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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Changes in total plasma content of electrolytes and proteins with maximal exercise.

To determine to what extent the increases in concentration of plasma proteins and electrolytes with short maximal work were a result of hemoconcentration, the changes in plasma volume and total content of the plasma constituents were simultaneously evaluated. The results obtained from six human subjects indicated that in comparison to preexercise values there was a net decrease in total content of plasma protein, sodium, and chloride in the first 2 min of the postexercise period, due primarily to a significant loss (13-15%) of plasma fluid. The total plasma potassium content was increased immediately after exercise but was significantly below the preexercise plasma content after 2 min of recovery.

Van Beaumont, W.↗
NASA NTRS1974

Therapeutic hand-exercising device with cycling pressure value

Device exercises hands of persons whose fingers are generally straight and need to be flexed inward toward palms of hands. Device is extremely simple in design, which reduces costs, and fits all hand sizes. Patient can instantly free hand from device by pulling flap free from wrist of straps.

Barthlome, D. E.↗
NASA NTRS1973

Computer model of cardiovascular control system responses to exercise

Approaches of systems analysis and mathematical modeling together with computer simulation techniques are applied to the cardiovascular system in order to simulate dynamic responses of the system to a range of exercise work loads. A block diagram of the circulatory model is presented, taking into account arterial segments, venous segments, arterio-venous circulation branches, and the heart. A cardiovascular control system model is also discussed together with model test results.

Croston, R. C.↗
NASA NTRS1975

Temperature responses to infusion of electrolytes during exercise

Past studies on the influence of various metal ions on heat regulation in mammals are reviewed, and results of a study on the effect of Na and citrate in isotonic and hypertonic concentrations on temperature elevation during exercise in dogs are presented. Hypertonic administration of Na before or during treadmill running and dosis of citrate during treadmill running significantly raised core temperature over controls and isotonic cases. Thus the higher the plasma Na-osmotic concentration, the greater the inhibition of heat dissipation.

Greenleaf, J. E.↗
NASA NTRS1977

Vectorcardiographic changes during extended space flight (M093): Observations at rest and during exercise

The objectives of Skylab Experiment M093 were to measure electrocardiographic signals during space flight, to elucidate the electrophysiological basis for the changes observed, and to assess the effect of the change on the human cardiovascular system. Vectorcardiographic methods were used to quantitate changes, standardize data collection, and to facilitate reduction and statistical analysis of data. Since the Skylab missions provided a unique opportunity to study the effects of prolonged weightlessness on human subjects, an effort was made to construct a data base that contained measurements taken with precision and in adequate number to enable conclusions to be made with a high degree of confidence. Standardized exercise loads were incorporated into the experiment protocol to increase the sensitivity of the electrocardiogram for effects of deconditioning and to detect susceptability for arrhythmias.

Smith, R. F.↗
NASA NTRS1977

Recovery from exercise at varying work loads - Time course of responses of heart rate and systolic intervals

The time course of the recovery period was characterized by noninvasive measurements after 4 minute bicycle exercise at 3 separate work loads in volunteers with normal peak responses. Most responses started immediately to return toward resting control values. Left ventricular ejection time and stroke volume change are discussed. Changes in pre-ejection period were determined by changes in isovolume contraction time, and factors affecting the degree and rate of return are considered. The rates of change in the ejection time index and in the ratio pre-ejection period/left ventricular ejection time were virtually independent of load throughout most of recovery.

Nandi, P. S.↗
NASA NTRS1974

Evaluation of exercise-respiratory system modifications and preliminary respiratory-circulatory system integration scheme

The respiratory control system, functioning as an independent system, is presented with modifications of the exercise subroutine. These modifications illustrate an improved control of ventilation rates and arterial and compartmental gas tensions. A very elementary approach to describing the interactions of the respiratory and circulatory system is presented.

Gallagher, R. R.↗
NASA NTRS1973

User's instructions for the high speed version of the cardiovascular exercise model

A mathematical model and digital computer simulation of the human cardiovascular system and its controls were developed to simulate transient responses to bicycle ergometer exercise. The purpose of the model was to provide a method to analyze cardiovascular control hypotheses which cannot be easily tested in an animal or human or in a spaceflight environment.

Croston, R. C.↗
NASA NTRS1980

Physical exercises on a bicycle-ergometer and running track to prevent hypodynamia in workers of intellectual labor

A program of exercises was developed and tested, consisting of a 12 minute session on a variable load bicycle ergometer and a 10-11 min. run with brief stretching and resting sessions between. Physical performance capacity was measured before, during, and after the period of the experiment and physical exams conducted. After a 4 month test period involving 30 men, aged 25-35, the program was found to be successful in increasing physical performance capacity. The PWC170 increased an average of 22 percent and maximum oxygen consumption 14 percent. Arterial pressure dropped (120/75 to 114/68), vital capacity of lungs increased by 6 percent, strength of respiratory muscles by 8.8 percent, duration of respiratory delay by 18 percent. Duration of cardiac cycles increased, stress index decreased. Cardiac contraction rate 2 minutes after work on the ergometer decreased from 118 to 102 bt/min.

Vasilyeva, V. V.↗
NASA NTRS1982

Induced venous pooling and cardiorespiratory responses to exercise after bed rest

Venous pooling induced by a specially constructed garment is investigated as a possible means for reversing the reduction in maximal oxygen uptake regularly observed following bed rest. Experiments involved a 15-day period of bed rest during which four healthy male subjects, while remaining recumbent in bed, received daily 210-min venous pooling treatments from a reverse gradient garment supplying counterpressure to the torso. Results of exercise testing indicate that while maximal oxygen uptake endurance time and plasma volume were reduced and maximal heart rate increased after bed rest in the control group, those parameters remained essentially unchanged for the group undergoing venous pooling treatment. Results demonstrate the importance of fluid shifts and venous pooling within the cardiovascular system in addition to physical activity to the maintenance of cardiovascular conditioning.

Convertino, V. A.↗
NASA NTRS1985

Response to muscular exercise following repeated simulated weightlessness

The effects of 10-d 6-deg-head-down bed rest (BR1), 14 d of recovery, another 10 d bed rest (BR2), and another 14-d recovery on the cardiovascular response to a graded supine cycle ergometer test (4 min unloaded 60-rpm pedaling followed by 15-W/min increasing work load to volitional fatigue) are investigated experimentally in seven male nonsmokers of mean age 41 yrs, mean weight 80.2 kg, mean height 178 cm, and mean body fat content 22.3 percent. Ergometer tests are performed before BR1, after BR1 and BR2, and 14 d after BR2. The results are presented in tables, and it is found that the significantly decreased maximum-O2-uptake, gas-exchange-aerobic-threshold, and plasma-volume responses and the increased submaximal and maximal heart rates observed (relative to pre-BR1 levels) after BR1 and BR2 return to pre-BR1 values 14 d after BR2. It is inferred that 14 d of mild exercise are adequate for recovery from even repeated exposure to this type of simulated weightlessness.

Convertino, V. A.↗
NASA NTRS1985

Effects of exercise-heat acclimation on fluid, electrolyte, and endocrine responses during tilt and +Gz acceleration in women and men

Two aspects of prolonged endurance training were investigated: (1) the effects of exercise-heat acclimation (on a cycle ergometer at 40 C, 42 rh) on orthostatic tolerance (70 deg head-up tilt) and on a +Gz (head-to-foot) acceleration tolerance of male and female subjects; and (2) comparison of their fluid-electrolyte shifts and hormonal (plasma epinephdrine, norepinephrine, renin, and vasopressin) responses during tilting and centrifugation. The adaptive responses during the 12 d, 2-h acclimation did not alter acceleration tolerance of either men or women, or the women's tilt tolerance, but did increase men's tilt tolerance from 30.4 min before to 58.3 min after acclimation. The patterns of fluid, electrolyte, and protein shifts at tolerance in acceleration and tilting tests were virtually the same in men and women. On the other hand, the hormonal plasma epinephrine, norepinephrine, renin, and vasopressin resonses displayed different shift patterns during acceleration and tilting. It is concluded that the responses to tilting cannot be used to predict responses to acceleration. Future experiments for relating the orthostatic and the acceleration tolerances, and the practical questions of the training regimens for future astronauts are discussed.

Greenleaf, J. E.↗
NASA NTRS1985

Exercise hyperthermia as a factor limiting physical performance - Temperature effect on muscle metabolism

The effect of trunk cooling on the muscle contents of ATP, ADP, AMP, creatine phosphate (CrP), and creatine, as well as of glycogen, some glycolytic intermediates, pyruvate, and lactate were assessed in 11 fasted dogs exercised at 20 C on treadmill to exhaustion. Without cooling, dogs were able to run 57 min, and their rectal (Tre) and muscle (Tm) temperatures increased to 41.8 and 43.0 C, respectively. Cooling with ice packs prolonged the ability to run by 45 percent, and resulted in lower Tre (by 1.1 C) and Tm (by 1.2 C). Depletion of muscle content of total high-energy phosphates (ATP + CrP) and glycogen, and increases in contents of AMP, pyruvate, and lactate were lower in cooled dogs than in non-cooled dogs. The muscle content of lactiate correlated positively with TM. These results indicate that hypothermia accelerates glycolysis, and shifts the equilibrium between high- and low-energy phosphates in favor of the latter. The adverse effect of hypothermia on muscle metabolism may be relevant to the limitation of endurance.

Kozlowski, S.↗
NASA NTRS1987

Considerations in prescribing preflight aerobic exercise for astronauts

The physiological effects of prolonged exposure to weightlessness are discussed together with the effects of aerobic exercise on human characteristics affected by weightlessness. It is noted that, although early data on orthostatic intolerance after spaceflight led to a belief that a high level of aerobic fitness for astronauts was detrimental to orthostatic tolerance on return to earth, most of the data available today do not suport this contention. Aerobic fitness was found to be beneficial to cardiovascular function and to mental performance; therefore, it may be important in performing extravehicular activities during flight.

Frey, Mary Anne Bassett↗
NASA NTRS1989

Effects on motor unit potentiation and ground reaction force from treadmill exercise

This study was conducted to analyze the characteristics of motor unit potentiation (MUP) and ground reaction force (GRF) in treadmill exercise at the inclines of 0, 5.5 and 11 percent with conjuctive speeds of 7.5, 6, and 5 mph respectively. These speeds and corresponding inclines were set to provide equivalent physiological workloads at 12.5 METS. EMG recordings were taken from the rectus femoris and gastrocnemius of the right leg from 5 subjects. Simultaneous GRF recordings were obtained from a Delmar Avionic treadmill rigged with load cells. Measures for MUP and GRF were taken over a period containing 10 strides at steady pace. It was concluded that the gastrocnemius was more evident in EMG activity in all speed/incline settings over the rectus femoris, and that inclines from 5.5 to 11 percent produced greater GRF's over 0 percent. Recommendations for future studies was made.

Elam, Reid P.↗
NASA NTRS1989

Effect of swim exercise training on human muscle fiber function

The effect of swim exercise training on the human muscle fiber function was investigated in swimmers trained in a typical collegiate swim-training program followed by an intensified 10-day training period. The measured parameters included the peak tension (P0), negative log molar Ca(2+) concentration (pCa)-force, and maximal shortening speed (Vmax) of the slow-twitch type I and fast-twitch type II fibers obtained by biopsy from the deltoid muscle. The P0 values were found to be not altered after either the training or the 10-day intensive program. The type I fibers from the trained swimmers showed pCa-force curves shifted to the right, such that higher free Ca(2+) levels were required to elicit a given percent of P0. The training program significantly increased the Vmax in the type I fibers and decreased that of the type II fibers, and the 10-day intensive training produced a further significant decrease of the type II fibers.

Fitts, R. H.↗
NASA NTRS1989

A prototype gas exchange monitor for exercise stress testing aboard NASA Space Station

This paper describes an easy-to-use monitor developed to track the weightlessness deconditioning aboard the NASA Space Station, together with the results of testing of a prototype instrument. The monitor measures the O2 uptake and CO2 production, and calculates the maximum O2 uptake and anaerobic threshold during an exercise stress test. The system uses two flowmeters in series to achieve a completely automatic calibration, and uses breath-by-breath compensation for sample line-transport delay. The monitor was evaluated using two laboratory methods and was shown to be accurate. The system's block diagram and the bench test setup diagram are included.

Orr, Joseph A.↗
NASA NTRS1989

Work capacity during 30 days of bed rest with isotonic and isokinetic exercise training

Results are presented from a study to determine whether or not short-term variable intensity isotonic and intermittent high-intensity isokinetic short-duration leg exercise is effective for the maintenance of peak O2 (VO2) uptake and muscular strength and endurance, respectively, during 30 days of -6 deg head-down bed rest deconditioning. The results show no significant changes in leg peak torque, leg mean total work, arm total peak torque, or arm mean total work for members of the isotonic, isokinetic, and controls groups. Changes are observed, however, in peak VO2 levels. The results suggest that near-peak variabile intensity, isotonic leg excercise maintains peak VO2 during 30 days of bed rest, while peak intermittent, isokinetic leg excercise protocol does not.

Greenleaf, J. E.↗