Countermeasure

Proceedings of a workshop sponsored by the National Aeronautics and Space Administration Washington, DC, and held at Lyndon B. Johnson Space Center Houston, Texas 1989

Preface

The National Aeronautics and Space Administration's continuing goal is to explore the far reaches of the galaxy and universe. With the success of the Space Transportation System and advanced astrological observations, mankind's desire to explore is limitless. However, at the very core of this journey the question is raised, "Can man survive in space?" This certainly not new and has been asked since the onset of the manned space-flight program. Numerous biomedical investigations from the United States and Russian space programs make up the foundation for our knowledge of space-flight physiology. These studies support the hypothesis that the human body can adapt to any environment, even microgravity.

Even though the process of space adaptation is a natural phenomenon, it presents special problems to human performance and long-term survival. If humans were to adapt to a particular microgravity environment and remain in space, the problems in physiological performance would be predictable. Unfortunately, this is not the case. Astronauts and cosmonauts will be required to adapt to many different environments on their travels into space. One example of this would be a trip to Mars. Crewmembers will begin on Earth in a one-g environment, launch into space and stay for a time in a microgravity environment, and then land on Mars that has one third of the gravitational force of the Earth. During the entire mission, crewmembers will be required to maintain an adequate level of proficiency for contingency and/or emergency procedures.

The challenge to life sciences is clear-maintain crew health, performance, and safety in all environments. The tasks are many: (1) understanding how various gravitational fields effect the human body; (2) identifying those changes that will significantly affect crew health and retard crew performance; (3) developing measures to those adverse alterations; and (4) ensuring the appropriate response of the countermeasures, i.e., efficacy.

For many years now, both the United States and Russian programs have extensively used a number of countermeasures to maintain the crew's health and fitness, the premise that maintaining crew fitness results significantly in reducing the adverse effects of prolonged exposure to a microgravity environment. These effects vary from the onset of orthostatic intolerance following short-term space flight to the development of bone demineralization following long-term space flight. One thing is clear and that is the variable gravitational fields and the numerous translations found during space travel underscore the need to be prepared for all contingencies. Only the most trained and fit crewmembers will be prepared for these types of environments.

The countermeasure used most effectively in flight is exercise. Data from numerous ground-based and in-flight studies have shown the benefits of using exercise to mitigate the effects of a microgravity environment on the adaptation of the major human physiological systems.

These studies have led to the development of exercise countermeasures for space flight. However, much more knowledge needs to be gained before exercise can be used effectively and efficiently. For example, recent studies on aerobic conditioning of astronauts in flight have shown a dramatic decrease in heart rate while running on a treadmill in flight when compared to the same activity performed in one g. The study suggests that the basic characteristics of exercise to near maximum effort, particularly in-flight running, may be quite different. Extrapolating from this, other exercise modalities may be different when carried out in a rnicrogravity environment and, perhaps, other variant gravitational fields.

In the fall of 1989, the NASA Johnson Space Center's Exercise Countermeasures Project hosted a workshop to examine the use of exercise as a countermeasure for specific responses. Some of the leading scientists participated in free communication and open debates regarding the use of exercise as a tool to influence physiological systems. This workshop entitled, "Countering

Space Adaptation with Exercise: Current Issues," included topics on: bone demineralization, aerobic fitness and orthostatic tolerance, cardiovascular deconditioning, concentric versus eccentric exercise training, electrical stimulation, biomechanics of movement in a microgravity environment, detraining, the effects of exercise response and rehabilitation, and psychophysiology of exercise and training.

The goal of this workshop was to explore those issued related to the application of countermeasures to increase overall understanding and gain insight into the use of these countermeasures in our nation's space program.

Bernard A. Harris, Jr., M.D.

Science Plan

Bernard A. Harris, 'jr MD.

Project Manager

Prepared by Christine Wogan and the ECP Team

7ohnson Space Center

7une 1989

Science

Operations Technology

EXERCISE COUNTERMEASURES PROJECT

SCIENCE PLAN

INTRODUCTION PURPOSE: This document describes the overall science plan for the Exercise Countermeasures Project. The goal of the Project is to minimize the effects of deconditioning during spaceflight using individualized exercise "prescriptions" and inflight exercise facilities. This document sets the direction for the exercise countermeasures program at National Aeronautics and Space Administration's Johnson Space Center. SCOPE: This document describes the scientific, operational, and technological goals of the Exercise Countermeasures Project, and gives a broad overview of the approach that will be used to achieve these goals. The Science Plan includes critical questions, investigational outlines, and timelines. Administrative and managerial information can be found in the Exercise Countermeasures Project Plan. BACKGROUND: One of the ways the human body reacts to the reduced physiological and mechanical demands of microgravity is by deconditioning of the cardiovascular, musculoskeletal, and neuromuscular systems. Deconditioning produces a multitude of physical changes such as loss of muscle mass, decreases in bone density and body calcium: it is also responsible for decreased muscle performance (strength and endurance), orthostatic intolerance, and overall decreases in aerobic and anaerobic fitness. Deconditioning presents operational problems during spaceflight and upon return to 1-g. Changes in the sensory system during adaptation to microgravity can cause motion sickness during the first few days in flight; muscular and cardiovascular deconditioning contribute to decreased work capacity during physically demanding extravehicular activities (EVAs); neuromuscular and perceptual changes can precipitate alterations in magnitude estimation, or the so-called "input-offset" phenomenon; and finally, decreased vascular compliance can lead to syncopal episodes upon reentry and landing. Countermeasures are efforts to counteract these problems by interrupting the body's adaptation process. Effective countermeasures will assure mission safety, maximize mission success, and maintain crew health. Other countermeasure programs have included evaluating lower body negative pressure (LBNP) devices and saline loading to counteract cardiovascular deconditioning (1,2,4,8), and fluoride and calcium supplementation to counteract bone demineralization (3,5,6). These measures have proven effective, but narrow in scope. In contrast, results from experiments on the Gemini, Apollo, and Skylab missions

1

suggest that regular exercise is helpful in minimizing several aspects of spaceflight deconditioning (7,9,10). In fact, exercise is the only countermeasure that can potentially counteract the combined cardiovascular, musculoskeletal and neuromuscular effects of adaptation. The Exercise Countermeasures Project will systematically examine the effectiveness of exercise in retarding or preventing the deleterious effects of space adaptation. It will define the specific effects of exercise on the cardiovascular, musculoskeletal, and neuromuscular systems, and characterize the body's responses to exercise in 1-g and in microgravity. Specifically, the ECP will provide individualized exercise prescriptions that will improve (pre-flight), maintain (inflight) and regain (post-flight) aerobic and anaerobic fitness, orthostatic tolerance, muscular performance (including ligament and tendon strength and elasticity), bone demineralization, and body composition. The ECP will also design and build interactive inflight exercise facilities consisting of exercise devices and physiological monitors that will provide feedback to the exercising subject. OVERALL GOALS AND OBJECTIVES: The overall goal of the Exercise Countermeasures Project is to provide a program of exercise countermeasures that will minimize the operational consequences of microgravity-induced deconditioning. This program will include individualized exercise "prescriptions" for each crew member, and interactive exercise facilities for preflight, inflight, and postflight training. The primary objectives of the Exercise Countermeasures Project are: Science: Through characterizing physiological changes in the musculoskeletal, cardiovascular, and neuromuscular systems induced by microgravity, develop training protocols to address deconditioning in these systems that will serve as the basis for exercise prescriptions operations: To build upon these training protocols and develop individualized exercise prescriptions designed to minimize or prevent the operational consequences of deconditioning during extended spaceflight Technology: To develop prototype flight exercise hardware and associated software, including physiological & biomechanical measurement devices 2 SCIENCE PLAN APPROACH: Countermeasures developed by this Project will address the established priorities of assuring mission safety, maximising mission success, and maintaining crew health before, during, and after missions. Assuring mission safety is defined as (1) preserving piloting proficiency, from deorbit through landing, including nominal and manual override operations; (2) preserving the entire crew's ability to perform atmospheric emergency operations, (3) nominal egress, and (4) post-landing emergency egress. Mission success is defined as proficiency at extravehicular and intravehicular activities (EVAs and IVAs). The former addresses prolonging EVA operational effectiveness; the latter focuses on maintaining operational proficiency for orbital piloting, payload, and critical maintenance activities. Maintaining health, applicable to all crewmembers, includes (1) using exercise to maintain preflight baselines during and after progressively longer spaceflights, and (2) using exercise to return to baseline after after multiple flights. Meeting these priorities forms the basis of the ECP's approach to developing a countermeasure program. Our approach is summarized in the following general questions: * What physical functions are critical to performing the required tasks (egress, landing, EVA/IVA, return to flight status)? * How do these functions change, in terms of both biomechanics and physiology, in microgravity? * How do these changes affect crew performance? * How can exercise be used to interrupt deconditioning and thereby maintain effective levels of performance? The next section, "Critical Questions," asks more detailed questions within this framework. These critical questions will drive the development of ground-based and inflight investigations. These investigations have been divided into 3 broad categories: Science (includes limited basic research): Operations (includes development of countermeasures that address specific needs in flight: and Technology (designing and building necessary hardware and software). Science, operational, and Technological Investigations are closely interrelated, and heavily interdependent. Science Investigations lay the groundwork for assuring the effectiveness of countermeasures: These investigations will clarify the specific physiological effects of deconditioning on the human body: they will establish the differences between the body's responses to exercise in 1-g and its responses in microgravity: and they will establish biomechanical requirements for performing critical mission tasks. Operational investigations will apply results from the Science Investigations to developing exercise prescriptions that will address operational concerns. Technological Investigations comprise development of prototype exercise hardware and software, and exploration of new techniques of measuring and monitoring physiological parameters. The key to employing exercise as a countermeasure lies in defining the specificity of its effects on the cardiovascular, musculoskeletal 3 and neurosensory systems. To date, there have been few studies that relate rigorously controlled forms of exercise (see Table 1) to specific parameters of physical fitness (see Table 2). All of the investigations in this program involve the evaluation of many measures of physical fitness. Physical fitness (and in turn the effectiveness of training programs, exercise equipment, monitors, and computerdriven control devices) will be assessed in the areas of muscle performance (both biomechanical and physiological); energy metabolism; anthropometry (body composition, biomechanical anthropometry); bone structure and metabolism; and aardiovascularrespiratory function. Table 2 provides a tentative list of indices measurable in each of these 5 areas; this list will be trimmed or supplemented as studies progress. The ECP brings rich multidisciplinary resources to these investigations. Project members include researchers in physiology, biomechanics, bioengineering, and artificial intelligence (see Laboratories of the ECP). Each discipline contributes to science, operational, and technological investigations: and each plays a role in achieving project goals. The next section begins with the critical questions that will drive the Project's investigations. Next follow outlines of the approaches to be used in Science, Operational, and Technological Investigations, with accompanying timelines. Finally, after these outlines, an organizational chart and capsule laboratory descriptions describe the structure of the ECP. 4 CRITICAL QUESTIONS TO BE ADDRESSED BY THIS PROJECT science Investigations 1-1 How many types of exercise (e.g., weight training, bicycling, rowing, swimming, running) are necessary to train all of the organ systems affected by deconditioning? 2A-1 Which indices are the most reliable indicators of changes in fitness (e.g., muscle fiber typing, lung volumes, muscle performance characteristics; see Table 2)? Are they equally reliable in 1-g and in microgravity? 2A-2 How do indices of fitness differ in microgravity with respect to 1-g norms? Are these differences significant? 2A,2C-1 How can microgravity-induced changes in specific muscle groups best be quantified? 2A-4 Which reliable indicators of changes in fitness best describe the changes caused by deconditioning? 2B-6 Can classic analogues of microgravity (bedrest, neutral buoyancy, parabolic flight) be used to simulate physiological changes in fitness in true 0-g? Are there differences in physiological adaptation to microgravity over time (i.e., with increasing flight duration)? 2C-3 How do changes in muscle functioning interact with changes in orthostasis and perception? 2D-7 Does the rate or type of deconditioning change with repeated exposure to microgravity? 3B-1 How does training in microgravity differ from training in 1-g? 3A,B,C-3What effect does changing variables in a training protocol (such as duration, intensity, frequency, etc.) have on longterm fitness? 3A-1(KSC)What are the differences between training muscle groups using eccentric contractions vs using concentric contractions? 3B-4 What are the differences between training that includes impact forces and training that uses nonimpact (torsional) forces? 3D-1 What are the physiological and psychological changes that accompany overtraining? 3D-2 Is overtraining expressed differently in microgravity than in 1-g? 6 3D-3 Which physiological or psychological variables might be predictive of overtraining? 4-1 Can an artificial intelligence expert system be developed to aid in monitoring, controlling, and adjusting prescriptions? 5-1 What effects will wearing space suits have on astronauts' work performance? Operational Investigations 2-2 How does initial fitness level (with or without preflight training) affect the rate and type of deconditioning? 2-3 How does preflight exercise training affect the adaptation process? 2-4 How does inflight exercise training affect the adaptation process? 2-5 What combinations of countermeasures (exercise, LBNP, PAT, etc.) optimize crew performance of critical mission tasks (egress, landing, EVA)? 3-1 How can exercise be used to enhance rapid reconditioning? 5-1 Which muscle groups are critical in the performance of egress, landing, and EVAs? 5-2 Which of the indicators of microgravity-induced change in muscle function can be correlated with possible difficulty in performing egress, landing, and EVAs? 5B-1 Does the rate or type of deconditioning change with length of mission? 5C-x. Can the expert system detect physiological changes and readjust the prescription as training (or detraining) progresses? 5c-x. How does the inflight expert system compare to the groundbased expert system and to the human examiner? Technological Investigations 1-1 Which commercially available exercise devices can be modified for use in flight? 1.2-1 Are such devices physiologically, biomechanically, and mechanically effective in microgravity? 2-1 Which commercially available monitoring and measurement devices can be modified for use in flight? [back to Index]

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Workshop on Countering Space Adaptation with Exercise:
Current Issues

Exercise Countermeasures Project

Science Plan

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Workshop on Countering Space Adaptation with Exercise: Current Issues

Exercise Countermeasures Project

Science Plan

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Workshop on Countering Space Adaptation with Exercise:
Current Issues