ISS. Alterations to the ISS to make it a more user-friendly environment have still not resolved the issue of high levels of work pressure among the American crew.