Urine 17-Ketogenic Steroids. The urinary excretion rate data of the
17-ketogenic steroids is found in Table XI. It is reported for the same
time periods as the other urinary excretion measurements... There were statis-
tically significant differences for time of collection (p< .01) for both
dict conditions, with the excretion rate of 17-ketogenic steroids being
greatest during the second morning for the crash diet and greatest overnight
for the normal diet. The only statistically significant difference due to
the diet was for the overnight collection period, with the values lower
(p < -001) for the crash diet than for the normal diet.

COMPLEX PERFORMANCE.

Composite Score Data. The overall composite score data (treatment means
and standard deviations) are shown in Table XII as a function of dict for
each of the three periods of an experimental session. Overall composite per~
formance scores were significantly higher (p< :05) in the fasting condition
than in the normal-diet condition. Overall performance was also significantly

lower in the second and third periods of a session compared to the first
period.

Composite scores (means and standard deviations) for each task are shown
in Table XIII for the main effects of diet, workiuad and period. These data
show that the significant effect of diet in overall scores was due to higher
performance in the fasting condition in three tasks--the monitoring of green
lights, monitoring of meters and mental arithmetic. Increasing workload
produced a significant (p< .01) decline in performance in the same three
tasks, in tracking, and in problem solving. Performance was generally high-
est inthe first period of an experimental session and lowest in the second
period. Slight recovery was typical in the third period in all tasks but
tracking and meter monitoring. The main effect of test period.was signifi-
cant in meter monitoring (p< .05) and mental arithmetic (p< .01).

Table XIV shows the significant interaction (p< .01) of diet with work-
load in meter monitoring. In both diet conditions, meter monitoring perform-
ance was similar in the low workload condition and decreased with increasing
workload, but the decline was less in the fasting condition. This interaction
of diet with workload was also present in green light monitoring and mental
arithmetic scores, but was not statistically significant.

TABLE X11. Overal? Composite Scores as a Function of Diet and Period

Test Period 1 2 3
Crash Diet
Mean 532 500 508
S.D. 435.3 430.2 +25.6
Normal Diet
Mean 508 472 481
S.D. 424.6 436.9 434.1

a8 uw

= N0



Task 6: Problem Solving (PS).

Each test panel is equipped with five response buttons, a “task active"
light, and three "feedback" lights, all located at the left center of
the test panel. The problem is to discover the correct sequence in
which to press tne five response buttons. Each button appears only
once in a given trial. Subjects are instructed to use a trial-and-
error procedure and a left-to-right search pattern. An amber feedback
light is illuminated every time a button is pressed to show that the
response is =cknowledged by the system. Pressing buttons in incorrect
order causes a red light to turn on and stay on until the next correct
response is made. Pushing all five buttons in correct order causes a
blue light to turn on. When a problem is solved, a lapse of 15 seconds
oceurs, followtng which the same problem is presented a second time.
The subject is expected to reenter the previous solution from memory
on the second, or confi: tion presentation. After another 15 seconds
anew problem is presented. Performance measures for this task are:
(1) mean response latency in the solution stage (time to solve the
problem divided by the total number of responses); (ii) mean response
latency in the confirmation stage; (iii) the standard deviation of
response latencies for the solution; (iv) the standard deviation of
response latencies for the confirmation; (v) the percentage of “non-
redundant" responses made during the solution phase; and (vi) the pro-
portion of "correct" responses made during the confirmation phase.

MIPB Procedure. A basic 45-min schedule of the five MIPB tasks was
used. This 45-min period was divided into three 14-min. intervals. Tests 1,
2 and 3 were given throughout the schedule. In the first interval of each
period, Test 4 was also active. In the third interval, Tests 4, 5 and 6
were active.

These three-interval schedules were named the low, medium and high work~
load conditions, respectively, and were always presented in the same order im
each periad.

The fqur practice sessions were each of four 45-min periods. The
experimental test sessions and the “refresher” practice sessions given 24 h
prior to eath experimental test were each. three 45-min periods.

- Performance was assessed in terms of’ raw and composite scures for each
task. Composite scores summarized ali measures of performance for the par-
ticular task. An overall composite score. (all subjects) was also obtained.
Individual composite scores were calculated as follows: for each raw data
measurement on each task, the scores for each subject over all experimental
treatments were converted to standard scores with a mean of 500 and a stand-
ard deviation of 100. Thus, the task score. for each subject and experimental
treatment was the mean of standard scores on-each performance measurement.

An overall composite score was also calculated for each subject and treatment
by averaging the composite scores for different tasks so that each task made
an equal contribution to the variance. Analyses of task and overal} composite
scores wec:: made because they: (1) simplify the evaluation of a large amount
of data; (ii) have been found to be more sensitive to the effects of experi-
mental conditions than the individual measurements of performance; and (iii)
have higher reifability than raw score data on individual performance measures
(6,14).


TABLE XVIII.

The Main Effects of Diet, Workload and Period for Individual
Performance Measures in the Mental Arithmetic and Tracking Tasks

Task Diet Workload Test Period
: Crash Normat Low Medium High i 2 3

Arithmetic

Mean Response Mean 10263 11050 10120 ----- 11192*%* 10002 11214 10753**

Latency (ms) S.D. 17760-2551 2172 2163 2054 2197-2272

TIntrasubject

S.D. of Resp. Mean 3831 4415** 3614 4632%* 3877 «4403 4089*

Latency (ms) $.D. 4112)—=«21179 1274 1083, 1272 1303-1228

Percent Mean 93.9 91.8 91.34% 94.2 91.7 92.6

Correct $.D. 7.2 10.7 9.8 7.4 9.6 10.2
Tracking

Absolute Mean 4432 4518 3890 = 5061** 4368 4449 4609

Error (Hor.) $.D. 1026 1100 970 799 1096 «©1034 =—1048

RMS Error 70.9 73.4 64.0 80.3%* 70.0 71.4 74.9
(Hore) 14.7) 14.8 13-4 12.5 14.8 15.3. 13.8
Absolute 4557-4525 4066 = 5016** 4336 ©4679 = 4608*
Error (Vert.) 909 1048 952 754 1018 ©1028 854
RMS Error Mean 73.9 75.2 w--- 67.7 B81. 38* 71.5 76.4 75.6
(Vert.) S.D. 13.0 14.5 ~--- 13.5 10.2 14.6 14.1 11.9
Absolute Mean 6519 6598 ---~ 5730 7388** 6336 6626 6714
Error (Vector) S.D. 1339-1521 1356 947 1502 1476) =—-1285

RMS Error Mean 99,2 101.7 89.8 111.1** 96.6 101.7 103.0%
(Vector) S$.D. 18.2 19.57 w= 17.8 13.2 19.9 19.8 16.4

4 = Statistical significance at or below the .05 level.
kk w Statistical significance at or below the .0] level.

15 ot


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Although a major decrement in blood glucose to hypoglycemic leveis
(< 50 mg percent) is not ordinarily, associated with a 24-h fast (21), the
change in blood glucose was determined in the event of such a decrement
which could adversely affect performance or other measurements in this
study.

Although activity level appears to have been reduced during the crash-
diet condition, subjects did not report any greater feeling of fatigue.
Even the significantly lower serum glucose levels during the crash-diet
condition apparently had no effects on the subjective feelings of fatigue.

The values for the urinary 17-ketogenic steroids produced the only
important findings for the analyses made of the urine collected in this
study. During the crash diet the values were much lower during the night
sleep period than during the same period for the normal diet. Other
reports (16,17) have indicated decreases in 17-kerosteroids. These studies
did not, however, evaluate the reduction by periods within the day as did
our study. Our reported reduction during the sleep period only, though,
would result in a reduction of the 24-h output and is thus consistent with
those studies.

The energy conservation pattern apparent in physiological responses to
the crash diet may have both protected mental functions mediating complex
performance in the MIPB and prevented abnormal subjective fatigue as revealed
by the FCL. Indeed, performance was significantly better, statistically, in
the crash-diet condition than in tie normal-diet condition in three tasks~~
meters, green lights, and arithmetic. Performance was also nominally better
in the crash-diet condition in the other tasks except red lights.

The beneficial effect of the crash diet was to reduce decrements in
performance due to increasing workload in meters, green lights, and arith-
metic in the medium and high workload conditions. There was no effect of
diet on any task in the low workload condition. There was no interaction
of the effects of diet with time during a session. The effects of crash
diet were relatively constant in all three 42-min periods of a session.

The mechanism causing effects of diet is not clear, but may have
involved a general arousal effect of hunger resulting in increased alert~
ness in the crash-diet condition, or may have been due to decreased arousal
in the normal-diet condition due to the meal prior to testing. Although
performance was enhanced in the crash-diet condition in several tasks of
this experiment, and the effects were consistent and statistically signifi-
cant, it should be noted that their magnitude was small, less than one
standard deviation, relative to both intersubject and intrasubject variability.
Although the practical significance of these effects may be questionable,
they definitely indicate that the crash diet caused no performance deficits
in the present situation.

The lack of performance deficits in the erash-diet condition at the
12,500-ft simulated altitude in the present study contrasts with the findings

18



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TABLE VIIL.

Nat Excretion Rate (milliequivalents per hour)

Urine Electrolytes

Time Condition Mean s.D.
2200 © Crash Diet 6.66 42.44
Normal Diet 9.56 ¥3.45
0630 Crash Diet 3.01 +1.02
Normal Diet 5.24  #2.54
1030 Crash Dict 4.71 41.26
Normal Diet 9.16  ¥3.97

xt gxcretion Rate (millicquivalents per hour)

‘Time Condition Mean $.D-
2200 Crash Diet 2.06 40.71
Normal Diet 2.12 30.83
0630 Crash Diet 1,08 +0.46
Normal Diet 1.24 $0.47
1030 Crash Diet 2.45 40.81
Normal Diet 2.61 40.58
nat/Kt (ratio)
Time Condition Mean $.D.
2200 Crash Diet 3.61 13.69
Normal Dict 5.15 $3.62
0630 Crash Diet 2.99 41.00
Normal Dict 4.70 43.11
1030 Crash Diet 2.23 +1.20
Normal Diet 3.79 42.00



. PHYSIOLOGICAL, BIOCHEMICAL, AND PERFORMANCE
RESPONSES TO A 24-HOUR CRASH DIET

INTRODUCTION

The problem of obesity in the American population is receiving increased
attention, by both medical and lay writers. Victor Cohn (7), in a recent
article in the Washington Post, states:

Americans are too fat and getting fatter. Despite a new

“ “nationwide passion for exercise...only ‘one group, white
middle~ and upper-class women past their 20's so far have
been getting thinner. Obesity has reached epidemic pro-
portions, say the medical experts, and too much weight
remains one of the most important medical and public
health problems of our time.

As Cohn points out, there have been improvements in certain socioeconomic
grcugs, but statistics dorived from the population in. general are not so
Yeansuring. in fact, ¥S of both mon and weme: were at least 20 per-
cent overweight increased during the period 1971-1974 in comparison to the
prior survey period 1961-1962 (4).

According to Federal Aviation Administration (FAA) statistics derived from
the population of aetive airmen during the period 1969-1979, the average weight-
to-height ratio for male pilots increased during the observation period (1,2).
Using guidelines recommended during. the Fogarty Center Conference on Obesity in
1973 (3), it can’ be calculated that the average male pilot is 22.7 1b above the
average acceptable weight. Female pilots on the other hand were found to be
somewhat less obese, although their average weight was 9.1 1b over the average
acceptable level for their height; this figure remained at least 10.0 Ib under
the maximum acceptable weight. Thus, female pilots tend to be less overweight

than males and.approximate the middle-class and upper-class women mentioned by
Cohr (7).

The recognition of an increased prevalence of obesity and descriptions
of it as "a hazard to health and a detriment to well-being" (4) have led to
&@ great increase in the number of strategies for correcting the problem.

One of these methods, the crash diet, is worthy of consideration as a poten-
tial threat to aviation safety for the following reasons: (4) Although other
regimens usuaily provide for some kind of calovic intake, the crash diet
requires a complete abstinence from all food for at least 24 h. Such fasting
has been show to effect a number of physinlogical and metabolic changes,
including shifts in body water (8) and mobilization of fat stores (19). (44)
Common experiencd tells us that abstinence from food for any period can pro-
duce some discomfort which can distract these occupied in vigilance tasks

or complex psychomotor tasks such as those associated with flying.



18.

19.

22.

24.

” 25.

Kassouny, M. E., C. G. Halcomb, and B. P, McFarland: Effects of Temporal
and Quantitative Dietary Variables on Vigilance Performance, Technical
Report, Center of Biotechnology, Fatigue, and Human Performance, Texas
Tech. University, Lubbock, Texas, 1970.

Keys, A., J. Brozek, A. Henschel, 0. Mickelsen, and J. L. Taylor: The
Biology of Human Starvation, Vol. I, Ch. 35, pp. 756-757. The University
of Minnesota Press, Minneapolis, 1950.

Keys, A., J. Brozek, A. Henschel, 0. Mickelsen, and J. L. Taylor: The
Biology of Human Starvation, Vol. Il, Ch. 38, p. 840. The University of
Minnesota Press, Minneapolis, 1950.

King, C. G., H. A. Bickerman, W. Bonnet, C. J. Harrer, J. R. Oyler, and
C. P. Seitz: Aviation Nutrition Studies: 1. Effects of Pre~flight and
In-flight Meals of Varying Composition With Respect to Carbohydrate,
Protein and Fat, J. Aviat. Med., 16:69-84, 1945.

Koerker, D. J., C. H. Goodner, E. W. Chideckel, and J. W. Ensinch:
Adaptation to Fasting in Baboon If: Regulation of Lipolysis Early
and Late in Fasting, Am. J. Physiol., 229:350, 1975,

McFarland, R. A.: Human Factors in Ait Transportation. McGraw-Hill,
New York, 1953.

Merimee, T. J., and J. E. Tyson: Stab{tization of Plasma Glucose During
Fasting, New Engl. J. Med., 24:1275-1278, 1974.

Pearson, R. G. and G. E. Byers, Jt.: The Development and Validation of
a Checklist for Measuring Subjective Fatigue. USAF School of Aerospace
Medicine Report No. TR-56-115, 1956.

Simonson, E., J. Brozek, and A. Keys: Effects of Meals. on Visual
Performance and Fatigue, J. Appl. Physiol., 1:270-278, 1948.

Snedecor, G. W. and’W. G. Cochran: Statistical Methods, Sixth Edition,
the Iowa State University Press, Ames, Iowa, 1969.

Winer, B. J.: Statistical Principles in Experimental Design, Second
Edition, McGray-Hill Book Company, 1971.

“21

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ACKNOWLEDGMENT

The authors are indebted to Ms. Linda C. Foreman for conducting
training and data collection on the Multiple Task Performance Battery
(MTPB) during the early part of this study. The authors gratefully
acknowledge the assistance of Ms. Marlene Wicks and Ms. Mary Ann White
in subject monitoring and collection of physiological and biochemical
data and also Ms. Deborah K. Taylor in MIPB training and data collection.
Mr. Russell Moses, Ms. Patsy R. Fowler, and Ms. White were responsible
for much of the biochemical analyses. Mr. Clay F. Tucker was respon—
sible for logistical assistance.

We also wish to thank Drs. Audie W. Davis, Jr., and Marinus Flux
for conducting the preselection physical examinations and Mr. David
Hehmeyer for assistance in setting up the oxygen breathing system and
the masks at the MIPB site.

ik

ioe

Lise:



Technical Report Documentation Page

Ve, Report New 2. Gaverament Accession No. 3. Recaprent'» Cotoleg Ne.

f

FAA~AN-81-8 AD-03 LY3

Title ond Subtitie 3. Report Date

Aprft "1981

«VE. Pevforming Organiranen Cede

IPHYSLOLOGICAL, BIOCHEMICAL, AND PERFORMANCE
RESPONSES TO A 24-HOUR CRASH DIET | ces

[@. Perlorming Organezation

7 Aube!) EB. Arnold/Higgins, Henry W./Mertenty.—.—----

9, Performing Orgonixotion Nome and Address = VO.” Wark Unit No. (TRAISH

|FAA Civil Aeromedical Institute ~~ .
P.O. Box 25082 Contract or Grant No.
OkLahoma City, Oklahoma 73125

TE. Type of Report ond P.

12, Sponsoring Agency Name ond Address : i
Office of Aviation Medicine OAM Report: :
Federal Aviation Administration

800 Independence Avenue, S.W. . . . Ta. Sponsoring Agency
Washington, D.C. 20591 a

15. Supplementary Notes se

Work was done under approved tasks AM-A-80-PHY-123 and AM-A-80-PSY~85.

16, Abstract

‘twelve overweight male subjects were evaluated once on a normal dict and once on a
24h crash dict (low-calorie liquids only). Experiments were 1] wk apart. During i
24-h_ complex performance tests given at the end of the diet period, subjects breathed
an 03/Np gas mixture equivalent to 12,500 ft. There were no significant phystoloni-
cal and biochemical findings due to diet for heart rate, blood pressure, serum cle
trolytes, subjective fatigue and urinary excretion of K’, epinephrine and norepineph-
rine. Body temperatures were lower (p< .05) for the crash diet than for the normal
diet. Serum glucose levels were normal but increased during the normal diet and
decreased during the crash diet. Wematocrit increased from pretest to posttest under
both conditions but was greater for the crash diyt (p< .05) than for the normal dict
Urinary excretion of 17-ketogenic steroids was less (p< -001) for the sleep period
for the crash diet than for the normai dict. Urinary excretion rate of Nat was less
(p< .001) for the crash dict than for the normal diet. Complex performanév showed
no significant differences when subjects were tested under low workloads. Several
measurements showed enhancement. of performance during the crash diet when subjects
were being tested under the medium and high workload conditions.

17, Key Words TB. Distribution Statement

¢ ’
Aviation environment, Simulation, Document is available to the public through
Performance? Physiology; Biochemistry the National Technical Information Service,

Springfield, Virginia 22161.

TS. Security Close:l, (of thes rupertl WD, Security Class, (of this poge! 21. No. of Poges 72. Pree
Unclassified Unclassified 21
Form DOT F 1700.7 (8-72) Reproduction of completed page authorized

~ i



TABLE IX.

inary Epinephrine Excretion Rate
(micrograms per hour)

Time Condition Mean §.D.

2200 Crash Diet 553.9 #176.4
Normal Diet 681.6 +255.0

0630 Crash Diet 403.7 +180.7
Normal Diet 318.3 #130.8

1030 Crash Diet 1089.8 + -+447.9
Normal Diet 1014.8 4265.7

TABLE X.

Urinary Norepinephrine Excretion Rate
(micrograms per hour)

Time Condition Mean S.D.

2200 Crash Diet 2044.7 #699.4

Normal Diet 2393.1 4956.9

0630 Crash Diet 2250.8 +1074.9
Normal Diet 2232.2 41221.7

1030 Crash Diet 3510.2 +1570.3
Normal Diet 3963.8 4949.7

TABLE XI. -

Urinary 17-Ketogenic Steroid Excretion Rate
(milligrams per hour)

Time Condition Mean S.D.
2200 Crash Dict 0.4635 40.4032
Normal Diet 0.3857 +0.2087
9630 Crash Diet 0.3402 40.1521
Normal Diet 1.0045 +0.3957
1030 Crash Diet 0.9227 +0.5598
Normal Dict 0.7098 +0.2087

19

Swe ae



TE

LIST OF FIGURES

. Page 7
H

Figure 1, Console of the Multiple Task Performance Battery- 4 ,
}

iv

tee amee Se Nd ee a eee a ee ee



i
TABLE XIX.

The Main Effects of Diet, Workload and Period for
Individual Performance Measures in the Problem Solving Task

Problem Solwing Diet Workload Test Period
Task Measure Crash Normal Low Medium High 1 2 3
SOLUTION
Mean Time/ Mean 861 905 . 812 954%* 867 918 865
Response (ms) $§.D. 156 218 — 131 214 137 230 190
Intrasubject
S.D. of Time/ Mean 1148 = 1225 - 772-1601 2110 «12911158
Response (ms) $S.D. 601 684 / 374 590 531 714 662
Percent
Nonredundant Mean 96.5 96.1 _ 96.4 96.2 96.9 95.5 96.4
Response s.D. 2.6 3.0 on 2.9 2.7. 2.4 3.4 2.3
CONFIRMATION
Mean Time/ Mean 1006 =1041 -— 899 =:1148 999 1077 994
Response (ms) S.D. 218 337 _ 184 331 238 335 263
Intrasubiect
S.D. of Time/ 1317-1326 B68 -1775%* 1255 3596 1328
Response (ms) 620 851 402 732 674 825 720
PercenTM 83.3 81.6 Smead 85.9  79.1** 84.2 82.4 80.8%
Correct 9.6 9.6 - 8.8 9.2 9.2 8.8 10.5

* = Statistical significance at or below the .05 level.
xk = Statistical significance at or below the .01 level.



UNCLASSIFIED

Techni has
Report



Subjects were weighed at the beginning and at the end of the experiment.
Rectal thermistor probes were inserted for internal body temperature measure~
ments (Tye), which were recorded hourly from 1100 the first day through 1000
the second day. Subjects were also fitted with adhesive chest electrodes
which were connected to an electromagnetic tape recorder for continuous heart
rate (HR) recording. Each subject filled out the First Fatigue Checklist
(FCL) (22) at 1030 on the first day. Additional FCL'3 were completed at 1500
and 2200 the first day and at 0630 and 1030 on the following day.

Subjects slept in a dormitory from 2230 the first evening to 0615 the
following morning. The 24-h MIPB test sessions were administered from 0800
to 1015 on the second morning. During the MIPB test sessions, subjects
breathed a gas mixture containing 13.3 to 13.4 percent oxygen in nitrogen.
This mixture provides a partial pressure of oxygen approximately equivalent
to 12,500 ft (3,810 m) of altitude. Subjects breathed room air through the
masks during several of the training sessions; .the masks were adjusted to
assure a proper fit for each subject.

The CAMI MIPB was used to measure time-shared performance in up to six
component tasks simultaneously. The MIPB system is computerized; task pres
entation and data collection are automatic. The test panel displays and

_ response controls are depicted in Fig. 1. The system has been described
* in detail (13). A bricf description follows:

Tasks 1 and 2: Monitoring of Ked and Green Karain Li

This is a choice/reaction time task involving the monitoring of five
green lights (normally on) and five red lights (normally off). The 10
lights were arranged in pairs of green and red, One pair is located in
each corner of the test panel and a fifth pair is located in the center
of the panel, The light lenses also serve as the pushbutton/switch.
The subject was instructed to push the light/switch whenever the light
changed state. The measures of performance on this task are mean and
standard deviation of response latency and percent signals detected.
These measures are recorded separately for red and green lights.

Task 3: Monitoring of Meters.

This task involves monitoring four meters whose pointers move at random
around a vertical position. The subject responds to a shift in the mean
position of the pointer by pressing one of two buttons under the meter
to report a left or right shift. The four meters are arranged across
the top of the test panel. Performance measures are mean and standard
deviation of response latencies and percent signals detected.

Task 4: Mental Arithmetic.

The subject is required mentally to add two numbers and subtract a third
number from the sum of the first two. All numbers are of two digits.
Answers.are recorded by a 10-key response panel. The arithmetic task
display is located in the lower center of the test panel with the key-
board to the right of the display. Performance measures are the mean
and standard deviation of response latency and percent correct answers.



METHODS

Twelve subjecte were evaluated on two occasions, once while they were
eating a normal diet and once after they had consumed only low-calorie liquids
for over 24 h before the experimental session. Six subjects were fed during
their first experiment and dieted on the second experiment; the other six
subjects experienced reverse order of fasting and feeding. All subjects were
healthy, male, paid volunteers who were 5 to 15 percent overweight. The
weight-per-height norms of the Framingham Study (9) were the basis for cal-

culating the degree of overweight. The physical characteristics for the sub-
jects are listed below in Table I.

TABLE I. Physical Characteristics of Study Participants

Characteristic Mean Range
Age (yrs) 24.25 18-32
Height (cm) 180.00 171-186
Weight (kg) 92.30 79,1-106.8
Weight-to-Height 0.51 0.46-0.58

Ratio (kg/cm)

Each subject was required to pass an FAA Class IIE medical examination.
Each was fully informed about the experiment and told that he could withdraw
from the study at any time. Each participant was given four. 3-h training
gessioas on the Civil Aeromedical Institute's (CAMI) Multiple Task Performance
Battery (MIPB) to be described later in this section.

After training, subjects underwent two 2B-h experiment sessions held 1 wk
apart. Subjects reported to the laboratory at 0700 and were fed a standard
breakfast. During the sessions in which the subjects were fed, the subsequent
meals were served at 1200 and 1700 the frst day and at 0700 the following
morning. Al‘breakfasts consisted of two scrambled eggs, two slices of bacon,
two slices of toast with butter and jelly, and milk and coffee. Lunch and
supper consisted cf one meat dish, two vegetables, bread, dessert and drink.
At 0800 the first day, they received a 2%-h refresher training session on the
MIPB. At 1015 they voided and discarded urine, emptying the bladder as com-
pletely as possible. After this, urine was. collected for periods ending at
2200 the first day, at 0630 the following morning (the overnight/sleep period)
cand at 1030 when the experiment was concluded. Urire volumes were recorded
and portions of each sample frozen for later analyses of 17-ketogenic steroids
(11), catecholamines (12) and the electrolytes Nat and Kt which were measured
with an atomic absorption-emission spectrophotometer (Instrumentation Laborator
Inc., Model 353). :

At approximately: 1030 the first day, the first venous blood sample was
drawn (baseline). At the conclusion of the experiment, at approximately 1030
the second day, a final blood sample was drawn. These samples were analyzed ©
for hematocrit and blood glucose. Plasma from these samples was frozen and
later analyzed.for Na* and Kt levels.


TABLE I.

TABLE Il.

- TABLE IIL.

oy
of TABLE Iv.

TABLE, V.
TABLE VI.
TABLE VII.
TABLE VITI.
TABLE IX.
TABLE x.

TABLE XI.

TABLE XII.

TABLE XIII.
TABLE XIV.
TABLE XV.
TABLE XVI.
TABLE XVII.
TABLE XVIII.

TABLE XIX.

LIST OF TABLES

Physical Characteristics of Study Participants

Weight (kg)

Fatigue Checklist (points)

Serum Glucose (mg percent)

Internal Body Temperature (°C)

Heart’ Rate (beats per minute)

Hematocrit (percent red cells)

Urine Electrolytes

Urinary Epinephrine Excretion Rate (micrograms per hour
Urinary Norepinephrine Excretion Rate (micrograms per hour)

Urinary 17-Ketogenic Steroid Excretion Rate
(milligrams per hour)

Overall Composite Scores as a Function of Diet and Period

Composite Scores for Individual Tasks for the Main Effects of
Die, Workload and Period

Composite Scores for Monitoring of Meters as a Function of
Diet and Workload

Composite Scares for Mental Arithmetic Performance as a
Function of Workload and Period

Composite Scores for Tracking Performance as a Function of
Workload and Period

The Main Effects of Diet, Workload and Period for Individual
Performance Measures in Each Monitoring Task

The Main Effects of Diet, Workload and Period for Individual
Performance Measures in the Mental Arithmetic and Tracking Tasks

The Main Effects of Diet, Workload and Period for Individual
Per.‘armance Measures in the Problem Solving Task

dii

10
10

10

lL

12

13

13

13

14

15

16

Triana wnten ece A a



TABLE XIV.

Composite Scores for Monitoring of Meters
as a Function of Diet and Workload

Diet Workload
Low Medium High
Crash 551 527 475
Normal 555 488 404
TABLE XV.

Composite Scores for Mental Arithmetic Performance
as a Function of Workload and Period

Workload ‘Test Period
i 2 3
Low 580 511 521
High 475 431 482
TABLE XVI.

Composite Scores for Tracking Performance
as a Function of Workload and Period

Workload Test Period

1 z 3
Medium 612 562 535
High 428 426 436

13



of King et al. (18) that a perceptual-motor task, the Minnesota block place-
ment test, was adversely affected after several hours of food deprivation at
both ground level and an altitude of 15,000 toe 17,000 ft. The lack of a
similar deficit in the present study in the tracking task, also a perceptual~
motor task, is unexplained. King et al. also found that both high protein
and high carbohydrate meals produced performance superior to the no~meal
condition. The latter finding conflicts with the results of Simonson et al.
(23), who found that performance level on a demanding visual vigilance task
was highest following a "standard" or high fat meal and lowest after a carbo-
hydrate meal. Performance associated with no meal was intermediate. This
interaction of type of meal with type of task should receive. further
attention.

Although the long-term effects of diet on altitude tolerance have
received considerable attention in the literature (20), little attention
has been given short-term dietary variations. The small number of prior.
studies of short-term food deprivation have typically dealt with deprivation
periods up to 10h (5,15,18,23). The present findings suggest that when a
physiological energy conservation pattern is possible, deficits may not
occur at fasting intervals up to at least 26 h.

Our findings suggest a need for additional investigations of the
interactions of various dicting strategies and altitude exposure. Of par-
ticular interest are the possibly contributing effects of mental and” phys~
ical fatigue and the effects of "refeeding" high carbohydrate meals after

2 of fasting. The latter effect, known to produce sometimes drastic
reductions in blood glucose levels shortly after a meal of carbohydrate,
has not been studied in people during exposure to moderate hypoxia. . Other
factors that have not been evaluated with respect to diet and altitude are
age and circadian cycle. It should also be pointed out that Jong-term -
dieting, which may produce effects entirely different from those of short
fasts, has not been studied for possible effects on pilot proficiency.

In summary, we have found that 24 h of crash dieting did aot adversely
affect the performance of complex tasks by male pilot surrogates who were
5 to 15 percent overweight when they were tested under sedentary conditions
while breathing oxygen/nitrogen mixtures equivalent to an altitude. of
12,500 ft (3,810 m). Our results indicate that fasting subjects were better
able to sustain performance in the face of an increasing workload. This
finding should not be construed as a positive one, however. Other condi-
tions (e.g., heavy physical workload or +Gz stress) which may be imposed on
the airman during flight were not investigated in our study. These and
other factors could offset any possible beneficial effects of fasting and
should be studied before any but the most tentative conclusions can be made.

19




RESULTS

All physiological and biochemical data were treated by analysis of
variance techniques (25).

Weight. Table II shows the mean weights before and after éach
experiment.

TABLE Il. Weight (kg)

Crash Diet Normal Diet
Pretest Posttest Pretest Postrest
Mean 93,25 91.89 92.85 92.66
, S.D. 47.57 +7.51 47.51 47.48

Subjects demonstrated no statistically significant difference for their
pretest weights for the two experimental conditions. There was also no sig-
nificant difference between the pretest and posttest weights when subjects »
had the normal diet. As anticipated, the only statistically significant dif-
ference (p< -001) was found for the pretest vs. the posttest weight in the !
erash-diet condition.

Fatigue Chespkist. Scores on the FCL can range from 0 to 20; the lower
the score, the more fatigued the individual feels. The FCL'’s were administered
periodically during the experiments and the results are presented in Table III
by time of day in sequential order. “ .

TABLE LII. Fatigue Checklist (points)

Time Condition Mean S.D.
1030 Crash Diet 12.4 42.9
. Normal Diet 10.6 ¥3.8 -
1500 Crash Diet 11.1 #1.7
Normal Dict 10.0 43.6
2200 Crash Diet 7.3 42.2 .
Normal Diet 8.5 $3.1
0630 Crash Diet 10.7 42.5
Normal Diet 10.4 44.2 q
1030 Crash Diet 10.8 43.0
Normal Diet’ 11.4 43.6

These data were treated by analysis of variance (25). There was no
statistically significant difference due to the diet. There was, however,
a significant difference (p< -01) for time of day, with the greatest
fatigue being reported at the end of the first day regardless of diet.

ETAL. LIBRARY

6



TABLE VI. Heart Rate (beats per minute)

Day 1 Overnight Day 2
Diet Crash Normal Crash Normal Crash Normal
Mean 82.6 87.9 73.6 74.8 91.8 93.0
S.D. 49.7 412.4 48.5 49.8 46.8 47.4

Hematocrit. Hematocrit measurements were made pretest and posttest
for both experiments. The results are presented in Table VII. By analysis
of variance, the findings were: (i) an increase from pretest to posttest
(p< .001), with a greater increase occurring during the crash diet; and
(44) a significantly higher hematocrit for the crash diet than for the
normal diet (p< .05). There were no significant interactions.

TABLE VIL. Hematocrit (percent red cells)

Crash Diet Normal Diet
Pretest Posttest Pretest Posttest
47,94 50.69 47.44 49.25
41.246 41.65 41.77 42.05

Serum Electrolytes. The pretest and posttest blood samples were analyzed
for the serum NaTM and Kt. There were no significant findings.

Urine Electrolytes. Urine samples were also analyzed for nat and Kr.
‘The findings are given in Table VIII. For the urinary Nat excretion rate,
collection periods were significantly different at the p< .0C1 level, with
the overnight values being much lower than the daytime values. The crash-
diet values were significantly lower than the normal-diet values (p < 091).
There was no significant interaction. For Kt, the only significant finding
was for the period of collection, with the overnight values being lower
than the daytime values (p< .001). The Nat/Kt ratio, on the other hand,
demonstrated no difference for time of collection, indicating that when one
electrolyte dropped significantly so did the other. The ratios were highly
significant for diet (p< .001) with ratios being higher for the normal diet
than for the crash diet. There was also, a significant interaction between
time of collection and diet, with the ratio of crash-diet values to normal-
diet values greatest for the second morning and least for the first day
(p < .02).

Urine Catecholamines. The urinary excretion rates of catecholamines
are listed in Table 1X (epinephrine (E)) and Table X {norepinephrine (NE)).
They are reported for the same time periods as the urinary excretion rates
of the electrolytes. There were no statistically significant effects due
to diet, nor was there any significant interaction between diet and time of
collection. There were, however, significant effects (p < .001) for time
of- collection, with the 1039 collection of the second day demonstrating the
Highest values for both E and NE.



ts

#23 Wes ke



‘The interaction of workload with test period was significant (p< .05)
in the composite score data of the mental arithmetic and tracking tasks.
Those interactions are. shown in Tables XV and XVI. For both tasks, the dif-
ference in performance under @ifferent workload conditions decreased during
successive periods of an experimental session. This was mainly due to pér~
formance in the low and medium workload intervals declining toward the lower,
but more stable, level of performance under high workload.

Raw Score Data. Raw score data (means and standard deviations) on
individual performance measures in each task are shown in Tables XVII, XVIII,
and XIX as a function of the main effects of diet, workload and test period.
These data show that. in the monitoring of green lights and meters, and in
mental arithmetic, the enhancement of performance by fasting was consistent
in all measures. This effect was statistically significant in the case of
intrasubject variability (standard deviation) of response latencies in all
three tasks. The percentage of signals detected,was also significantly
higher in the case of monitoring of green lights. Nominal superiority of
performance in the fasting condition also occurred, with few exceptions, in
measures of performance on tracking and problem solving although these
effects were small and not statistically significant.

Increasing workload consistently caused a v:crease in performance in
all tasks but monitoring of red lights. Measures on all tasks except meter
monitoring and tracking typically show best perfcrmance in the first period,
worst performance in the second period, and slight recovery in the third
perisd. Measures of performance on meter monitoring and tracking typicaliy
show a steady decline in successive periods. These effects of workload”
were, in most cases, statistically significant. The effect of test, period
was significant only in raw score performance measures of arithmetic and
tracking tasks, and in the confirmation phase of the problem solving task.
Individual raw score performance measures again typically show best perform-
ance in the first period, a substantial decline in performance in the second
period and partial recovery during the third test period.

DISCUSSION

The significantly lower Tre (p< -05) for subjects during the crash
diet when compared to the normal diet is possibly indicative of a decrease
in activity level. There was not a statistically significant difference
between the beginning mean T,, for the two conditions. The initial mean
values were 37.40°C for the crash diet and 37.31°C for the normal diet.-~
Therefore, the lower T,, during the Grash diet was not the result of a lower
initial value for that condition. The possibility of a reduced activity
level was supported by the HR data. Although statistical significance was

_ mot reached (p"= .069), mean HR values were lower during the crash diet

than during the normal diet for all three reporting periods. In one’
reported study (10), energy expenditure in fasting obese men was signifi-
cantly reduced during fasting. The most marked decrement, from 2.8 to 2.2
keal/kg/h, occurred with walking. In that study, however, the subjects
were men with a mean weight excess of 89 percent and thus are not completely
comparable to our population.

E.R.A.U. LIBRARY

17


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JACK R. HUNT MEMORIAL LIBRARY
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12.

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14.

REFERENCES

Aeromedical Certification Statistical Handbook, 1969. USDOT, FAA, CAMI,
‘Aeromedical Certification Branch, Medical Statistical Section, 1969.

Aeromedical Certification Statistical Handbook, 1979. USBOT, FAA, CAMI,
‘Keromedical Certification Branch, Medical Statistical Section, 1979.

Bray, George A. (Ed.): Obesity in Perspective. Vol. 2, Pt. 1, Fogarty
International Center Conference, Washington, D.C.: U.S. Government
Printing Office, DHEW No. (NIH) 75-708, 1975... --

Bray, G. A.: Obesity in America, Int. J. Obes., 3:363-375, 1979.
Champion, R. A. and R. K. Field: Human Performance and Short Term Food
Deprivation, Aust. J. of Psych., 15:187-190, 1963.

Chiles, W. D., A. E. Jennings, and G. West: Multiple Task Performance
as a Predictor of the Potential of Air Traffic Controller Trainees. FAA
Office of Aviation Medicine Report No. AM-72-5, 1972.

Cohn, Victor: Our Obesity Neurosis, The Washington Post, pp- Al-A2,
September 1, 1980.

Consolazio, C. F., L. 0. Matoush, H. L. Johnson, R. A. Nelson, and H. J-
Krzywicki: Metabolic Aspects of Acute Starvation in Normal Humans Qo
Days), Am. J. Clin. Nutr., 20(7) 2672-683, 1967.

Dawber, T. R., J. E. Moore, and G. V. Mann: Coronary Heart Disease in
the Framingham Study, J. Publish. Health, 47:4, 1967.

Drenick, E. J. and H. F. Dennin: Energy Expenditure in Fasting Obese
Men, J. Lab. Clin. Med., 81(3):421-430, 1973.

Few, J. D.: A Method for the Analysis of, Urinary 17-Hydroxycorticosteroids,
J. Endocrinol., 22:31-46, 1961.

Fiorica, V. and R. Moses: Automated Differential Fluoremctric Analysis of
Norepinephrine and Epinephrine in Blood Plasma and Urine, Biochem. Med.,
5:483-504, 1971.

Higgins, E. A., W. D. Chiles, J. M. McKenzie, A. W. Davis, Jr., Gs E.
Funkhouser, A. E. Jennings, S. R. Mullen, and P. R. Fowler: Effects of
Lithium Cerbonate on Performance and Biomedical Functions. FAA Office of
Aviation Medicine Report No. AM-77-17, 1977.

Jennings, A. E., W. D. Chiles, and G. West: Methodology in the Measurement

of Complex Human Performance: Two-Dimensional Compensatory Tracking. FAA
Office of, Aviation Medicine Report No. AM-72-21, 1972.

20 .



Figure 1. Console of the Multiple Task Performance Battery

Task 5: Two-Dimensional Compensatory Tracking (TRK).

The tracking task display is an oscilloscope screen mounted in the top
center of the subject's panel. The target on the screen is a det of
light abort 1 mm in diameter. A varying amplitude disturbance is
imparted to the target in each dimension; the subject attempts to
counteract the disturbance, keeping the dot at center screen, by moving
a control stick with his right hand. Performance is measure¢ by analog
circuitry in terms of mean integrated absolute error and mean error
squared for both horizontal and vertical dimensions. “These data are
converted to measures of absolute vector error and root-mean-square
vector error. “


Blood Pressure. Blood pressure measurements were taken at 1130, 1500
and 2200 the first day and at 0630 and 1015 the second day of the experiment.
Neither systolic pressure, diastolic pressure nor pulse pressure demon-
strated any statistically significant differences due to diet. The analysis
of variance yielded a difference for time of day, with systolic pressure

(p< .01) and pulse pressure (p < .001} being greatest at the end of the
experiment and the diastolic pressure being greatest (p< .05) just before
retiring the first evening.

Serum Glucose. The serum glucose levels are presented in Table IV.

None of the individuals exhibited any unusual drop in serum glucose level
as a result of the crash diet. The lowest value recorded was 70 mg percent.
There was, however, a statistically significant difference (p< .01) between

~ the crash-diet condition and the normal-diet condition, with a decline of
2.2 mg percent during the crash dict and an increase of 3.8 mg percent dur-
ing the crash diet and an increase of 3.8 mg percent during the normal diet.

TABLE IV. Serum Glucose (mg percent)

Crash Diet Normal Diet
Pretest Posttest Pretest Posttest
86.6 B4.4 89.9 93.6
49.7 #95 48.1 +6.2

Bf

Nteinal Body Temperature.

Rectal temperatures were recorded hourly
and then meaned for three reporting periods--the first day, the overnight
(sleep) period, and the second day of the experiment. The results of the
Tre measurements are reported in Table V.

TABLE V. Internal Body Temperature (°C)

Day 1 Overnight Day 2
Diet Crash Normal Crash Normal Crash Normal.

Mean 37.12 37.29 36,51 36.55 36.99 37.06
SD. 40.37 40.16 40.15 +0.20 40.19 +0.20
There was a statistically significant difference due to the reporting
period (p< .001) with the. overnight readings being the lowest. There was
a significant difference due to diet (p<, .05) with the crash-diet readings
being lower than the normal-diet readings.

Heart Rate. HR, although recorded continuously, was separated into
three reporting periods as was the case with Tre. The results of the
HR measurements are reported in Table VI. There was a highly significant
difference (p< .001), for the period reported, with the lowest HR overnight.
There was no significant interaction hetween diet and reporting period.
Although the HR was lower during the crash diet than during the normal diet
for each period reported, the decrease was not statistically significant
(p = .069).