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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Exercise countermeasures for bed-rest deconditioning

The purpose for this 30-day bed rest study was to investigate the effects of short-term, high intensity isotonic and isokinetic exercise training on maintenance of working capacity (peak oxygen uptake), muscular strength and endurance, and on orthostatic tolerance, posture and gait. Other data were collected on muscle atrophy, bone mineralization and density, endocrine analyses concerning vasoactivity and fluid-electrolyte balance, muscle intermediary metabolism, and on performance and mood of the subjects. It was concluded that: The subjects maintained a relatively stable mood, high morale, and high esprit de corps throughout the study. Performance improved in nearly all tests in almost all the subjects. Isotonic training, as opposed to isokinetic exercise training, was associated more with decreasing levels of psychological tension, concentration, and motivation; and improvement in the quality of sleep. Working capacity (peak oxygen uptake) was maintained during bed rest with isotonic exercise training; it was not maintained with isokinetic or no exercise training. In general, there was no significant decrease in strength or endurance of arm or leg muscles during bed rest, in spite of some reduction in muscle size (atrophy) of some leg muscles. There was no effect of isotonic exercise training on orthostasis, since tilt-table tolerance was reduced similarly in all three groups following bed rest. Bed rest resulted in significant decreases of postural stability and self-selected step length, stride length, and walking velocity, which were not influenced by either exercise training regimen. Most pre-bed rest responses were restored by the fourth day of recovery.

Greenleaf, John↗
NASA NTRS1989

Exercise countermeasures for bed rest deconditioning

The major objectives were to evaluate the efficiency of different modes of exercise (isotonic and isokinetic) for countering the effects of bed rest deconditioning on work capacity (peak oxygen uptake), muscular strength, orthostatic tolerance, posture, equilibrium and gait; and to collect additional data of a more fundamental nature to help understand how these deconditioning responses occur. These data will be used for writing prescriptions for exercise to be utilized by astronauts for maintaining work capacity and well-being on Freedom Station, and to determine what exercise devices should be place in the station.

Greenleaf, John↗
NASA NTRS1995

Exercise Training During Bed Rest Attenuates Deconditioning

A 30-day 6 deg. head-down bed rest study was conducted to evaluate high-intensity, short-duration, alternating isotonic cycle ergometer exercise (ITE) training and high-intensity intermittent isokinetic exercise (IKE) training regiments designed to maintain peak VO2 and muscle mass, strength, and endurance at ambulatory control levels throughout prolonged bed rest. Other elements of the deconditioning (acclimation) syndrome, such as proprioception, psychological performance, hypovolemia, water balance, body composition, and orthostatic tolerance, were also measured. Compared with response during bed rest of the no exercise (NOE) control group: the ITE training regimen (a) maintained work capacity (peak VO2), (b) maintained plasma and red cell volume, (c) induced positive body water balance, (d) decreased quality of sleep and mental concentration, and (e) had no effect on the decrease in orthostatic tolerance; the IKE training regimen (a) attenuated the decrease in peak VO2 by 50%, (b) attenuated loss of red cell volume by 40%, but had no effect on loss of plasma volume, (c) induced positive body water balance, (d) had no adverse effect on quality of sleep or concentration, and (e) had no effect on the decrease in orthostatic tolerance. These findings suggest that various elements of the deconditioning syndrome can be manipulated by duration and intensity of ITE or IKE training regiments, and that several different training protocols will be required to maintain or restore physiological and psychological performance of individuals confined to prolonged bed rest.

Greenleaf, J. E.↗
NASA NTRS1997

Intensive Exercise Training During Bed Rest Attenuates Deconditioning

Intensive exercise training during bed rest attenuates deconditioning. Med. Sci. Sports Exerc., Vol. 29, No. 2, pp. 207-215, 1997. A 30-d 6 deg head-down bed rest project was conducted to evaluate variable high-intensity, short-duration, isotonic cycle ergometer exercise (ITE) training and high-intensity intermittent resistive isokinetic exercise (IKE) training regimens designed to maintain peak VO2 and muscle mass, strength, and endurance at ambulatory control levels throughout prolonged bed rest. Other elements of the deconditioning (adaptive) syndrome, such as proprioception, psychological performance, hypovolemia, water balance, body composition, and orthostatic tolerance, were also measured. Major findings are summarized in this paper. Compared with response during bed rest of the no exercise (NOE) control group: the ITE training regimen (a) maintained work capacity (peak VO2), (b) maintained plasma and red cell volumes, (c) induced positive body water balance, (d) decreased quality of sleep and mental concentration, and (e) had no effect on the decrease in orthostatic tolerance; the IKE training regimen (f) attenuated the decrease in peak VO2 by 50%, (g) attenuated loss of red cell volume by 40% but had no effect on loss of plasma volume, (b) induced positive body water balance, (i) had no adverse effect on quality of sleep or concentration, and 0) had no effect on the decrease in orthostatic tolerance. These findings suggest that various elements of the deconditioning syndrome can be manipulated by duration and intensity of ITE or IKE training regimens and that several different training protocols will be required to maintain or restore physiological and psychological performance of individuals confined to prolonged bed rest.

Greenleaf, John E.↗
NASA NTRS1989

Lunar power system summary of studies for the lunar enterprise task force NASA-office of exploration

The capacity of global power systems must be increased by a factor of ten to provide the predicted power needs of electric power by the year 2050. The Lunar Power System (LPS) would collect solar energy at power bases located on opposing limbs of the moon as seen from Earth. LPS can provide dependable, economic, renewable, and environmentally benign solar energy to Earth. A preliminary engineering and cash flow model of the LPS was developed. Results are shown for a system scaled to a peak capacity of 355 GWe on Earth and to provide 13,600 GWe-Yrs of energy over a 70 year life cycle of construction and full operation. The growth in capacity of the reference system from start of installation on the moon in 2005 to completion of its nominal life cycle in the year 2070 is shown. World needs for power could be accommodated by expansion in capacity of the reference LPS beyond 344 GWe. This would be done by steadily incorporating newer technology during full operation and by establishing additional bases. The results presented encourage consideration of a faster paced program than is assumed herein.

Criswell, David R.↗
NASA NTRS1988

Performance evaluation of NASA/KSC CAD/CAE graphics local area network

This study had as an objective the performance evaluation of the existing CAD/CAE graphics network at NASA/KSC. This evaluation will also aid in projecting planned expansions, such as the Space Station project on the existing CAD/CAE network. The objectives were achieved by collecting packet traffic on the various integrated sub-networks. This included items, such as total number of packets on the various subnetworks, source/destination of packets, percent utilization of network capacity, peak traffic rates, and packet size distribution. The NASA/KSC LAN was stressed to determine the useable bandwidth of the Ethernet network and an average design station workload was used to project the increased traffic on the existing network and the planned T1 link. This performance evaluation of the network will aid the NASA/KSC network managers in planning for the integration of future workload requirements into the existing network.

Zobrist, George↗
NASA NTRS1998

Key Metrics and Goals for NASA's Advanced Air Transportation Technologies Program

NASA's Advanced Air Transportation Technologies (AATT) program is developing a set of decision support tools to aid air traffic service providers, pilots, and airline operations centers in improving operations of the National Airspace System (NAS). NASA needs a set of unifying metrics to tie these efforts together, which it can use to track the progress of the AATT program and communicate program objectives and status within NASA and to stakeholders in the NAS. This report documents the results of our efforts and the four unifying metrics we recommend for the AATT program. They are: airport peak capacity, on-route sector capacity, block time and fuel, and free flight-enabling.

Kaplan, Bruce↗
NASA NTRS2009

Effect of Pharmacologically-Induced Hypovolemia on Aerobic Capacity

Decreased peak oxygen consumption (VO2pk) and an elevated exercise heart rate (HR) response are associated with a reduction in plasma volume (PV) after space flight and bed rest, a space flight analog. Reduced VO2pk and submaximal exercise tolerance would negatively impact an astronaut s ability to perform near maximal work that would be required in the event of an emergency. We previously have administered IV furosemide followed by a low salt diet to model PV loss and orthostatic intolerance observed after spaceflight. Purpose: To determine whether a pharmacologically-induced reduction in PV results in decreased VO2pk and elevated exercise HR response. Methods: Six subjects (5M, 1F) performed two graded peak cycle tests (work rate increased by 35 or 50 W every 3 min), once while normovolemic and once while hypovolemic. HR and expired respiratory gases were continuously measured. To induce hypovolemia, subjects were administered a single dose of IV furosemide (0.5 mg.kg-1) 30 hr before exercise testing and then consumed a low-salt diet (10 mEq.d(sup -1)). PV was measured using carbon monoxide rebreathing. Exercise HR and VO2 responses were quantified as the area under the curve (AUC) calculated over each quartile of the peak test, based on test time in the hypovolemia condition. Paired t-tests were used to test for differences in PV, VO2pk, and peak HR between conditions. Repeated-measures ANOVAs were used to test for differences in AUC between conditions. Results: PV (3.32+/-0.12 vs. 2.77+/-0.16 L, p<0.05) and VO2pk (3.30+/-0.67 vs. 2.90+/-0.57 L.min(sup -1), p<0.05) were lower during hypovolemia than during normovolemia, but peak HR was not different (187+/-5 vs. 187+/-5 bpm). The AUC for VO2 and HR was different (p<0.05) between conditions only in the highest quartile: HR was 4% higher and VO2 was 5% lower during the hypovolemia condition. Conclusion: The mean difference in VO2pk (-12%) between normovolemia and hypovolemia was similar to the mean difference in PV (-17%). Similar decreases in PV and VO2pk have been observed following short duration space flight, suggesting that pharmacologically-induced PV loss can be used to model microgravity-induced reductions in VO2pk.

Everett, Meghan E.↗
NASA NTRS1987

Aerobic fitness in women and responses to lower body negative pressure

The role of tolerance to orthostatic stress in the maintenance of high aerobic fitness in women was investigated by examining the responses of heart rate, stroke volume, cardiac output, Heather index of contractility, arterial pressure, peripheral resistance, change in calf circumference, and thoracic impedance of healthy female subjects to lower body negative pressure (LBNP) applied for 5 min at -50 mm Hg or until a subject became presyncopal. The testing protocol involved a stepwise reduction in pressure and consisted of two parts: an LBNP test in supine position followed by a treadmill test to peak aerobic capacity. Women were found to exhibit the same response pattern to LBNP as was previously reported by Convertino et al. (1984) for men. The results do not support the hypothesis that orthostatic tolerance in women is inversely related to aerobic fitness, as demonstrated by a finding that the peak aerobic capacity of subjects who became presyncopal did not differ from the peak of the tolerant subjects, and that hemodynamic responses to LBNPL were not a function of aerobic capacity.

Frey, Mary Anne Bassett↗
NASA NTRSDate not supplied

Development of Lunar EVA Fitness for Duty Standards for Aerobic Capacity and Muscle Strength

Current aerobic Fitness Standards for NASA astronauts are based on peak aerobic capacity (i.e. VO2peak (ml/kg/min))and are related to aerobic metabolic requirements for Extravehicular Activity (EVA) in microgravity and in 1 g operational environments. Standards for muscle strength need to be developed. Fitness for Duty Standards for partial gravity EVA (e.g. 1/6 g EVA on the Lunar surface) are not developed in terms of aerobic fitness and muscle strength. Defining thresholds for aerobic fitness and muscle strength will help to provide guidance in determining recommendations for optimal fitness necessary for partial g EVA success.

D Frisco↗
NASA NTRS1986

Bedrest-induced peak VO2 reduction associated with age, gender, and aerobic capacity

A study measuring the peak oxygen uptake (V02), heart rate (HR), and exercise tolerance time of 15 men of 55 + or - 2 yr and 17 women of 55 + or - 1 yr after 10 days of continuous bed rest (BR) is presented. The experimental conditions and procedures are described. Following BR a decrease in peak VO2 of 8.4 percent in men and 6.8 percent in women, a reduction in exercise tolerance time by 8.1 percent in men and 7.3 percent in women, and an increse in HR of 4.4 percent and 1.3 percent for men and women, respectively, are observed. These data are compared with data from Convertino et al. (1977) for men 21 + or - 1 yr and women 28 + or - 2yr. It is concluded that BR-induced aerobic deconditioning is independent of age and sex, since the relative decrease in peak V02 in the older and younger subjects and men and women are similar.

Convertino, V. A.↗
NASA NTRS2003

Excercise Within LBNP as an Artificial Gravity Countermeasure

Previous exercise in space has lacked sufficient loads to maintain preflight cardiovascular and musculoskeletal mass and function. Lower body negative pressure (LBNP) produces a static force equivalent to one Earth body weight by each 52 mm Hg of LBNP during supine posture. LBNP also provides transmural blood pressures simulating upright exercise. Thus, this artificial-gravity concept may help maintain cardiovascular and musculoskeletal systems of crewmembers during prolonged exposure to microgravity. Currently available, bungee cord assisted, treadmill exercise is limited by harness discomfort, lower than normal loads, abnormal post-flight gait, and the absence of gravitational blood pressures within the vascular system. PURPOSE: This project evaluates a method to create artificial gravity using supine LBNP treadmill exercise to prevent loss of physiologic function in microgravity simulated by 30 days of bed rest. Identical twins were used as volunteers so that statistical power could be maximized. This countermeasure is being transitioned to space flight. CURRENT STATUS OF RESEARCH Methods: Six sets of identical twins (6 females and 14 males, 21-36 years) remained in 6 head-down tilt (HDT) bed rest for 30 days to simulate prolonged microgravity. Six subjects were randomly selected to exercise supine in an LBNP chamber for 40 minutes six days per week (EX group), while their twin brothers served as non-exercise controls (CON). Pressure within the exercise LBNP chamber was adjusted to increase load, hence increasing exercise intensity. During supine treadmill exercise, LBNP (52-63 mmHg) was applied to produce foot ward forces equivalent to those for upright running on Earth at 1.0-1.2 times body weight (BW) and subjects performed an interval exercise protocol (40-80% peak exercise capacity [VO2pk]). Five minutes of resting LBNP immediately followed each exercise session. Results: Orthostatic tolerance time decreased significantly after 30 days bed rest in the CON group, but was relatively maintained in the EX group. VO2pk was maintained in EX males, but not in CON males. Isokinetic knee strength (extension, peak torque) decreased significantly in CON males, but was preserved in EX males. The EX group had significantly higher spine muscle strength after bed rest than the CON group. The cross-sectional area of spinal muscle at L4/5 level decreased significantly in the CON group but not in the EX group. Urinary n-telopeptide excretion, an index of bone resorption, was increased during bed rest in CON, but not in EX subjects. This suggests protection by LBNP exercise against the increase in bone resorption typically seen in simulated and actual microgravity. Significant changes in bone mineral density (BMD) in the spine and ribs were observed in CON subjects, but not in EX subjects. Conclusions: Our treadmill exercise protocol within LBNP plus a short period of post-exercise LBNP maintains orthostatic responses, upright exercise capacity and other important physiologic parameters during bed rest. These results document the efficacy of our apparatus and exercise protocol for maintaining physiologic structure and function during long-duration microgravity as simulated by 30 days of HDT bed rest. FUTURE PLANS: More sets of female identical twins are needed to reach significance. The LBNP exercise chamber will be redesigned for flight.

Hargens, A. R.↗
NASA NTRS1998

Exercise Countermeasures Demonstration Project During the Lunar-Mars Life Support Test Project Phase 2A

This demonstration project assessed the crew members' compliance to a portion of the exercise countermeasures planned for use onboard the International Space Station (ISS) and the outcomes of their performing these countermeasures. Although these countermeasures have been used separately in other projects and investigations, this was the first time they'd been used together for an extended period (60 days) in an investigation of this nature. Crew members exercised every day for six days, alternating every other day between aerobic and resistive exercise, and rested on the seventh day. On the aerobic exercise days, subjects exercised on an electronically braked cycle ergometer using a protocol that has been previously shown to maintain aerobic capacity in subjects exposed to a space flight analogue. On the resistive exercise days, crew members performed five major multijoint resistive exercises in a concentric mode, targeting those muscle groups and bones we believe are most severely affected by space flight. The subjects favorably tolerated both exercise protocols, with a 98% compliance to aerobic exercise prescription and a 91% adherence to the resistive exercise protocol. After 60 days, the crew members improved their peak aerobic capacity by an average 7%, and strength gains were noted in all subjects. These results suggest that these exercise protocols can be performed during ISS, lunar, and Mars missions, although we anticipate more frequent bouts with both protocols for long-duration spaceflight. Future projects should investigate the impact of increased exercise duration and frequency on subject compliance, and the efficacy of such exercise prescriptions.

Lee, Stuart M. C.↗
NASA NTRS1979

Electromagnetic propulsion alternatives

Mass drivers can serve to propel massive objects by expelling any available material as reaction mass, however, mass driver engines have several limitations such as relatively large payload size and dynamic stability problems. A number of alternative acceleration mechanisms exist which offer advantages for certain applications, such as higher acceleration at a sacrifice in efficiency, smaller possible size and decreased complexity at a sacrifice in service life, etc. The alternative concepts include several variants of the railgun, a family of superconducting slingshot oscillators, a momentum transformer, an impulse induction motor, and a family of hybrid synchronous accelerators. A potential application of considerable interest is the earth-based launching of space cargo or nuclear waste by using off-peak generating capacity to accelerate one ton cargo cylinders at intervals of several minutes.

Kolm, H.↗
NASA NTRS1993

Practical limits to the performance of magnetic bearings: Peak force, slew rate, and displacement sensitivity

Magnetic bearings are subject to performance limits which are quite different from those of conventional bearings. These are due in part to the inherent nonlinearity of the device and in part to its electrical nature. Three important nonideal behaviors are presented: peak force capacity, force slew rate limitation, and sensitivity to rotor motion at large displacements. The problem of identifying the dynamic requirements of a magnetic bearing when used to support a known structure subject to known loads is discussed in the context of these limitations. Several simple design tools result from this investigation.

Maslen, E.↗
NASA NTRS2004

Journal of Air Transportation, Volume 9, No. 2

The following articles from the "Journal of Air Transportation" were processed: Future Requirements and Concepts for Cabins of Blended Wing Body Configurations:A Scenario Approach; Future Scenarios for the European Airline Industry: A Marketing-Based Perspective; An Application of the Methodology for Assessment of the Sustainability of the Air Transport System; Modeling the Effect of Enlarged Seating Room on Passenger Preferences of Domestic Airlines in Taiwan; Developing a Fleet Standardization Index for Airline Pricing; and Future Airport Capacity Utilization in Germany: Peaked Congestion and/or Idle Capacity).

Bowen, Brent↗
NASA NTRS2002

Role of skin blood flow and sweating rate in exercise thermoregulation after bed rest

Two potential mechanisms, reduced skin blood flow (SBF) and sweating rate (SR), may be responsible for elevated intestinal temperature (T(in)) during exercise after bed rest and spaceflight. Seven men underwent 13 days of 6 degrees head-down bed rest. Pre- and post-bed rest, subjects completed supine submaximal cycle ergometry (20 min at 40% and 20 min at 65% of pre-bed rest supine peak exercise capacity) in a thermoneutral room. After bed rest, T(in) was elevated at rest (+0.31 +/- 0.12 degrees C) and at the end of exercise (+0.33 +/- 0.07 degrees C). Percent increase in SBF during exercise was less after bed rest (211 +/- 53 vs. 96 +/- 31%; P < or = 0.05), SBF/T(in) threshold was greater (37.09 +/- 0.16 vs. 37.33 +/- 0.13 degrees C; P < or = 0.05), and slope of SBF/T(in) tended to be reduced (536 +/- 184 vs. 201 +/- 46%/ degrees C; P = 0.08). SR/T(in) threshold was delayed (37.06 +/- 0.11 vs. 37.34 +/- 0.06 degrees C; P < or = 0.05), but the slope of SR/T(in) (3.45 +/- 1.22 vs. 2.58 +/- 0.71 mg x min-1 x cm-2 x degrees C-1) and total sweat loss (0.42 +/- 0.06 vs. 0.44 +/- 0.08 kg) were not changed. The higher resting and exercise T(in) and delayed onset of SBF and SR suggest a centrally mediated elevation in the thermoregulatory set point during bed rest exposure.

NASA Discipline Cardiopulmonary↗
NASA NTRS2006

The Effects of Very Light Jet Air Taxi Operations on Commercial Air Traffic

This study investigates the potential effects of Very Light Jet (VLJ) air taxi operations adding to delays experienced by commercial passenger air transportation in the year 2025. The affordable cost relative to existing business jets and ability to use many of the existing small, minimally equipped, but conveniently located airports is projected to stimulate a large demand for the aircraft. The resulting increase in air traffic operations will mainly be at smaller airports, but this study indicates that VLJs have the potential to increase further the pressure of demand at some medium and large airports, some of which are already operating at or near capacity at peak times. The additional delays to commercial passenger air transportation due to VLJ air taxi operations are obtained from simulation results using the Airspace Concepts Evaluation System (ACES) simulator. The direct increase in operating cost due to additional delays is estimated. VLJs will also cause an increase in traffic density, and this study shows increased potential for conflicts due to VLJ operations.

Smith, Jeremy C.↗