A historical perspective on in-flight exercise in the U.S. manned space program is given. We have learned a great deal in the 25 years since the inception of Project Mercury. But, as we look forward to a Space Station and long-duration space flight, we must recognize the challenge that lies ahead. The importance of maintenance of the crewmember's physical condition during long stays in weightlessness is a prime concern that should not be minimized. The challenge lies in the design and development of exercise equipment and protocols that will prevent or minimize the deleterious sequelae of long-duration space flight while maximizing valuable on-orbit crew time

Moore, Thomas P.

English

NASA Technical Reports Server

N91-10577
The History of In-Flight Exercise in the
U.S. Manned Space Program
Thomas P. Moore, M.D.
Methodist Hospital of Indiana, Inc.
Indianapolis, Indiana
In the days before manned space flight, the
physiologic consequences of weightlessness on the
human body were totally unknown. Today, we find it
surprising, if not amusing, to think that before the
first U.S. astronaut was launched, some scientists
predicted, and even President John F. Kennedy's
advisory committee on space expressed concern, that
the human body would not be able to withstand the
rigors imposed on it during space flight and that our
astronauts would not survive. As a result of these
uncertainties, prospective astronauts for Project
Mercury underwent comprehensive and very
extensive medical testing. As Tom Wolfe documented
in his book "The Right Stuff," and as was subsequently
graphically depicted in the movie of the same name,
every conceivable physical parameter was tested,
every possible laboratory value was measured, and
every orifice was probed in an attempt to find any
identifiable medical or physiological flaw in the
candidates. Consequently, the astronauts who
survived the selection process were viewed by many as
a breed of supermen. The maintenance of physical
conditioning and exercise became an unwritten rule
in the astronaut cadre. This esprit de corps arose
partly because of the unknown possibility that
physical fitness and athletic ability might become a
crew selection criterion and also possibly out of the
desire to maintain this superimage.
During Project Mercury, little attention was
paid to in-flight exercise. The Mercury manned flight
program began with two suborbital flights,
progressed to John Glenn's three Earth orbits on
Mercury 6, and ended with Gordon Cooper's 34-hour
flight on Mercury 9. The short duration of these
flights and, more importantly, the fact that these
flights took place in a very small, compact, and
cramped vehicle precluded the need or the ability to
perform in-flight exercise.
From Project Mercury, we progressed to the
Gemini Program and the development of two-man
spacecraft, the fi rst of which was launched in March of
1965. The vehicles remained extremely small and
available space for unrestricted movement was still
severely limited. It was, however, on the second
manned Gemini mission, Gemini IV, that the first
experiment using an in-flight exerciser was
performed. The objective of this experiment was to
make day-to-day evaluations of the cardiovascular
response to a calibrated workload under space-flight
conditions. The exercise device consisted of a pair of
rubber bungee cords attached to a nylon handle at
one end and to a nylon footstrap at the other. The
flight bioinstrumentation system was utilized to
obtain pulse rate, blood pressure, and respiratory
rate. The exercise device required about 70 pounds of
force to stretch the rubber bungee cords maximally
through an excursion of 12 inches. The exercise
periods lasted 30 seconds, during which time the
astronauts stretched the bungee cords through one
contraction and relaxation cycle per second. Each of
the astronauts performed approximately 15 exercise
bouts during the 4-day mission. In flight, the heart
rate of the command pilot and the pilot reached 105
bpm during exercise. There was no significant
difference from their preflight values for exercise
heart rate or for recovery heart rate. From this
minimal level of exercise, the investigators concluded
that there was no evidence of "deconditioning" at
any time during the Gemini IV mission. In the
postflight physical exam, using a Harvard step test as
an index of physical fitness, no decrement in physical
condition was found. Consequently, use of the
bungee device was continued on Gemini flights,
including Gemini VII, which at that time was our
longest stay in space, 14 days. For this 14-day flight, a
simple isometric routine was designed and astronauts
performed the routine about three times a day along
with the bungee apparatus. This in-flight exercise
program did not serve as a conditioning program but
did relieve disuse discomfort stemming from both
weightlessness and the relative immobilization caused
by the cramped quarters.
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After theGeminiProgram,we movedinto the
ApolloProgramwitha three-crewmemberspacecraft.
Thegoalof Apollowasto goto the Moon,explorethe
lunarsurface,andreturnsafelyto Earth. TheApollo
Programwasinitiallystructuredto havea competent
exercise device on board a somewhat larger
spacecraft.A sma((boxergometerwith pedalson
eithersidewasdeveloped;however,it contributedto
spacecraftweightproblemsandtheexerciseprogram
wascanceled.Consequently,only a very informal
exercise program existed through the Apollo
Program.Theonlyon-boardexercisedevicewasone
of the rope-and-pulleyvariable-friction machines.
Thecrewusedthis itemsporadically,againprimarily
for relief of the discomfortof crampedconfinement.
DuringApollo, two of the crewmemberson eachof
the six lunar landing missionsreceivedadditional
exerciseduring their lunar extravehicularactivities(EVA's).Theactivitiesincludedcollectinggeological
coresamples,settingup experiments,and gathering
variouslunarsamplesandMoonrocks. It wasduring
the ApolloProgramthat evidencebeganto appear
and a patternto evolveof deconditioning,weight
loss,lossof musclemass,and,in particular,decreased
exercisecapacityduring the immediatepostflight
periodin 20of the 27Apollocrewmemberstested.
Theexercisecapacitywasmeasuredon ergometers
beforeand after flight. Significantconcernswere
raisedregardingspace-flight"deconditioning" and
about the use of exercise as a prophylactic measure,
especially in planning for the upcoming long-duration
Skylab missions.
Skylab was a large orbiting laboratory that to
date has been the only long-duration space-flight
experience in the U.S. space program. There were
three Skylab missions, identified as SL-2, SL-3, and SL-
4, carrying three crewmembers each on missions of 28,
59, and 84 days. Skylab missions were flown during
the time period of May 1973 to February 1974. For the
initial Skylab flight, a bicycle ergometer capable of a
wide range of workloads was developed. Coupled
with the bicycle was the capability for measuring
heart rate, respiration, and blood pressure and for
obtaining electrocardiograms. A mass spectrometer
gas analyzer was also on board, capable of giving the
crew and investigators oxygen and carbon dioxide
parameters. The device was used in the experimental
testing mode approximately every fifth day on all
three Skylab flights. The data obtained provided a
longitudinal look at exercise capacity as a function of
time in weightlessness. The bicycle was also available
in flight for use as a daily exercise device. All exercise
done was carefully logged and reported.
Consequently, a complete record of in-flight exercise
was obtained. On the first manned Skylab mission, SL-
2, the bicycle ergometer was the only exercise device
on board. Because of problems with the design of the
shoulder harness and the eventual discarding of it
completely, it took the SL-2 crew approximately 10
days to learn how to ride the bicycle in zero g. From
that point on, the astronauts had no difficulty in
achieving the same feedout oxygen readings at the
same workloads with approximately the same heart
rates in flight as they had before flight. The problem
with making comparisons with preflight norms was
that the norms were established 6 to 12 months
before flight, and because of significant improved
conditioning of the astronauts prior to flight, the
initial in-flight workload levels were artificially low
and were subsequently corrected. The SL-2 crew
improvised, with commander Charles Conrad
diligently using the bicycle not only in its conventional
mode but also as an upper body ergometer. After
crew return, postflight testing revealed cardiovascular
deconditioning and decreased upper and lower body
muscle strength. As a result of this finding, along with
the crewmembers' comments and recommendations,
changes were made in the exercise program for SL-3.
To facilitate increased upper body exercise, two
devices, identified as Mark I and Mark II, were added
on board. Mark I was a modified commercially
available product named the Mini Gym. It was
another rope-pull type of device that worked on a
centrifugal braking action that approximated
isokinetic exercise. The Mark II was a pair of handles
between which five springs could be attached giving a
maximum of 25 Ib/ft that could be developed on
extension. On SL-3, the crewmember's average
exercise time on the bicycle was increased by more
than 100 percent over that done on SL-2.
During this time, work was also begun on the
development of a treadmill for Skylab 4. After
returning from their 59-day mission, the SL-3 crew was
found to be in better cardiovascular condition than
was the SL-2 crew. Postflight muscle strength testing
showed improvements in maintenance of arm
strength, but significant leg strength decrements
were still found. On SL-4, a Teflon treadmill devised
by astronaut William Thornton, M.D., was flown on
board. It consisted of a Teflon-coated aluminum
walking surface attached to the Skylab isogrid floor.
Four rubber bungees provided an equivalent weight
of 80 kilograms and were attached to a shoulder and
waist harness worn by the astronaut. By angling the
bungees, the equivalent of a slippery hill was
presented to the subject, who then had to climb it.
Astronaut Gerald Carr, commander of SL-4, stated
that he used the treadmill regularly to walk for
2O
/approximately 15 minutes. He then would perform
what amounted to basically a sprint on the device, the
sprint being time limited to about 1 to 1-112 minutes
because of overheating to his socks and feet. He also
would use the harness/bungee setup to do squats and
toe raises for additional leg muscle exercise. His
recollection was that the other two crewmembers,
Edward Gibson and William Pogue, used the device in
a similar fashion. The SL-4 crew continued the use of
the Mark I and II. In addition, they further increased
the time on the bicycle to 130 percent of that of the
first Skylab crew and added some improvised torso
isometric exercises. After 84 days in space, the third
Skylab crew returned in better condition than did the
crews on the the other two missions, as evidenced by
less strength loss, less weight loss, less leg volume
decreases, and im proved postfl ight exercise testing.
It was evident from the in-flight cardiovascular
testing that all of the SL-4 crewmembers had actually
improved their physical conditioning in flight.
Commander Carr believed that other than for some
unsteadiness caused by vestibular readaptation0 he
would have been physically able to perform
emergency procedures including walking away from
the spacecraft or vehicle under his own power if
necessary.
After Skylab and the U.S.-U.S.S.R.
Apollo-Soyuz flight, planning for the Space Shuttle
Program proceeded. From the Skylab experience, a
passive treadmill was devised by William Thornton,
M.D., and developed and built by Henry Whitmore of
Whitmore Enterprises. The Space Shuttle treadmill
consists of aluminum plates with rollers on the end
that are connected in a series to form a belt. The
treadmill is nonmotorized and purely passive so that
the astronaut must make the metal belt move by
walking or jogging on it. The down-pull of the
bungee/harness system can be manually adjusted by
the astronaut to approximate his/her own body
weight. The treadmill was first flown on STS-3 in 1982
and has been flown with a more recently improved,
updated model on every subsequent Space Shuttle
flight. By mission flight rules, all astronauts on a
Space Shuttle mission have a daily exercise period
allotted to them in their crew activity plan. The use of
the exercise time is left to the discretion of the
individual astronauts to be used as he or she may wish.
There is no mission requirement to perform exercise in
flight; however, the majority of the astronauts usually
do exercise at some time during flight. The treadmill
is generally used more frequently by the commander
and the pilot, because these crewmembers have
mission-critical duties during landing that require use
of the legs to push rudder pedals, to steer, and to
apply brakes. Other crewmembers on the relatively
short Space Shuttle missions are sometimes w_lling to
sacrifice their exercise time and endure some
temporary deconditioning for the opportunity to take
advantage of the unique sightseeing that space flight
provides.
Other than comments related to the noise of
the treadmill and concerns regarding the minute
acceleration forces imparted to the Orbiter during its
use that can disturb zero-g-critical experiments, no
significant problems have been experienced with the
Space Shuttle treadmill.
Extravehicular activity, or space walks, provide
the only other significant in-flight exercise. The first
EVA's during the Gemini Program were found to be
very demanding with heart rates averaging about 150
bpm. With improved space-suit design and preflight
training, EVA's have become somewhat less
demanding from a cardiovascular standpoint.
However, it should be recognized that essentially all
of the physical work involved in EVA is performed by
the upper extremities. The only real function of the
lower extremities during EVA is to be anchored in foot
restraints in order to facilitate working at various
workstations without floating free. Some of the
Space Shuttle EVA mission objectives have ranged
from the manual retrieval of malfunctioning satellites
to simulated space station construction activities to
the fine electrical repairs of satellites. Some Space
Shuttle EVA's have lasted as long as 7 hours. As a
result of the duration and the varied nature of the
EVA tasks and objectives, significant physical exertion
can occur during EVA. This fact should be realized and
taken into consideration in Space Station planning,
especially during the anticipated EVA-intensive
construction phase.
In this paper, I have attempted to give a
historical perspective on in-flight exercise in the U.S.
manned space program. We have learned a great
deal in the 25 years since the inception of Project
Mercury. But, as we look forward to a Space Station
and long-duration space flight, we must recognize the
challenge that lies ahead. The importance of
maintenance of the crewmember's physical condition
during long stays in weightlessness is a prime concern
that should not be minimized. The challenge lies in
the design and development of exercise equipment
and protocols that will prevent or minimize the
deleterious sequelae of long-duration space flight
while maximizing valuable on-orbit crew time.
21


The history of in-flight exercise in the US manned space program

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