ALBERT

Description: During extended periods of skeletal unloading, losses in strength and density of the proximal femur will occur. In long-duration spaceflight, resistive exercise is used to replace the normal loads exerted on the spine and hip. At the present time, there is no conclusive evidence that hip bone loss has been prevented in this scenario. Our group has recently developed and clinically evaluated a multifunctional exercise system, the Combined Countermeasure Device (CCD). The CCD comprises a low-footprint Stuart Platform for lower-body resistance exercise and balance training, and a cardiovascular exercise bicycle. A consideration for resistance exercise was targeting of the hip abductor and adductor muscles, which attach directly at the hip and which should subject it to the largest loads. In our training study, we found that CCD exercise increased hip adductor and abductor strength, and modeling results suggest that this exercise exerts forces on the hip of approx. 4-6 body weights at 1g, compared to forces of approx.2.5 body weight y squatting exercise. In our current study, we hypothesize that abductor and adductor exercise will increase the density and strength of the proximal femur.

Description: Orthostatic intolerance after spaceflight is still an issue for astronauts as no in-flight countermeasure has been 100% effective. Future anti-gravity suits (AGS) may be similar to the Shuttle era inflatable AGS or may be a mechanical compression device like the Russian Kentavr. We have evaluated the above garments as well as elastic, gradient compression garments of varying magnitude and determined that breast-high elastic compression garments may be a suitable replacement to the current AGS. This new garment should be more comfortable than the AGS, easy to don and doff, and as effective a countermeasure to orthostatic intolerance. Furthermore, these new compression garments could be worn for several days after space flight as necessary if symptoms persisted. We conducted two studies to evaluate elastic, gradient compression garments. The purpose of these studies was to evaluate the comfort and efficacy of an alternative compression garment (ACG) immediately after actual space flight and 6 degree head-down tilt bed rest as a model of space flight, and to determine if they would impact recovery if worn for up to three days after bed rest.

Description: Orthostatic intolerance after space flight is still an issue for astronaut health. No in-flight countermeasure has been 100% effective to date. NASA currently uses an inflatable anti-gravity suit (AGS) during reentry, but this device is uncomfortable and loses effectiveness upon egress from the Shuttle. The Russian Space Agency currently uses a mechanical counter-pressure garment (Kentavr) that is difficult to adjust alone, and prolonged use may result in painful swelling at points where the garment is not continuous (feet, knees, and groin). To improve comfort, reduce upmass and stowage requirements, and control fabrication and maintenance costs, we have been evaluating a variety of gradient compression, mechanical counter-pressure garments, constructed from spandex and nylon, as a possible replacement for the current AGS. We have examined comfort and cardiovascular responses to knee-high garments in normovolemic subjects; thigh-high garments in hypovolemic subjects and in astronauts after space flight; and 1-piece, breast-high garments in hypovolemic subjects. These gradient compression garments provide 55 mmHg of compression over the ankle, decreasing linearly to ~35 mmHg at the knee. In thigh-high versions the compression continues to decrease to ~20 mmHg at the top of the leg, and for breast-high versions, to ~15 mmHg over the abdomen. Measures of efficacy include increased tilt survival time, elevated blood pressure and stroke volume, and lower heart-rate response to orthostatic stress. Results from these studies indicate that the greater the magnitude of compression and the greater the area of coverage, the more effective the compression garment becomes. Therefore, we are currently testing a 3-piece breast-high compression garment on astronauts after short-duration flight. We chose a 3-piece garment consisting of thigh-high stockings and shorts, because it is easy to don and comfortable to wear, and should provide the same level of protection as the 1-piece breast-high garments evaluated in hypovolemic test subjects.

Description: Long-term bed rest (BR), a model of spaceflight, results in a decrease in aerobic capacity and altered submaximal exercise responses. The strongest BR-induced effects on exercise appear to be centrally-mediated, but longer BR durations may result in peripheral adaptations (e.g., decreased mitochondrial and capillary density) which are likely to influence exercise responses. PURPOSE: To measure tissue oxygen saturation (SO2) and hydrogen ion concentration ([H+]) in the vastus lateralis (VL) using near infrared spectroscopy (NIRS) during cycle ergometry before and after . 30 d of BR. METHODS: Eight subjects performed a graded exercise test on a cycle ergometer to volitional fatigue 7 d before (pre-BR) and at the end or 1 day after BR (post-BR). NIRS spectra were collected from a sensor adhered to the skin overlying the VL. Oxygen consumption (VO2) was measured by open circuit spirometry. Blood volume (BV) was measured before and after BR using the carbon monoxide rebreathing technique. Changes in pre- and post-BR SO2 and [H+] data were compared using mixed model analyses. BV and peak exercise data were compared using paired t-tests. RESULTS: BV (pre-BR: 4.3+/-0.3, post-BR: 3.7+/-0.2 L, mean+/-SE, p=.01) and peak VO2 (pre-BR: 1.98+/-0.24, post-BR: 1.48 +/-0.21 L/min, p〈.01) were reduced after BR. As expected, SO2 decreased with exercise before and after BR. However, SO2 was lower post compared with pre-BR throughout exercise, including at peak exercise (pre-BR: 50+/-3, post-BR: 43+/-4%, p=.01). After BR, [H+] was higher at the start of exercise and did not increase at the same rate as pre-BR. Peak [H+] was not different from pre to post-BR (pre-BR: 36+/-2; post-BR: 38+/-2 nmol/L). CONCLUSIONS: Lower SO2 during exercise suggests that oxygen extraction in the VL is higher after BR, perhaps due to lower circulating blood volume. The higher [H+] after BR suggests a greater reliance upon glycolysis during submaximal exercise, although [H+] at peak exercise was unchanged. Taken together, these data suggest that longer duration BR induces a number of changes that result in peripheral adaptations which contribute to cardiovascular and muscular deconditioning as measured by NIRS-derived SO2 and [H+] in the VL and may contribute to lower post-BR exercise tolerance. Supported by the National Space Biomedical Research Institute through NASA NCC 9-58

Description: The cephalad fluid shift induced by microgravity has been hypothesized to cause an elevation in intracranial pressure (ICP) and contribute to the development of the Visual Impairment/Intracranial Pressure (VIIP) syndrome, as experienced by some astronauts during long-duration space flight. Elevated ambient partial pressure of carbon dioxide (PCO2) on ISS may also raise ICP and contribute to VIIP development. We seek to determine if the combination of mild CO2 exposure, similar to that occurring on the International Space Station, with the cephalad fluid shift induced by head-down tilt, will induce ophthalmic and cerebral blood flow changes similar to those described in the VIIP syndrome. We hypothesize that mild hypercapnia in the head-down tilt position will increase choroidal blood volume and cerebral blood flow, raise intraocular pressure (IOP), and transiently reduce visual acuity as compared to the seated or the head-down tilt position without elevated CO2, respectively.

Description: Adaptation to microgravity could impair crewmembers? ability to perform required tasks upon entry into a gravity environment, such as return to Earth, or during extraterrestrial exploration. Historically, data have been collected in a controlled testing environment, but it is unclear whether these physiologic measures result in changes in functional performance. NASA?s Functional Task Test (FTT) aims to investigate whether adaptation to microgravity increases physiologic stress and impairs performance during mission-critical tasks. PURPOSE: To determine whether the well-accepted postflight tachycardia observed during standard laboratory tests also would be observed during simulations of mission-critical tasks during and after recovery from short-duration spaceflight. METHODS: Five astronauts participated in the FTT 30 days before launch, on landing day, and 1, 6, and 30 days after landing. Mean heart rate (HR) was measured during 5 simulations of mission-critical tasks: rising from (1) a chair or (2) recumbent seated position followed by walking through an obstacle course (egress from a space vehicle), (3) translating graduated masses from one location to another (geological sample collection), (4) walking on a treadmill at 6.4 km/h (ambulation on planetary surface), and (5) climbing 40 steps on a passive treadmill ladder (ingress to lander). For tasks 1, 2, 3, and 5, astronauts were encouraged to complete the task as quickly as possible. Time to complete tasks and mean HR during each task were analyzed using repeated measures ANOVA and ANCOVA respectively, in which task duration was a covariate. RESULTS: Landing day HR was higher (P 〈 0.05) than preflight during the upright seat egress (7%+/-3), treadmill walk (13%+/-3) and ladder climb (10%+/-4), and HR remained elevated during the treadmill walk 1 day after landing. During tasks in which HR was not elevated on landing day, task duration was significantly greater on landing day (recumbent seat egress: 25%+/-14 and mass translation: 26%+/-12; P 〈 0.05). CONCLUSION: Elevated HR and increased task duration during postflight simulations of mission-critical tasks is suggestive of spaceflight-induced deconditioning. Following short-duration microgravity missions (〈 16 d), work performance may be transiently impaired, but recovery is rapid.

Description: No abstract available

Description: No abstract available

Description: Future human space travel will primarily consist of long-duration missions aboard the International Space Station (ISS) or exploration class missions to Mars, its moons, or nearby asteroids. These missions will expose astronauts to increased risk of oxidative and inflammatory damage primarily from radiation, but also from psychological stress, reduced physical activity, diminished nutritional status, and, in the case of extravehicular activity, hyperoxic exposure. There is evidence that increased oxidative damage and inflammation can accelerate the development of atherosclerosis. PURPOSE The purpose of this proposal is to identify biomarkers of oxidative and inflammatory stress and to correlate them to indices of atherosclerosis risk before, during, and after long-duration spaceflight. METHODS To meet the objectives of the study, we will study astronauts before, during, and up to 5 years after long-duration missions aboard ISS. Biomarkers of oxidative and inflammatory stress, some of which we have previously shown to be elevated with spaceflight, will be measured before, during, and after spaceflight. Arterial structure will be monitored using ultrasound to measure carotid intima-medial thickness before, during, and after weightlessness. Carotid intima-medial thickness has been shown to be a better indicator than Framingham Risk scores for prediction of atherosclerosis. Arterial function will be monitored using brachial flow-mediated dilation before flight and after landing. Brachial flow-mediated dilation is a good index of endothelium-dependent vasodilation, which is a sensitive predictor of atherosclerotic risk. This is the first study to propose assessing atherosclerotic risk using biochemical, structural, and functional measures before, during, and immediately after spaceflight and structural functional measures for up to 5 years after landing. EXPECTED RESULTS We hypothesize that these biomarkers of oxidative and inflammatory stress will be increased with spaceflight and will correlate with increased carotid intima-medial thickness in- and postflight and with decreased flow-mediated dilation after the mission. Furthermore, we hypothesize that measures of oxidative stress will return to baseline after flight, but that biomarkers of inflammatory stress and vascular indices of atherosclerosis risk will remain elevated.

Description: Orthostatic intolerance following spaceflight has been observed since the early days of manned spaceflight, and no countermeasure has been 100% effective. During re-entry NASA astronauts currently wear an inflatable anti-gravity suit (AGS) which compresses the legs and abdomen, but this device is uncomfortable and loses effectiveness upon egress from the Space Shuttle. We previously reported that foot-to-thigh, gradient compression stockings were comfortable and effective during standing after Shuttle missions. More recently we showed in a ground-based model of spaceflight that the addition of splanchnic compression to the foot-to-thigh compression stockings, creating foot-to-breast high compression, improved orthostatic tolerance in hypovolemic subjects to a level similar to the AGS. Purpose: To evaluate a new three-piece, foot-to-breast high gradient compression garment as a countermeasure to post-spaceflight orthostatic intolerance. Methods: Fourteen astronauts completed this experiment (7 control, 7 treatment) following Space Shuttle missions lasting 12-16 days. Treatment subjects were custom-fitted for a three-piece, foot-to-breast high compression garment consisting of shorts and foot-to-thigh stockings. The garments were constructed to provide 55 mmHg compression at the ankle and decreased gradually to 15 mmHg over the abdomen. Orthostatic testing occurred ~30 days before flight (without garments) and ~2 hours after flight (with garments for treatment group only) on landing day. Blood pressure (BP) and heart rate (HR) were acquired for 2 minutes while the subject lay prone and then for 3.5 minutes after the subject stood. Data are reported as mean +/- SE. Results: The compression garment successfully prevented the tachycardia and hypotension typically seen post-spaceflight. On landing day, treatment subjects had a smaller change in HR (11+/-1 vs. 21+/-4 beats/min, p〈 or =0.05) and no decrease in systolic BP (2+/-4 vs. -9+/-2 mmHg, p〈 or =0.05). Garments also received good comfort ratings and were relatively easy to don. Conclusion: In this small group of astronauts, foot-to-breast high gradient compression garments seem to have prevented these negative effects of spaceflight on the cardiovascular responses to standing.