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NASA Conference
Publication 3252
Workshop on Countering
Space Adaptation with Exercise:
Current Issues
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
Contents
1 MUSCULAR TRAINING
Muscular activity and
its relationship to biomechanics and human performance . 1
Gideon Ariel, Ph.D.,
Ariel Dynamics
Eccentric exercise
testing and training . 99
Priscilla M. Clarkson,
Ph.D., University of Massachusetts
Exercise detraining:
Applicability to microgravity. ________._
_ _ _ _
Edward F. Coyle, Ph.D.,
University of Texas at Austin
2 CARDIOVASCULAR FITNESS
Aerobic fitness and orthostatic tolerance: Evidence against an association . 121
Thomas J. Ebert, M.D., Ph.D., Medical College of Wisconsin
Does training-induced orthostatic hypotension result from reduced carotid
baroreflex responsiveness? 129
James A. Pawelczyk, Ph.D. and Peter B. Raven, Ph.D.
Texas College of Osteopathic Medicine
Cardiac output and cardiac contractility by impedance cardiography
during exercise of runners . 141
W. G. Kubicek, Ph.D. and R. A. Tracy, Ph.D.
University of Minnesota Medical School
3 SKELETAL COUNTERMEASURES
Weightlessness and the human skeleton: A new perspective .
Michael F. Holick,
Ph.D., M.D., Boston University School of Medicine
Irreversibility of
advanced osteoporosis - limited role for pharmacologic. intervention. 169 A.
M. Parfitt, M.D., Henry Ford Hospital
Exercise and osteoporosis: Methodological and practical considerations . 175
Jon E. Block, Ph.D., A. L. Friedlander, P. Steiger, Ph.D., and
H. K. Genant, M.D., University of California at San Francisco
4 ELECTRICAL STIMULATION IN EXERCISE TRAINING
Electrical stimulation in exercise training. _________._
__ _ _
Walter Kroll, Ph.D.,
University of Massachusetts at Amherst
iii
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
v
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.
Exercise
Countermeasures Project
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
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
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
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?
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?
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