II. Correlation
of
Pulse Rate
with
Oxygen
Consumption
Gordon R. Cumming, M.D., F.R.C.P.(C), and R. Danzinger
Clinical Investigation Unit, the Children’s Hospital of Winnipeg, and the University of Manitoba
(Submitted December 18, 1962; accepted for publication February 19, 1963.)
Supported in part by the Manitoba Heart Foundation.
ADDRESS: (C.R.C.) Children’s Hospital of Winnipeg, 683 Bannatyne Avenue, Winnipeg 3.
PEDIATRICS, August 1963
T
HE PULSE RATE METHOD of determiningthe physical working capacity (P.W.C.)
of children has been discussed in a
previ-ous communication from this center1 and
by others. 2-4 Preliminary evidence
sug-gested that the physical working capacity
of Winnipeg children might be less than
that of children in other areas. The
possi-hility was raised that relative inactivity
over the long severe winter might account
for this decreased physical working
ca-pacity. To test this factor, P.W.C. was
de-termined in a group of children in the
sprii;g and again in the fall after the
summer vacation.
The validity of the pulse rate method in
determining working capacity is
depend-ent on a linear relationship between
oxy-gen consumption and pulse rate. In the
average adult the oxygen consumption at
a minute pulse rate of 170 is about 80%
of the maximum obtainable oxygen
con-sumption.5 This relationship has not been
fully studied in children.
METHODS
An attempt was made to study all
stu-dents from two grade 5 classes. All
stu-dents were 10 to 11 years of age. Subjects
were exercised on an electronically braked
bicycle ergometer6 for two successive
6-minute work periods, and the work load at
an anticipated minute pulse rate of 170
was determined by extrapolation. This
work load is defined as the P.W.C. Of
the 49 students initially studied in May,
1962, 41 were restudied in September. In
addition, 24 students were selected for
oxygen consumption studies. Cardiac rate
was followed by an electrocardiogram and
cardiotachometer during the exercise.
Utilizing the previous exercise studies, a
work load was selected to produce a
mm-ute pulse rate of 170, and after allowing 3
minutes for a steady state to be reached,
expired air was collected in weather
bal-loons over the next 2 minutes. Following
this, the work load was raised to a level
that previous studies indicated would
pro-duce a pulse rate in excess of 200 and
would constitute a maximal effort for each
subject in that it was a work load that
could not be sustained for more than a
few minutes. All subjects were able to
maintain the rate of pedalling between
60 and 70 revolutions per minute for all
tests. Expired air was collected from the
second to third minute of this work period.
Oxygen content of expired air was
de-termined by a Beckman oxygen analyzer.
CO2 content by a Beckman CO2 meter,
and gas volume by a gas meter.
RESULTS
The mean physical working capacities
of the children studied both in May and
September are indicated in Table I. Of the
19 boys studied, 5 showed no change, 7
showed an increase, and 7 showed a
de-crease in physical working capacity. There
is no signfficant difference between the
means of the working capacities obtained
in May and September.
Of the 22 girls studied, 4 showed no
change, 10 showed an increase, and 4 a
TABLE I
CoIIAIiIsoN OF PHYSICAL WORKING CAPACITY IN Sf’JIING AND FALL
Subjects Boys (;irh Numn- height ber (cm) 19 140 22 143 Weight (kg) 39.6 36.0 Surface (112) -1.14 1.20 P.JV.C. (kg u/mm)
______
May Sept. 411±135 396±118 336±68 348±60 Increase DecreaseNo (kg= .lf/mmiin) (kg if/mum)
(‘Image p--- j .\o. Average No. .4rerage
5 7 34 7 73
4 10 50 4 79
the boys, the means of the working ca- the male subjects a pulse rate of 180 was
pacities of the girls did not change sig- inadvertently reached. During the
maxi-nificantly. mal test the pulse rate was under 200 in
The oxygen consumption data are pre- only four subjects-three males and one
sented in Table II. The subjects are listed female. The highest rate recorded was 215
in order of decreasing working capacities beats per minute. These maximal pulse
as determined in the initial studies. The rates are comparal)le to the results obtained
pulse rate as recorded by the cardiota- by Astrand. The absolute oxygen
consump-chometer during the expired air collections tions in liters per minute are indicated for
is given for the submaximal and maximal each work load, and finally the oxygen
test. In most subjects it was possible to pulse ratio defined as the oxygen
consump-obtain a pulse rate of about 170 beats per tion divided by the pulse rate is given for
minute for the submaximal test. In two of each subject.
TABLE II
OXYGEN CoNSuMPTIoN DATA
Subject Surface Area (.%II) . P.J3’.C. (kg=M/ . main/if’
Submaximal Test Mazimal Test
2.0.
SIJBMAXIMAL WORK LOAD
GIRLS
MAXIMAL WORK LOAD
BOYS
x
1,
0 0
0
0
1 .4
0
0
C E
z
0
>-x
0
0
0
1.2
‘C
0
. 0
S
1.0’
S
S
S 0
.
0.8’
200 300 400 500 600 700 800
WORK LOAD (Kg M /min
Fic. 1. Oxygen consumption versus work load in all subjects. Pulse rates were 170 to 215. Values were obtained at submaximal and maximal work loads.
900
COMMENT
The lack of any improvement in P.\V.C.
over the summer months suggests that
climatic factors do not exert a major
influ-ence on this determination. Our findings
varied a little from those of Adams et al.,
who found that Swedish children with
lower working capacities tended to
im-prove doting the summer vacation. There
was no pattern to the changes observed
in working capacity over the summer
months in our subjects. Increases or
de-creases in working capacities were found
whether the initial value was above or
be-low average. Improvement in working
ca-pacity as measured by the pulse rate
method can easily be demonstrated after
mild exercise programs in sedentary
adults.s In the absence of a determined
effort at physical training, summer activity
would seem to be insufficient to improve
P.W.C. in normal children.
There is a wide variation in individual
working capacities in children. Some
chil-dren develop a marked tachycardia with
only small work loads and thus score very
low when pulse rate is used as the sole
cii-tenon of working capacity. However, the
validity of the pulse rate method in
de-termining working capacity was confirmed
by the oxygen consumption studies. A
linear relationship was found between
oxygen consumption and work load for all
subjects, even at the high pulse rates of
170 and 210 beats per minute. This
rela-tionship is shown in Figure 1 where the
oxygen consumption of all subjects is
plotted against the work load in
kilogram-meters per minute.
BOYS 0
GIRLS S 0
1 .6
1.5
. 1.4
-S-C E S-. 1.3
z 0
!
1.21.1
< 1.0
0.9
0
S 0 0.
S
S 0
0
S
500 600
A R
V U
0 100 200 300 400
WORKING CAPACITY (Kg M 1mm /M2
Fic. 2. Maximum oxygen consumption versus working capacity (work done
at a pulse rate of 170 beats per minute).
was usually constant from the second to
the sixth minutes of each exercise period,
and it was only when near maximal work
loads were reached that a rise of over 8
beats per minute was observed. This
con-stancy in pulse rate is taken to indicate
that a steady state has been reached, and
was one of the conditions laid down by
Wahlund5 in his original description of
the pulse rate method for the
determina-tion of working capacity. Oxygen
con-sumption during submaximal exercise
in-creases rapidly during the first minute to
reach a plateau by the end of the second
minute. This was shown to be so in large
numbers of children during treadmill
running by Cassels and slorse.#{176} During
maximal work loads there is a progressive
rise in pulse rate until the subject gives in
to the feeling of exhaustion.
Probably the best available measure of
the maximum working capacity of an
mdi-vidual is the maximum oxygen
consump-tion determination. In Figure 2 the
maxi-mum oxygen consumption is plotted
against the physical working capacity of
the subjects as determined by the pulse
rate method of selecting that work load at
a minute pulse rate of 170 as the working
capacity. Although there is a moderate
scatter in this graph, the P.W.C. appears
BOYS 0
GIRLS S a
4, -a
0 4,
C4
C E
0
(-.4
0
0
7i
6
5
4
3
‘1
0
consumption. Some of this scatter might
be due to the inaccuracy of determinations
of maximal oxygen consumption with
single tests.
Another index of physical fitness has
been the oxygen pulse ratio, namely the
oxygen (in milliliters) consumed per heart
beat. This ratio at a minute pulse rate of
170 is plotted against the working capacity
in Figure 3. A straight line relationship
exists between these two variables. Thus,
the P.W.C. determined by the pulse rate
method in children correlates well with
oxygen consumption data, either expressed
as maximal oxygen consumption, or
oxy-gen pulse ratio. Even at minute pulse rates
above 170, oxygen consumption is directly
related to work load. It would seem then
that the pulse rate method of determining
working capacity in children is a valid one,
and that the additional time involved in
measuring oxygen consumption does not
add a great deal of information.
8
It was of concern that individuals who
developed tachycardia so readily with mild
exertion might be able to do more
addi-tional work beyond that required to raise
the pulse rate to 170 compared to those
subjects whose pulse rates rise more
gradu-ally. If this were so, a submaximal work
test based on pulse rate would
underesti-mate the maximum working capacity of
the former subjects. One way of studying
this is to compare the oxygen
consump-tion values for the submaximal (pulse rate
170) and maximal work loads and relate
this comparison to the working capacity.
This has been done in Figure 4. At a
mm-ute pulse rate of 170 the subjects with the
lowest working capacities were taking up
70% or less of the maximal amount of
oxy-gen they were capable of, whereas most of
those with the higher working capacities
were consuming over 75% of their maximal
oxygen uptake when their pulse rates
reached 170 beats per minute. Thus,
sub-0 100 200 300 400 500 600
PHYSICAL WORKING CAPACITY (Kg M 1mm /M2)
S
0
0
S
BOYS 0
GIRLS #{149}
S
0
S S
0
0
0
90’
85’
C-.’
0
80’
75’
8 0 ::: 70’
0
:
65’ 2< S
(-4 55’ 0
50’
S 0
0
S 0
S
0
0
100 200
U U U I U
300 400
PHYSICAL WORKING CAPACITY
500
(Kg M 1mm /M2
600
Fic. 4. Oxygen consumption at a pulse rate of 170 beats per minute expressed as a ir cent of
maxi-mum oxygen consumption versus working capacity. Those with the higher working capacities are
con-siiming over 75% of their maximal oxygen consumption when their minute heart rates are about 170.
maximal work tests based on the pulse rate
method will slightly underestimate the
actual working capacity of the poorer
con-ditioned subjects. Also of note is the fact
that
the mean oxygen consumption at apulse rate of 170 was 73% of the maximal
oxygen consumption in our subjects
corn-pared to the value of 80% found by
Wah-lund5 in adult subjects.
SUMMARY
AND
CONCLUSIONS
The working capacities of children
tested on a bicycle ergometer in the spring
and again in the fall showed no significant differences. The pulse rate method of
de-termining working capacity in children has
been validated by additional oxygen
con-sumption studies. Oxygen consumption is
proportional to the work load even with
pulse rates from 170 to 215 beats per
min-ute. The physical working capacity as
de-termined by the pulse rate method shows
a direct relationship to maximal oxygen
consumption or oxygen pulse ratio. The
determination of oxygen consumption
would appear to offer no particular
ad-vantages, and physical working capacity
of children may be determined with
confi-dence
by
simply determining the pulserate at known work loads. The working
capacity of those in poor condition may be
slightly underestimated when pulse rate
methods are used.
REFERENCES
1. Cumming, C. R., and Cumming, P. M. :
Bi-cycle ergometer studies in children. Canad.
Mcd. Ass. J., 88:351, 196:3.
2. Adams, F. H., Linde, F. \I., and Miyoka, F!.:
The physical working capacity of normal
school children: I. California. PEDIATRICS,
28:55, 1961.
L. EMMETT HOLT,
Ja.,
M.D.of normal school children: II. Swedish City and Country. PEDIATRiCS, 28:243, 1961.
4. Bengtsson, E. : Studies on the Electrocardio-gram and Working Capacity in Healthy Subjects and Cases with Certain
Electro-cardiographic Abnormalities during Acute
Infectious Disease. Stockholm, P. E. Norstedt
and Sener, 1957.
5. Wahlund, H.: Determination of physical work-ing capacity. Acta Med. Scand., Suppl. 215, 1948.
6. Holmgren, A., and Mattson, K. H.: A new
ergometer with constant load at varying ped-aling rate. Scand. J. Clin. Lab. Invest., 6:
137, 1954.
7. Astrand, P. 0.: Experimental Studies of Phy-sical Working Capacity in Relation to Sex
and Age. Copenhagen; Ejnar Munksgaards
Forlag, 1952.
8. Waxman, W. IN. : Physical Fitness Develop-ments for Adults in the Y.M.C.A. Colloquium on Exercise and Fitness, Monticello, Illinois, 1959. Page 18:3, Athletic Institute.
9. Cassels, D. E., and Morse, M. :
Cardiopul-monary Data for Children and Young Adults.
Springfield, Thomas, 1962, pp. 52-65.
Acknowledgment
This study was made possible through the
co-operation of Mr. K. C. Vidruk, Director of
Phy-sical Education, Winnipeg School Division 1, and Mr. W. E. Saunders, Principal, and students, Weston Public School.
PHENYLKETONUBIA; edited by Frank L.
Ly-man; Springfield, Illinois; Charles C
Thomas, Publisher; 315 pp., 1963, $12.75.
The chapter headings of this book bespeak
its quality: Incidence and Inheritance, by
Eu-gene Knox; Biochemistry, by Marvin
Arm-strong; chapters on The Clinical Picture, the
Pathology and the Pathogenesis of the Mental Defect, by George Jervis; on the Detection,
Tests and Reagents, by Willard Centerwall,
Helen Berry, and L. I. Woolf; the
Manage-ment, by Horst Bickel and W. Gruter; a
chap-ter on Diets and Recipes, by Frank Lyman;
and, finally, The Experimental Approach, by
Harry Waisman. It is clear that the leading
authorities on the various aspects of the disease have been tapped and given space to tell their
story. An introductory chapter on the discovery of the disease by Siegried and Willard
Center-wall gives a charmingly written picture of
Asbj#{246}rnFolling-”the man who started it all.”
There are faults in this book. as in all books. The proofreading of the chapter on the patho-genesis of the mental defect leaves something to be desired. In discussing the alterations in
5-hydroxy tryptophan metabolism it is
con-fusing to read about the conversion of 5- hy-droxy phenylalanine to 5 hydroxy phenylacetic
acid (5 hydroxy tryptophan and 5 hydroxy
indolacetic acid are meant); 5 hydroxy
in-dolacetic acid is also referred to as 5 hydroxy acetic acid. The two chapters dealing with de-tection and tests fail to mention that essential histidinemia may cause confusion in diagnosis since imidazol pyruvic acid gives positive tests with both ferric chloride and phenystix paper. The defects are, however, few, and the
bibliog-raphy is extraordinarily complete-some 641
