Download Variations in Maximal Oxygen Intake with

Variations in Maximal Oxygen Intake with
Physical Activity in Middle-Aged Men
By JoHN R. MCDONOUGH, M.D., FuSAKo KusuMI, B.S.,
AND ROBERT A. BRUCE, M.D.
SUMMARY
Data
on
maximal exercise performance
are
presented for normal middle-aged
men
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free of cardiovascular disease. Maximal oxygen intake, oxygen pulse, heart rate, and
lactate levels all decrease with increasing age.
Physical activity defined by habitual running of any amount had a highly significant
effect on maximal oxygen consumption. The enhanced effect of physical activity was
found equivalent to nearly 10 years of age effect on maximal aerobic capacity.
Multivariate analysis revealed significant association between maximal oxygen intake
and several coronary risk factors; specifically, physical activity, vital capacity, cigarette
smoking, and body weight. Notably lacking in significance were other known risk
factors, serum cholesterol, and blood pressure.
Data for maximal oxygen intake on healthy men aged 40 to 70 years are presented
by age group and physical activity class; and regression equations are provided for
estimation of maximal oxygen intake from age, physical activity status, and duration of
the multistage treadmill test. These data should prove useful as normal standards for
assessment of aerobic capacity in middle-aged men until such time as larger numbers
of data on maximal exercise testing become available.
Additional Indexing Words:
Blood pressure
Age
Exercise
Coronary risk factors
Cholesterol
Vital capacity
uninterrupted submaximal and maximal exercise is utilized.13 The linear relationship
between duration of effort and oxygen intake,
under these testing conditions, varies in
healthy middle-aged men with age and
physical status. Accordingly, when these items
are known, maximal oxygen intake may be
estimated from observed duration of exertion.
Methods
Oxygen intake (Vo2) was measured during the
FUNCTIONAL aerobic capacity (power)
which is best defined by measurement of
maximal oxygen intake1 varies with body
weight, especially lean body mass," 2 physical
activity status, and aging.3-'2 Usually measurement of maximal oxygen intake requires two
or more tests of maximal exercise to demonstrate an asymptotic relationship between
intake and work load.' It is of interest,
therefore, to report that maximal oxygen
intake can be measured in a single testing
procedure, when a multistage treadmill test of
last 2 to 4 minutes of treadmill exercise on 86
healthy middle-aged men (84 Caucasians, one
Oriental, and one Negro) in the YMCA cohort.
Expired air samples were collected at 1-min
intervals in evacuated neoprene bags; volumes
were measured in a calibrated gasometer and
corrected to standard temperature and barometric
pressure. Oxygen and carbon dioxide concentrations in aliquots from each bag were measured
using micro-Scholander technic. The final minute
of gas collection during which maximal exercise
tolerance and highest oxygen intake were reached
From the Department of Medicine (Cardiology),
University of Washington, Seattle, Washington.
This study has been supported by Grants-In-Aid
HE-09773 from the National Heart and Lung Institute and HS-00092 from the National Center for
Health Services.
Received November 19, 1969; revision accepted for
publication December 29, 1969.
Csrculation, Volume XLI, May 1970
Cigarette smoking
Weight
743
McDONOUGH ET AL.
744
was used for maximal oxygen consumption (Vo2
max), whereas one to three samples immediately
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preceding at submaximal work loads defined the
approach to the maximal level. Fingertip blood
samples, under standardized conditions, were
obtained after exercise for measurement of lactate
concentration by the method of Strom.'4
Of 225 Seattle YMCA men who were recruited
as part of a cohort studied annually since
1962,15-18 150 were retested during 1968. Seven
were found with cardiovascular disease, and the
remaining 143 were clinically healthy. The 75
men in the cohort not tested during 1968
included 28 who had moved from the area, six
who died, 32 who refused the test, and nine for
whom testing was contraindicated. Follow-up of
health status was successful for all 225 men, and
details appear elsewhere.'9 Oxygen intake measurements were obtained on 86 of the 143 healthy
men. In the remaining 57, it was not feasible
because of technical and scheduling problems.
Physical activity levels for this group were
assessed by questionnaire which included recreational, occupational, and exercise participation at
the YMCA and were defined as follows: (1)
sedentary-no evidence of significant exercise
from occupational or recreational sources, and
nonparticipation in YMCA exercise, (2) lightparticipation in exercise activities such as weightlifting or calisthenics, but no regular running
exercises, (3) moderate-habitual runrning exercises (jogging, running, handball, squash, etc.)
equivalent to less than 3 miles/week, (4)
heavy-habitual running exercises in excess of 3
miles/week. Since all the men included in this
study were volunteers, the data obtained will not
necessarily be identical to data obtained in a
probability sample from the population at large.
Only eight of 86 men smoked cigarettes.
Results
Relationship of Oxygen Intake to
Duration of Multistage Exercise
The 225 measurements of Vo2 for the 86
healthy men have been plotted for the last 2
to 4 consecutive min of treadmill exercise
to define the relationships of oxygen intake to
duration of this particular multistage test.
Several aspects of the relationship are of
interest. First, despite stepwise increases in
the work load every 3 min the cardiovascular
oxygen transport response is virtually linear
during the 6 to 12-min range over which Vo2
was measured (table 1; fig. 1). Second, the
relationship is highly precise as seen by the
close proximity of the mean values to the
regression line, and by the narrow range of
Aerobic cost
multistage treadmill test
healthy men aged 40-69
(mean± 1 s. e.)
50 C
Table 1
Relationships of Oxygen Intake to Duration of
Multistage Treadmill Test*
40 ^
x
30
-
20
-
cm
Multistage test,
stage
(speed, grade)
II
(2.5 mph, 12%)
III
(3.4 mph, 14%)
IV
(4.2 mph, 10%)
V
t02
Min
N
6
7
8
9
10
11
12
13
(mI/kg X min)
Mean*
SE
6
24.5
0.50
15
43
58
59
33
9
1
27.7
31.5
33.7
37.2
42.2
44.2
47.2
0.45
0.31
0.36
0.46
0.52
0.93
E
00,,z
0
(5.0 mph, 18 %)
*
Of values observed, rather than from regression
equation.
10I °lleV
2
=
4.5+(min x 3.3)
1 2 3 4 5 6 7 8 9 10 11 12
treadmill exercise (min)
Figure 1
Aerobic cost of multiple treadmil test of healthy
men, aged 40 to 69 years (mean
SE). Regression
equation to estimate Vo2 from duration of maximally
tolerated exertion with this multistage test is: Estimated Vo2max (mi/kg X min) = 3.26 (min) + 6.14.
Coefficient of correlation, a, equals +0.85; P < 0.001.
Circulation, Volume XLU, May 1970
745
MAXIMAL 02 INTAKE WITH AGE AND ACTIVITY
Table 2
Maximal Aerobic Capacity for Normal Middle-Aged Men by Age Group
Duration of exercise
V02 max
(mI/kg X min)
Age group
(yr)
N
Mean
SD
40-44
45-49
50-54
55-59
60-64
65-69
10
24
20
19
9
3
40.5
38.4
37.5
4.7
5.3
5.3
36.2
32.6
27.7
2 SD
SD
31-50
28-49
27-48
10.3
10.2
9.8
1.1
1.1
1.3
8-12
8-12
7-12
5.7
25-48
9.3
1.6
6-12
4.7
4.2
23-42
8.7
7.5
1.6
3.0
5-12
2-10
x
2 SD
19-36
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coefficient of age and Vo2 max was r = 0.43,
and the regression equation for predicting V02
max from age for healthy males is Vo2 max
(ml/kg x min) = 55.8-0.41 (years of age)
for sedentary men. The corresponding regression equation for physically active men is
predicted: Vo2 max = 58.5-0.39 (years of
age).
From measured maximal heart rate (HR
max) and Vo2 max, maximal oxygen pulse
(02 pulse max) can be derived from the Fick
equation*; this represents the product of maximal stroke volume and peripheral oxygen
*Vo = HR x SV x AVo2.
VO2maxof healthy men
by age group
(mean ± 1 s. d.)
VO2 MaX
The healthy subjects studied spanned an
age of 40 to 69 years. Data were sufficient to
examine the effect of age on Vo2 max in 5-year
age groups from 40-44 through 65-69 years
(table 2; fig. 2). Mean Vo2 max decreased
linearly from 40.5 ml/kg x min for age group
40-44 years to 36.2 ml/kg x min for age group
55-59 years. This represents a loss of V02 max
of approximately 0.3 ml/kg x min for each
year of age during the 15 years spanned by
the min-intervals of these age groups. Beyond
age 60, the decline in V02 max appears to be
further accelerated with a mean of 27.7
ml/kg x min seen for the 65-69 year age
group, a mean annual decrease from 60 to 69
years of 0.8 ml/kg x min. The correlation
Circulation, Volume XLI, May 1970
X
Mean
the standard errors which were 0.3 to 0.5 ml/
kg x min for most means. Third, when the regression line is extrapolated to zero time,
the Vo2 approximates 6 ml/kg x min which is
similar to the metabolic rate of men at standing rest. Because energy costs of this test are
well defined, Vo2 max can be roughly
estimated with reasonable precision if duration of the test is known. The linear response
of Vo2 (to the nonlinear stepwise progression
of work loads every 3 min used in multistage
testing) allows the use of test duration as an
estimator of Vo2 max. For healthy men the
regression equation was found to be:
Vo2 max (ml/kg x min) = 3.26 (min) + 6.14
This equation is not preferred for the
estimation of oxygen intake at submaximal
work loads.
Effect of Age on
(min)
r
W
X 40-
.
'\
30
CN 20
0
10.
-A.
40
a
45
I
I
50
55
60
I
65
70
Age (years)
Figure 2
Vo2max of healthy men by age group (mean
+
1 SD).
746
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extraction (maximal arteriovenous oxygen
difference). From table 3 it can be seen that
both HR max and 02 pulse max parallel Vo2
max in showing a downward trend with advancing age. Whether the decrease of 02
pulse max with age represents diminished
stroke volume, oxygen extraction, or both,
cannot be determined from these data. Others
have shown slightly lower stroke volumes and
slightly higher arteriovenous oxygen differences in older compared to younger men at
equivalent levels of submaximal exercise.20
Physical Activity and Vo, max
The groups of sedentary, light, moderate,
and heavy physical exercise individuals previously described were analyzed for a series of
variables including age, body size, pulmonary
function, blood chemistry, and response to
exercise; and the data appear in table 4. The
only variables showing significant associations
were: age, with moderate and heavy groups
being somewhat older; resting heart rate, with
moderate and heavy groups averaging 8 to 9
beats/min slower; and test duration, Vo2 max
and 02 pulse max all showing higher values
in moderate and heavy as contrasted with
sedentary and light physical activity groups.
To assess the joint effect of age and physical
activity on these variables, 5-year ages were
combined to form three 10-year groups, and
sedentary was combined with light, while
moderate and heavy physical activity groups
were combined. Since this division into two
activity classes separates the runners from the
nonrunners, this appears to be a reasonable
cut-point for a 3 by 2 table analysis.
Data on various parameters of oxygen
transport appear in tables 5 and 6. Large and
highly significant differences in Vo2 max and
02 pulse max are seen at every age when
contrasting sedentary with physically active
groups. HR max was significantly lower
(P < 0.001.) for active men aged 40 to 49, but
differences were not significant between sedentary and active men at the older ages.
Lactate levels immediately following exercise
did not differ significantly between groups,
except for the anticipated fall in both active
and sedentary men with advancing age. The
McDONOUGH ET AL.
magnitude of the differences in Vo2 max and
02 pulse max can be seen from the age trends.
Although age trends are parallel, the heavy
activity group consisting of runners has
approximately a 10-year advantage in Vo2 and
a 20-year advantage in 02 pulse max over the
light activity group composed of nonrunners
of similar ages.
Multivariate Analysis
Stepwise multiple regression analysis was
done using Vo2 max as a dependent variable
and the factors listed in table 4 as independent variables. Test duration was found to
have the highest individual correlation with
V02 max (r =0.85), while inclusion of the
other variables raised the multiple regression
coefficient to r = 0.88.
Because of its overwhelming influence on
the other variables, test duration was removed
and the analysis repeated. The multiple r was
0.80 for 18 variables, of which the first six
provided a multiple r of 0.73. In decreasing
order of their influence on Vo2 max these
variables were lactate level, physical activity,
age, vital capacity, cigarette smoking, and
body weight (table 7).. It should be noted that
both age and smoking were inversely related,
with negative rather than positive coefficients.
Thus younger nonsmokers had higher V02
max values than older smokers.
Discussion
Maximal oxygen intake has recently been
proposed as a standard for cardiovascular
fitness.21 Its importance is based on the fact
that it defines in otherwise healthy and
motivated subjects maximal performance for
cardiovascular transport capacity in terms of
the maximal cardiac output and maximal
whole body arteriovenous oxygen difference
(which encompasses maximal distribution of
blood flow to working muscle and maximal
oxygen extraction).22 Since approximately 85%
of arterial oxygen content is extracted during
maximal exercise, and since oxygen extraction
is nearly complete in blood delivered to
strenuously exercising muscle, the rate limiting
factor in Vo2 max is the cardiac output.23
Aging diminishes Vo2 max by decreasing
Circulation, Volume XLI, May 1970
MAXIMAL 02 INTAKE WITH AGE AND ACTIVITY
7477
Table 3
Maximal Heart Rate and Oxygen Pulse for Normal Middle-Aged Men by Age Group
HR max
(beat/min)
Age
group
(yr)
N
Mean
SD
40-44
45-49
50-54
55-59
60-64
65-69
10
24
20
19
9
3
184
178
171
175
165
150
9.6
12.2
9.3
12.6
14.9
6.8
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maximal cardiac output, and this effect seems
to be partly due to a decreased maximal heart
rate.24' 25 Measurement of '02 max has been
shown to be a precise, reliable, and useful
method for assessing impairment in functional
capacity or reserve resulting from cardiac
disease.1' 13 Irrespective of the lesion (outflow
obstruction, regurgitant flow, impaired myocardial contractility, decreased ventricular
distensibility, etc.), the common denominator
for all lesions producing cardiac impairment is
reduced maximal forward cardiac output.26' 27
In the absence of changes in maximal A-Vo2
difference, this impairment is readily quantified by measurement of Vo2 max during the
multistage maximal treadmill test.2"2
To assess cardiovascular performance in
terms of fitness or its complement, impair-
Xi4 2 SD
165-203
154-202
152-190
150-200
135-195
136-164
02 pulse max
(ml 02/kg X min X beat)
Mean
SD
2 SD
0.22
0.22
0.21
0.20
0.20
0.18
0.02
0.03
0.04
0.03
0.02
0.02
0.18-0.26
0.16-0.28
0.13-0.29
0.14-0.26
0.16-0.24
0.14-0.22
groups exceeded their sedentary comparison
groups of similar age. Thus, if one knows the
age and whether a subject habitually engages
in running exercises, and if the subjects are
then tested to maximal using duration of the
multistage treadmill test or by measuring V02
on any test of maximal capacity, individual
performance can be compared to normal men
of the same age and activity status by
referring to the data in tables 2 and 5. By
using the data or the regression equation
which appears at the bottom of these tables a
predicted Vo2 max can be determined for a
given subject. Using this value as a denominator, and the measured (or estimated from test
duration) Vo2 max as a numerator, individual
performance can be derived as a percentage
of average normal capacity, as follows:
- Observed Vo2 max
x 100.
% Average normal V02 max - Pred ed Vo2 maxf
Predicted V02 max for age
ment, two major influences on Vo2 max,
namely, age and habitual physical activity
level, should be considered. In the present
study a simple classification was found to
discriminate adequately. This was whether the
individual engaged routinely in running,
either as jogging, or in sports activity such as
tennis, handball, squash, etc. The fact that the
individual engaged in running appeared more
important as a discriminator than the amount
of running. This is shown in the analysis of
Vo2 max levels comparing men who ran less
than 3 miles/week with those who ran more
than that amount. Both groups were found to
have similar levels of Vo2 max, and both
Csrculation, Volume XLI, May 1970
This expression relates individual performance
to a normative standard for the appropriate
peer group. When oxygen intake is not
measured, a reasonable estimate may be
derived from the duration of maximal exercise
with this multistage exercise test. Examples of
this derivation are shown in table 8.
The results of the multivariate analysis were
of interest in identifying the noncardiovascular variables which bear a relationship to (o2
max in order of importance and after removing the correlation between independent
variables by covariance analysis. The important variables aside from serum lactate, which
is known to reflect the intensity of exercise, are
McDONOUGH ET AL.
748
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MAXIMAL 02 INTAKE WITH AGE AND ACTIVITY
749
Table 5
Maximal Aerobic Capacity for Normal Middle-Aged Men by Age and Physical Activity*
V02 max (ml/kg X min)t
Active
Sedentary
Age group
(yr)
N
Mean
SD
N
Mean
SD
Mean differencet
40-49
50-59
60-69
15
7
5
36.8
33.1
29.4
5.4
5.8
5.0
19
32
7
40.9
37.6
32.9
4.3
5.1
4.0
4.1
4.5
3.5
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* Sedentary-nonrunners; active runners (jogging, tennis, handball, basketball, squash,
etc. regardless of amount).
tRegression equations to estimate Vo2 max from age:
V02 max (ml/kg X min) according to physical activity status
58.3-0.39 (age in yr)
Active =
Sedentary = 55.8-0.41 (age in yr)
(active vs. sedentary: P < 0.001).
t Significance of the difference between active and sedentary for the entire group is P < 0.001.
Table 6
Maximal Heart Rate, Oxygen Pulse, and Lactate for Normal Middle-Aged Men by Age and
Physical Activities *
02 pulse max
(ml O2'/kg X. min X beat)
SD
Mean
(yr)
N
HR max
(beats/min)
SD
Mean
Sedentary
40-49
50-59
60-69
Active
15
7
5
185 9.3
180 14.3
174
0.20
0.18
0.18
40-49
50-59
60-69
19
32
7
176 11.6
171 7.1
164 11.0
0.23
0.21
0.20
Age group
Mean
SD
0.03
0.03
0.02
105
100
56
33
58
20
0.02
0.04
0.02
94
91
67
21
20
33
* Contrasts between sedentary and active men for: HR max P < 0.001 for ages
for ages 50-54 and 60-69; 02 pulse max P < 0.001; lactate, P NS
physical activity, age, vital capacity, cigarette
smoking, and body weight. All of these
variables (except lactate which has not been
studied) have been shown to have a significant association with coronary heart disease
incidence in prospective studies.33 Whether
Vo2 max is a predictor of coronary disease risk
is an intriguing question and remains unanswered, principally because data have not
been collected on a large enough population
followed for an adequate number of years.
Acknowledgment
The authors wish to acknowledge with gratitude
the assistance of the following persons: Mrs. Gladys
Pettet, Research ECG Technician, and Mrs. Myrella
Circulation, Volume XLI, May 1970
Lactate
(mg/100 ml)
40-49, NS
Beyer, Data Processing Technician, Division of
Cardiology, University of Washington School of
Medicine; Mr. Belvin Doane and Mr. Gaylon Kipp,
Staff members, Seattle YMCA; physicians previously
connected with the follow-up evaluation of this
cohort: Drs. Allen Doan, Albert Most, John Mazzarella, and Tom Homsten; and especially the subjects
themselves who so willingly gave of their time and of
themselves.
References
1. TAYLOR HL, BusiRK E, HENSCHEL A: Maximal
oxygen intake as an objective measure of
cardio-respiratory performance. J Appl Physiol
8: 73, 1955
2. BusxnIR E, TAYLOR HL: Maximal oxygen intake
and its relation to body composition, with
McDONOUGH ET AL.
750
Table 7
Maximal Oxygen Intake Stepwise Multiple Regression Analysis*
Independent variable
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r
F
Coefficient
Lactate (mg/lOO ml)
Physical activity (sed., It., mod., heavy)
Age (yr)
Vital capacity (L)
Cig. smoking (never, quit, current sm)
0.541
0.605
0.655
0.688
0.715
23.4
6.7
6.3
5.9
3.9
0.56
2.18
-0.12
3.86
-0.94
Body weight (kg)
HR max (B/min)
Diastolic BP max (mm Hg)
Height (cm)
Systolic BP max (mm Hg)
Serum K (mEq/L)
HR rest (B/min)
Systolic BP rest (mm Hg)
Hct (vol %)
Diastolic BP rest (mm Hg)
Heart vol (cc)
Serum cholesterol (mg/100 ml)
FEV1 (L)
0.734
0.747
0.759
0.770
0.778
0.785
0.790
0.794
0.795
0.795
0.796
0.796
0.797
2.6
2.4
2.1
2.1
1.4
1.4
1.0
0.7
0.1
0.1
0.1
0.1
0.1
-0.14
0.06
0.09
-0.25
0.06
-1.66
0.07
-0.04
-0.10
*
3.
4.
5.
6.
7.
8.
0.02
-0.001
0.004
-0.31
When test duration is not included as a variable
special reference to chronic physical activity
and obesity. J Appl Physiol 11: 72, 1957
RORINSON S: Experimental studies of physical
fitness in relation to age. Arbeitsphysiologie
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DILL DB, CONSOLAZIO CF: Responses to exercise
as related to age and environmental temperature. J Appl Physiol 17: 645, 1962
ANDERSON KL, HERMANSEN L: Aerobic work
capacity in middle-aged Norwegian men. J
Appl Physiol 20: 432, 1964
AsTRAND I: Aerobic work capacity in men and
women with special reference to age. Acta
Physiol Scand 49 (suppl. 169): 14, 1960
SALTIN B, AsTRAND PO: Maximal oxygen uptake
in athletes. J Appl Physiol 23: 353, 1967
RoBINsON S, HARMON PM: Effects of training
and of gelatin upon certain factors which limit
muscular work. Amer J Physiol 133: 161,
1941
9. KHEHi CA, DmIL DB, NEUFELD W: Training and
its effects on man at rest and at work. Amer J
Physiol 136: 148,,1942
10. ROWELL LB: Factors affecting the prediction of
the maximal oxygen intake from measurements
made during submaximal work. Ph.D. Thesis,
University of Minnesota, 1962
11. NAUGHrON V, NAGLE F: Peak oxygen intake
during physical fitness program for middleaged men. JAMA 191: 103, 1965
12. SALITIN B, BLOMQvISr G, MITCHELL JH, ET AL:
Responses to exercise after bed rest and after
13.
14.
15.
16.
17.
training. Circulation 37 (suppl VII): VII-1,
1968
BRUCE RA, KusuMI F: Aerobic costs of
multistage treadmill test. Unpublished observations, 1970
STR6M G: The influence of anoxia on lactic and
utilization in man after prolonged muscular
work. Acta Physiol Scand 17: 440, 1949
DoAN AE, PETERSON DR, BLACKMON JR, ET AL:
Myocardial ischemia after maximal exercise in
healthy men. Amer Heart J 69: 11, 1965
DOAN AE, PETERSON DR, BLACKMON JR, ET AL:
Myocardial ischemia after maximal exercise in
healthy men. Amer J Cardiol 17: 9, 1966
BRUCE RA: Comparative prevalence of segmental
ST depression after maximal exercise in healthy
men in Seattle and Taipei: Physical Activity
and the Heart. In Proceedings of a Symposium,
Table 8
Example of Clinical Appraisal by Estimated TVO2
Max for a 50-year-old male, weighing 80 kg, when
predicted 1702 max = 38 ml/kg X min or
3.04 L/min
Observed
duration
(min)
8.5
10.0
11.5
Estimated Vo2 max
ml/kg X min L/min
33.9
38.7
43.6
2.71
3.10
3.79
Estimated
Predicted
(%)
89
102
124
Circulatioe, Volume XLI, May 1970
MAXIMAL 02 INTAKE WITH AGE AND ACTIVITY
Helsinki, Finland, edited by MJ Karvonen, AJ
Barry. Springfield, Illinois, Charles C Thomas,
Publisher, 1967, p 326
18. MOST MD, HORNSTEN TR, HOFER V, ET AL:
Exercise ST changes in healthy men. Arch
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Intern Med (Chicago) 121: 225, 1968
19. MCDONOUGH JR, BRUCE RA: Earlier detection of
coronary heart disease: Appraisal of 1125 man
years of ECG observation by periodic maximal
exercise testing of healthy middle-aged men.
Unpublished data
20. BEVEGARD BS, SHEPHERD JT: Regulation of the
circulation during exercise in man. Physiol Rev
47: 178, 1967
21. SHFEPHARD RJ, ALLEN C, BENADE AJS, ET AL: The
maximum oxygen intake: An international
standard of cardiorespiratory fitness. Bull
WHO 38: 757, 1968
22. MITCHELL JH, SPROULE BJ, CHAPMAN CB: The
physiological meaning of the maximal oxygen
intake test. J Clin Invest 37: 538, 1958
23. ASTRAND PO, CUDDY TE, SALTIN B, ET AL:
Cardiac output during submaximal work. J
Appl Physiol 19: 268, 1964
24. AsTRAND I, ASTRAND PO, RODAHL K: Maximal
heart rate during work in older men. J Appl
Physiol 14: 562, 1959
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25. HANSEN JS, TABAKIN BS, LEvY AM: Comparative exercise-cardiorespiratory performance of
normal men in the third, fourth, and fifth
decades of life. Circulation 37: 345, 1968
26. BLACKMON JR, ROWELL LB, KENNEDY JW, ET
AL: Physiological significance of maximal
oxygen intake in "pure" mitral stenosis. Circulation 36: 497, 1967
27. BRUCE RA: The role of exercise in cardiovascular
diagnosis. Extract from Symposia of the
International Congress of Cardiology, 1966,
pp 448-459
28. BRUCE RA: Evaluation of functional capacity in
patients with cardiovascular disease. Geriatrics
12: 317, 1957
29. BRUCE RA, JOHNSON W: Exercise tolerance in
pregnant cardiac patients. Clin Obstet Gynec
4: 665, 1961
30. BRUCE RA, BLACKMON JR, JONES JW, ET AL:
Exercise testing in adult normal subjects and
cardiac patients. Pediatrics 32: 742, 1963
31. BRUCE RA, HORNSTEN TR: Exercise stress testing
in evaluation of patients with ischemic heart
disease. Progr Cardiovasc Dis 11: 371, 1969
32. BRUCE RA, McDONOUGH JR: Coronary disease
and exercise. Texas Med 65: 73, 1969
33. STAMLER J: Lectures on Preventive Cardiology.
New York, Grune & Stratton, Inc., 1967
752
AMERICAN HEART ASSOCIATION
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Minuscule Review
Symposium on Physiological and Clinical Aspects of Cardiac Rehabilitation.
Cagliari, Sardinia, June 1968.
Mallatie Cardiovascolari 10: nos. 1 and 2, 1969.
A 1968 symposium, sponsored by the Council for Rehabilitation of the International
Society of Cardiology and Cagliari University in Sardinia, attempted to review the physiologic, clinical, psychologic, and social aspects of rehabilitation in cardiovascular
diseases. This initiative, by distinguished practicing cardiologists and researchers,
points up the important integration under way between the discipline of traditional
diagnostic and therapeutic medicine, and those of preventive, rehabilitative, and social
medicine. The volume contains much information of interest to the physician in
practice in readable, short presentations. As in the case of most symposia, their
quality is not uniform.
Considerable attention is given to stress testing including concepts and information about the freedom from rigid testing constraints now possible by the use of more
"equivalent" physiologic stresses relating to maximal work capacity or to target
heart rates, the relatively good repeatability of progressive stress tests, a large experience of maximal tests in post-infarction patients, and the advantages of beat-tobeat cardiac monitoring during stress tests. Method and procedure are discussed
including telemetry and extended monitoring of heart rate and blood pressure
during stress tests and during daily activities.
A phenomenon that most have observed, the delayed ischemic response occurring
during recovery, is explored and partly explained by findings on indirect estimations
of cardiac work during recovery.
Evidence is presented that the exercise ECG response in post-infarction patients
is predictive of subsequent risk of reinfarction. The characteristics, advantages, and
disadvantages of different types and modes of exercise testing are well reviewed.
Among the problems discussed are those relating brachial artery pressure measured
during work to a tension-time index (cardiac work and myocardial oxygen consumption). Evidence is presented that peripheral blood pressure measurement overestimates the work load of the ventricles during exercise.
Exercise studies in hypertensive subjects revealed higher work blood pressures and
vascular resistance with normal cardiac output. Exercise studies in coronary patients
revealed normal hemodynamic responses when they remained "within the limits of
their work capacity." Inappropriate hemodynamic responses to work are described
in some cardiac patients.
Heart volume during work and its changes as a result of conditioning are discussed, as well as variations of total hemoglobin which are found to relate to age,
to physical restriction, and to hypoxia, but not otherwise to the type or severity of
chronic cardiopulmonary diseases.
Evidence is given of the remarkable pressure load imposed on the heart by static
work and its potential danger to the cardiac patient.
The response to physical conditioning is found to depend on the initial level of
fitness in relation to one's potential, expressed as the expected "normal level" for
age. Potential for conditioning is very low at advanced ages.
Some of the experience is recounted of formal, ongoing conditioning programs
among cardiac patients, in the U. S. and in Europe.
HENRY BLACKBURN
Circulation, Volume XLI, May 1970
Variations in Maximal Oxygen Intake with Physical Activity in Middle-Aged Men
JOHN R. MCDONOUGH, FUSAKO KUSUMI and ROBERT A. BRUCE
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Circulation. 1970;41:743-752
doi: 10.1161/01.CIR.41.5.743
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