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NASA NTRS2004

Foot-ground reaction force during resistive exercise in parabolic flight

INTRODUCTION: An interim resistance exercise device (iRED) was designed to provide resistive exercise as a countermeasure to spaceflight-induced loss of muscle strength and endurance as well as decreased bone mineral density. The purpose of this project was to compare foot-ground reaction force during iRED exercise in normal gravity (1 G) vs. microgravity (0 G) achieved during parabolic flight. METHODS: There were four subjects who performed three exercises (squat, heel raise, and deadlift) using the iRED during 1 G and 0 G at a moderate intensity (60% of maximum strength during deadlift exercise). Foot-ground reaction force was measured in the three orthogonal axes (x, y, z) using a force plate, and the magnitude of the resultant force vector was calculated (r = square root(x2 + y2 + z2)). Linear displacement (LD) was measured using a linear transducer. Peak force (Fpeak) and an index of total work (TWi) were calculated using a customized computer program. Paired t-tests were used to test if significant differences (p < or = 0.05) were observed between 1 G and 0 G exercise. RESULTS: Fpeak and TWi measured in the resultant axis were significantly less in 0 G for each of the exercises tested. During 0 G, Fpeak was 42-46% and TWi was 33-37% of that measured during 1 G. LD and average time to complete each repetition were not different from 1 G to 0 G. CONCLUSIONS: Crewmembers who perform resistive exercises during spaceflight that include the movement of a large portion of their body mass will require much greater external resistive force during 0 G than 1 G exercise to provide a sufficient stimulus to maintain muscle and bone mass.

Physical Education and Training↗

NASA NTRS2003

Foot-Ground Reaction Force During Resistance Exercise in Parabolic Flight

An interim Resistance Exercise Device (iRED) was designed to provide resistive exercise as a countermeasure to space flight-induced loss of muscle strength and endurance as well as decreased bone mineral density. The purpose of this project was to compare foot-ground reaction force during iRED exercise in normal gravity (l-g) versus micro gravity (O-g) achieved during parabolic flight. METHODS: Four subjects performed three exercises using the iRED (squat, heel raise, and deadlift) during I-g and O-g at a moderate intensity (60% of maximum strength during deadlift exercise). Foot-ground reaction force was measured in three axes (x,y,z) using a force plate, and the magnitude of the resultant force vector was calculated (r = ~X 2 + y2 + Z2 ). Range of motion (ROM) was measured using a linear encoder. Peak force (PkF) and total work (TW) were calculated using a customized computer program. Paired t-tests were used to test if significant differences (p.::::0.05) were observed between I-g and O-g exercise. RESULTS: PkF and TW measured in the resultant axis were significantly less in O-g for each of the exercises tested. During O-g, PkF was 42-46% and TW was 33- 37% of that measured during I-g. ROM and average time to complete each repetition were not different from I-g to O-g. CONCLUSIONS: When performing exercises in which body mass is a portion of the resistance during I-g, PkF and TW measured during resistive exercise were reduced approximately 60-70% during O-g. Thus, a resistive exercise device during O-g will be required to provided higher resistances to induce a similar training stimulus to that on Earth.

Lee, Stuart M. C.↗

NASA NTRS1999

Carotid Baroreflex Function During Prolonged Exercise

Astronauts are often required to work (exercise) at moderate to high intensities for extended periods while performing extra-vehicular activities (EVA). Although the physiologic responses associated with prolonged exercise have been documented, the mechanisms involved in blood pressure regulation under these conditions have not yet been fully elucidated. An understanding of this issue is pertinent to the ability of humans to perform work in microgravity and complies with the emphasis of NASA's Space Physiology and Countermeasures Program. Prolonged exercise at a constant workload is know to result in a progressive decrease in mean arterial pressure (MAP) concomitant with a decrease in stroke volume and a compensatory increase in heart rate. The continuous decrease in MAP during the exercise, which is related to the thermoregulatory redistribution of circulating blood volume to the cutaneous circulation, raises the question as to whether there is a loss of baroreflex regulation of arterial blood pressure. We propose that with prolongation of the exercise to 60 minutes, progressive increases on central command reflect a progressive upward resetting of the carotid baroreflex (CBR) such that the operating point of the CBR is shifted to a pressure below the threshold of the reflex rendering it ineffectual in correcting the downward drift in MAP. In order to test this hypothesis, experiments have been designed to uncouple the global hemodynamic response to prolonged exercise from the central command mediated response via: (1) continuous maintenance of cardiac filling volume by intravenous infusion of a dextran solution; and (2) whole body surface cooling to counteract thermoregulatory cutaneous vasodialation. As the type of work (exercise) performed by astronauts is inherently arm and upper body dependent, we will also examine the physiologic responses to prolonged leg cycling and arm ergometry exercise in the supine positions with and without level lower body negative pressure (-10 torr) to mimic spaceflight- related decreases in cardiac filling volumes.

Raven, P. B.↗

NASA NTRS1996

Trabecular Bone Mechanical Properties and Fractal Dimension

Countermeasures for reducing bone loss and muscle atrophy due to extended exposure to the microgravity environment of space are continuing to be developed and improved. An important component of this effort is finite element modeling of the lower extremity and spinal column. These models will permit analysis and evaluation specific to each individual and thereby provide more efficient and effective exercise protocols. Inflight countermeasures and post-flight rehabilitation can then be customized and targeted on a case-by-case basis. Recent Summer Faculty Fellowship participants have focused upon finite element mesh generation, muscle force estimation, and fractal calculations of trabecular bone microstructure. Methods have been developed for generating the three-dimensional geometry of the femur from serial section magnetic resonance images (MRI). The use of MRI as an imaging modality avoids excessive exposure to radiation associated with X-ray based methods. These images can also detect trabecular bone microstructure and architecture. The goal of the current research is to determine the degree to which the fractal dimension of trabecular architecture can be used to predict the mechanical properties of trabecular bone tissue. The elastic modulus and the ultimate strength (or strain) can then be estimated from non-invasive, non-radiating imaging and incorporated into the finite element models to more accurately represent the bone tissue of each individual of interest. Trabecular bone specimens from the proximal tibia are being studied in this first phase of the work. Detailed protocols and procedures have been developed for carrying test specimens through all of the steps of a multi-faceted test program. The test program begins with MRI and X-ray imaging of the whole bones before excising a smaller workpiece from the proximal tibia region. High resolution MRI scans are then made and the piece further cut into slabs (roughly 1 cm thick). The slabs are X-rayed again and also scanned using dual-energy X-ray absorptiometry (DEXA). Cube specimens are then cut from the slabs and tested mechanically in compression. Correlations between mechanical properties and fractal dimension will then be examined to assess and quantify the predictive capability of the fractal calculations.

Hogan, Harry A.↗

NASA NTRS2016

NASA'S Standard Measures During Bed Rest: Adaptations in the Cardiovascular System

Bed rest is a well-accepted analog of space flight that has been used extensively to investigate physiological adaptations in a larger number of subjects in a shorter amount of time than can be studied with space flight and without the confounding effects associated with normal mission operations. However, comparison across studies of different bed rest durations, between sexes, and between various countermeasure protocols have been hampered by dissimilarities in bed rest conditions, measurement protocols, and testing schedules. To address these concerns, NASA instituted standard bed rest conditions and standard measures for all physiological disciplines participating in studies conducted at the Flight Analogs Research Unit (FARU) at the University of Texas-Medical Branch. Investigators for individual studies employed their own targeted study protocols to address specific hypothesis-driven questions, but standard measures tests were conducted within these studies on a non-interference basis to maximize data availability while reducing the need to implement multiple bed rest studies to understand the effects of a specific countermeasure. When possible, bed rest standard measures protocols were similar to tests nominally used for medically-required measures or research protocols conducted before and after Space Shuttle and International Space Station missions. Specifically, bed rest standard measures for the cardiovascular system implemented before, during, and after bed rest at the FARU included plasma volume (carbon monoxide rebreathing), cardiac mass and function (2D, 3D and Doppler echocardiography), and orthostatic tolerance testing (15- or 30-minutes of 80 degree head-up tilt). Results to-date indicate that when countermeasures are not employed, plasma volume decreases and the incidence of presyncope during head-up tilt is more frequent even after short-duration bed rest while reductions in cardiac function and mass are progressive as bed rest duration increases. Additionally, while plasma volume loss can be corrected and cardiac mass can be prevented with properly applied countermeasures, orthostatic tolerance is more difficult to protect when supine exercise is the only countermeasure. Similar results have been observed after space flight. Plasma volume, cardiac chamber volume, and orthostatic tolerance recover relatively quickly with resumption of ambulation and normal activity levels after bed rest but restoration of cardiac mass is prolonged.

Lee, Stuart M. C.↗

NASA NTRS1997

Cycle-Powered Short Radius (1.9 m) Centrifuge: Effect of Exercise Versus Passive Acceleration on Heart Rate in Humans

In addition to extensive use of lower extremity physical exercise training as a countermeasure for the work capacity component of spaceflight deconditioning, some form of additional head-to-foot (+Gz) gravitational (orthostatic) stress may be required to further attenuate or prevent the signs and symptoms (nausea, vertigo, instability, fatigue) of the general reentry syndrome (GRS) that can reduce astronaut performance during landing. Orthostatic (head-to-foot) stress can be induced by standing, by lower body negative pressure, and by +Gz acceleration. One important question is whether acceleration training alone or with concurrent leg exercise would provide sufficient additive stimulation to attenuate the GRS. Use of a new human-powered centrifuge may be the answer. Thus, the purpose for this study was to compare heart rate (HR), i.e., a stress response during human-powered acceleration, in four men (35-62 yr) and two women (30-31 yr) during exercise acceleration versus passive acceleration (by an off-board operator) at 100% (maximal acceleration = A(max)), and at 25%, 50%, and 75% of A(max). Mean (+/-SE) A(max) was 43.7 +/- 1.3 rpm (+3.9 +/- 0.2Gz). Mean HR at exercise A(max) was 189 +/- 13 b/min (50-70 sec run time), and 142 +/- 22 b/min at passive A(max) (40-70 sec run time). Regression of mean HR on the various +Gz levels indicated explained variance (correlations squared) of r(exp 2) = 0.88 (exercise) and r(exp 2) = 0.96 (passive): exercise HR of 107 +/- 4 (25%) to 189 +/- 13 (100%) b/min were 43-50 b/min higher (p less than 0.05) than comparable passive HR of 64 +/- 2 to 142 +/- 22 b/min. Thus, exercise adds significant physiological stress during +Gz acceleration. Inflight use of this combined exercise and acceleration countermeasure may maintain work capacity as well as normalize acceleration and orthostatic tolerances which could attenuate or perhaps eliminate the GRS.

Greenleaf, J. E.↗

NASA NTRSDate not supplied

INFLUENCE OF ACTN3 GENE ON MUSCLE HEALTH AND PHYSICAL FITNESS TO INFORM FUTURE INTERVENTIONS IN SPACEFLIGHT MISSIONS

INTRODUCTION: Exposure to reduced gravity environments leads to diminished muscle size, strength, and endurance. Preservation of physical fitness is critical for mission essential tasks such as extravehicular activities or adaptation to changes in gravity loads. Current countermeasures to maintain ISS astronauts’ muscle mass and fitness include dedicated time for a combination of cardiovascular exercise and resistance training. Countermeasure effectiveness is monitored through VO2 max and isometric mid-thigh pulls. It is important to understand both environmental and genetic contributors to astronaut physical fitness. Multiple genes, including ACTN3, are known to correlate with exercise phenotypes and have the potential to help personalize countermeasures based on an astronaut’s genotypic makeup. TOPIC: The ACTN3 gene encodes a protein expressed only in fast-twitch muscles and correlates with sprint and power phenotypes. A common polymorphism in ACTN3 gene is R577X (rs1815739), produced by a C−to−T base substitution resulting in a nonsense mutation from arginine (R) to a premature stop codon (X) present in approximately 18% of the population. This polymorphism causes an absence of α−actinin−3 in type II muscle fibers but does not lead to a disease phenotype. The RR genotype is associated with elite athletes, especially in sprint and power sports. The XX genotype is believed to be more common in endurance athletes. The ACTN3 gene also has potential associations with training adaptation, post-exercise recovery, and exercise-associated injuries. APPLICATION: Understanding how ACTN3 and other genetic determinates of fitness phenotypes affect astronaut physical performance can inform personalized exercise and recovery prescriptions. For example, individuals with the RR or RX genotype may respond better to high-load and low repetition exercise, while XX may benefit from high repetition with low weight exercise. Since the wild-type protein may confer more resistance to muscle damage, those individuals with the RR or RX genotype may benefit from high intensity interval training for improved VO2 max, whereas those with an XX genotype may benefit from low intensity, high volume endurance activity. Additionally, omics data related to health and performance could be used as biomarkers to monitor astronaut fitness and the effectiveness of training regimens during a mission. Learning objectives: • Learn about the phenotypic effects on muscle function and fitness secondary to R577X mutation in the ACTN3 gene • Learn how mutations in the ACTN3 gene may inform future countermeasures for future spaceflight missions

Lynn K Stanwyck↗

NASA NTRSDate not supplied

Monitoring Biomarkers for Muscular Atrophy Using an Electrochemical Chip for Astronaut Space Health

Skeletal muscle atrophy is a serious health problem for astronauts in long-duration space flight under microgravity conditions. Preventative measures against muscle atrophy require specific exercise and dietary regimens. Preemptive measurements to improve treatment have the potential to streamline these regimens, decreasing their daily footprint and increasing astronaut quality of life. The objective of our proposed project is to (1) develop a fully integrated disposable microelectrode array chip (with the size of a stamp) that can be interfaced with a handheld electronic system for simultaneous detection of the a panel of biomarkers to monitor the progression of skeletal muscle atrophy due to disuse under microgravity in long-duration spaceflights; and (2) use such quantitative information to guide the combined countermeasures of physical exercise and pharmaceuticals (i.e. specific protease inhibitors) so that the intensity, duration and frequency of exercise can be reduced. Note: The presentation includes voice commentary and plays best as a slide show. The voice begins once the presentation starts, and only requires the user to click to the next slide each time. With a run time of ~15 mins.

Biosensor↗

NASA NTRSDate not supplied

Monitoring Biomarkers for Muscular Atrophy using an Electronic Chip for Astronaut Health

Biosensing↗

NASA NTRS2005

Nutrition for Space Exploration

Nutrition has proven to be critical throughout the history of human exploration, on both land and water. The importance of nutrition during long-duration space exploration is no different. Maintaining optimal nutritional status is critical for all bodily systems, especially in light of the fact that that many are also affected by space flight itself. Major systems of concern are bone, muscle, the cardiovascular system, the immune system, protection against radiation damage, and others. The task ahead includes defining the nutritional requirements for space travelers, ensuring adequacy of the food system, and assessing crew nutritional status before, during, and after flight. Accomplishing these tasks will provide significant contributions to ensuring crew health on long-duration missions. In addition, development and testing of nutritional countermeasures to effects of space flight is required, and assessment of the impact of other countermeasures (such as exercise and pharmaceuticals) on nutrition is also critical for maintaining overall crew health. Vitamin D stores of crew members are routinely low after long-duration space flight. This occurs even when crew members take vitamin D supplements, suggesting that vitamin D metabolism may be altered during space flight. Vitamin D is essential for efficient absorption of calcium, and has numerous other benefits for other tissues with vitamin D receptors. Protein is a macronutrient that requires additional study to define the optimal intake for space travelers. Administration of protein to bed rest subjects can effectively mitigate muscle loss associated with disuse, but too much or too little protein can also have negative effects on bone. In another bed rest study, we found that the ratio of protein to potassium was correlated with the level of bone resorption: the higher the ratio, the more bone resorption. These relationships warrant further study to optimize the beneficial effect of protein on both bone and muscle during space flight. Omega3 fatty acids are currently being studied as a means of protecting against radiation-induced cancer. They have also recently been implicated as having a role in mitigating the physical wasting, or cachexia, caused by cancer. The mechanism of muscle loss associated with this type of cachexia is similar to the mechanism of muscle loss during disuse or space flight. Omega3 fatty acids have already been shown to have protective effects on bone and cardiovascular function. Omega3 fatty acids could be an ideal countermeasure for space flight because they have protective effects on multiple systems. A definition of optimal nutrient intake requirements for long-duration space travel should also include antioxidants. Astronauts are exposed to numerous sources of oxidative stress, including radiation, elevated oxygen exposure during extravehicular activity, and physical and psychological stress. Elevated levels of oxidative damage are related to increased risk for cataracts, cardiovascular disease, and cancer. Many groundbased studies show the protective effects of antioxidants against oxidative damage induced by radiation or oxygen. Balancing the diet with foods that have high levels of antioxidants would be another ideal countermeasure because it should have minimal side effects on crew health. Antioxidant supplements, however, are often used without having data on their effectiveness or side effects. High doses of supplements have been associated with bone and cardiovascular problems, but research on antioxidant effects during space flight has not been conducted. Much work must be done before we can send crews on exploration missions. Nutrition is often assumed to be the simple provision of food items that will be stable throughout the mission. As outlined briefly above, the situation is much more complex than food provision. As explorers throughout history have found, failure to truly understand the role of nutrition can be catastrophic. When huns are in environments unlike any they have seen before, this is more true than ever.

Smith, Scott M.↗

NASA NTRS1983

Cardiovascular responses to hypogravic environments

The cardiovascular deconditioning observed during and after space flight is characterized in a review of human space and simulation studies and animal simulations. The various simulation techniques (horizontal bed rest, head-down tilt, and water immersion in man, and immobilization of animals) are examined, and sample results are presented in graphs. Countermeasures such as exercise regimens, fluid replacement, drugs, venous pooling, G-suits, oscillating beds, electrostimulation of muscles, lower-body negative pressure, body-surface cooling, and hypoxia are reviewed and found to be generally ineffective or unreliable. The need for future space experimentation in both humans and animals is indicated.

Sandler, H.↗

NASA NTRS1989

Biomedical perspectives on locomotion in null gravity

A number of important features of various locomotor activities are discussed, and approaches to the study of these activities in the context of space flight are suggested. In particular, the magnitude of peak forces and the rates of change of force during terrestrial cycling, walking, and running are compared. It is shown that subtle changes in the conditions and techniques of locomotion can have a major influence on the biomechanical consequences to the skeleton. The various hypotheses that identify locomotor exercise as a countermeasure to bone demineralization during weightlessness deserve to be tested with some degree of biomechanical rigor. Various approaches for achieving such scrutiny are discussed.

Cavanagh, Peter R.↗

NASA NTRS1994

Immune Response and Function: Exercise Conditioning Versus Bed-Rest and Spaceflight Deconditioning

Immune responses measured at rest immediately or some hours after exercise training (some with and some without increase in maximal oxygen uptake) gave variable and sometimes conflicting results; therefore, no general conclusions can be drawn. On the other hand, most immune responses were either unchanged (immunoglobulin, T cells, CD4+, and natural killer activity) or decreased (blood properdin, neutrophil phagocytic activity, salivary lysozymes, brain immunoglobulin A and G, and liver B lymphocytes and phytohemagglutinin activity) during prolonged bed rest. Some data suggested that exercise training during bed rest may partially ameliorate the decreased functioning of the immune system. Exercise and change in body position, especially during prolonged bed rest with plasma fluid shifts and diuresis, may induce a change in plasma protein concentration and content, which can influence drug metabolism as well as immune function. Leukocytosis, accompanied by lymphopenia and a depressed lymphocyte response, occurs in astronauts on return to Earth from spaceflight; recovery may depend on time of exposure to microgravity. It is clear that the effect of drugs and exercise used as countermeasures for microgravity deconditioning should be evaluated for their effect on an astronaut's immune system to assure optimal health and performance on long-duration space missions.

Greenleaf, J. E.↗

NASA NTRS1997

The Role of GH/IGF-I Axis in Muscle Homeostasis During Weightlessness

Exposure to reduced gravity during space travel profoundly alters the loads placed on bone and muscle. Astronauts suffer significant losses of muscle and bone strength during weightlessness. Exercise as a countermeasure is only partially effective in remedying severe muscle atrophy and bone demineralization. Similar wasting of muscles and bones affects people on Earth during prolonged bed rest or immobilization due to injury. In the absence of weight bearing activity, atrophy occurs primarily in the muscles that act in low power, routine movements and in maintaining posture. Hormonal disfunction could contribute in part to the loss of muscle and bone during spaceflight. Reduced levels of human Growth Hormone (hGH) were found in astronauts during space flight, as well as reduced GH secretory activity was observed from the anterior pituitary in 7-day space flight rats. Growth hormone has been shown to be required for maintenance of muscle mass and bone mineralization, in part by mediating the biosynthesis IGF-I, a small polypeptide growth factor. IGF biosynthesis and secretion plays an important role in potentiating muscle cell differentiation and has been shown to drive the expression of myogenin, a myogenic specific basic helix-loop-helix factor. IGF-I has also been shown to have an important role in potentiating muscle regeneration, repair and adult muscle hypertrophy.

Schwartz, Robert J.↗

NASA NTRS1996

Effect of spaceflight on the functional, biochemical, and metabolic properties of skeletal muscle

This paper summarizes the effects of spaceflight on the functional, morphological, and biochemical properties of human and rodent skeletal muscle. The findings suggest that following as little as 5-6 in space there are deficits in both human and rodent motor capacity, strength, and endurance properties of skeletal muscle. The reduced strength is associated, in part, with a reduction in muscle mass as reflected in smaller cross-sectional areas of both fast- and slow-twitch fibers. Available evidence in animal models suggests that slow-twitch fibers are more sensitive to the atrophying process. Accompanying the atrophy is a transformation of slow to fast protein phenotype involving myosin heavy chain and sarcoplasmic reticulum protein isoforms. These transformations appear to be regulated, in part, by pretranslational processes. Data on the oxidative capacity of rodent skeletal muscle suggest a bias toward preferential utilization of carbohydrate as the primary substrate. These collective findings suggest that skeletal muscles comprised chiefly of slow fibers are highly dependent on gravity for the normal expression of protein mass and slow phenotype. Future studies need to focus on elucidating the mechanisms associated with the atrophy response, as well as identifying suitable exercise and other countermeasures capable of preserving the structural and functional integrity of skeletal muscle.

NASA Discipline Musculoskeletal↗

NASA NTRS1999

Regulatory Physiology

As noted elsewhere in this report, a central goal of the Extended Duration Orbiter Medical Project (EDOMP) was to ensure that cardiovascular and muscle function were adequate to perform an emergency egress after 16 days of spaceflight. The goals of the Regulatory Physiology component of the EDOMP were to identify and subsequently ameliorate those biochemical and nutritional factors that deplete physiological reserves or increase risk for disease, and to facilitate the development of effective muscle, exercise, and cardiovascular countermeasures. The component investigations designed to meet these goals focused on biochemical and physiological aspects of nutrition and metabolism, the risk of renal (kidney) stone formation, gastrointestinal function, and sleep in space. Investigations involved both ground-based protocols to validate proposed methods and flight studies to test those methods. Two hardware tests were also completed.

Lane, Helen W.↗

NASA NTRS2010

Biosensors for EVA: Improved Instrumentation for Ground-based Studies

During lunar excursions in the EVA suit, real-time measurement of metabolic rate is required to manage consumables and guide activities to ensure safe return to the base. Metabolic rate, or oxygen consumption (VO2), is normally measured from pulmonary parameters but cannot be determined with standard techniques in the oxygen-rich environment of a spacesuit. Our group has developed novel near infrared spectroscopic (NIRS) methods to calculate muscle oxygen saturation (SmO 2), hematocrit, and pH, and we recently demonstrated that we can use our NIRS sensor to measure VO 2 on the leg during cycling. Our NSBRI project has 4 objectives: (1) increase the accuracy of the metabolic rate calculation through improved prediction of stroke volume; (2) investigate the relative contributions of calf and thigh oxygen consumption to metabolic rate calculation for walking and running; (3) demonstrate that the NIRS-based noninvasive metabolic rate methodology is sensitive enough to detect decrement in VO 2 in a space analog; and (4) improve instrumentation to allow testing within a spacesuit. Over the past year we have made progress on all four objectives, but the most significant progress was made in improving the instrumentation. The NIRS system currently in use at JSC is based on fiber optics technology. Optical fiber bundles are used to deliver light from a light source in the monitor to the patient, and light reflected back from the patient s muscle to the monitor for spectroscopic analysis. The fiber optic cables are large and fragile, and there is no way to get them in and out of the test spacesuit used for ground-based studies. With complimentary funding from the US Army, we undertook a complete redesign of the sensor and control electronics to build a novel system small enough to be used within the spacesuit and portable enough to be used by a combat medic. In the new system the filament lamp used in the fiber optic system was replaced with a novel broadband near infrared LED light source. The compact grating spectrometer was replaced with a chip-scale spectrometer. With this new design, the sensor is 4 in 2 in 0.5 in, weighs 60 g, and no fiber optic cables are needed. The sensor, which contains the light source and the spectrometer, is adhered directly to the skin with medical grade adhesive. The sensor can be powered via the USB port of the laptop computer that controls the sensor operation. Alternatively, for studies in the spacesuit, the sensor can be powered by a small battery pack and operated by an ultra-portable hand-held computer. Both the handheld computer and battery pack will easily fit within the PLSS of the test spacesuit. System automation was significantly improved, to add features suggested by our colleagues in the Cardiovascular Laboratory and the NASA JSC Exercise Physiology and Countermeasures Project. The functionality and portability of this system were demonstrated in our UMass laboratory.

Soller, B.↗

NASA NTRS2014

On-Command Force and Torque Impeding Devices (OC-FTID) Using ERF

Various machines have been developed to address the need for countermeasures of bone and muscle deterioration when humans operate over extended time in space. Even though these machines are in use, each of them has many limitations that need to be addressed in an effort to prepare for human missions to distant bodies in the solar system. An exercise exoskeleton was conceived that performs on-demand resistivity by inducing force and torque impedance via ElectroRheological Fluid (ERF). The resistive elements consist of pistons that are moving inside ERF-filled cylinders or a donut-shaped cavity, and the fluid flows through the piston when the piston is moved. Tests of the operation of ERF against load showed the feasibility of this approach. ERF properties of high yield stress, low current density, and fast response (less than one millisecond) offer essential characteristics for the construction of the exoskeleton. ERFs can apply very high electrically controlled resistive forces or torque while their size (weight and geometric parameters) can be very small. Their long life and ability to function in a wide temperature range (from -40 to 200 C) allows for their use in extreme environments. ERFs are also nonabrasive, non-toxic, and nonpolluting (meet health and safety regulations). The technology is applicable as a compact exercise machine for astronauts' countermeasure of microgravity, an exercise machine for sport, or as a device for rehabilitation of patients with limb issues.

Bar-Cohen, Yoseph↗