oxygen intake of about 85 per cent in going
from sea level to an altitude of 9,500 feet, the
respective sea level values would have been
2946 ml/min for Forbes and 3030 ml/min
for Keys. The records of 1962 indicate that
Forbes had nearly maintained that level of
“physical fitness” while Keys had dropped to
almost two-fifths of his original work capacity.
At altitude, therefore, the work capacity of the
lG@-year older Forbes surpassed that of Keys
markedly.

Date Expt, =P, Viney Vangrg RQ
mm Hg min — \/min
83-44 E 709 74.9 97.7 1.05
8-20-44 E 706 90.8 119 1.01
8-26-44 E 540 94.5 165 1.08
9.1144 E 540 102.0 179 1.27
5-26-55 E 745 104.2 130 1.06
62-55 E 446 60.7 131.3 1.07
6-23-55 T 740 112: 139 1.07
7-11-55 E 455 80.2 170 1.11
7-28-55 E 455 774 164 1.13
8-18-55 E 455 79.5 170 1.13
8-11-56 T 445, 64.4 139 1.12
6-13-62 T 733 «100.8 126 1.12
79.62 E 488 66.4 130 1.04
7-24-62 E 455 63.9 133.5 1.01

*Following about two weeks at Ps 535
**Following about four weeks at Ps 535 or 488

Taste 4: Exercise tolerance at sea level and at altitude:

ht 182 cm; age 54.

The most complete record of maximum per-
formances is that of Balke (see Table 4). In
1944 when his sea level maximum was 3910
ml of oxygen per minute he reached 3540

ml/min at an elevation of 10,000 feet. Eighteen
years later when his sea level maximum was
3440 ml/min the maximum oxygen intake was
2730 ml/min after a few days at 12,600 feet
and two weeks later 2805 ml/min on the sec-
ond day at 14,200 feet.

vco, vo, _—_—-Heart Blood Notes

m/min ml/min Rate Pressure

3860 3670 188 210/56 active but
untrained

3950 = 3910 184 =. 215/65 in-training

3640 3390 1176 210/75 2 days ai alt.

4480 3540 180 200/70 3 weeks at

, alt.

4230 3990 180 200/45 in-training

2875 2700 178 190/65 Chamber

4380 4080 188 190/65 intraining

3280 2960 174 190/65 3 days at alt.

3320 2925 164. 200/65 3 weeks at
alt.

3160 =. 2805 164 195/80 6 weeks at
alt.

3000 26380 168 220/60 2 weeks at
alt.

3840 3440168) 214/75 un-trained

2855 2730 160 225/85 2 day: at
alt.*

2830 862805 = 150 2 days at
alt.**

Balke, Summer of 1962: wt 74 kg;


ed 79% of this at 82% of his sea level maxi-
mum. Dill, the oldest, reached 87% of his sea
level after four weeks at altitude and finally
86% at Ps 485 after five weeks at altitude. Tal-
bott who exercises regularly, including skiing,
was limited to 56% of his sea level maximum at
P; 485 after two days at altitude: the correspon-
ding figure for McFarland was 56. Forbes after
two days at Ps 537 reached 79% of his sea level
maximum and a week later at Ps 485, 67%.
Keys was not examined at sea level until 10
months after the altitude study. His sea level
maximum was only 5% greater than his oxygen
intake at Ps 485 after two days at altitude. The
two young men after six to seven weeks at allti-
tude performed the Balke test at Ps 485. Newton
reached 66% of his sea level maximum on the
treadmill and Terman, 77%. Part of the dis-
parity between individuals can be attributed to

the difference in performance in walking with -

step-wise increases in slope and on the ergo-
meter with increments in brake load. This differ-
ence is small in the cases of Balke, Dill and
Newton but large in the cases of Robinson and
Terman.

The best performances at Ps 485 expressed
in ml of oxygen per min and per kg, rated in
the order of decreasing oxygen intake, are as
follows:

Subject Age Days at altitude ml O,/min:kg
Balke 54 28 38*
Terman 23 44, 37
Forbes 69 9 26
Robinson 59 10 24
Dill Ti 33 24
Talbott 60 2 19
Newton 27 36 18
Keys 59 2 17
McFarland 61 3 14
*At Ps 455; all others at

Ps 485.

In reaching maximum performance at alti-
tude it is noteworthy that the volume of air
breathed is as great or greater than in maximum
performance at sea level, at least in the more
fit subjects. Sometimes the volume decreases at
the greatest altitude, e.g., Christensen, but not
always, e.g., Pugh’s mountaineers. The bellows
system, aided by the lower air density, is ade-
quate to move the same volume of air over 4
wide range of oxygen saturation of arterial

blood.

While the ability to ventilate the lungs is not
only unimpaired but might even be increased
at high altitude there can be no doubt that the
attainment of the maximum breathing capacity
during work sets a limit to the amount of physi-
cal work to be tolerated. Generally, the simul-
taneous decline in maximum oxygen consump-
tion should be accompanied by a decline in
cardiac output. A decrease in heart rate, there-
fore, is usually observed with decreasing baro-
metric pressure. At uccasions, however, investi-
gators have been puzzled by the drastic reduc-
tion of the maximum heart rate during exercise
at high altitude. Generally, the decline in at-
tainable oxygen consumption is relatively great-
er than the dectine in heart rate. Here are two

examples:

Subject P, ml Vo,/min mi Op/minzheart rate
Christensen 760 3720 19.6
Christensen 401 1800 13.6

Balke 753 3440 20.5

Balke 455 2805 18.7

In the light of our findings it is clear that
neither does age bar successful adaptation to
high altitude nor does youth insure a high de-
gree of success.

ACKNOWLEDGEMENT

Our pleasant weeks at the laboratories of the White Mountain Research
Station were made possible by Drs. Nello Pace and Raymond J. Hock and
their staff. Drs. F. G. Hall, W. H. Forbes and Mr. James L. Terman assist-

ed in the study.


These results show that even at the age of 71
sufficiently high demands can cause an aug-
mentation of the capacity to cope more effi-
ciently with stress situations: a relatively short
stay at the physiologically more demanding alti-
tude of 14,200 feet was followed by a marked
improvement of work capacity at the lower ele-
vation of 12,500 feet at which no progress had
been made during a period of almost two weeks.

Although, in 1962, work capacity at sea level
was only 66 per cent, and at an elevation of
9500 feet, only 71 per cent of that in 1935, the
relative losses of work capacity with increasing
altitudes were nearly the same in both years
(see the bracketed values in tabulation above).

Observations on Talbott are summarized in
Table 3A. Some of these observations are from
unpublished fatigue laboratory records; those
of 1935 are from Christensen (*). The maxi-
mum oxygen intake capacity at age 26 was

3930 ml/min, at 34 years of age 2910 ml/min
(or 74% of the former) and at age 60 it was
2510 ml/min (or 64% of the value 34 years
ago). In 1935 work capacity dropped at an allti-
tude of 9500 feet to 74 per cent of that shown
at sea level, at 12,500 it was 75 per cent, and
at 15,000 feet 85 per cent of the sea level value.
This relative improvement at the higher altitude
was probably due to a physical iraining effect.
In 1962, on the third day at altitude (12,500
feet) his maximum oxygen intake on the bicy-
cle ergometer was 56 per cent of his sea level
maximum on the treadmill. Both the peak values
at sea level and at-altitude in 1962 were 64 per
cent of the comparable values in 1935.

Forbes and Keys had good records at high
altitude in 1935 as shown in Table 3B and 3C.
The data reported by Christensen (*) lack re-
cords of the maximum oxygen intake at sea
level. Assuming an average decrease in peak

Date Expt =P, Varn Vanes RQ. veo, VO, Blood Heart Blood
Lactate Rate Pressure

mm Hg I/min min ml/min m/min mg%

A. Talbott; summer of 1962; wt 74 kg; ht 173 cm; age 60 /

12-10-28 T 760 117 142 0.99 3900 3930 82

4-30-29 E 759 85 103 0.94 2560 2700 64

7-25-29 E 523 72 131 0.99 215 2170 66 152 132/90

1935 E 543 43 75 2170

1935 E 489 A5 88 2200

1935 E 429 54.5 123 2470

12-18-36 T 764. 99 119 1.34 3900 2910 70 189 164/66

5-12-62 T 742 92 114 1.42 3580 2510 72 180 184/104

7-23-62 E 490 32.3 62.9 1.15 1610 1400 27 152 205/126

B. Forbes; summer of 1962: wt 71 kg; ht 178 cm: age 69

1935 E 543 54 95 2500

1935 E 429 42.5 96 ~ 2080

1935 E 401 38 93 1850

10-17-61 T 741 71.4 89.0 1.22 3350 2730 99 170 150/80

6-30-62 E 535 43.7 77.2 0.96 2100 2170 152 180/90

76-62 E 491 37.4 72.4 1.09 2000 1830 130 185/100

C. Keys; summer of 1962: wi 72 kg; ht 172 em; age 59

1935 E 543 51 89 2580

1935 E 489 43.3 85 2100

1935 E 429 53 1206 2100

1935 E 401 20 49 1100

7-23-62 E 490 25.6 50.0 1.05 1160 1110 124 202/92

5-563 E 736 39.9 50.0 1.12 1426 1270 152 162/88

Tasie 3: Exercise tolerance at sea level and at altitude.

—3—


Finally, Table 5 includes records of four who
had had no previous measurements at altitude.
In each case maximum performance was as-
sessed at sea level on both the treadmill and
ergometer. After only 2 days at the 12,500 foot
level Robinson reached 595; of his sea level
record on the ergometer; 9 days later he reached
70%. Newton after about 5 weeks at this alti-
tude reached 66% while Terman after 7 weeks

Date Expt P Vv,

B sTPD

Vorre BO.

mm Hg Wmin 1/min

attained 83% of his capacity on the ergometer
at sea level. At sea level Robinson and Terman
attained higher levels of oxygen intake on the
treadmill than on the ergometer: 2700 vs 2170
for Robinson and 3650 for Terman. Based on
these maxima the percentages attained at alti-
tude were 56 for Robinscn and 76 for Terman.
After 3 days at the same altitude McFarland
reached 56% of his sea level capacity.

A. Robinson; summer of 1962: wt 64 kg; ht 171 em; age 59

11-15-61 T 745 86.1 106.5 1.12
11-16-61 E 733 (97.2 115.2 1.28
7-30-62 E 487 39.6 71.7 111
87-62 E 487 52.4 102.7 1.24

B. Newton; summer of 1962: wt 106 kg; ht 183 cm; age 27

11-15-61 T 745 70.1 86.6 1.09
11-16-61 E 733 (91.5 108.4 1.17
7-30-62 E 488 45.5 89.1 114

C. Terman; summer of 1962: wt 75 kg; ht 188 cm; age 23

2-26-62 T 737 = 86.1 107.7 1.05
2-162 E T41 94.0 116.9 1.12
8-7-62 E 487 71.0 139.2 4.15

D. McFarland; summer of 1962: wt 97 kg; ht 192 em; age 61

7-13-62 E 488 24.9 49.3 0,92
7-13-62 E 488 26.9 53.0 0.99
3-27-63 E 739° 55.7 69.5 1.01
3-27-63 T 739 = 49.7 62.0 0.94

vco, VO, Blood ~— Heart Blood
Lactate Rate Pressure
mi/min ml/min mg %
3210 2700 83 162 225/105
2770 2170 95 150 220/115
1440 1290 46 148 228/122
1880 151031 162
3140 2880 55 185 205/80
3500 2980 82 184 200/90
2230 1960 24 152 212/110
3870 3650 94 196 180/80
3810 3380 98 192 180/100
3220 2790 161
1200 1306 185/100
1260 1270 27 144 192/?
2340 2310 17 136 180/75
2040 2160 13 130 180/82

Tae 5: Exercise tolerance at sea level and at altitude,


REFERENCES

1, Dill, D. B.: Reunion at high altitude. The Physiologis:
640-43, 1963.

2, Dill, D. B., W. H. Forbes, J. L. Newton, and J. W. Ter.
man: Respiratory adaptations to high altitude as related
to age. In press as a chapter in the volume, Relations of
Development and Aging. Chas C. Thomas & Co., Spring:
field, MM.

3. Terman, J. W. and J. L. Newton: Changes in arterial and
alveolar gas tensions as related to altitude and age. In
press, J. Appl. Physiol, 1963.

. Dill, D. B., J. W. Terman, and F. G. Hall: Hemoglobin
at high altitude as related to age. In press, Clinical
Chemistry.

5. Dill, D. B.: Hypoxi
Medicina Thoracalis.

»

: High altitudes revisited. In press,

~

10.

uu. K

. Dill, D. B., H. T. Edwards,

. Newton, J. L.: The assessment of maximal oxygen in-

take. J. Sports Med. and Physical Fitness, 3:164, 1963.

A. Folling, S. A. Oberg, A. M.
Pappenheimer, Jr., and J. H. Talbott: Adaptations of the
organism to changes in oxygen pressure, J. Physiol..
71:47-63, 1931.

. Christensen, E. H.: Sauerstoffauinahme und respirator-

ische Fuactionen in grossen Hohen. Skand. Arch, Physiol.,
76:88-100, 1937.

. Hurtado, A.: Animals in high altitudes: resident man.

Chapt. 54 in Adaptation to the Environment, Washington,
D. C.: Am. Physiol. Soc., 1964.

Pugh, L. C. G. E.: Animals in high altitudes: man above
5000 meters; mountain exploration. Chapt. 55 in Adap-
uation to the Environment, Washington, D. Cc. Am. Phys-
iol. Soc., 1964.

The physiology of life at high altitudes. The
mal expedition to Chile, 1935. The Scientific
Monthly, 43:289-312, 1936.

ULS, GOVERNMENT PRINTING OFFICE. 1964 0—732-429


Af ?
AD 603 Far

WORK TOLERANCE: AGE AND ALTITUDE

D. B. DILL, Ph.D. Pa
- §, ROBINSON, Ph.D. oa we?
J. L. NEWTON, M.S. qi
Department of Anatomy and Physiology
Indiana University, Bloomington, Indiana

B. BALKE, M.D.
Biodynamics Branch

63-33

FEDERAL AVIATION AGENCY
CIVIL AEROMEDICAL RESEARCH INSTITUTE
AERONAUTICAL CENTER
OKLAHOMA CITY, OKLAHOMA
DECEMBER 1963



Discussion:

We have found few records in the literature
comparable in most respects to ours. One is that
of Christensen (*). On himself as subject when
he was about 30 years old his sea level maxi-
mum was 3720 ml per min. In successive ap-
proximately 10-day stays at four altitudes his
maxima were as follows:

Altitude P, Vores vo: Heart
Feet mmHg Vmin ml/min rate
S.L. 760 129 3720 190
9,000 543 123 3020 170

12,000 489 108 2560 150

15,000 429 136 2190 135

17,000 401 90 1800 132

Hurtado (°) has assessed the capacity of
Peruvians dwelling at Morococha (Ps 455, 4540
m) in terms of the performance of sailors at
sea level. Ten men ran at 132.4 m/min on a
grade of 11%. The high altitude dwellers sur-
passed the sailors in every respect: their mean
tolerance time in this endurance run was 53
min vs 34 min for the sailors. The sailors were
slightly less efficient: 1333 vs 1167 m1 02/min
x m? BSA. In another even more impressive per-
formance 12 sea level athletes and 12 Moro-
cocha residents ran at 135.3 m/min on a grade
of 18.9%. Again the high altitude residents
proved superior despite the fact that their coun-
terparts were athletes. The oxygen debt was
greater in the athletes: evidently they had to
rely more on anaerobic reserves than did the
residents of Morococha.

Pugh (7°) has reported observations on moun-
taineers of the 1960-61 Everest expedition.
Their performance was as follows:

No. Altitude P, Verrs vo: Heart
feet mmHg = i/min mi rate
6 SL. 750 120 3400 192
5 14,500 440 165 2580 159
4 18,000 380 159 2140 144
4 21,000 340 169 1950 146
2 23,500 300 120 1400 135

Pugh remarks that the several months spent at
a barometric pressure of 380 mm Hg resulted
in some deterioration. Experiences of Chilean
sulfur miners support his observation. As Keys

has related (77), an attempt to establish a vill-
age at 570C m near the mine failed. At the time
of our visit the highest community was at 5340
m, Ps 400; it had been established many yeers
before. The miners climbed each morning 300
or 400 meters to their place of work. Evidently
the critical barometric pressure above which the
long-range net effect is deterioration even for
rugged mountaineers is between 400 and 380
mm Hg.

A few generalizations are warranted. The ob-
servations of Hurtado on residents at Meroco-
cha indicate that they were completely ‘adapted
to that altitude since they out-performed young
men at sea level. Since in no case at lower and
higher altitudes any of our oxygen consump-
tions in the Balke test did reach sea level values
it follows that in this respect acclimatization is
slow, taking months, perhaps years.

Does this capability have a genetic factor?
This may well be the case although it is unlikely
that the responsible genes are peculiar to the
Indians of the Andes and to the inhabitants of
central Asia. We found a high degree of adap-
tation among the miners at 5340 meters in
Chile. Some at least had come from sea level.
‘We were told that the first three days were criti-
cal; many quit during this period while most of
those who stuck it out that long were able to
continue. Thus, it seems likely that some have
inherent characteristics favoring adaptation to
high altitudes while others lack them.

Practical experience in mountain climbing
expeditions also supports the idea that there is
a wide range in ability to adapt; particularly
in the rate of adaptation. For measuring the rate
of adaptation it appears that two criteria are
of most importance: the amount of restful sleep
and the capacity for oxygen intake in maximum
exercise. The importance of the former criteri-
on, as far as our observations go, is a matter of
conjecture. On the other hand, our measure-
ments of maximum oxygen consumption reveal
considerable individual differences in rate of
adaptation. There was no common pattern of
response; the following brief statement about
each individual makes this clear. Balke, the
most fit and the most experienced at altitude,
had a VOz at sea level of 3440 ml/min at age

54. After two weeks chiefly at Ps 535 he reach-

—6—


WORK TOLERANCE:

AGE AND ALTITUDE

D. B. DILL, Ph.D.
S. ROBINSON, Ph.D.
J. L. NEWTON, MS.

B. BALKE, M.D.

It is a curious fact that the unpleasant experi-
ences during the first days at high altitude are
most manifest when metabolism is lowest — in
sleep — and when it is highest — in strenuous
exercise. Sleep is interrupted by Cheyne-Stokes
breathing; morning may find one with heac-
ache and nausea. Then if one attempts to climb
or even walk briskly there may be cardiac dis-
tress, and certainly will be breathlessness and
hyperventilation. In a few days however exer-
cise becomes more tolerable and within a week
climbing is apt to become a pleasure. Some will
nod their heads in assent to the above statement
but others will consider it ridiculous. This is
understandable: there are a great many factors
that affect the onset and degree of mountain
sickness. Among these are the rate and nature
of the ascent, the altitude reached, the age and
fitness of the individual and his individual sus-
ceptibility. While physiologists have learned
much about the physiological and biochemical
changes that accompany adaptation to high alti-
tude they cannot answer the question: why does
one man adapt more rapidly and more com-
pletely than another? It was to learn more
about this problem that we undertook in_ the
Summer of 1962, a study of adaptation to high
altitude as related to age. Several aspects of the
study have been described ('****); in this
paper special attention will be given to work
tolerance.

Research Supported in part hy FA Contract #2049

Methods:

The subjects were studied near sea level a
few months lefore or several months after the
altitude studies. One or both of two types of
experiments were employed in assessing the
eapacity for oxygen supply. In one the tread-
mill was set at a grade of 9%. While walking
15 min at 94 m min on this grade metabolic
rate was measured. This bout was followed by
a 10-minute recovery period and then by a run
on the same grade at the rate of 124, 156 or
188 m per min — depending on the estimated
capability of the subject. For the run a 5-liter
mixing chamber was interposed near the inlet
to the gasometer: this was flushed out by the
subject with expired air before he started run-
ning. Gasometer gauge readings were taken
every 15 seconds and gas samples were drawn
from the mixing chamber into 50-ml syringes
for analysis on the Haldane apparatus. The first
sample was drawn over the first half-minute,
the second in the second half-minute and then
one each minute through the fifth minute if the
subject could run that long. An example of this
type of experiment is found in Table 1.

In the other type of experiment the work rate
was increased minute-by-minute either by in-
creasing the grade of the treadmill or by adding
to the brake load on the ergometer. Respiratory
volumes were measured and gas samples col-
lected and analyzed as described above. Or,


Time Vere CO,

min I/min %
O Start
1% 27.3 © 3.87
i 28.1 4.35
2 56.3 5.00
3 66.2 4.88
31% Stop 71.4 4.72

Vo, *

On vco, . Heart
% ml/min mi/min °— rate

16.74 1050 1170 126
15.94 1229 1450 144
15.78 2800 2920 160
16.71 3210 2670 165
16.91 3350 2730 170

Taste I: Typical treadmill run: W. H. Forbes, October 17, 1961, P, 741 mm; t = 25° C; wt.
69 ke: ht 278 cm; rate 156 m/min; grade 9%.

expired air was collected in Douglas bags dur-
ing the last few minutes. The monitored heart
rate and blood pressure enabled one to judge
when the subject was approaching his limit and
when the collection of samples should begin. A
comparison of these and other methods for as-
sessing work performance has been reported by
Newton. (°)

The subjects on whom work capacity was
measured were Dill, Forbes, Balke, Talbott,
Keys, McFarland and Robirson with age ranges
of 54 to 71 and Terman and Newton, ages 23
and 27, respectively. Our primary interest was
in observations in the basal state. Exercise
studies were only carried out when they did not
interfere with the objective of making observa-
tions in the basal state.

Date = Expt «=P, Vay Vorrs RQ.
mm Hg 2/min Vmin

12.3-28 T 760 86.5 104.7 1.09
5-2-29 E 750 69.0 84.7 1.05
75-29 E 526 56.0 100.9 1.04
4-17.35 T 750 85.8 105.3 1.16
1935 E 543 59 103

1935 E 489 46 90

1935 E 429 55 124

11-16-61 E 733 60.2 75.7 1.16
6-30-62 E 535 40.8 72.2 1.04
76-62 E 485 37.2 72.0 1.20
7-762 E 485 34.4 67.1 1.08
7-17-62 E 485 37.0 72.8 1.00
7-25-62 E 455 35.6 75.2 1.05
7-31-62 E 490 38.7 75.4 1.03
8-762 E 762 61.5 74.2 1.10
8-22-62 E 737 58.5 73.2 1.03
T = Treadmill

E = Ergometer (Bicycle)

Results:

Table 2 includes observations on Dill during
the five weeks at altitude in 1962, observations
at high altitude in 1929(*) and in 1935, plus
contemporaneous sea level observations in each
case. In 1962 the peak oxygen intakes at alti-
tude, relative to the value of 2010 ml/min at
sea level, were as follows:

on day at the altitude of per cent
(1935)
2 9,500 feet 87 (80)
10-20 12,500 feet 76 (69)
28 14,200 feet 73 (77)
34 12,500 feet 86
vco, vO, Blood ~—- Heart Blood
Lactate Rate Pressure
m/min ml/min mg %
3580 3290 7
2760 2620 17
2190 2110 152 158/95
3520 3040 167
2440
2100
2340
2280 1960 80 148 175/95
1820 1740 134 172/90
1660 1380 118 170/90
1650 1530 116 170/100
1540 1530 35 115 170/85
1540 1470 28 120 190/100
1790 1730 43 120 175/88
2280 2070 135
2080 2010 142 162/75

Taste 2: Exercise tolerance at sea level and at altitude: Dill, summer of 1962: wt 72 kg;

ht 178 cm; age 71.

—2—