MEAN OF ALL SUBJECTS

—oKe— + MANILA 1
PREFLIGHT DAY +1 DAY + 2 DAY +3 DAY +4 DAY +6 DAY +8
be t 200 1
' z |z
_ i. 1s [8
& lg 3 x80
gis ]F
i, FE saS 00S |
sig 18 |e!
ZB ly |g
Pt 3 13
le |e |
| |
ary 00 380
to6e 200
1g ri
ra j
Foe d / \
a"ty A bo
# 1Z iso id \ re ° i a I
= |g \ » J ! elie \
gisok \ ° le °
alg .
12
|
T6e 100

3
e

RECTAL TEMPERATURES (¢e9. C)

___EVAP. WATER LOSS (mgm/min.+ em?)
3
$—————s—— — —s

lo

\
l\

|
|
|

|

2

s

06 12 18 24 06 06 12 18 24 06 06 12 18 24 06 06 12 18 24 06.06 12 18 26 06 06 I2 18 24 06 06 I2 18 24 06
‘—oKkc— + MANILA:

20 02 OB 14 20 20 02 08 14 20 20 O2 OB 14 20 20 02 08 14 20 20 02 08 14 20 20 02 08 14 20 20 02 08 14 20
OKC

MANILA +

Ficure 1. Mean plottings of data obtained in Oklahoma City (preflight) and in Manila (layover).

7. Subjective Fatigue. The level of subjective
fatigue was measured by means of checklists
that were developed by the scale discrimination
method and that were shown to reflect. signifi-
cantly the effects of perceptual-motor work and,
also, the effects of pharmacological treatment.

C. Subjects —Four healthy, adult, male volun-
teers were drawn from the professional and tech-
nical staffs of the Civil Aeromedical Research In-
stitute. During all periods of assessment, pre-

flight, overseas, and post-return flight, the subjects
were quartered in wards permitting supervision
of activity. Finally, the subjects were instructed
to maintain their daily living habits in accordance
with the local time of the overseas destination
immediately following arrival.

III. Results.
A. Primary Shift—The results obtained dur-
ing the preflight (Oklahoma City) and postflight



at neutral ambient temperatures unlike those un-
der which acclimatization indexes become evident.

In contrast to the time lags seen for the physio-
logical functions, the duration of psychological
deficit was exceedingly short. In fact, this deficit,
which was occasioned presumably by the joint
effects of time displacement and prolonged flight,
appeared to have been eliminated by the first
night of sleep in Manila. This elimination was
also found in the Tokyo flight. The short dura-
tion of this performance deficit was surprising
because a higher degree of relationship was ex-
pected between duration of deficit and the time
required for the physiological functions to shift
to Manila time. The basis for this expectation
consisted of the comments volunteered by the
subjects, indicating that “adjustment” to Manila
time as subjectively perceived by the subjects
was closely related to the course of physiological
adjustment. Such comments pertained to sleep,
eating, and other similar habitual daily regimens.
And, at times, the remark would be made that
as soon as they “got on schedule,” they would be
able to perform better on the psychological tasks.
The fact that the duration of performance deficit
is also unrelated to subjectively perceived “adjust-
ment” serves to enhance significantly the practical
implication of this finding. Finally, it should be
made explicit that the duration and extent of
performance deficit demonstrated might well be
a function of the simplicity of the functions
assessed. Had the assessment schedule permitted
the time required for the testing of much more
complex functions such as higher-order decision
making, extent and duration of deficit might have
been greater.

The results of the return flight to Oklahoma
City, which agree with earlier studies ° and with
the results of the Tokyo flight, * are also of prac-
tical importance. Evidence that would serve
to explain why the return to the environment of

origin appears to impose a much less severe re-
quirement upon the adjustive processes involved
is not available. Based upon speculation that has
been advanced,* however, it could be argued that,
within the period of time at Manila, certain bio-
logical functions may not have completed the
shift of phase. For others, possibly, phase shift-
ing might not have begun. These, then, upon
return to the environment of origin, could have
exerted a synchronizing effect upon those more
labile functions whose phase had shifted, and, if
sufficiently dominant, such an effect could have
accelerated the back shift to the extent demon-
strated.

V. Summary and Conclusions.

At periodic intervals throughout the biological
day, biomedical assessments were made for a
week prior to jet flight to Manila, for 8 days of
layover at Manila, and for a week following
return to the environment of origin. From the
obtained data, the following conclusions were
derived :

(1) Rapid translocation through the 10 time
zones effected a primary shift of phase of the
circadian periodicity manifested by the physiclog-
ical functions assessed. For rectal temperature
and heart rate, the time required for completion
of phase shift was approximately 4 days, and for
palmar evaporative water loss, approximately 8
days.

(2) Return back to the environment of origin
also effected a shift of phase that required no
more than 1 day for completion,

(3) Behavioral integrity was degraded during
the primary period of transition and, to a lesser
extent, during the period of transition occasioned
by return to the environment of origin.

(4) Duration of behavioral impairment was
much shorter than the lag time of physiological
phase shifts.


palmar evaporative water loss, however, its time
lag is about that of rectal temperature.

4. Respiratory Rate. In contrast to the other
physiological functions, respiratory rate does not
show a periodicity of well-defined and consistent
nature.

5. Reaction Time. The reaction-time values
shown in Figure 1 represent the average speed of
appropriate manual response to a variety of stim-
uli and stimulus conditions throughout each day
of assessment. Using the preflight value as a
basis for comparison, reaction time is seen to in-
crease substantially (ie., become slower) during
Day + 1. On Day + 2, reaction time decreases
(improves in speed) to a level slightly below that
attained during preflight. Analyses of the vari-
ance attributable to replicated days of assessment
reveal the increment of reaction time on Day + 1
to be significant at the >0.05<0.10 level of con-
fidence. The gradual improvement of reaction
time shown during the subsequent days in Manila
may be attributed largely to “practice effect,”
which was not completely eliminated by the con-
siderable amount of practice given the subjects
prior to the last 2 preflight days of assessment.

6. Decision Time. The values plotied for de-
cision time in Figure 1 represent the daily mean

080

080
060 080
3 f 060,
Z ‘oso 060
3 =
s 3
z
fod
060)
ono oo |g |S
é
a - L oso
i 3 040
60
a| “ 5

os
(erie)

(oKe)

940
7

ITITS

LOCAL TIME

040:

20

Fieure 8. Mean plottings of palmar evaporative water
Joss during preflight (Oklahoma City) and during lay-
over period in Manila.

speed of decision as this has been defined. As in
the case of reaction time, decision time increases
(becomes slower) on Day + 1, returns toward
the preflight level on Day + 2, and remains about
this level for the remaining days of assessment
in Manila. ‘In using the above-mentioned model
for analysis of variance, the increase in decision
time noted for Day + 1 was found to be highly
significant (P = 0,001).

1. Subjective Fatigue. The index of subjective
fatigue was scaled from “extremely fatigued”
to “extremely alert”; consequently, the higher the
daily mean values seen plotted in Figure 1, the
more fatigued the subjects felt themselves to be.
From the curves of psychological function seen
thus far, subjective fatigue would be expected to
be greater on Day + 1; this is borne out. On
Day + 2, the mean value has returned to pre-
flight level and remains about this level during
the subsequent days in Manila. This increment
observed for Day + 1 was also found to be sta-
tistically significant (P = 0.01).

8. Critical Flicker-Fusion. Jt was expected
that the curve of mean flicker-fusion thresholds
seen in Figure 1 would agree with the other
curves of psychological function. Had this oc-
curred, a substantial decrease would have been
evidenced on Day + 1. Since this is not in evi-
dence, it must be concluded that efficiency of
cerebral function was either improperly assessed.
or negligibly affected.

B. Back Shift—Due to commercial carrier
schedules, the return flight to Oklahoma City
could not be made under comparable conditions
of transit. Whereas the flight to Manila was
made in a total of 23-14 hours with no more than
2-14 hours for any layover, the return flight re-
quired a total of 34 hours and an overnight lay-
over in Los Angeles. Arrival time in Los Angeles
was 2330 hours CST, departure was 1100 hours
the following day, and arrival in Oklahoma City *
was 1830 hours. The first day of postflight as-
sessment followed the day of arrival in Okla-
homa City. This difference must be kept in
mind when comparing the primary and back
shifts.

The results are presented by Figure 4. Here,
the basis for determining the effects of time dis-
placement occasioned by the flight back to Okla-
homa City consists of the values obtained during
the last assessment day in Manila.



(Manila) days of assessment are given by
Figure 1.

Here, for each assessed function, the plotted
values are the means of the four subjects for each
hour for rectal temperature; for each assessment,
period for palmar evaporative water loss, heart
rate, and respiratory rate; and for each day
of assessment for the psychological functions.
The values plotted for preflight represent the
pooled means of the four subjects for the last 2
days of preflight assessment, which were observed
as being least contaminated by novelty or un-
familiarity.

1. Rectal Temperature. Examination of the
preflight curve of rectal temperature reveals the
periodicity and amplitude of stored heat typically
obtained under normal circumstances; i., fol-
lowing awakening, temperature is seen to increase
steadily, plateau between 1400 and 2000 hours,
then decline steadily to the beginning of the next,
biological day. In contrast, the curve of rectal
temperatures obtained the first day in Manila
(Day + 1) is distinctly out of phase with the
local time of Manila and with the time of Okla-
homa City. It is not until Day + 4 that the
phase shift appears to have been completed. This
gradual shifting of phase is shown more clearly
in Figure 2, in which the rectal-temperature
means for each day are plotted with separate
ordinates on a common abscissa (local time).

Another major alteration in the daily curves of
internal body temperature is shown in Figure 1.
In Oklahoma City, the upper mean level of in-
ternal thermal stability is seen to be approxi-
mately 87.1°C. In Manila, aiprogressive increase
in mean level occurs, resulting in an elevation of
thermal stability to a level of approximately
37.8°C by Day + 8.

2. Palmar Evaporative Water Loss. Plotted
with the temperature curves in Figure 1 are the
mean values for resting palmar evaporative water
loss obtained during each period of assessment.
As is revealed by the preflight plottings, this
function also appears to manifest circadian peri-
odicity with a phase closely associated with that
of rectal temperature. This association, however,
is markedly affected by the time displacement in-
curred. The shift in phase of internal tempera-
ture appears to have been completed on Day + 43
the complete shift of phase of palmar evapora-
tive water loss does not occur until Day + 8. A
clearer representation of this phase shift is given

38.0:
pee
(Menite)
37.0 38.0
s
¢
z
s o+6
(Manila)
36.0 38.0 37.0
ry
&
<
064
37.0 (Menita) 36.0 38.0
7
+
nf
%
2
38.0 36.0 Dts 37.0
Manila)
a
a
£
ore
37.0 Anenitay 38.0 36.0
a
=
&
s
36.0 38.0 37.0
pe
(Manito) =
:
fa
g
2
37.0 36.0
g ¢oKe)
2

ei
ee
Roo:

S
JS s

o
8
S
2
4
z
a

Fieure 2. Mean plottings of rectal temperature during
preflight (Oklahoma City) and during layover period in
Manila.

by Figure 3. Also revealed by Figures 1 and 3
is the gradual elevation of palmar evaporative
water loss from a mean plateau value of 0.048
mg/min sq cm in Oklahoma City to 0.070 mg/min
sq cm on Day + 8 in Manila.

Because of the fatigued state of the subjects
due to their arrival time and customs delay,
assessments could only be made at 1500 and 1900
hours but not at 2300 hours.

3. Heart Rate. Circadian periodicity is also
revealed by the preflight values plotted for heart
rate (Figure 1) and, as for palmar evaporative
water loss, its phase is seen to be closely associ-
ated with that of internal temperature. Unlike


38.0
38.0 pes 37.0
(ore) 3
:
3
g
e
37.0 oes 38.0 36.0
a (oxe)
%
|
36.0 38.0 aN 37.0
z
Dee g
(Manito) sé
37.0 an 36.0
E ;
és ;
Se (/ PREFLIGHT
L a3 one)
ae
=
36.0

ao ramet
SIs
g vs re

LOCAL TIME

Fieure 5. Mean plottings of rectal temperature during
preflight (Manila - Day + 8) and following return to
Oklahoma City.

2. Psychological Functions. In general sup-
port of the foregoing are the curves of reaction
time, decision time, and subjective fatigue plotted
in Figure 4. Some deficit does occur on Day + 1
but to a much less extent than on Day + 1 in
Manila.

IV. Discussion.

Despite differences in extent of time displace-
ment, flight duration, arrival time, test conditions,
and sampling, the data reported here are in agree-
ment with data obtained in the previous flightTM
which, while primarily a feasibility study, did
yield information pertinent to the questions un-
derlying this research.

With respect to the first such question then
(namely, biological lag time of phase shifting),
it would appear that statements or assumptions of
biological adjustment to time displacement must
be qualified by restricting adjustment in this in-
stance to the specific function or functions as-
sessed. As has been seen, the time lag of the
primary phase shift of rectal temperature was
approximately 4 days and for palmar evaporative
water loss was approximately twice as long.

Other functions may be characterized by even
longer time lags.

The progressive daily mean rise in rectal tem-
perature and palmar evaporative water loss ob-
served. during the period of assessment in Manila
cannot be attributed directly to any differences
in thermostasis due to acute shifts in environ-
mental thermal exposure. Even if it were to be
argued that the difference between the mean level

‘noted in Oklahoma City (preflight) and that

evidenced on Day + 8 in Manila (0.7°C) reflects
the dead-zone range of biothermal control, such
an elevation of internal temperature would be
expected to occur within a few hours following
arrival in Manila. Moreover, these data were
collected from subjects resting under conditions
of controlled ambient temperatures for periods
more than long enough to permit dissipation of
any stored heat due to thermal loading by prior
exercise or heat exposure. This elevation cannot
be attributed to any degree of thermal-stress
acclimatization since the measured adjustment
period was too short, and only a mild degree of
thermal stress was encountered. Further, these
tempenatures were taken under conditions of rest

r -080
060
3
3 Des
% (one)
S| + 060
+3 (oxer
040 0809 ros ls
°
a
e
“ .040
fsosiier
PREPcionT
060 4 fF 060
E
Es =
eg +
ge >
z 1
be \, é
a toKe) \\
0404 oe L 040
¥ J y
Is LY,

JS
S
LOCAL TIME

Fieure 6. Mean plottings of palmar evaporative water
loss during preflight (Manila - Day + 8) and following
return to Oklahoma City.



AM 65-28 .

PHASE SHIFTS OF THE HUMAN CIRCADIAN SYSTEM
AND PERFORMANCE DEFICIT DURING THE
PERIODS OF TRANSITION:

I. East-West Flight

G. T. Hauty, Ph. D.
T. Adams, Ph. D.

Approved by Released by
~ oe
J. Ropert Ditix, M.D. P. V. Steen, M.D.
Cuter, Crvi AEROMEDICAL Feperat Arr Surcroy
InstirvTE

December 1965

FEDERAL AVIATION AGENCY

Office of Aviation Medicine





wv

a

2

REFERENCES

. Apams, T., FunkHouser, G. E., and Kennan, W. W.:

Measurements of Evaporative Water Loss by a Ther-
mal Conductivity Cell. J. Appl. Physiol., 18: 1291-
1293, 1963.

Avams, T., FunKHouseR, G, E., and Kenpatt, W. W.:
A Method for the Measurement of Physiological
Evaporative Water Loss, CARI Report No. 63-25,
Federal Aviation Agency, 1963.

Ascuorr, J., and Wever, R.: Spontanperiodik des
Menschen bei Ausschluss aller Zeitgeber. Natwrwis-
senschaften, 49 : 837-342, 1962.

. Brozex, J., Stmonson, E., and Keys, A.: Changes in

Performance and in Ocular Functions Resulting from
Strenuous Visual Inspection. Amer. J. Psychol., 63:
51-66, 1950.

. Bucarn, P., and Henry, M.: Quelques Aspects de In

Fatigue dans Aviation de Transport. La Presse Med-
icale, 69 : 1903-1906, 1961.

; Bunnine, H.: The Physiological Clock. Academic

Press, Inc., New York, 1964.

Burton, A. C.: ‘The Clinical Importance of the Phys-
iology of Temperature Regulation. Canad. Med.
Assoc. Journal, 75: T15-720, 1956.

. Fink, E. B,, and Dor, R. P.: Effect of Sudden Time

Displacement by Air Travel on Synchronization of
Adrenal Function. Proc, Soc, Exptl. Biol. (New
York), 100: 498-501, 1959.

9. Geretrzen, F.: The Diurnal Rhythm in Water, Chlo-
ride, Sodium, and Potassium Excretion During a
Rapid Displacement from Hast to West and Vice
Versa. J. Aerospace Med., 83: 697-T01, 1962.

10. Haury, G. 'T.: Relationships Between Operator Pro-
ficiency and Effected Changes in Biological Circadian
Periodicity. J. Aerospace Med., 34: 100-105, 1963.

11. Haury, G. T,, and Apams, 'T.: Phase Shifting of the
Human Circadian System. In Circadian Clocks,
J. Ascnorr, ed. North-Holland Publishing Co., Ams-
terdam, 1965.

12, Krerrman, N.: Sleep and Wakefulness. Univ. of
Chicago Press, Chicago & London, 1968.

13. Lewis, P. R., and Lospan, M, C.: Dissociation of
Diurnal Rhythms in Human Subjects Living on
Abnormal Time Routines. J. Haptl. Phys, 42: 371-
3886, 1957.

14, Mean, J., and Bosrmanrro, ©. L.: The Reliability of
Rectal Temperature as an Index of Internal Body
Temperature. J. Appl. Physiol., 2: 97, 1949.

15. Pearson, R. G., and Byans, G, E.: The Development
and Validation of a Checklist for Measuring Subjec-
tive Fatigue. USAF Report No. 56-115, School of
Aviation Medicine, 1956.

16, Sasaxr, T.: Effect of Rapid Transposition Around
the Earth on Diurnal Variation in Body Temperature.’
Proc. Soo, Hxptl, Biol. Med., 115: 1129-1181, 1964.

66-4345



MEAN

OF ALL SUBJECTS

MANILA OKC: 1
PREFLIGHT DAY +1 DAY +3 DAY+5
58 tf 200 “y
ai, EE j
213 12 [aud .
w ty 2 o: ‘o cy
Fasge tees |
Bis (8 -
3 if 5 = 480 enone ba _
4 —— oti henteeste ts
oe ye lf) scoop =
' | =z /s | Tipo ep - - a enna Een
386 14 00 380
tee 200
lg
ili
i &
sok
Ely ‘ I aan
g ‘
3 | = 150
= 1g \ AR
60k \. v \
am \
12 °
ned 100
080 38.
“i, rT] 7
§ 8 | | ly |
¢ 2 |
tle |
z 15
B.060 5 37 | A | |
. /8 i
B18 A iat
Fy \I .
|g Y hl | ¥
a \ 41 |
m0 ee Oe Te Tb 2 08 06 12 18 24 06 06 fe 18 2 06
MANILA ca ‘OKC:
20 02 08 14 20 20 02 08 14 20 20 02 08 14 20
—~oKe— t MANILA:
Figure 4. Mean plottings of data obtained in Manila (preflight) and in Oklahoma City (return flight).

1. Physiological Functions. In contrast to the
time lag for the primary shift, the lag in time
during the back shift would seem to be shorter.
Both rectal temperature and palmar evaporative
water loss curves show a complete shift in phase
to Oklahoma City time on Day + 1. The mean
levels of internal temperature and of palmar
evaporative water loss have fallen to the Okla-

homa City preflight level on Day + 1 and remain
at this baseline level throughout the remaining
days of assessment. Figures 5 and 6 exhibit
these findings more clearly.

An exception, perhaps, to the “immediate”
back shift may be that of heart rate. Apparently,
the phase shift of this function is not complete
until Day + 8.


chological functions were sequentially assessed
by highly standardized procedures. Simultane-
ously, assessment was also made of several differ-
ent physiological functions. Time required for
such a period was approximately 25 minutes.

The decision to test on alternate days was
based on the results of the feasibility flight
(Tokyo), which indicated that successive days of
assessment placed a greater than expected im-
position upon the subjects and may have contrib-
uted to their self-reported state of fatigue. The
duration of the testing period in Manila (8 days)
was also derived from the feasibility flight, which
revealed the period of time required for the
shift of phase to Tokyo time.

B. Assessments.—The biomedical assessments
to be reported include:

1. Rectal Temperature. Internal body temper-
ature was measured by a portable, indicating
bridge circuit, calibrated to a thermistor rectal
probe. In order to reduce the indicated artifacts
of rectal-temperature recording,“ the rectal
probe was inserted to a depth of 10-cm, worn
continuously throughout each assessment day,
and removed only for bathing or evacuation. Dur-
ing transitional overseas movements, the rectal
probe was worn from 0600 hours on the day of
departure through 5 successive days, and subse-
quently for 24-hour periods on alternate days.
During the waking portion of the day, the subject
read and recorded his own temperature to the
nearest 0.1°C at 30-minute intervals; for the re-
mainder of the day, a technician recorded the
sleeping subject’s temperature at the same inter-
val. No untoward consequences, other than minor
inconvenience, were reported by the subjects as a
consequence of the prolonged periods of rectal-
probe insertion.

2. Evaporative Water Loss. The method for
quantitatively measuring skin-surface evaporative
water loss has been described earlier.» * For each
assessment period, a small plastic capsule, samp-
pling from a 1-sq cm skin area, was sealed to
the skin at the center of the left palm. Meas-
urements of evaporative water loss from this
area were made continuously throughout each as-
sessment, evaluating both steady-state “basal”
levels during rest before and after each assess-
ment period and increased evaporative rates dur-
ing identified assessment increments. These data
were examined to provide measurements of
“basal” evaporative water loss, increases in instan-

taneous rates related to matched assessments,
and the total amount of water evaporated during
the entire assessment period and its individual
subcomponents.

3. Heart and Respiratory Rates. A lightweight,
plastic and elastic chest strap was improvised to
house three silver electrodes for heart-rate meas-
urements and a mercury-in-rubber strain gage to
monitor respiratory rate as a function of changes
in chest circumference. The chest strap was fitted
to the subject at the’ beginning of each assess-
ment period and removed at the end of the period.
Heart rates were recorded from a standard indi-
cating cardiotachometer (Phipps-Bird, Model 70-
781) at 30-second intervals. Respiratory move-
ments were recorded through an appropriate
matching bridge (Model 270 Plethysmograph,
Parks Elect. Lab.) on a millivolt strip-chart re-
corder.

4. Reaction Time. The speed of manual re-
sponse to a variety of stimuli and stimulus con-
ditions was measured by means of a Lafayette
Multi-Choice Reaction Timer modified to pre-
clude secondary cues. Responses were elicited in
order by three successive presentations of a single
auditory stimulus, three successive presentations
of a single visual stimulus, six successive and ran-
domly determined presentations of one of three
possible visual stimuli, and finally by one presen-
tation of the single auditory stimulus. Intervals
of presentation were irregular.

5. Decision Time. This was obtained for each
assessment period by subtracting the mean time
of responding to the three presentations of the
single visual stimulus from the mean time of
responding with the correct response to the six
presentations of one of the three different visual
stimuli. This value is taken to represent the
average time required to “decide” which of the
three possible responses was the correct response
to be made.

6. Critieal Flicher-Fusion. Three ascending
and three alternating descending thresholds were
determined by a Lafayette Flicker-Fusion ap-
paratus. In indicating the highest rate at which
this type of input can be adequately processed,
these thresholds are generally considered repre-
sentative of the state of efficiency of cerebral
function, and, when used as an index of fatigue,
an inverse relationship between flicker-fusion
threshold and hours of work is sometimes re-
ported.*


PHASE SHIFTS OF THE HUMAN CIRCADIAN SYSTEM AND
PERFORMANCE DEFICIT DURING THE PERIODS OF TRANSITION:
I. East-West Flight

I. Introduction.

Since rapid translocation through many time
zones involves disruption of circadian periodi-
city with pronounced subjective effects, it is un-
derstandable that intercontinental air carrier
crews would claim these effects to be partially
responsible for the production of fatigue. Fur-
ther, such a claim is enhanced by the possibility
that crew scheduling may be at variance with the
time lag for readjusting biological processes be-
cause present schedules are not based on ob-
jective determinations of the effects concerned or
derived from relevant scientific information. Such
determinations have yet to be made, and sufficient
relevant information is not available.

Most of the experimental studies of human
periodicity ® »* % 2° have been prompted by etio-
logical considerations necessitating environmental
conditions and controls that preclude fruitful ex-
trapolation. Studies that have dealt directly
with the problem are few.’-* 1° With one excep-
tion,’ the respective subject-population size was
small, and, for the most part, only a single func-
tion rather than a spectrum of biological activi-
ties was assessed.

Accordingly, a series of intercontinental flights
was undertaken for the purpose of obtaining in-
formation pertinent to those basic questions most
obviously in need of initial and definitive answer:

(1) What is the extent of time lag for biologi-
cal phase shifts under these circumstances?

(2) To what extent, if any, is proficiency ad-
versely affected during the period of transition?

(3) What is the extent and nature of differ-
ences manifested during the primary and the
back shifts and their respective transitional
periods?

(4) To what extent do individuals differ in lag
time and adverse effects upon proficiency?

The first flight, a jet flight from Oklahoma
City to Tokyo and return, was primarily a feasi-

bility study of the problems of experimental con-
trol, logistics, and tolerances of volunteer sub-
jects. With the obtained information," three
subsequent flights were planned and completed:
(1) East-West; (2) a West-East round-trip jet
flight that permitted a comparative analysis of
bidirectional time-zone displacement effects; and
(3) a North-South jet flight that, as a “control,”
provided an appraisal of those effects solely at-
tributable to prolonged flight.

Subjects were selected from a group whose
daily habits of work and sleep were representa-
tive of the general, adult, male population be-
cause of the need for a reference against which to
compare findings obtained from intercontinental
air carrier crews.

Owing to the large volume of data, these flights
will be reported separately and in the order of
their occurrence. First to be reported is the
East-West flight, which originated in Oklahoma
City and consisted of jet flight to and from Ma-
nila. Time of departure was 1800 hours CST,
total time in transit 23-14 hours, time of arrival
in Manila 0730 hours local time, and time dis-
placement was 10 hours.

II. Method.

A. Schedule of Assessment.—Periodic biomedi-
cal assessments were made on alternate days dur-
ing the week immediately prior to flight, during
a period of layover at Manila, and during the
week following return to Oklahoma City. This
schedule provided a reference of biological time
set to the environment of origin (Oklahoma City)
and periods of transition for the “primary”
shift (Oklahoma City-Manila) and for the
“back” shift (Manila-Oklahoma City).

Biomedical assessments were repeated at 0700,
1100, 1500, 1900, and 2300 hours (local time) on
each day of assessment. During each of these
five periods of assessment, several different psy-



Qualified requestors may obtain Aviation Medical Reports from Defense Documentation
Center. The general public may purchase from Clearinghouse for Federal Scientific and
Technical Information, U.S. Dept. of Commerce, Springfield, Va. 22151