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An investigation of oxygen-pulse time course as a measure of cardiorespiratory adaptation to exercise

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An investigation of oxygen-pulse time course as a measure of cardiorespiratory adaptation to exercise

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Content AN INVESTIGATION OF OXYGEN-PULSE TIME COURSE
AS A MEASURE OF CARDIORESPIRATORY ADAPTATION TO EXERCISE
by
Robert Allen Wiswell
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(Physical Education)
July 1975
UNIVERSITY OF SOUTHERN CALIFORNIA
THE GRADUATE SCHOOL
UNIVERSITY PARK
LOS ANGELES, CALIFORNIA 90007
This dissertation, written by
Robert Allen Wiswell
.
under the direction of h_'!-..~--- Dissertation Com
mittee, and app1·oved by all its members, has
been presented to and accepted by The Graduate
School, in partial fulfilhnent of requirements of
the degree of
DOCTOR OF PHILOSOPHY
~~~
·---------------------------------------------------z=------------------------
Dean
Date ___ _
1-- __ /_J __ J ____ --·---------
DISSERTATIO ~O IMITTEE
-
I c/ :c _ l~
--~ ---------------- ;_i;. ~------ _LJ._ -_r=~~---
/ h ~
------------·---- ----------
TABLE OF CONTENTS
LIST OF ILLUSTRATIONS .
• •
. . . . . . . . . . .
LIST OF TABLES
LIST OF FIGURES
Chapter
. . . . . . . . . . . . . . . . . . .
. .
• •
. . . . . . . . . . .
1.
2.
3.
INTRODUCTION . . . . . . . . . .
• • • • • • •
Statement of the Problem . . . . . . . . .
Significance of the Study . . . . . . . . .
Definition of Terms
• • • • • • • •
. .
• •
Oxygen pulse (V02/HR)
Oxygen-pulse peaker
. . . . . . . . .
. . . . . . . . . .
Oxygen-pulse non-peaker . . . . . . . .
.
VE/R ratio .
• •
. . . . . . . . . . . .
Delimitations ..
• •
. . . . . . . . . . .
REVIEW OF THE LITERATURE .
• • • •
. . .
Circulo-respiratory Adjustment
Significance of Oxygen Pulse
• • • • • •
. . . . . . .
Prediction of Maximal Oxygen Consumption
•
Comparison of Bicycle Ergometer to
Treadmill Data ......... .
• • •
PROCEDURE
Subjects
. . . . . . . . . . . . . . . . . .
• • • • • • • • • • • • • • • • •
Experimental Design.
• • • • • • • • • • •
V
V
vi
1
3
4
5
6
6
6
6
6
8
8
12
17
22
26
26
27
ll
Chapter
4.
5.
6.
Instrumentation
• • • • • • • • • • • • •
Respiratory gas analyzer
• • • • • • •
Treadmill . . . . .
• • • • • • • • • •
Bicycle ergometer.
• • • • • • • • • •
Electrocardiographic monitoring
sys tern . . . . . . . . . . . .
• • •
Protocol . . . . . . . . . . . . . . . . .
Data Reduction
• • • • • • • • •
. . .
• •
RESULTS
• • • • •
. .
• • • • • •
. . . .
• •
Description of Subjects
• • • • • • • • •
Time Course of Oxygen Pulse . . . . . . .
27
28
33
33
34
34
37
41
41
43
Comparison of Bicycle and Treadmill Data . 46
Effects of Fitness on the Time Course
of Oxygen Pulse ......... .
• •
70
Prediction of Maximal Oxygen Consumption . 72
Discrimination of Peaking and Non-peaking
Groups . . . . . . . . . . . . . . . . 8 5
DISCUSSION
• • • • • • • • • • • • • • • • •
90
Oxygen-pulse Time Course as Affected by Ex
ercise Modality and Level of Fitness . 90
Prediction of Maximal Oxygen Consumption . 92
Physiological Explanation of Group Discri
mination Relationships . . . . . . . . 94
Validity and Practicality of the Balke
Hypothesis of "Optimal Work Capacity" . 100
SUMMARY, FINDINGS, CONCLUSIONS, AND
RECOMMENDATIONS ....... . . . .
• •
Summary
• • • • • • • • • • • • • • • • •
103
103
lll
Chapter
• • • • • • • • • • • • • • •
Findings . .
Conclusions
• • • • • • • • • • • • • • •
Recommendations
• • • • • • • • • • • • •
BIBLIOGRAPHY .....
• •
. . . . . . . . . .
• • •
104
105
106
108
.
lV
LIST OF ILLUSTRATIONS
1. Treadmill . . . . . . . . . . . . . . . . . . .
2. Bicycle Ergometer . . . . . . . . . . . . . . .
LIST OF TABLES
1. Description of Subjects
• • • • • • • • • • • •
2. Percentage of Maximal Heart Rate and Maximal
Oxygen Consumption at which Oxygen
31
32
42
Pulse Peaked . . . . . . . . . . . . . . . . 44
3.
4.
5.
Differences Between Group 1 (Peakers) and
Group 2 (Non-peakers) at Maximal
Oxygen Consumption ......... .
• • •
Differences Between the Treadmill and Bicycle
Ergometer at Maximal Oxygen Consumption.
• •
Means and Standard Deviations of High-fit
and Low-fit Subjects on the Treadmill
and Bicycle Ergometer ........ .
• • •
6. Prediction of Maximal Oxygen Consumption from
Subrnaximal V02 Using Steady-state Data from
a Bicycle Ergometer and Continuous Exercise
47
60
71
Data from a Treadmill. . . . . . . . . . . . 77
7. Prediction of Maximal Oxygen Consumption from
Submaximal Oxygen Pulse Using Steady-state
Data from a Bicycle Ergometer and
Continuous Exercise Data from a Treadmill . . 78
8. Relationship of Maximal and Submaximal Exercise
Variables at 50, 100, and 150 Watts to
Maximal Oxygen Consumption . . . . . . . . . 79
9.
10.
Comparison of Observed Versus Predicted
Maximal Oxygen Consumption from Steady
state Data on the Bicycle Ergometer ...
• •
Prediction Accuracy . . . . . . . . . . . . . .
84
86
V
11. Prediction Accuracy . . . . . . . . . . . . .
LIST OF FIGURES
1. Relationship of Oxygen Consumption to Heart
Rate (02 Pulse) in Treadmill
88
Non-peakers (n = 12) . . . . . . . . . . . 48
2. Relationship of Oxygen Consumption to Heart
Rate (02 Pulse) on Treadmill
Peakers (n = 18) . . . . . . . . . . . . . 49
3. Relationship of Oxygen Consumption to Heart
4 •
5.
6.
7 .
8.
9.
10.
11.
12.
Rate (02 Pulse) on Bicycle
Non-peakers (n = 17). . . . . . . . . . . . 50
Relationship of Oxygen Consumption to Heart
Rate (O2 Pulse) in Bicycle
Peakers (n = 13) .......... .
Oxygen Pulse Time Course in Treadmill
. .
Non-peakers (n = 12) ....... .
• • •
Oxygen Pulse Time Course in Treadmill
Peakers (n = 18) ....... .
• • • • •
Oxygen Pulse Time Course in Bicycle
Non-peakers (n = 17) .....
• •
. . .
Oxygen Pulse Time Course in Bicycle
Peakers (n = 13) . . . . . . . . . . . . .
Relationship of Percentage of Maximal Oxygen
Pulse to Percentage of Maximal Work
Load on Bicycle and Treadmill (n = 30)
• •
Relationship of Percentage of Maximal Oxygen
Pulse to Percentage of Maximal Work
Load in Treadmill Peakers and
Non-peakers (n = 30) .......... .
Relationship of Percentage of Maximal Oxygen
Pulse to Percentage of Maximal Work
Load in Bicycle Peakers and
Non-peaker s ( n = 3 0) • • • • • • • • • • •
Differences in Maximal Oxygen Consumption
and Maximal Heart Rate Between Bicycle
and Treadmill (n = 30) ....... .
• •
51
52
53
54
55
56
57
58
61
.
Vl
13. Differences in Maximal Oxygen Consumption
and Maximal Heart Rate Between Bicycle
and Treadmill (n - 30) ....... .
14. Differences in Maximal Ventilation and
Maximal Respiratory Exchange Ratio
Between Bicycle and Treadmill (n - 30)
15. Differences in Maximal Ventilation and
Maximal Respiratory Exchange Ratio
Between Bicycle and Treadmill (n - 30)
. .
• •
• •
16. Differences in Maximal Oxygen Pulse and Maxi
mal Ventilatory Equivalent for Oxygen
61
62
62
Between Bicycle and Treadmill (n - 30). . . 63
17. Differences in Maximal Oxygen Pulse and Maxi-
mal Ventilatory Equivalent for Oxygen
Between Bicycle and Treadmill (n - 30). . . 63
18. Relationship of HR, vo
2
, and VE to Time on
the Bicycle ............. . . .
19. Relationship of VE/V02, 02 Pulse, and RER
to Time on the Bicycle ....... .
• •
20.
• • • •
Relationship of HR, VO2, and VE to Time on
the Treadmill ............ . . .
21. Relationship of VE/V02, o
2
Pulse, and RER
to Time on the Treadmill ...... . . .
22. The Percentage of Maximal HR, VE, R, V02, and
02 Pulse as a Function of Percentage of
64
65
66
67
Maximal Work Load on the Bicycle (n - 30) . 68
.
23. The Percentage of Maximal HR, VE, R, VO2, and
O2 Pulse as a Function of Percentage of
Maximal Work Load on the Treadmill
(n - 30) . . . . . . . . . . . . . . . . . 69
24.
25.
Treadmill Low-fit Group (n - 7)
Treadmill High-fit Group (n - 7)
• • • • • • •
. . . . . . .
26. Bicycle Low-fit Group (n - 7)
• • • • • • • •
27.
28.
Bicycle High-fit Group (n - 7)
• • • • • • • •
Observed Versus Predicted Maximal Oxygen
Consumption Using the Fifth Minute of
Steady-state Bicycle Data at 50 Watts . . .
73
74
75
76
8
vii
29. Observed Versus Predicted Maximal Oxygen
Consumption Using the Fifth Minute of
Steady-state Bicycle Data at 100 Watts
30. Observed Versus Predicted Maximal Oxygen
Consumption Using the Fifth Minute of
Steady-state Bicycle Data at 150 Watts
• •
• •
81
82
...
Vlll
Chapter 1
INTRODUCTION
Individuals involved in physical conditioning programs
are interested in (a) how intense the exercise should be
and (b) how improvement can be assessed. These questions
have been the impetus for and have given direction to many
investigations in exercise physiology. The answers are not
as well delineated at this time as the questions. It
.
lS
known, for example, that exertion accelerates aerobic meta
bolism, and an oxygen demand is created. Furthermore, it
has been suggested that an individual's capacity for work
is limited by the combined ability of the respiratory and
cardiovascular systems to meet the increased oxygen demand
of the muscles. Therefore, it can be assumed that the
answer to the question of intensity and improvement in
exercise should be evaluated based upon an accurate ap
praisal of changes in and limitations of these two func
tional systems.
An assessment of cardiorespiratory function can be
made at rest but generally speaking is more definitive when
appraised under exertion stress. Higher levels of stress
up to maximal exertion seemingly allow a more reliable,
valid measurement of the adaptive capacities of an
1
individual. This capacity may be measured either inva-
sively or non-invasively. Invasive measurements require
catheterization and may yield information about oxygen
saturation in the blood, arterial pressures, cardiac out
put, and other measures which directly relate to the circu
latory adjustment to stress. Non-invasive measures, such
as maximal oxygen consumption, blood pressure, and the
exercise electrocardiogram, assess cardiorespiratory capac
ity indirectly and appear to correlate highly with invasive
techniques.
Of the non-invasive measures, maximal oxygen consump
tion is regarded by exercise physiologists as the best
single measurement of physical working capacity and, there-
0
fore, of cardiorespiratory capacity (Astrand, 1952;
Mitchell, Sproule, and Chapman, 1958; Taylor, Wang, Rowell,
and Blomqvist, 1963). Maximal oxygen consumption is highly
related to maximal cardiac output and is an excellent dis
criminatory measure of an individual's prior exercise his-
0
tory (Astrand and Rodahl, 1970). As a test, however, it
has several major, practical limitations which one must
consider before administering such a test. For example, it
is an exhaustive test which requires high levels of motiva
tion on the part of the subject. Furthermore, in order to
obtain a valid and reliable measurement, it may have to
be repeated several times on separate days. The test may
also invoke an overwhelming demand on a pathologically
2
compromised myocardium and is , therefore, not feasible for
appraising working capacity in diseased or older indivi
duals .
With these major drawbacks in mind, many attempts have
been made to appraise physical working capacity by means of
0
submaxirnal exercise tests (Astrand and Rhyming, 1954 ;
Issekutz, Birkhead, and Rodahl, 1962; Wyndham, 1967); how
ever, while these tests are reasonably predictive, they may
on occasion seriously underestimate or overestimate an indi
vidual's maximal exercise tolerance.
A reasonable alternative to prediction of maximal oxy
gen consumption from submaximal work loads would be to find
another measure of working capacity independent of maximal
oxygen consumption which does not involve maximal exertion.
Consequently, the search for such a parameter constitutes a
valuable research endeavor.
Balke (1954) suggested that maximal oxygen pulse, the
quantity of oxygen utilized by an individual for each heart
beat, may provide as much information about cardiorespira
tory performance as maximal oxygen consumption but at lower
heart rates and lesser work loads. Balke's hypothesis was
based upon the observation that oxygen pulse reached a peak
value before maximal oxygen consumption or maximum heart
rates were reached.
Statement of the Problem
Generally , the purpose of this paper was to investigate
3
the feasibility of using maximal oxygen pulse as an assess
ment of cardiorespiratory adaptation to stress. More
specifically, the purposes of this paper were to:
1. Test the hypothesis proposed by Balke that oxygen
pulse reaches a maximum before maximal oxygen consumption
by observing the time course of oxygen pulse throughout
maximal exercise stress.
2. Compare the bicycle ergorneter and treadmill in
regard to the elicited oxygen-pulse time course as well as
to the maximal oxygen consumption and heart rate.
3. Determine the effect of an individual's level of
condition on the oxygen-pulse progression.
4. Evaluate the use of oxygen pulse and oxygen con
sumption at steady-state submaximal levels to predict maxi
mal oxygen consumption.
5. Discern those physiologic variables which might
predispose an individual to reach a peak oxygen pulse if,
in fact, such a phenomenon were observed at submaximal
levels of exercise.
Significance of the Study
The appraisal of circulatory mechanics during exertion
yields much pertinent information about positive effects of
conditioning as well as the negative effects of bed rest or
disease upon specific organ systems. As a general rule,
the higher the level of exertion at which measurements are
made, the greater the knowledge gained about the maximal
4
capacity of that system. While this concept may be quite
valid in most healthy individuals, one must ask whether the
test itself could have certain negative effects upon the
individual; and, therefore, is the test a safe and useful
tool for all individuals involved. The question of whether
the possible negative effects of the test on the individual
are outweighed by information gained must certainly be
answered on both academic and ethical bases.
Since it has been suggested that at maximal exertion
the heart and circulatory system may fail to meet the de
mands placed upon them, as evidenced by a drop in oxygen
pulse, the present study may help provide information as to
the time at which the circulatory decompensation occurs if,
in fact, it occurs at all. Thus, a physiologically rational
end point for exercise might be provided, which would be
as valid a measure of working capacity as maximal oxygen
consumption but at less stress and possible risk to the
subjects involved.
This investigation should also provide information
about the possible effects of the testing modality on the
time course of physiologic adaptations during stress. It,
therefore, aids the future investigator in making a deci
sion as to which exercise device may be most useful in
appraising cardiorespiratory functiou.
Definition of Terms
Oxygen pulse (V02/HR). The volume of oxygen utilized
5
by an individual for each heart beat is defined as oxygen
pulse. It is used as an indirect measure of cardiovascular
fitness and is highly correlated with stroke volume.
Oxygen-pulse peaker. An oxygen-pulse peaker is an
individual who reached a maximal oxygen pulse or a plateau
in oxygen pulse prior to maximal oxygen consumption. Oxy
gen pulse was considered to have plateaued if the value
prior to the maximal oxygen pulse was not more than .5 ml
per beat below the maximal value. For further group dis
crimination, all peaking subjects were assigned membership
into a Group 1 classification.
Oxygen-pulse non-peaker. An oxygen-pulse non-peaker
is an individual who demonstrated a continuous rise in
oxygen pulse throughout the time course of exercise to
maximal oxygen consumption. For group discrimination all
non-peaking subjects were assigned membership into a
Group 2 classification
VE/R ratio. The VE/R ratio is the quotient of venti-
lation and respiratory exchange ratio. It represents the
extent to which ventilatory mechanisms respond for a given
respiratory exchange ratio.
Delimitations
To eliminate the problem imposed by lack of the
availability of a physician, only young, normal, healthy
volunteer subjects who were currently enrolled at the
university, who were actively involved in a regular
6
exercise program, and who had a current medical examination
on file at the health services were recruited for the study.
With this type of subject population, generalizations of
the data to other populations (aged, unconditioned, and
others) are certainly limited. However, due to the medical
and legal implications, this limitation had to be accepted.
7
Chapter 2
REVIEW OF THE LITERATURE
This review is divided into four major subsections;
they are: (a) circulo-respiratory adjustment to exercise,
(b) significance of oxygen pulse, (c) prediction of maximal
oxygen consumption, and (d) comparison of bicycle ergometer
to treadmill data.
Circulo-respiratory Adjustment
to Exercise
It is the purpose of this section to review the phys
iologic changes that occur as a result of an increasing
demand upon circulation and respiration.
Changes in the heart and circulation at the beginning
of exercise are mediated fro~ the cerebral cortex of the
brain. Cortical involvement causes a stimulation of sym
pathetic activity and decreases parasympathetic impulse
traffic. An increase in arterial vasodilatation causes a
shift in blood flow from the skin and splanchnic area to
0
the working muscles (Astrand and Rodahl, 1970; Corcondilas,
Koroxenidis, and Shepherd, 1964). There is also a concomi
tant constriction in the capacitance vessels accompanied
by the pumping action of the muscles to assist venous
return to the heart (Holmgren and Ovenfors, 1960). At the
8
beginning of exercise and with increasing intensity of
exercise, the sympathetic drive mediated both neurally and
humorally allows the heart to increase contractile force as
0
well as frequency (Astrand and Rodahl, 1970).
As intensity increases, ventilation also increases;
however, this is a linear increase which becomes exponen
tial at high intensities. At low intensities, the venti
lation is increased primarily due to increased tidal
volume, while at heavier work intensities the respiration
rate is also greatly increased (Dejours, 1965; Grimby,
19 6 9) .
Throughout exercise, cardiac output (Q) is increased
to facilitate oxygen transport to the working muscles.
Cardiac output increases with oxygen consumption but not
linearly if the range from rest to the maximum is consider-
0
ed (Astrand and Rodahl, 1970; Bevegard, Holmgren, and
Jonsson, 1960). The relationship of oxygen consumption,
cardiac output, and oxygen given off by the blood can be
described in terms of the Fick equation (Asmussen, 1965),
in which V02 = Q x (a-v 02 Difference). Cardiac output
can be described as the product of stroke volume and heart
•
rate. Q = Stroke Volume x Heart Rate.
As exercise intensity increases, cardiac output and
a-v oxygen difference increase. Cardiac output may be six
to seven times as great during maximal exercise as it is
at rest, while a-v oxygen difference may increase as much
9
as 3 to 3 1/2 times. To assist the adaptive changes in
cardiac output and to allow for better utilization of oxy
gen, there is a redistribution of blood flow to increase
the supply to the working muscles; and the oxygen dissocia
tion curve is shifted so that more oxyhemoglobin is reduced
than normally at a given partial pressure for oxygen, Bohr
0
effect (Astrand and Rodahl, 1970; Bevegard and Shepherd,
1966).
The change in cardiac output with exertion is brought
about by an increase in both stroke volume and heart rate.
Stroke volume increases with oxygen consumption up to
approximately 40 percent of maximum oxygen consumption
0
(Astrand, Cuddy, and Saltin, 1964). At maximal oxygen
consumption, it is usually not more than 10 percent greater
than the supine resting value (Wang, Marshall, and
Shepherd, 1960). Heart rate increases linearly with in
creased work load in most individuals. The rate of in
crease, however, is subject to great variability dependent
upon the emotional status as well as fitness level. Maxi
mal heart rates also vary among subjects based upon age
and conditioning (Robinson, 1938).
Oxygen pulse, or the quotient of oxygen consumed
divided by heart rate over the same period, is affected
by and is an indirect measure of all of the aforementioned
circulatory adjustments during exercise , a relationship
that can be described by substitution as:
10
a-v 02 Difference x Q or (SV x HR)
02 Pulse= HR
Therefore, any circulatory adjustment which improves
a-v oxygen difference (e.g., redistribution of blood flow
to the active muscle) or increases cardiac output (e.g.,
increased stroke volume due to greater venous return) will
effect an improvement in oxygen pulse. Hence, oxygen pulse
becomes elevated in muscular exercise due to increased
stroke volume as well as increased a-v oxygen difference.
The increase in oxygen pulse with work load (relative work
load in percentage of maximum oxygen consumption) is linear
above 50 percent relative work loads (Anderson, Seliger,
Rutenfranz, and Berndt, 1974).
In discussing oxygen pulse as an estimate of circula
tory efficiency, Asmussen (1965) stated:
It is easy to see that the oxygen pulse
must be lower in less fit persons than in well
trained athletes. Assuming that the a-v oxygen
difference may reach the same maximal value in
trained as in untrained subjects, the magnitude
of the oxygen pulse must depend primarily on
the size of the stroke volume. At a heart rate
of 180 the oxygen pulse was 4 ml/beat in child
ren 4 to 7 and 16 ml/beat in 20 year olds. For
an athlete capable of taking up more than 5
liters of oxygen per minute at a pulse rate of
180 beats per minute the oxygen pulse must be
about 30 ml. The athletes' maximal stroke
volume, consequently, should be twice as large
as the average normal adult's--an estimate that
corresponds well with the actual determination.
(p. 966)
Anderson et al. (1974) also emphasized the effect of
stroke volume on oxygen pulse and further suggested that
11
a-v oxygen difference was unrelated to sex or age during
growth. They concluded that the oxygen pulse reflects the
variability in stroke volume with age and sex. They also
reported that due to plateauing of stroke volume at approx
imately 50 percent maximum oxygen consumption, the increase
in oxygen pulse above that level could be attributed to
increased a-v oxygen difference.
As the intensity of exercise increases, oxygen pulse
increases. At maximal oxygen consumption it may begin to
plateau or even fall off. In discussing the possible
0
mechanisms for such a drop, Karlsson, Astrand, and Ekblom
(1967) suggest that a possible decrease in a-v oxygen
difference or a decreased stroke volume could explain the
decline in oxygen pulse. They qualified this explanation,
however, by pointing out that a drop in a-v difference in
the light of increasing temperature and decreasing pH seems
unlikely and that previous studies do not support the hypo
thesis of a drop in stroke volume at maximal oxygen con
sumption. It was their conclusion that:
The most probable explanation is a de
creased stroke volume, but further experiments
are necessary to interpret the tendency of a
reduction in the oxygen pulse during maximal
exercise. (p. 1064)
Significance of Oxygen Pulse
As early as 1914 investigators were considering oxy
gen pulse as an important measure of cardiovascular
12
function. Henderson and Prince (1914) in reporting this
relationship of oxygen pulse to work duration and heart
rate concluded, "It is the oxygen pulse which more than any
other factor determines the total energy which a man can
command for the most strenuous moments of life" (p 106).
Furthermore, it was their observation that the maximal
values of oxygen pulse depend upon the stroke volume of
the heart as well as hemoglobin concentration in the blood~
These authors were the first to graphically report a
plateau or fall in oxygen pulse at higher heart rates.
They hypothesized that this was the normal case when
subjects were exercised beyond their "powers" to extreme
tachycardia and attributed this fall to any of several
mechanisms (i.e., temperature, excitement, carbon dioxide
content in inspired air) which could increase the heart
rate more than oxygen uptake.
Balke, Grillo, Konecci, and Luft (1954), in an attempt
to quantify the physiological response of subjects after
blood donation, recorded the oxygen-pulse time course
throughout exercise. They observed:
Immediately after starting work the oxygen
pulse rose sharply. With an increasing work the
amount of oxygen taken up per pulse beat increased
slightly to a maximal point from which it leveled
off or tended to fall. All series of experiments
manifested a similar pattern. (p. 233)
It was their contention that the maximal oxygen pulse
coincided with the respiratory exchange ratio exceeding
unity and with an abrupt decline in alveolar carbon dioxide
13
J
tension as exhibited by a sharp rise in ventilation at that
point.
Balke (1954) and Wells, Balke, and Van Fossan (1956)
in an attempt to identify an "optimal working capacity"
used the oxygen-pulse plateau as a limitation not to be
exceeded during exercise. The term "optimal" represented
the level of physical performance that could be tolerated
over the course of several hours without producing undue
physical fatigue. Thus, a fall in oxygen pulse (sauer
stoffpuls), by implication, seemed to mark the onset of
anaerobic processes and functional inefficiency at least
in terms of one's ability for long-term work endurance.
In the six subjects studied, Wells et al.,reported, as did
Balke et al., a mean drop in oxygen pulse at higher work
intensities (from 15.9 to 15.6 ml/beat). Whether or not
this phenomenon was seen in every subject was not reported.
Karlsson et al. (1967) also reported a marked decrease
in oxygen pulse at high work intensities, which they claim
ed could not be explained by methodological errors. They
did not attempt to explain why this phenomenon occurred
but stated that:
Oxygen pulse is a function of the arterio
venous oxygen differences and the stroke volume
and the knowledge about these two functions at
extremely high work intensities is very limited.
(p. 1064)
From their observation they concluded that the drop in
oxygen pulse could reflect a lowering stroke volume and/or
14
a decreased arteriovenous oxygen difference. Furthermore,
they suggested that for optimal training of the oxygen
transport system, work intensities should not be so high as
to provoke a fall in the oxygen pulse (Karlsson et al.,
1967).
Konig (1968) investigated the relationship of oxygen
pulse to heart volume at various work intensities on a
bicycle ergometer. He observed a high correlation between
the oxygen pulse and volume of the heart as measured radio
graphically. This relationship is based, he claimed, phys
iologically on the fact that the functional capacity of the
heart (as measured by oxygen pulse) depends on its volume.
He further reported that cardiac insufficiency or pathology
could be implied in those individuals who exhibited large
heart volumes with a below-average oxygen pulse. In his
post-myocardial infarction patients, the oxygen pulse per
heart volume relationships were out of range but could be
normalized through regular exercise.
Several investigators have suggested that oxygen
pulse is a good measure of cardiorespiratory capacity.
Wasserman, Van Kessel, and Burton (1967) stated that "at
any given work rate the subject with the greatest maximal
working capacity has the highest oxygen pulse" (p. 79).
Stoboy (1968) in reviewing an earlier study that
Hollman completed in 1965 reported the average values of
maximum oxygen pulse in different ages from 12 to 80 for
15
1 1
over 450 subjects; trained subjects averaged 21.6 ml/beat,
while in the similar age group of untrained subjects, the
maximum oxygen pulse averaged 16.8 ml/beat. The highest
oxygen-pulse scores were reported by Hanson (1973) on
members of the U.S. Nordic Ski Team, in which the average
value of oxygen pulse was 29.9 ml/beat. Hermansen and
Saltin (1969) also reported higher oxygen-pulse scores in
athletes versus untrained subjects during submaximal and
maximal exercise on both the bicycle ergometer and tread
mill.
Improvement in physical condition has been demonstra
ted to improve maximal as well as submaximal oxygen pulse.
Pollock, Cureton, and Greninger (1969) reported an improve
ment in oxygen pulse from 16.60 ml/beat to 19.81 ml/beat as
a result of a two-day-a-week training program, while those
training on a four-day-a-week basis for the 20-week period
improved from 16.32 to 21.65 ml/beat. Wilmore, Royce,
Girandola, F. Katch, and V. Katch (1970) reported similar
results of training in those who participated in a jogging
program for 10 weeks. Those subjects who exercised 12 min
utes a day for three days a week improved from a maximal
oxygen pulse of 17.80 ml/beat to 19.73 ml/beat. In those
who trained 24 minutes a day for three days a week, the
improvement was from 18.99 ml/beat to 21.37 ml/beat. In
both groups the changes were statistically significant.
In summary, one would expect that oxygen pulse:
16
1. is highly correlated with heart volume (Konig,
1968).
0
2. is an indirect measure of stroke volume (Astrand
and Rodahl, 1970).
3. has a tendency to reach a maximal point and then
decline during high-intensity exercise in some individuals
(Balke, 1954; Henderson and Prince, 1914; Karlsson et al.,
1967; Wells et al., 1956).
4. serves as a good submaximal index of physical fit
ness (Hermansen and Saltin, 1969; Wasserman et al., 1967).
5. is highest in highly trained subjects (Hanson,
1973) and
6. can be improved as a result of physical training
(Ekblom, Astrand, Saltin, Stenberg, and Wallstrom, 1968;
Pollock et al., 1969; Wilmore et al., 1970).
Prediction of Maximal
Oxygen Consumption
The major thrust of this investigation is to assess
the importance of maximal and submaximal oxygen pulse as a
measure of the response to exercise of the cardiorespira
tory system. One method of interpreting the significance
of oxygen pulse in assessing work capacity would be to
define the submaximal levels of oxygen pulse in terms of
their relationship to maximal oxygen consumption, in other
words to determine the correlation coefficient between
submaximal oxygen pulse and maximal oxygen consumption.
17
The predictive significance of oxygen pulse would thereby
be measured. It is the purpose in this section to review
those studies that have reported the predictive signifi
cance of various metabolic parameters as thev relate to
maximal oxygen consumption.
Wyndham (1967) reported:
Exercise physiologists have tried to devel
op a test using submaximal effort which will
give a reliable and accurate estimate of an
individual's true maximal oxygen intake. Suc
cess in this field of research has been as
elusive as that for the philosopher's stone.
In consequence there are almost as many sub
maximal tests of maximal oxygen consumption as
there are exercise physiologists. (p. 736)
With this statement as background, a brief review of
those studies reporting prediction of maximal oxygen
consumption will follow. A review of those studies that
have attempted to report the limitation to prediction will
also be presented.
Astrand and Rhyming (1954), using a submaximal step
test or a submaximal work load on a bicycle ergometer, re
ported an accuracy of +9.5 percent in women and of +7.3
percent in men in predicting maximal oxygen consumption.
Work loads were set at app. oximately 50 percent of maximal
oxygen consumption with an average heart rate of 128 beats
per minute for men and 138 beats per minute for women.
Wyndham, Strydom, Maritz, Morrison, Peter, and
Potgieter (1959) suggested the need to fit appropriate
curves to the data to test their "goodness of fit" rather
18
0
than to extrapolate to maximal heart rate as Astrand (1952)
had done. By curve fitting, Wyndham was able to reduce the
coefficient of variation in prediction to 4.3 percent pre
training and 3.5 percent after training.
Issekutz et al. (1962) reported that respiratory ex
change ratio (R) or the change in R (~ R) from .75 could be
used to accurately predict maximal oxygen consumption. He
reported that 6 R increased logarithmically and that maximal
oxygen consumption was reached when the ~ R value was .40.
His 32 subjects pedaled for five minutes on a bicycle ergo
meter. The accuracy reported was +10 percent when pre
dicting maximal oxygen consumption using ~RQ.
Margaria, Aghemo, and Revelli (1965) predicted maximal
oxygen per unit body weight from heart rate at two submaxi
mal work loads on a 30 cm and 40 cm stepping bench. The
variability of the data was within +7 percent when compared
to the data directly determined using 118 determinations on
47 subjects.
Wyndham, Strydom, Leary, and Williams (1966a) had
subjects run at three work levels on a treadmill, a bicycle,
and step bench for seven minutes to a heart rate of less
than 150. A line connecting the three heart rate points on
each modality was extrapolated to a point corresponding to
the subject ' s estimated maximal oxygen consumption. In
another study, Wyndham, Williams, Morrison, and Watson
(1966b) reported a comparison of step test prediction
19
using four submaximal rates of work to prediction based on
shoveling sand into a mine car (one-ton capacity) and/or
pushing the mine car (traming). Shoveling prediction
proved to be in good agreement with the estimate from bench
stepping; traming did not, due to low heart rates while
pushing the mine car.
0
Von Dobeln, Astrand, and Bergstrom (1967) testing 84
male construction workers on a bicycle ergometer reported
a standard error of the prediction of 8.4 percent using
submaximal heart rate, work load, and age as the predicting
variables. The equation was:
J
Work Load (kpm) x - .00884 (age)
Max vo
2
= 1.29 HR - 60
Mastropaolo (1970) used stepwise regression to pre
dict maximal oxygen consumption. The multiple correlation
was .93, and the standard error of the estimate was .172
liters per minute using steady state, R, work rate, VE,
diastolic blood pressure, and expired oxygen concentration
obtained at 600 kpm/min on a bicycle ergometer. Hermiston
and Faulkner (1971) similarly reported the use of multiple
stepwise regression in predicting maximal oxygen consump
tion. A multiple correlation of .90 was reported using
lean body mass, heart rate, FEc
O2
, and tidal volume as the
predicting variables on 28 subjects.
More recently, Fox (1973) reported the prediction
results on 87 college males u~ing just heart rate from the
fifth minute of steady-state exercise at 150 watts on a
20
I
1 ,
bicycle ergometer. Froelicher and Lancaster (1974) pre
dicted maximal oxygen consumption on 1,025 men using con
tinuous treadmill data using the Balke protocol. Using
maximal treadmill time, maximal oxygen consumption could be
predicted to +4.26 ml/kg/min (r = .72). Gupta, Verma,
Joseph, and Majumdar (1974) predicted maximal endurance
times from exercise "dyspnoea" above resting levels (a
hyperbolic relationship) and exercise heart rate. The
multiple R was .9652.
There are several basic assumptions that have been
reported as a justification to account for the expected
accuracy of predicting maximal oxygen consumption (Wyndham
et al., 1966a). They are:
1. Heart rate and oxygen consumption are linearly
related up to maximal levels.
2. Heart rate and oxygen consumption reach asymptotic
maximal values at a common high level of work.
3. Individual variation about population means is
small.
4. Maximal heart rate occurs at approximately the
same rate of work as maximal oxygen consumption.
The validity of these assumptions, however, is open
to question. Wyndham (1967) reported several errors in
estimating maximal oxygen consumption; individual variation
in heart rate was at a magnitude of 5 percent, as was the
variation in oxygen consumption for a given work load.
21
Estimation of oxygen consumption from work rate also
caused approximately 6 percent error in estimating maximal
oxygen consumption. Several other investigators have re-
ported similar limitations to prediction of maximal oxygen
0
consumption (Astrand, 1967; Davies, 1968; Rowell, Taylor,
and Wang, 1964; Taylor et al., 1963). Shephard (1967)
mathematically explained the errors in prediction due to
the lack of linearity between heart rate and oxygen con
sumption.
To summarize, the prediction of maximal oxygen con
sumption can be relatively accurate depending upon subject
population. Due to the errors of estimate, however, pre
diction of maximal oxygen consumption should not be used
if precise data are needed to appraise effectiveness of
conditioning and other factors. Prediction is still a
useful tool to estimate effects of conditioning when
maximal exercise may be contraindicated.
Comparison of Bicycle Ergometer
to Treadmill Data
The volume of oxygen consumed during exercise 1s
dependent upon the mass of the muscles involved and the
load placed upon them. Therefore, exercise using just the
legs, as in cycling, will result in a lower oxygen con
sumption than exercise involving greater muscle mass, such
as running or simultaneous arm and leg work. Since the
circulatory system adjusts differently to various types of
22
exercise, the possibility that the response of oxygen pulse
also differs is great. For this reason two separate exer
cise modalities were used in the present study.
Several investigators have reported differences be-
Cl
tween cycling and running (Astrand and Saltin, 1961;
Faulkner, Roberts, Elk, and Conway, 1971; Glassford,
Baycroft, Sedgwick, and MacNab, 1965; Hermanssen and
Sal tin, 1969). The reported differences have varied con
siderably between investigations, however. The reported
results range from "a few percent higher in running uphill
0
than in cycling" (Astrand and Saltin, 1961, p. 972) to
"routinely 10 to 15 percent higher running than cycling"
(Faulkner et al., 1971, p. 460). Faulkner et al., in an
attempt to explain the difference between modalities,
stated:
In bike and treadmill exercise the a-v
oxygen difference and heart rate are the same
and the lower maximal oxygen consumption in
cycling is due to a smaller cardiac output
and a smaller stroke volume. In cycling, the
contraction portion of the contraction
relaxation cycle is quite prolonged and the
peak loads are twice the load setting (Hoes,
1968). Running is a much more ballistic
movement with a very short contraction phase.
These biomechanical factors would contribute
to greater impairment in skeletal muscle blood
flow cycling than running. (p. 460)
0
In a carefully controlled study by Astrand and Saltin
(1961), the reported difference between cycling and running
was only .22 liters per minute of oxygen with the maximal
oxygen consumption on the bicycle being 4.47 and on the
23
treadmill 4.69 liters. The differences were significant at
the .05 level of confidence. Hermansen and Saltin (1969)
studied maximum oxygen consumption in 55 male subjects on
both bicycle and treadmill. While no differences were re
ported for maximal ventilation or heart rate, 47 of the 55
subjects had higher maximal oxygen consumption on the
treadmill with the average differences between devices of
.28 liters per minute, 7 percent. Glassford et al. (1965)
reported similar differences in 24 male subjects 17 to 33
years of age. The average maximal oxygen consumption in
Glassford's study was 8 percent higher on the treadmill
than cycling.
Wyndham et al. (1966a) stated:
At high oxygen intake values the bicycle
ergometer .•• seriously and significantly
underestimates the maximum oxygen intakes as
measured on the treadmill. Due to this effect,
the mean maximum oxygen intake of the 40 sub
jects obtained on the ergometer (2.84 +.282
1/min) is significantly lower than the-mean
maximum oxygen intake (3.08 +.376 1/min) ob
tained on the treadmill. (p~ 291)
Kaman and Pandolf (1972) reported a significantly lower
maximal oxygen pulse on the bicycle versus the treadmill.
From the studies cited, it can be expected that the
treadmill will provide higher oxygen consumption values
than the bicycle. Consequently, if the tendency to reach
a subrnaximal peak in oxygen pulse is related to work inten
sity, one would expect a greater number of subjects to peak
on the treadmill than on the bicycle. As yet, the
24
comparison between bjcycle and treadmill in relation to the
tendency to demonstrate a submaximal peak in oxygen pulse
has not been reported in the literature.
25
Chapter 3
PROCEDURE
The purpose of this study was to determine whether the
phenomenon of oxygen-pulse peaking at submaximal oxygen
consumption as reported by previous investigators (Balke et
al., 1954; Henderson and Prince, 1914; Karlsson et al.,
1967; Wells et al., 1956) could be duplicated using either
a bicycle ergometer or treadmill. The secondary purpose
was to investigate the physiologic factors which might
explain such a phenomenon.
This chapter describes the procedure used to gather
and reduce the data. It is divided into five subsections,
which are: (a) subjects, (b) experimental design, (c)
.
ins-
trumentation, (d) protocol, and (e) data reduction.
Subjects
Thirty male volunteers ranging in age from 18 to 25
(mean age was 20.5) were recruited for this study. Recruit
ment was restricted to those young, normal, healthy sub
jects who, by virtue of current athletic participation or
involvement in military preparation training, had been
cleared for physical activity by a medical examination
within six months prior to the study. Eighteen of the
26
subjects were currently enrolled in the Naval Reserve
Officers Training Corps Program and had received a thorough
medical examination from the Department of the Navy prior
to testing which cleared each for exercise. The other 12
were actively involved in sports or regular physical activ
ity at the university. The medical examination and health
clearance for exercise were provided by the University
Health Service within six months prior to testing. All
subjects were free of any clinical signs of disease or
cardiovascular dysfunction and were without any physical or
motor incapacities which would limit their ability to run
on a treadmill or ride a stationary bicycle.
Experimental Design
Each subject was randomly assigned by order of presen
tation to either run on the treadmill or ride the bicycle
ergometer on his first visit. The second visit was sched
uled seven days later at the same hour as the first test,
and the other testing modality was used. This randomiza
tion of initial test modality was done to reduce any pos
sible learning or conditioning effects which might have
occurred as a result of the first test or any changes in
the individual's level of condition which might have occur
red between Test 1 and Test 2.
Instrumentation
The instrumentation used in this study included (a) a
27
respiratory gas analyzer, (b) a treadmill, (c) a bicycle
ergometer, and (d) an electrocardiographic monitoring sys
tem.l Due to the sophistication of the equipment, each
device will be discussed separately in the following sec
tion.
Respiratory gas analyzer. The Avionics Model 800A
respiratory gas analyzer was used in the study. The in
strument consisted of an analyzer section and a computer
section to provide a minute-by-minute analysis of metabolic
parameters. The analyzer section had a total resistance to
air flow of 1.3 cm and 16.5 cm of water at peak flows of
100 liters and 400 liters per minute, respectively. The
analyzer portion was heated to 40 degrees Celsius to pre
vent condensation of water vapor in the saturated breath
and to control temperature for accurate volume and expired
gas composition measurements.
A positive displacement flowmeter, bellows type,
measured the volume of air expired by the subject during
each minute. Also, during each minute a true aliquot
(fixed percentage approximately 1.5 percent) of the expired
air was collected continuously to provide a sample repre
sentative of the total volume. At the end of each minute
the sample of gas was transferred to another cylinder. At
1
The treadmill, oxygen consumption computer, and heart
rate monitoring system were made available through the
courtesy of V. R. McCall, Administrative Assistant, Avionics
Biomedical Division of Del Mar Engineering Laboratories.
28
this point, any volume of expired gas previously collected
in excess of 200 ml was exhausted. The remaining volume
•
was then passed through a dryer (3A molecular sieve) and
then through the oxygen and carbon dioxide analyzer which
measured the percentage of carbon dioxide in the sample by
use of the infrared absorption method.
The oxygen analyzer determined the oxygen partial
pressure of the sample by measuring its magnetic suscepti
bility. The analyzer measured oxygen depletion in a range
from 20.93 percent to 9.92 percent.
The analyzer system also contained several computer
modules for computation and display of the data. A volume
computer digitized the electrical signal from the flow
meter and converted the volume to body temperature and
pressure saturated (BTPS) by correcting for body tempera
ture. The carbon dioxide volume (VCO) computer and the
respiratory quotient computer modules then transformed the
BTPS volume to standard temperature and pressure dry (STPD)
by the standard combined gas laws formula, as follows:
Where:
P - ambient pressure in mmHg
760 = standard pressure in rnmHg
(
273 \
.2 7 3 + 3 7 - ,
47 = the partial pressure of water vapor saturated
at body temperature
29
I
I!
II
37 = normal body temperature in degrees Celsius
273 = standard temperature in degrees Kelvin
The true carbon dioxide production was then calculated
by the following formula:
• •
VCO
2
(STPD) - VE (STPD)
-
F
I Ico
2
-
The oxygen consumption computer took the percentage of
carbon dioxide production, oxygen depletion or utilization,
and the volume output to calculate the oxygen consumed,
based upon the formula:
-
-
#
•
FE
vo
2
(STPD) - VE ( STPD)
Fro2I
N2
F I
Fr
:co2
N2
-
-
The respiratory exchange ratio computer module divided
the volume of carbon dioxide produced per minute by the
oxygen consumed per minute to obtain the respiratory ex
change ratio (R). Oxygen consumption per unit body weight
was also computed by dividing the oxygen consumed per min
ute by the subject's body weight, which had been previously
entered.
The outputs from all computer modules were digitally
displayed on a minute-to-minute basis on the front panel of
the analyzer (see Illustrations 1 and 2).
On the morning of each testing day, calibrations were
performed on the oxygen and carbon dioxide analyzers. A
previously calibrated test gas (concentration of 16.70
30
w
~
Treadmill
Illustration 1
Bicycle Ergometer
Illustration 2
32
percent oxygen, 4.08 percent carbon dioxide, and 79.22 per
cent nitrogen) was entered into the analyzer section at
flow rates between 10 and 12 liters per minute. Volume
calibrations were performed prior to the beginning of the
experiments and again near the end of the study using a
preheated 5-liter syringe.
Treadmill. An Avionics Model E-15 treadmill was used
in the study. It had a controlled speed range from Oto 10
miles per hour, using a one-horsepower variable speed DC
motor which also allows an elevation range from O percent
to 25 percent grade. The belt is 16 inches wide, and the
walking length is 47 inches long. Calibration tests were
performed periodically throughout the study to allow cor
rection of the belt speed displayed at the control unit to
the actual belt speed observed.
Bicycle ergometer. A Collins' Pedal Mode Ergorneter
was used in the study. It incorporated an electronically
controlled hysteresis braking system to produce adjustable
work loads throughout exercise. The work load was kept
constant through a pedal speed rate between 50 and 80 rpm
by a brake unit controller. As the subject pedaled faster,
the brake controller reduced the torque so that the work
load remained constant. The work load was adjustable over
a range of 25 to 400 watts and was found to be accurate to
within +2 percent from 75 to 400 watts throughout the pedal
speed range by Prony brake calibration. Below 75 watts the
33
work load setting actually underestimated the observed by
approximately 3.5 percent.
Electrocardiographic monitoring system. The Avionics
Model 2850 stress test monitor was used for visual display
of the subject's electrocardiographic (EKG) signal during
exercise testing. It provided a digital display of heart
rate and S-T segment deviation as well as electrocardio
graphic recordings of the last 10 seconds of each minute of
exercise. The output of the monitor was connected to the
respiratory gas analyzer to allow for a minute-by-minute
display of mean heart rate as well as the instantaneous
heart rate.
Three electrodes were placed on the subject before
each test. A reference electrode was placed at the top of
the manubrium, the active electrode in the VS position, and
a third electrode in the VSR position on the right side of
the chest to be used as the ground electrode. This system
provided the CMS electrode configuration which was display
ed and monitored continuously on the monitoring oscillo
scope.
Protocol
All tests were performed in the exercise physiology
laboratory of the Andrus Gerontology Center at the
University of Southern California. The tests were perform
ed between the hours of 10 a.rn. and 6 p.m., Monday through
Friday. The average temperature of the lab throughout the
34
experiments was 24.7 degrees Celsius; and the average
barometric pressure was 757.8 mm/Hg, the temperature rang
ing from 22.5 degrees to 26.5 degrees and the barometric
pressure ranging from 753.2 to 760.0 mm/Hg. Each test
required approximately one hour of the subject's time.
The subject was requested to be post-absorptive for at
least 2 1/2 hours prior to the test. It was further re
quested that the individual refrain from any moderate or
strenuous physical activity preceding the test.
Upon arrival at the laboratory, the subject changed
into workout apparel and was weighed and measured. Elec
trodes were applied to the chest as previously described.
The subject was then fitted with a mouthpiece (a modified
Otis-McKerrow breathing valve), and the nose clip was
applied. The individual was asked to stand quietly, if he
was to run on the treadmill, or sit quietly, if he was to
ride the ergometer, while a resting blood pressure and
electrocardiographic recording were obtained.
In order to test the hypothesis posited by Balke et
al. (1954), it was necessary to duplicate the same tread
mill protocol that they used in obtaining an oxygen-pulse
decrement. Therefore, in this study, as well as in his
study, the speed of the treadmill was held constant at
3.5 miles per hour. At the beginning of the test as the
subject walked, the treadmill was positioned horizontally.
At the end of the first minute, the angle of inclination
35
was increased by 2 percent. For every minute thereafter,
the inclination was further increased by 1 percent. The
test was continued until the subject had reached his level
of maximal oxygen consumption. The criteria for achieve
ment of maximal oxygen consumption were defined before the
study began as:
1. The subject's having reached a plateau or decrease
in oxygen consumption with increasing work load; if in
crease in work load by 25 watts did not increase oxygen
consumption by more than 100 ml/min, a plateau was reached
(Wyndham, 1967)
2. The respiratory exchange ratio having reached a
level greater than 1.05
3. The pulse rate reaching the age-adjusted maximal
level as reported by Robinson (1938)
4. The subject's inability to maintain the subsequent
work load for a one-minute duration
Due to the inclination limit of 25 percent grade on
the treadmill, the protocol had to be changed for three
subjects. If the maximal oxygen consumption criteria had
not been met by the time the subjects had reached the 25
percent grade, the grade and speed were held constant for
one minute after which the belt speed was increased by .5
miles per hour each minute until maximal levels were ob
tained.
The bicycle protocol required the subject to pedal
36
continuously for three five-minute steps at work loads of
50, 100, and 150 watts. Starting at the 16th minute, the
work load was increased by 12 1/2 watts each minute until
the maximal oxygen consumption criteria were met.
Upon completion of the exercise test, the subject
was required to pedal at a reduced work load or walk at a
slower speed and lower inclination, depending on the exer
cise device used, until his heart rate had returned to
below 120 beats per minute. At this time, the individual
was asked to sit in a chair and remain until his heart rate
was below 100 beats per minute. When this occurred, the
electrodes were removed; and the subject was free to shower
and leave.
Data Reduction
All metabolic data as well as heart rate and blood
pressure were recorded minute by minute throughout exer
cise on exercise data sheets. The data were then entered
into a Data General mini-computer (32K) where the oxygen
pulse, ventilatory equivalent, ventilation corrections to
STPD, and the change in respiratory exchange ratio were
computed. This information was then written onto magnetic
tape, where it was stored for further analysis.
The data tapes were rewritten into IBM format and
stored on discs at the university computer center. The
data were initially analyzed for kurtosis and skewness to
insure normally distributed results by using a condes-
37
criptive program from the Statistical Package for the
Social Sciences--SPSS (Nie, Hull, Jenkins, Steinbrenner,
and Bent, 1975). The results from this run included mean,
standard deviation, standard error, and range on all var
iables at each minute of exercise.
A discriminant function analysis from the SPSS pro
grams was run for group classification. All subjects were
classified into one of two groups based upon whether or not
they exhibited a plateau or drop in oxygen pulse during
exercise. Oxygen pulse was considered to have plateaued if
the value prior to the maximal oxygen puls e was not more
than .5 ml/beat below the maximal value. This plateauing
criteria was based on the standard deviation of oxygen
pulse collected from 21 samples at the same work load and
time on the same individual. The observed standard devia
tion was .609 ml/beat. Therefore, .5 ml/beat was less
than the observed error of the measurement based on test-
retest reliability. If the peaking characteristic was
observed, the subject was included in Group l; if not, he
was assigned to Group 2.
The discriminant function analysis used a stepwise
se ection procedure to provide a combination of variables
assumed to be linear which distinguished the two groups.
The criterion used to select variables was based on the
ability of the entering variable to minimize Wilk ' s lambda,
a non-parametric U statistic. The variable was considered
38
eligible for entering into the analysis based upon its uni
variate F ratio (one-way analysis of variance). The step
wise process was stopped when none of the remaining
variables could significantly contribute to group discrimi
nation. In this case as well as all comparisons in the
study, the 95 percent confidence level was used to reject
or accept the null hypothesis. The mathematical basis of
the discriminant analysis is fully described by Afifi and
Azen (1972). The discriminant analysis was performed to
select groups for both test modalities.
The 14 variables collected at the 5th, 10th, and 15th
minute of exercise were then entered into multiple regres
sion analysis to predict maximal oxygen consumption and
maximal oxygen consumption per unit body weight. The mul
tiple regression analysis used the same stepwise procedure
as the discriminant analysis. The criterion for a variable
to enter the equation was based upon its ability to signi
ficantly increase the multiple correlation coefficient
(R). The computed F value for the entering variable had
to be significant at the 95 percent confidence level, or
it was excluded from entry.
The final procedure included for data reduction was to
compare the results of all metabolic parameters at maximal
oxygen consumption obtained on the bicycle to the results
obtained on the treadmill. At test for correlated data
was used for this purpose. Furthermore, to appraise the
39
effectiveness of the random assignment as to the test
modality used initially, at test for difference between
uncorrelated means was performed. The group that initial
ly ran on the treadmill was compared to the group that ran
on the treadmill test on their second visit. The same
comparison was made for the bicycle.
40
Chapter 4
RESULTS
The results are divided into six maJor subsections;
they are: (a) description of subjects, (b) time course of
oxygen pulse, (c) comparison of bicycle and treadmill data,
(d) effects of fitness on the time course of oxygen pulse,
(e) prediction of maximal oxygen consumption, and (f) dif
ferences between peaking and non-peaking groups.
Description of Subjects
Thirty adult males ranging in age from 18 to 25 (mean
age was 20.5) participated as subjects for this study. A
basic description of the subjects, including height,
.
weight, and body surface area, is presented in Table 1.
Fourteen of the subjects ran on the treadmill on their
first visit; 16 pedaled the bicycle ergometer initially.
Using at test for uncorrelated data disclosed no signi
ficant order effect upon maximal oxygen consumption in
liters per minute or per unit body weight for either
treadmill or bicycle ergometer. All t values were less
than +1.018 and were not significant at the .05 level of
confidence.
41
Table 1
Description of Subjects
Age Height Weight Body
Subject
.
Surface in in in
Number Initials Years Inches Pounds Area (m2)
1 RQ*+ 24 68.00 175.0 1.98
2 BS 23 76.00 197.0 2.18
3 JN*+ 22 73.50 166.5 1.97
4 DM+ 21 75.00 217.0 2.29
5 GC 20 67.00 129.8 1.67
6 SS+ 19 70.50 154.0 1.86
7 KF 20 69.00 147.0 1.81
8 SR+ 19 72.00 163.0 1.93
9 JG 21 75.00 202.0 2.20
10 TH+ 20 72.00 182.2 2.06
11 FB* 21 73.00 170.0 1.99
12 MC+ 18 71.00 161.0 1.91
13 KS*+ 20 70.50 156.0 1.88
14 DK+ 19 76.75 215.2 2.29
15 GH*+ 20 70.50 162.0 1.92
16 PA+ 21 71.00 142.0 1.79
17 SS*+ 25 71.00 180.0 2.03
18 DM* 19 72.00 188.5 2.09
19 MB 22 70.00 185.0 2.05
20 JN* 21 72.00 160.0 1.91
21 MM*+ 19 75.00 202.5 2.20
22 SW+ 21 66.00 142. 0 1.75
23 RS*+ 19 69.00 183.0 2.03
24 RJ* 20 68.25 163.0 1.90
25 RC+ 21 75.00 199.8 2.19
26 EW 19 73.50 222.0 2.30
27 RS 19 74.00 179.0 2.05
28 MH*+ 21 71.50 183.0 2.06
29 RO+ 19 73.00 200.0 2.17
30 DM* 21 75.50 166.0 1.98
Mean 20.5 71.90 176.4 2.01
Range (18-25) (66-76.75) (129-222) (1.67-2.30)
SD 1.59 2.75 23.6 .164
r Correlation
with Max vo
2
.038 .675 .635 .681
*Achieved oxygen-pulse plateau or peak on bicycle
+Achieved oxygen-pulse plateau or peak on treadmill
42
Time Course of Oxygen Pulse
A group of subjects who exhibited a drop or plateau
(an increase of not more than .5 ml of oxygen per beat
with the standard increment in work load) in oxygen pulse
could be identified from the data on each exercise modal
ity. A total of 60 percent (18 of 30) reached a submaximal
peak in oxygen pulse on the treadmill while only 43 per
cent (13 of 30) peaked on the bicycle.
Table 2 presents a description of the levels at which
oxygen pulse plateaued or dropped in relation to percentage
of maximal heart rate and percentage of maximal oxygen
consumption in all subjects. The average heart rate at
which the oxygen pulse plateaued or declined on the tread
mill was 98.74 percent (range= 95.72-100.0) of maximal
heart rate while on the bicycle it was 98.34 percent
(range= 92.75-100.0). The average heart rate at maximal
oxygen pulse on the treadmill was 187.3 and on the bicycle
was 187.2. Average maximal heart rate in the group that
peaked on the bicycle was 194.2 beats per minute while on
the treadmill it was 191.3, a difference which was not
significant at the 95 percent level of confidence (t =
1.197). However, the percentage of maximal heart rate
when peaking occurred was significantly lower (t = 2.522)
in the group that peaked on the bicycle (X = 96.4 percent)
than in the treadmill group (X = 97.9 percent).
The differences between Group 1 (peakers) and Group 2
43
HR at
Subject Peak O2
Number Pulse
1 189
2
188
3 187
4 174
5 190
6 190
7 192
8 182
9 180
10 195
11 197
12 191
13 188
14 185
15 191
16 176
17 183
18 191
19 191
20 194
21 198
22 185
~ 23 195
~
Table 2
Percentage of Maximal Heart Rate and Maximal Oxygen
Consumption at which Oxygen Pulse Peaked
Treadmill Bicycle
HR at
.
Max. % Max.
% VO2 Peak 02 Max. % Max.
HR HR Max. Pulse HR HR
194 97.42 99.74 187 192 97.40
188 100.00 100.00 188 188 100.00
191 97.91 98.54 191 200 95.50
178 97.75 96.17 170 172 98.84
190 100.00 100.00 192 192 100.00
195 97.43 100.00 186 186 100.00
192 100.00 100.00 189 189 100.00
188 96.81 95.25 187 187 100.00
180 100.00 100.00 177 177 100.00
199 97.99 100.00 189 189 100.00
197 100.00 100.00 196 202 97.03
191 100.00 98.01 186 186 100.00
189 99.47 100.00 179 193 92.75
186 99.47 97.50 179 179 100.00
194 98.45 96.34 188 198 94.94
183 96.17 96.98 174 174 100.00
186 98.39 96.37 181 189 95.77
191 100.00 100.00 188 195 96.41
191 100.00 100.00 181 181 100.00
194 100.00 100.00 191 199 95.98
203 97.54 91.20 195 199 97.99
191 96.86 96.96 193 193 100.00
197 98.98 100.00 189 201 94.03
% vo2
Max.
96.73
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00
90.88
100.00
97.14
100.00
95.66
95.92
100.00
100.00
98.55
100.00
91.95
Subject
Number
~
U1
24
25
26
27
28
29
30
Mean
Range
SD
HR at
Peak 02
Pulse
198
189
188
188
194
179
180
188.27
(174-
198)
6.16
Table 2--Continued
Treadmill
Max. % Max.
HR HR
198 100.00
189 100.00
188 100.00
188 100.00
202 96.04
187 95.72
180 100.00
190.67 98.74
(178- (95.72-
203) 100)
5.99 1.61
% vo2
Max.
100.00
100.00
100.00
100.00
95.13
93.67
100.00
98.40
(93.67-
100)
2.29
HR at
Peak O2
Pulse
186
174
179
192
190
202
173
185.70
(170-
202)
7.42
Bicycle
Max. % Max.
HR HR
187 99.47
174 100.00
179 100.00
192 100.00
194 97.94
202 100.00
176 98.30
188.83 98.34
(172- (92.75-
202) 100)
8.84 2.11
%V02
Max.
97.07
100.00
100.00
100.00
100.00
100.00
96.04
98.61
(91.95-
100)
2.45
(non-peakers) in all variables at maximal oxygen consump
tion are presented in Table 3. It was observed by use of
the univariate F ratio (one-way analysis of variance) that
the maximal heart rates and maximal respiratory exchange
ratios were significantly higher (P>.05) in those who
peaked in oxygen pulse on the bicycle versus those who did
not. No significant differences were observed at maximal
exercise for those who peaked or did not peak on the
treadmill.
Figures 1 through 4 graphically present the observed
time course of oxygen consumption as a function of heart
rate in each individual for the peaking and non-peaking
groups. Figure 5 and Figure 6 present the time course of
oxygen pulse individually for the peaking and non-peaking
groups on the treadmill. Similarly, Figure 7 and Figure 8
display oxygen pulse as a function of time in the peakers
and non-peakers on the bicycle. Figure 9 presents a com
parison of oxygen pulse to work load between bicycle and
treadmill. Figures 10 and 11 present the same comparison
between peakers and non-peakers for both exercise modali-
ties. Interpretation of these graphs is difficult due to
the fact that a clear-cut peak was not demonstrated in all
of the peaking subjects.
Comparison of Bicycle and
Treadmill Data
At test for data with correlated means was used to
46
.i::,.
-..J
Table 3
Differences Between Group 1 (Peakers) and
Group 2 (Non-peakers) at Maximal Oxygen Consumption
Variables Group l* Group 2**
•
at vo
2
Max
Mean SD Mean SD
-
Treadmill
•
L/m VE (BTPS) 142.40 11.08 134.10 19.28
•
VO2 L/m 3.97 .54 3.91 .62
HR bpm 190.39 6.05 189.75 6.05
RER 1.11 .06 1.09 .03
yco
2
L/m 4.42 .66 4.26 .65
vo
2
ml/kg/m 49.69 3.81 49.41 7.67
?
2
fulse
20.87 2.86 20.62 3.49
VE/VO2 35.87 3.81 34.30 3.63
Bic¥cle
VE (BTPS) L/m 147.90 25.46 142.94 21.00
•
VO
2
L/m 3.75 .49 3.75 .63
HR bpm 192.15 6.37 184.71 8.14
RER 1.14 .04 1.11 .03
yco
2
L/m 4.28 .62 4.19 .74
vo
2
ml/kg/m 47.66 5.36 46.56 5.96
02 Pulse 19.51 2.56 20.37 3.54
VE/V02 39.29 6.29 38.07 3.31
*Treadmill n = 18, Bicycle n = 13
**Treadmill n = 12, Bicycle n = 17
ap >. 05
Univariate
F Ratio
2.253
.099
.094
.645
.419
.019
.051
1.419
.345
.002
7.39a
4.25a
.122
.278
.546
.493
..,:::.,
co
z
0
-
I-
a.
::i!:
:::>
Cl)
z
0
(.)
z
UJ
(!)
>
X
0
5.00
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
80 90 100 110 120 130
FIGURE 1
140
HEART RATE
150 160 170 180 190 200
RELATIONSHIP OF OXYGEN CONSUMPTION TO HEART RATE ( 02 PULSE) IN TREADMILL NON-PEAKERS N=12
z
0
-
I-
~
~
~
\.0
::,
(JJ
z
0
u
z
w
C)
>
X
0
5.00
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
FIGURE 2
110
120
130
140 150 160 170 180 190 200 210
80
0 100
HEART RATE
RELATIONSHIP OF OXYGEN CONSUMPTION TO HEART RATE ( 02 PULSE) ON TREADMILL PEAKERS N=18
z
0
I-
0..
:E
:::,
Cl)
z
0
u
z
..I.I
c::>
>-
X
0
l11
0
5.00
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
FIGURE 3
0 110 120 130 140
150 160 170 180 190 200
HEART RATE
RELATIONSHIP OF OXYGEN CONSUMPTION TO HEART RATE ( 02 PULSE) ON BICYCLE NON-PEAKERS N=17
.
u,
.......
z
0
...
CL
~
::>
(.')
z
0
(J
z
w
C,
>
X
0
5.00
FIGURE 4
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.ooL ______________________________________________________ _
100 110 120 130 140 150 160 170 180 190 200
HEART RATE
RELATIONSHIP OF OXYGEN CONSUMPTION TO HEART RATE ( 02 PULSE) IN BICYCLE PEAKERS N=13
Ul
1')
w
Cl)
_.
::,
0..
z ..
w
C,
>
)(
0
FIGURE 5
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
TIME
OXYGEN PULSE TIME COURSE IN TREADMILL NON-PEAKERS N=12
u,
w
w
V,
..J
::>
0.
z
w
(!>
>
X
0
FIGURE 6
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
TIME
OXYGEN PULSE TIME COURSE IN TREADMILL PEAKERS N=18
Ul
~
w
(./J
..J
::::,
Q.
z
w
C,
>
X
.Q
FIGURE 7
26
25
24
23
:n
21
19
18
17
16
15
14
13
12
11
10
9
8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 5 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
TIME
OXYGEN PULSE TIME COURSE IN BICYCLE NON-PEAKERS N=17
V1
V1
w
(n
..J
::>
Q.
2
LLJ
(!)
>
X
0
FIGURE 8
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
1 (,
9
8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
TIME
OXYGEN PULSE TIME COURSE IN BICYCLE PEAKERS N=13
100
QJ
(/}
90
3 80
P-1
~
QJ
01
:>i
8 70
~
0
QJ
01
~ 50
~
QJ
0
H
QJ
~
40
30
Treadmill= -
Bicycle =
0
- --.d
I
T _li
fl, - l
/l
I
/
6 /
/1
5 15 25 35 45 55 65 75 85 95
Percentage of Maximal Work Load
Figure 9
Relationship of Percentage of Maximal Oxygen Pulse
to Percentage of Maximal Work Load
on Bicycle and Treadmill (n = 30)
56
100 - Peakers =
Non-peakers = ~ - -6
T
•
90 -
Q)
en 8 0 -
~
::s
0..
T
c
Q)
tJ1
~ 70-
X
0
~
cu
s
l
• r-l
X 60-
cu
~
1
4-1 •
0
l
Q)
.
t'J150-
cu
.µ
s::
Q)
u
~
~ 40 -
30 -
"'.
1 L I I I I T I I I
5 15 25 35 45 55 65 75 85 95
Percentage of Maximal Work Load
Figure 10
Relationship of Percentage of Maximal Oxygen Pulse
to Percentage of Maximal Work Load in
Treadmill Peakers and Non-peakers (n = 30)
57
Peakers = --
100 Non-peakers - 6---4
T
90
(1)
Ul
M80
:::1
P-1
s::
(1)
tJ)
~
X70
0
M
cu
s
. ,.,
X
~ 60
4-l
0
(1)
tJ)
j 50
s::
(1)
C)
H
(1)
P-1 4 0
30
5 15 25 35 45 55 65 75 85 95
Percentage of Maximal Work Load
Figure 11
Relationship of Percentage of Maximal Oxygen Pulse
to Percentage of Maximal Work Load in
Bicycle Peakers and Non-peakers (n = 30)
58
test differences between the treadmill and the bicycle in
regard to the various exercise parameters. The results
are presented in Table 4. Significant differences were
observed in oxygen consumption, respiratory exchange ratio,
oxygen pulse, and ventilatory equivalent for oxygen at the
95 percent confidence level. Furthermore, heart rates
were higher and ventilation lower on the treadmill; but
the differences were not significant. Figures 12 through
17 graphically present the comparison of exercise modality
in each of the parameters measured.
The correlation coefficient rand the slope and
intercept are provided for each comparison. Oxygen pulse
showed the highest relationship between test device scores
(r = .8728), while respiratory exchange ratio showed the
lowest relationship (r = .0187).
The relationship of the exercise variables to time
and work load on each of the devices is provided in
Figures 18 through 21. As shown graphically in Figures 18
and 19 a noticeable plateauing was observed in all varia
bles with the exception of the ventilatory equivalent for
oxygen during the three submaximal work loads of 50, 100,
and 150 watts on the bicycle ergometer. Figures 22 and 23
present the variables in percentage of maximal as a func
tion of percentage of maximal work load.
59
Table 4
Differences Between the Treadmill and Bicycle
Ergometer at Maximal Oxygen Consumption
Parameter Test Mode
Ventilation (VE) Bicycle
Liters/Minute (STPD) Treadmill
Oxygen Consumption
(V02 Max) Bicycle
Liters/Minute Treadmill
Heart Rate (HR) Bicycle
Beats/Minute Treadmill
Respiratory Exchange Bicycle
Ratio (R) Treadmill
Oxygen Pulse
(O2 Pulse) Bicycle
ml of O2/Heart Beat Treadmill
Ventilatory Equivalent
for Oxygen Bicycle
• •
(VE/VO2) Treadmill
Oxygen Consumption
(V02 Max) Bicycle
ml/kg/min Treadmill
m
0
Note. n = 30
ap > . 05
Mean
145.08
139.67
3.75
3.95
187.93
190.16
1.12
1.10
20.03
20.76
38.85
35.77
47.04
49.54
SD
22.757
15.353
.573
.555
8.212
6.025
.040
.045
3.106
3.049
4.779
3.796
5.642
5.561
Std.
Error
4.155
2.803
.105
.101
1.499
1.101
.007
.008
.567
.557
.873
.694
1.030
1.015
Mean
Diff.
5.402
.200
2.233
.023
.721
3.098
2.503
Std. Error
of
Mean Diff.
17.483
.345
6.212
.047
1.564
3.362
4.376
t
Test
1.69
3.14a
1.97
2.62a
2.54a
5.05a
3.13a
5 . 0
4 . 5·-
s
"
H Q)4 . 0
rl
NU
0 !>1
·:> 0
°'
I-'
.,..;
~ i::Q
co
~ 3 . 5
3.
•
3 . 0
•
• •
•
•
•
•
. / .
• • •
•
•
•
•
• •
• •
•
•
•
• •
r = .811
Slope= .837
Intercept= .444
3 . 5 4 . 0 4 . 5
Max \l02 L/m
Treadmill
Figure 12
210
[ 200
..0
Q)
..µ Q)
co rl
p:; ~190
..µ u
H .,..;
co CQ
Q)
~
~ 180
~
170
5 . 0
170
•
•
•
"
,
. "
•
• r = • 658
Slope= . 896
Intercept= 17 . 399
I I I
180 190 20 0
Max Heart Rate bpm
Treadmill
Figure 13
210
Differences in Maximal Oxygen Consumption and
Maximal Heart Rate Between Bicycle and Treadmill (n = 30)
s
"
200
,-::i 175
- (1)
Cl) r-1
P--1 C)
8 :>-i
m o
- .,,
ml50
~
·>
X
rel
~
°'
rv
125
•
,
L .l
r = .641
Slope= .950
Intercept= 12.381
125 150 175 200
Max VE (BTPS) L/m
Treadmill
Figure 14
0::: (1)
~ r-1
0::: ()
:>-i
X CJ
rel -~
~m
1.20
•
•
• •
1.10
•
1.00
1.00
•
•
•
•
•
•
•
•
•
1/.
•
•
•
•
r = -.019
1
Slope= - . 906
Intercept= 15.122
1 . 10 1 . 20
Max RER
Treadmill
Figure 15
Differences in Maximal Ventilation and Maximal Respiratory
Exchange Ratio Between Bicycle and Treadmill (n = 30)
O'\
w
25
.µ
rd
(l)
,..Q
'-...
r-1
s (l)
r-1
(l)
0
20
Ul :>i
r-1 0
~ ·rl
P-ICQ
N
0
X
rd
~
15
-
..
I
15
•
•
•
•
•
•
/
•
•
•
/ •
•
• •
•
•
/
•
•
•
•
•
•
r = .873
Slope= .894
Intercept= 1 . 474
20
Max 02 Pulse ml/beat
Treadmill
Figure 16
25
45
•
40
L-
N
0 ~
. :> (l)
'-... r-1
r
~ C)
·:> &135
I
X ·.-t
rd ~
:E:
I
30
25
•
•
•
~
•
•
30
•
. ~
/ •
r = . 584
Slope= . 647
Intercept= 15 . 961
JS
Max VE/V02
Treadmill
Figure 17
4 5
Differences in Maximal Oxygen Pulse and Maximal Ventilatory
Equivalent for Oxygen Between Bicycle and Treadmill (n = 30)
•
220 3.60 80
L VE = •
VO2 = A
HR= +
•
200
3.10
70
,
t
•
,~
60 r
•
180 2.60
A
•
ll.
• •
•
-1-
~ E
6
a 160
•
t.
H 2.10 "-.50
6 a
+
11
..Q
H
/l,.
t
N
0:: 0
µ::J
t
::r::
·> ·> -
+
•
A
f-
I-
f
f-
140 1.60
4o r-
,
•
+ •
A
d
6
0
I-
•
t
t
4
30 L
•
120
1.10 ~
~
4
4
'1
A •
+ •
[
•
+
•
1-
__r---r-
100 • 60 20 t-
... +
+
r -t'
J
Work Load
I
I I
'
I
I
'
I
I
I
I
I I
'
•
I l
•
5 10 15 20
Time in Minutes
.
Figure 18
°'
Relationship of HR,
. . .
►~
vo2, and VE to Time on the Bicycle
m
u,
31
30
N
-~ 29
"
~
·>
28
27
26
0
19
• r-1
+ll.20
·>
1l
+-
70
a
•
a
♦
•
I
CJ
..
•
120 1.4
0
+
•
-r
•
so, t- •
..,.
+- •
•
100 1.0
I
•
•
•
•
•
301 -
Percent Grade
~ I
I
I
•
.,
I
I
I
'
•
,
I
I I
•
r
I
5 10 15 20
Time in Minutes
Figure 20
Relationship of HR,
•
and VE to Time on the Treadmill
VO2,
O"I
O"I
30
29
28
N
0
"> 27
O'i
-..J
"
rx:l
·>
26
25
24
19
17
Q)
Cl)
r-1
~15
~
N
0
13
11
9
RER =
•
I 02 Pulse = o
VE/V02 = +
I
0
·r-1
l
.µ
m
~
Q)
tJil.20
s::
m
~
u
X 1.10
rx:l
Ci
c:;
~
0
~
o 1. 00
a
.µ
a
m
~
• 90 7
·r-1
Pl
Cl) ...,.
Q)
...
~
+
•
• 80 -1
+
...
•
# •
'
' :=:
•
I '
5
Relationship of VE/V02,
•
-t
+
+-
J;1
..
a
a
~ a
(l
a
a +
C,
rJ
0
a
&J +
a
a
""
.+
•
•
•
•
+
•
•
•
+-
•
..
•
4-
•
Percent Grade
' '
t
I
I t
'
I
t t
'
I
l
10 15 20
Time in Hinutes
Figure 21
02 Pulse, and RER to Time on the Treadmill
O'\
00
1001 HR = •
•
90
80
~
cu
s
·M 70
~
cu
~ 60
4--1
0
a, 50
tJ'l
cu
+J
i:::! 4 0
a,
0
~ 30
~
20
10
VE = Cl
R = +
•
V02 = A
02 Pulse
+ ~ +
-+-+_+_+ __
/~
=o
•
/
•
o-
0
I
•
~--/
0
"~
6
/
A
, ___ b
0 / 0
o-a/
-·
D
--
o-
0
/
,
A
.. --
6
o
_o
•
+-/-+
•
"
A
01
Cl
/
A/
a
5 15 25 35 45 55 65 75 85 95
Percentage of Maximal Work Load
Figure 22
The Percentage of Maximal HR, VE, R, V02, and
o
2
Pulse as a Function of Percentage of
Maximal Work Load on the Bicycle (n = 30)
O"I
I..O
100-
90·
80·
r-1
ro
s
-~ 7 0-
~
ro
~
4-1
0
60-
OJ 50 ·
ty\
ro
+>
~ 4 O·
Q)
t)
H
OJ 30 ·
P-l
20 ·
10 •
HR = •
.
VE = Cl
R = +
•
V02 = 6
02 Pulse
. /;
= 0 • / -+ / •
./ .f / /r:,
+-----.... + _+ _._ .. 7+/ "/ /6.
+ _,,./' /• 0 ----b/ A
__,,,,. 0 ~
• ~ 0 ,,,,,,,,.-
~ a
·-·
0
0
~"
~~ ,/
..
d
6~/l
6. Cl _..o
0/
0-CJ~
7
.4
4 C
a
a
5 15 25 35 45 55 65 75 85 95
Percentage of Maximal Work Load
Figure 23
. .
The Percentage of Maximal HR, VE, R, vo
2
, and
o
2
Pulse as a Function of Percentage of
Maximal Work Load on the Treadmill (n = 30)
Effects of Fitness on the Time
Course of Oxygen Pulse
A categorization of subjects into high-fit and low
fit groups was accomplished by quartile separations. In
other words, the seven subjects (23.2 percent) demonstra
ting the highest maximal oxygen consumptions (upper quar
tile) were classified into the high-fit catego~y. Similar
ly, the seven subjects denonstrating the lowest maximal
oxygen consumption (lowest quartile) received low-fit
classification. Due to the homogeneity of the group, this
classification was somewhat misleading. According to
0
Astrand (1960), low-fit individuals achieved maximal oxy-
gen uptake at less than 2.79 liters per minute. The aver
age oxygen consumption for the low-fit group was 3.28
liters in this study, which placed the group into an
average-fitness group based on the Astrand norms. There
were only two individuals in the study who had a suffi
ciently low maximal oxygen consumption to be classified
as low fit.
Table 5 provides a descriptive comparison between
these two groups based upon their responses at maximal
oxygen consumption and by their height, weight, and body
surface area. One subject from each of the groups clas
sified demonstrated a peak in oxygen pulse based upon data
collected on the bicycle ergometer. On the treadmill, four
subjects in the high-fit group and three subjects in the
low-fit group plateaued or peaked in oxygen pulse. A
70
....J
i---a
Description
Height (in.)
Weight (lbs.)
BSA (m2)
Table 5
Means and Standard Deviations of High-fit and
Low-fit Subjects on the Treadmill and Bicycle Ergometer
Low Fit* High Fit*
Treadmill Bicycle Treadmill Bicycle
- - -
X SD X SD X SD X SD
70.00 3.055 68.89 1.935 75.17 1.161 74.00 1.848
158.67 26.199 152.85 18.288 195.36 20.174 197.50 20.657
1.89 .218 1.84 .141 2.16 .144 2.16 .155
Maximal Oxygen Consumption
•
VE (L/m) 127.05 12.738 117.84 16.260 155.63 9.985 163.01 17.636
.
(L/m) VO2 3.28 .134 3.08 .198 4.74 .083 4.50 .276
HR (bpm) 187.85 4.598 186.00 6.633 188.14 9.045 185.70 11.672
RER 1.09 .045 1.12 .029 1.10 .053 1.13 .050
•
(L/m) yco
2
3.58 .217 3.45 .275 5.22 .392 5.09 .544
V02
(ml/kg/m) 45.47 5.756 44.33 4.545 53.50 5.910 50.13 6.375
9
2
J?ulse
17.46 10.272 16.56 1.530 25.19 1.079 24.23 .911
YE/VO2
38.73 3.271 38.26 5.910 32.83 2.210 36.22 2.709
VE/R 116.56 11.379 105.39 14.699 141.48 10.116 144.26 12.913
-
*n = 7
comparison of oxygen-pulse time course as a function of
time and work load between the groups is presented in
Figures 24 through 27.
Prediction of Maximal
Oxygen Consumption
Linear regression analysis was used for prediction of
maximum oxygen consumption from submaximal oxygen uptake or
submaximal oxygen pulse on the bicycle ergometer. A com
parison of the results is presented in Table 6 and Table
7. In all cases, submaximal oxygen pulse was a better
predictor of maximal oxygen consumption than was submaximal
oxygen uptake.
A multiple stepwise regression analysis was performed
on all exercise variables and body surface area at the
three submaximal work loads on the bicycle in an attempt
to predict maximum oxygen consumption. Table 8 presents
the relationship of maximal and submaximal exercise varia
bles to maximal oxygen consumption. Figure 28, Figure 29,
and Figure 30 graphically display the actual versus the
predicted relationships obtained from the stepwise equa
tions. Submaximal steady-state data collected at the 5th
minute of bicycle exercise at 50 watts (Equation 1), 100
watts (Equation 2), and 150 watts (Equation 3) were used
for the prediction. The equations used were as follows:
1. Max V02 = 3.292(BSA) - .01324(HR) - .04296(VE)
+ .1025(V02 ml/kg/min) + 1.885. (50 watts)
72
....J
w
w
(I)
..J
::>
0.
z
w
C,
>-
X
0
FIGURE 24
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
1 2 3 4 5 6 7 8 9 1 0 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
TIME
TREADMILL LOW-FIT GROUP N=7
w
VJ
..J
:>
~
z
w
(!)
>
X
0
'-1
~
26
25
24
23
22
21
20
... 9
18
17
16
15
14
13
12
11
10
9
8
FIGURE 25
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
TIME
TREADMILL HIGH-FIT GROUP N=7
w
V,
..J
:)
c..
2
w
C,
>
X
0
-...J
Vl
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8 '/~
FIGURE 26
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 32 33
TIME
BICYCLE LOW-FIT GROUP N=7
w
Cl)
I
::>
0.
z
-...J
O'\
w
c:,
>
X
0
FIGURE 27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
TIME
BICYCLE HIGH-FIT GROUP N=7
~
Table 6
Prediction of Maximal Oxygen Consumption from
.
Submaximal vo
2
Using Steady-state Data from a Bicycle Ergometer
and Continuous Exercise Data from a Treadmill
5th Minute 10th Minute 15th Minute
Treadmill Bicycle Treadmill Bicycle Treadmill Bicycle
-
Submaximal X 1.650 1.000 2.223 1.451 2.835 2.092
•
VO2
SD .264 .089 .350 .078 .415 .089
-
Maximal X 3.946 3.751 3.946 3.751 3.946 3.751
•
VO2
SD .561 .564 .561 .564 .561 .564
r .504 .247 .586 .409 .605 .229
Slope 1.072 1.565 .937 2.966 .818 1.441
Intercept 2.177 2.185 1.861 -.553 1.624 .735
Std. Error .493 .556 .463 .524 .455 .559
-
Predicted X 3.946 3.750 3.944 3.751 3.943 3.751
•
Max vo
2
SD .283 .139 .328 .231 .339 .129
-
Percentage X 10.059 12.643 9.324 11.844 8.722 12.529
Error SD 6.654 6.777 6.346 6.388 6.996 7.215
-..J
-..J
Submaximal
02 Pulse
Maximal
.
VO2
r
Slope
Intercept
Std. Error
Predicted
•
Max vo
2
Percentage
Error
-.....J
00
X
SD
-
X
SD
-
X
SD
-
X
SD
Table 7
Prediction of Maximal Oxygen Consumption
from Submaximal Oxygen Pulse Using Steady-state
Data from a Bicycle Ergometer and Continuous
Exercise Data from a Treadmill
5th Minute 10th Minute
Treadmill Bicycle Treadmill Bicycle
14.111 10.006 15.822 12.189
1.837 1.624 2.012 1.773
3.946 3.751 3.946 3.751
.561 .564 .561 .564
.658 .529 .789 .578
.201 .184 .220 .184
1.107 1.910 .461 1.509
.429 .487 .351 .468
3.946 3.751 3.942 3.751
.369 .298 .442 .326
7.845 10.377 6.838 9.665
7 . 072 7.444 5.302 7.558
15th Minute
Treadmill Bicycle
17.299
14.593
2.288 1.718
3.946 3.751
.561 .564
.811 .699
.199 .229
.503 .399
.334 .410
3.946 3.741
.455 .393
6.259 7.878
5.200 6.874
Table 8
Relationship of Maximal and Submaximal Exercise Variables
at 50, 100, and 150 Watts to Maximal Oxygen Consumption
VE
. .
Work (BTPS) VO2
HR VCO2 02 Pulse
Level L/m L/m bpm RER Log ~R L/m ml/b VE/vo
2
50 Watts
Mean 27.3 1.00 101.7 .86 .86 10.01 27.35
SD 3.64 .09 13.5 .07 .12 1.62 3.04
r .104 .246 -.433 -.059 .132 .530 -.067
100 Watts
Mean 38.9 1.45 120.9 .91 -1.598 1.32 11.99 26.83
SD 5.52 .08 14.3 .06 .145 .11 1.77 3.54
r .203 .409 -.498 -.085 -.122 .192 .578 .045
150 Watts
Mean 57.4 2.09 145.0 .95 -.702 2.00 14.41 27.46
SD 6.81 .09 15.5 .05 .11 .14 1.72 3.09
r -.287 .229 -.659 -.276 -.249 -.090 .699 -.389
Maximal Oxygen Consumption
..... J
I..;)
Mean
SD
r
145.1
22.76
.706
3.75 187.9 1.12
.56 8.21 .04
1.00 .005 .135
-.429 4.23 19.99 38.90
.05 .67 3.13 4-. 78
-.124 .969 .952 -.308
VE/R
31.7
3.05
.007
42.6
4.79
.298
60.4
6.05
-.174
128.9
19.32
.705
'oo
0
s
'-...
...::l
~
co
5.0
::E: 4. 0
N
0
·>
'"d
Q)
.µ
u
·r-1
'"d
Q)
1-4
tl.i
3.0
•
•
•
••
•
•
-
•
•
-
•
•
•
•
r = .784
SE= +.377
3.0 4.0 5.0
Observed vo
2
Max L/m
Figure 28
Observed Versus Predicted Maximal Oxygen Consumption
Using the Fifth Minute of Steady-state Bicycle Data at 50 Watts
00
I-'
5 . 0 -
s
'-..
H
~
rd
~ 4 . 0
N
0
·:> -
"d
(ll
+J 1-
C)
·rl
"d
I
Q)
•
,,
~
I
•
P-1
3 . 0
3 . 0
•
r
•
/ /
.,
:/.
•
/ .
•
/
•
/ / .
~
/•
•
•
•
4.0
•
Observed VO~ Max L/m
~
Figure 29
r
r
•
•
•
r = .799
SE= +.380
5.0
Observed Versus Predicted Maximal Oxygen Consumption
Using the Fifth Minute of Steady-state Bicycle Data at 100 Watts
CX)
t\.)
5.0
E
'-...
H
~
~ 4. 0
I
N
0
·>
I
ro
(1)
.µ I
0
.,,
I
ro
(l)
I
~
~
3.0
•
•
/
/ ..
{
•
L_
•
/ •
.. /
•
•
r = .794
SE= +.369
3.0 . 4.0 5.0
Observed vo
2
Max L/m
Figure 30
Observed Versus Predicted Maximal Oxygen Consumption
Using the Fifth Minute of Steady-state Bicycle Data at 150 Watts
• •
2. Max VO
2
= 4.092(BSA) - .00984(HR) - l.139(VCO
2
)
+ .1363(V02 ml/kg/min) - 4.294. (100 watts)
• •
3. Max VO2 = l.137(BSA) - .01869(HR) + l.397(VO
2
•
1/min) - .00633(VE) + 1.5415. (150 watts)
The multiple correlation coefficient R for Equation 1
was .784 with a standard error of .377 liters; for
Equation 2, it was .779 with a standard error of .380
liters; and for Equation 3, it was .794 with a standard
error of the estimate of .369. The average percentage
error ranged from 7.18 percent with a standard deviation
of 5.54 percent at 50 watts to 6.13 percent error with a
standard deviation of 5.22 percent at 150 watts.
The differences between the observed and predicted
maximal oxygen consumption are presented in Table 9. As
one would expect, the higher the work intensity the
greater the prediction accuracy.
Maximal oxygen consumption per body weight was simi
larly predicted by utilizing stepwise regression analysis.
The resulting equations are:
4. V02 ml/kg/min= .9502(VO2 ml/kg/min) - .1828(HR)
- .5422(VE BTPS) + 65.5533. (50 watts)
5. VO2 ml/kg/min= l.040(V02 ml/kg/min) - .173(HR)
- 5.690(VC0
2
) + 56.4133. (100 watts)
6. vo
2
ml/kg/min= l.065(V02 ml/kg/min) - .2517(HR)
+3.397(V0
2
1/min) + 48.2068. (150 watts)
The corresponding multiple correlation coefficients
83
5th Minute,
vo
2
Liters
VO2 ml/kg/m
5th Minute,
VO2 Liters
vo
2
ml/kg/m
5th Minute,
.
yo
2
Liters
vo
2
ml/kg/m
00
..::::,..
Table 9
Comparison of Observed Versus Predicted Maximal
Oxygen Consumption from Steady-state Data
on the Bicycle Ergometer
Observed Observed Predicted
Submaximal Maximal Maximal
- -
X SD X SD X SD R
50 Watts
1.00 .089 3.75 .564 3.75 .564 .784
12.64 1.537 47.03 5.644 47.04 3.319 .588
100 Watts
1.45 .078 3.75 .564 3.75 .439 .779
18.36 2.118 47.03 5.644 47.04 3.184 .564
150 Watts
2.09 .089 3.75 .564 3.75 .465 .794
26.50 3.396 47.03 5.644 47.08 3.505 .621
Standard Percentage
Error of Difference
Estimate X SD
.377 7.19 5.27
4.821 7.79 5.59
.380 7.22 5.29
4.921 7.99 5.87
.369 6.72 5.45
4.672 7.47 5.72
(R) and standard errors are given for each equation as
follows:
4. R - .588, S.E. - 4.821
5. R - .564, S.E. - 4.921
6. R .621, S.E. - 4.672
These prediction equations used submaximal steady
state data collected on the bicycle ergometer at the 5th
minute of exercise at 50 watts for Equation 4, 100 watts
for Equation 5, and 150 watts for Equation 6.
Based upon results of these equations, one should be
able to predict with approximately 90 percent accuracy
either maximal oxygen consumption or maximal oxygen con
sumption per unit body weight in this type population
using submaximal data at any of the subrnaximal work loads
investigated.
Discrimination of Peaking and
Non-peaking Groups
To elucidate the differences between Group 1 (peakers)
and Group 2 (non-peakers) by exercise device, a discrimi
nant function analysis was performed, using both maximal
and submaximal exercise variables. Only those variables
which showed significant F differences were included in
the discriminant function analysis.
The discriminant function distinguished groups by
entering only those variables which will significantly
lower Wilk's lambda, a non-parametric U statistic. Each
85
entering variable results in greater separation of the
group centroids. The greater the separation between cen
troids, the greater the significance of the discrimination
and, therefore, the greater the accuracy of group predic
tion.
By using maximal heart rate and the VE/R ratio at the
15th minute of exercise on the bicycle, the discriminant
analysis produced the following equation: Group Centroid
.08233(Max HR) - .10511(VE/R) - 9.15258. From this equa
tion, group centroids were separated to Group 1 (peakers)
equaling .64812 and Group 2 (non-peakers) equaling -.4956.
In other words, the closer an individual came to one of
these two centroids, the greater the chance of falling
within its classification. Based upon the equation, Wilk's
lambda was minimized to .543; and the canonical correlation
was .676. Applying this formula, the prediction accuracy
of correctly classifying the subjects into groups was
83.33 percent. The prediction results were as follows:
Table 10
Prediction Accuracy
Number Predicted Predicted
Actual Group of Cases Group 1 Group 2
Group 1 13 10 3
(76.9%) (23.1%)
Group 2 17 2 15
(11.8%) (88.2%)
86
:
A stepwise regression analysis using these two varia
bles produced a multiple correlation coefficient of .676
with single correlations of -.457 and .420 for heart rate
.
and VE/R ratio, respectively. The correlations suggest
that those subjects with the higher maximal heart rates
and lower VE/R ratios would most likely be classified as
Group 1. The resulting equation to separate groups was
•
5.222 - .03288(HR) + .04196(VE/R) = Group.
Three variables--submaximal respiratory exchange
ratio (5th minute, 3 mph, 6 percent grade), submaximal
ventilatory equivalent for oxygen (5th minute), and sub
maximal heart rate (10th minute, 3.5 mph, 11 percent
grade)--contributed to group discrimination on the tread
mill. Wilk's lambda was minimized to .6307; the canonical
correlation was .608. Group centroids were separated
into Group 1 equaling -.05516 and Group 2 equaling .08273
by the following discriminant equation: .0358(A) - 2.422
(B) + .0058(C) + .3019 = Group Centroid, where A is sub
maximal ventilatory equivalent for oxygen at 5 minutes, B
is submaximal respiratory exchange ratio at 5 minutes, and
C is submaximal heart rate at 10 minutes.
The multiple correlation coefficient obtained by
stepwise regression for these three variables in regard
to group selection was .608 with individual linear cor
relations equaling -.392, .059, and .227 for submaximal
respiratory exchange ratio, ventilatory equivalent, and
87
heart rate, respectively. The resulting regression equa
tion for group selection was .0158(C) - 6.47(B) + .0959(A)
+ 2.198 = Group. The prediction results from the discri
minant analysis were as follows:
Actual Group
Group 1
Group 2
Table 11
Prediction Accuracy
Number
of Cases
18
12
Predicted
Group 1
14
(77.8%)
3
(25.0 % )
Predicted
Group 2
4
(22.2%)
9
(75.0%)
A total of 76.7 percent of grouped cases were cor
rectly classified.
These results indicate that those subjects exhibiting
higher submaximal respiratory exchange ratios, lower sub
maximal ventilatory equivalents, and lower submaximal heart
rates were generally included into Group 1 membership. If
fitness were an important determinant of group categoriza
tion, it would be difficult to explain the inconsistencies
(e.g., high R typical of low-fit individuals or low heart
rate typical of high-fit individuals). Fitness was not,
however, an important discriminant.
To summarize, it appears that there are distinguish
able physiologic differences between those who attain a
peak oxygen pulse dur·ng submaximal exercise and those who
do not. Irrespective of exercise modality, centroid
88
separation allowed for greater than 75 percent prediction
accuracy. The canonical correlations were significant on
both treadmill and bicycle discriminants.
89
Chapter 5
DISCUSSION
Discussion of the results will be organized into the
following subsections: (a) oxygen-pulse time course as
affected by exercise modality and level of fitness, (b)
prediction of maximal oxygen consumption, (c) physiological
explanation of group discrimination relationships, and
(d) validity and practicality of the Balke hypothesis of
"optimal work capacity."
Oxygen-pulse Time Course as Affected by
Exercise Modality and Level of Fitness
A comparison of the two testing modalities as they
relate to the time course of oxygen pulse indicates that:
(a) higher maximal oxygen pulses are observed on the
treadmill than on the bicycle, (b) there is a greater ten
dency for occurrence of submaximal peaking in oxygen pulse
on the treadmill than the bicycle, and (c) the approach of
submaxirnal oxygen pulse to maxim~l oxygen pulse in peakers
and non-peakers is different on the two devices.
Maximal oxygen consumption was significantly higher
on the treadmill than on the bicycle; maximal heart rate
was not. This is consistent with the findings of other
investigators (Faulkner et al., 1971; Kaman and Pandolf,
gn
1972). In that oxygen consumption is higher on the tread
mill. The results of this study support this observation.
The differences were statistically significant. The time
course response of oxygen pulse was similar on the two
modalities. However, the slope of the increase in oxygen
pulse seemingly was greater on the bicycle than on the
treadmill, indicating a more rapid onset of fatigue as the
subject approaches maximal oxygen consumption.
Why more subjects would peak on the treadmill than on
the bicycle is an open question. If the tendency for oxy
gen pulse to peak during submaximal work loads were re
lated to peripheral circulatory adjustments, it would be
reasonable to assume that the exercise involving greater
muscular involvement would most likely effect a greater
redistribution of blood during high-intensity work. This
can only be a partial explanation that does not explain
why the phenomenon exists or why there are different re
sponses in different individuals.
Based upon the results, there were no observable
reasons why an individual would peak on one device but not
on the other. Yet, 10 individuals peaked on the treadmill
that did not peak when cycling; and 5 individuals peaked
on the bicycle who did not peak on the treadmill. Further
more, it is difficult to explain why the peakers exhibited
a more favorable cardiorespiratory response to the stress
of cycling, as evidenced by a higher oxygen pulse for a
91
given work intensity and a less favorable response in
running on the treadmill than did the non-peakers. These
questions certainly deserve future study if the explana
tions are to shed light on individual cardiorespiratory
adaptation to various test modalities.
The results indicate that fitness was not an important
criterion for categorizing an individual as a peaker or a
non-peaker. However, a noticeable difference in the slope
of oxygen pulse versus time was observed. The low-fit
individual starts exercise at a higher percentage of maxi
mal oxygen pulse, and the rate of increase is less than the
fit counterpart, particularly on the treadmill (Figures 24
and 25). While the maximal oxygen pulse was higher in the
fit group, the number of individuals who peaked from each
group was not different on either bicycle or treadmill.
This observation lends greater support to the contention
that fitness is not important in determining an indivi
dual's proneness to peaking or non-peaking.
Prediction of Maximal
Oxygen Consumption
The results of this study indicate that maximal oxy
gen consumption is best predicted using stepwise regres-
sion analysis. In disagreement with many of the previous
0
investigators (Astrand and Rhyming, 1954; Wyndham, 1967),
heart rate and subrnaximal oxygen uptake were not the
best predictors of maximal oxygen consumption. At all
92
levels of submaximal exercise, oxygen pulse had a higher
correlation to maximal oxygen consumption than did sub
maximal oxygen consumption (Table 6 and Table 7).
Body surface area, submaximal oxygen pulse, and sub
maximal heart rate were used for the prediction equations
at the three levels of steady-state exercise on the bicy
cle. It is not surprising that body surface area was the
variable most highly correlated with maximal oxygen con
sumption on the bicycle, in which muscle mass is an imper-
tant factor in turning the pedals. Its significance was
not so great in predicting maximal oxygen consumption from
subraaximal treadmill data.
The standard error of the prediction estimate was at
all levels less than +10 percent, an error which is better
0
than that reported by many previous investigators (Astrand
and Rhyming, 1954; Davies, 1968; Fox, 1973; Wyndham,
1967). As one would expect, the standard error was small
er at higher work intensities.
The results are in agreement and support the observa
tion of Wasserman et al. (1967) that for any level of
exercise the individual with the highest oxygen pulse is
the most fit. Spearman Rank-order Correlation of .854
for the bicycle data and of .873 for the treadmill indi
cates that rank did stay relatively constant between sub
maximal oxygen pulse at the 10th minute of exercise on
either device and maximal oxygen consumption.
93
Physiological Explanation of Group
Discrimination Relationships
As described previously in the review of the litera
ture, there are three probable physiologic explanations
for a decreased oxygen pulse with further increases in work
intensity and oxygen uptake. The first explanation is that
a decreased stroke volume accounts for the drop in oxygen
pulse (Karlsson et al., 1967). The second is that there is
a drop in a-v oxygen difference at high work intensities
which accounts for the decrease (Anderson et al., 1974)
and, finally, that a disproportionate increase in heart
rate to oxygen uptake, due to such factors as emotion,
heat, or increased inspired carbon dioxide, accounts for
the drop in oxygen pulse (Henderson and Prince, 1914).
Stroke volume and a-v oxygen difference were not mea-
sured in this investigation. Therefore, any implication as
to changes in these parameters as reported in this study
can only be hypothetical. Nevertheless, in order to attach
significance to the variables which discriminated peaking
and non-peaking groups, it is necessary that the variables
should relate to and be consistent with the possible physi
ologic explanations as described.
It is also necessary to relate the physiologic varia-
bles which were used for group selection on the tread
mill to those used for group selection on the bicycle.
Therefore, if the results are to be considered physiologi
cally significant, they should be consistent between
94
exercise modalities or at least explicable. In the sub
sequent paragraphs, the interrelationship between the
discriminating variables on the bicycle and treadmill will
be discussed as well as their role in explaining the
physiology of oxygen-pulse peaking.
The peaking groups on both bicycle and treadmill exhi
bited higher maximal values for: heart rates, respiratory
exchange ratios, ventilations, and carbon dioxide produced.
While the only statistically significant difference was
maximal heart rate, the group tendency seemed to be consis
tent between modalities.
A significant discriminating variable on the bicycle
was an increased maximal heart rate, while on the treadmill
a lower submaximal heart rate was a significant distin
guishing variable. If fitness were an important factor in
determining one's proneness to peak, lower submaximal heart
rates would seem inconsistent with increased maximal heart
rates (Robinson, 1938). However, fitness was not an
important selection variable. It has often been observed
that some individuals may have a high submaximal heart
rate and low maximal heart rate and/or oxygen consumption.
Also, there are those who show the reverse tendency. In
fact, this was one of Wyndham's (1967) major criticisms of
prediction of maximal oxygen consumption that involved the
use of extrapolation to maximal heart rates. The possi
bility therefore exists that individuals who exhibit
95
submaximal peaking in oxygen pulse may be responsible for
and/or contribute significantly to the large variance and
standard errors found when extrapolating submaximal data to
predict maximal oxygen consumption.
Those who demonstrated a submaximal peak in oxygen
pulse on the bicycle had significantly lower submaximal
VE/R ratios; while on the treadmill, they had significantly
lower submaximal ventilatory equivalents for oxygen and
higher submaximal respiratory exchange ratios. A decreased
VE/R ratio during exercise could be the result of either a
lower ventilation or a higher respiratory exchange ratio
for a given amount of work on the bicycle ergometer. While
•
the submaximal VE/R ratio was not significantly different,
the same tendency was observed on the treadmill as exhib
ited by a higher Rand a lower ventilation (VE/V0
2
) for a
given work intensity. While the variables are different
between the modalities, the physiologic implication is the
same.
To summarize, it appears that regardless of exercise
devices used, those individuals who demonstrate low heart
rates at low work load intensities, high maximal heart
rates, and a disproportionate increase in R for a given
ventilation are most likely to exhibit a submaxirnal peak
in oxygen pulse. In other words , factors such as a hypo
reactivity to metabolic acidosis, an inability of the
central nervous system or respiratory control centers to
96
stimulate ventilation for a given level of anaerobiosis, or
a psychologically or physiologically mediated rise in heart
rate at maximal oxygen consumption may account for the
observed peaking phenomenon.
Unfortunately, the explanations leave something to be
desired. For example, one would expect an individual to
peak or not peak based upon physiologic adaptation to
stress independent of the type of exercise device used.
Yet, several subjects peaked on one device who did not peak
on the other (eight on the treadmill and five on the
bicycle). This difference is not easily explained based
upon present knowledge of individual variation with respect
to modality. An attempt will not be made to relate those
variables which were significant in group discrimination to
the possible physiologic explanations for submaximal
oxygen-pulse peaking as discussed earlier in this chapter.
A higher maximal heart rate as a contributing factor
to one's proneness to obtain a submaximal peak in oxygen
pulse could be explained in two ways. First, the higher
heart rate may have been stimulated by some factor which
contributed to a disproportionate rise in heart rate rela
tive to oxygen consumption. This factor could be an indi
vidual's reactivity to heat or metabolic acidosis; or,
perhaps, from a psychological viewpoint, it may be an emo
tional factor related to the individual's perception of and
ability or inability to tolerate the pain of exhaustion.
97
If this were the case , one would expect the terminal slope
in heart rate when plotted against work load to rise more
rapidly in the peaking groups. The results of this study
indicate that this may be true. When the last three min
utes of bicycle exercise were considered in the peakers and
non-peakers, the average heart rates over the time period
were 184.3, 188.8, and 194.2 for the peakers and 176.3,
180.2, and 184.7 in the non-peakers. The average increase
from the next-to-the-last minute to the last minute of
exercise was 5.4 beats per minute in the peakers versus 4.4
beats per minute for the non-peakers.
The second explanation for peaking as a result of
increased maximal heart rate may be related to the effect
of t~chycardia on stroke volume and cardiac output.
generally accepted that cardiac output decreases when
heart rate increases beyond a critically high value
.
It lS
(Sugimoto, Sagawa, and Guyton, 1966; Wegria, Frank, Wang,
and Lammerant, 1958). The decrease in cardiac output is
caused by an impaired filling of the ventricles at high
rates. Sugimoto et al. (1966) reported that as long as
the atrial pressure increased along with the increased
cardiac frequency, the drop in stroke volume could be
avoided. It can, therefore, by hypothesized that heart
rate alOile is not responsible for the drop in stroke volume
and/or oxygen pulse but that venous return and atrial
pressure also affect the drop . This may provide indirect
98
support of the observation reported by Balke et al. (1954)
that a drop in pulse pressure accompanied the drop in oxy
gen pulse with increased work intensity.
The influence of ventilation and respiratory exchange
ratios on oxygen pulse is not so easily explained. How
ever, the possibility exists that the unresponsiveness of
the respiratory centers to increase ventilation for a
given level of anaerobic metabolism may indicate ineffi
cient respiratory mechanics. Furthermore, if the slower
increase in ventilation for a given work load was caused
by an anatomical factor such that it would cause an in
crease in resistance to air flow, the work of respiration
would be increased. In order to meet the increased demand
for work in the respiratory system. blood would have to be
redistributed away from the working muscle toward the mus
cles of respiration. This could then cause a drop in a-v
oxygen difference which would in effect account for a drop
in oxygen pulse. The fact that a drop in a-v oxygen dif
ference can occur at high levels of exercise is supported
•
by the studies of Astrand et al. (1964) and Ekblom et al.
(1968).
To summarize, the interpretation of results as pre
sented is entirely hypothetical. The physiological inter
pretation of the results seems rational and plausible, but
future studies must be conducted in order to support the
previously mentioned hypothesis.
99
Validity and Practicality of the Balke
Hypothesis of "Optimal Work Capacity"
Before attempting to critique the practicality of
using maximal oxygen pulse as an indication of "optimal
working capacity" (along with heart rate greater than 180
and R greater than 1.00) as proposed by Balke (1954) and
Wells et al. (1956), it is necessary to point out certain
differences between this investigation and the Balke
investigations. Wells et al. studied six normal, healthy,
adult males ranging in age from 22 to 47; the average was
32 years. The average weight, height, and body surface
area were 163 pounds, 70.5 inches, and 1.93 square meters,
respectively. In the present study, 30 young, healthy
males were studied with the age ranging from 18 to 25; the
average was 20.5 years. The average weight, height, and
body surface area were 176 pounds, 71.9 inches, and 2.01
square meters, respectively. The average maximal oxygen
pulse was 15.9 in Balke's study, while it was 20.7 in
this study. In other words, while the procedures were
the same in both studies, the subjects were not. The sub
jects were younger, heavier, taller, and more fit in the
present investigation.
Another important factor which may account for the dif
ferent results between studies is in regard to the effect
of temperature on cardiac function. As reported by Ekelund
and Holmgren (1964) and Rowell, Murray, Brengelmann,
10()
and Kraning (1969), increased temperature can effect a
decrease in cardiac output with increasing exercise in some
individuals. However, neither Balke et al. nor Wells et
al. reported laboratory temperature or humidity; therefore,
comparisons cannot be made between the present investiga
tion and these prior studies. Due to these differences, it
is impossible to generalize about the validity of the
previous studies. Nevertheless, there were several simi
larities and dissimilarities that should be reported.
Balke suggested that submaximal peaking or at least
the achieving of plateau values of oxygen pulse at 180
heart rate is a typical phenomenon. He did not report
individual time-course data on each subject but based his
hypothesis on the average value for his six subjects. Of
the 30 subjects tested in this study, 60 percent, or 18
of 30, peaked in oxygen pulse at submaximal oxygen consump
tion; 40 percent did not. It does not therefore appear
that all individuals demonstrate the aforementioned phenom
enon. Perhaps in older, less-conditioned subjects a
greater percentage would peak, but that cannot be inferred
from the present results.
It was further hypothesized that the peak in oxygen
pulse coincided with the respiratory exchange ratio
exceeding 1.0 and at a heart rate of approximately 180
beats per minute. That was not the case in this study.
The results indicate that R reached unity at an average
101
heart rate of 170.7 beats per minute. The average heart
rate at maximal oxygen pulse was 187.3, significantly
higher physiologically than 180 beats per minute. Had the
oxygen pulse peaked at a heart rate of 180 beats per min
ute in this study, the percentage of maximal heart rate
would have been 94.0 percent. However, in this study the
observed percentage of maximal heart rate was 98.6 percent,
or 4.6 percent different. In other words, if the test had
been stopped at 180 heart rate as suggested by Balke, only
three individuals of the 30 subjects would have reached a
maximal oxygen pulse. The data presented here do not sup
port the use of 180 heart rate as an end point for exercise
in young, healthy, reasonably fit subjects.
102
Chapter 6
SUMMARY, FINDINGS, CONCLUSIONS, AND RECOMMENDA'I'IONS
Summary
The purpose of this study was to investigate the time
course of oxygen pulse as a measure of cardiorespiratory
response from low intensity to maximal intensity exercise.
It was further proposed to investigate the possibility that
oxygen pulse reaches a maximal level during submaximal
exercise and may, consequently, provide information in
regard to an optimal level of circulatory response to
stress. Although previous investigators have observed this
phenomenon, a carefully controlled study which reports in
dividual responses with a relatively large sample size has
not yet been reported.
In this investigation each subject was evaluated on
both a treadmill and bicycle to evaluate the cardiovascu
lar response to stress. A modification of the Balke proto
col was used on the treadmill. A group of 30 young,
healthy, relatively fit males served as subject. Each sub
ject was classified into a subgroup as a consequence of
whether or not a maximal oxygen pulse or a plateauing of
oxygen pulse was demonstrated during submaximal exercise.
lOJ
A statistical analysis was conducted on the data to iden
tify physiological differences between subgroups.
Findings
The results of this investigation indicate that sub
maximal peaking or at least the achieving of plateau
values of oxygen pulse does in fact occur in some but not
all individuals. It was observed that this phenomenon
occurs at a relatively high percentage of maximal heart
rate and maximal oxygen consumption. There were statis
tically significant differences between those individuals
who did or did not reach a submaximal peak in oxygen con
sumption, which can be theoretically explained based upon
the results of previous physiologic experimentation. It
appeared that individuals who demonstrate low heart rates
at low work intensities, high maximal heart rates, and a
disproportionate increase in R for a given ventilation
are most likely to reach a submaximal peak in oxygen
pulse.
The treadmill test proved to be a more sensitive
procedure for the appraisal of oxygen-pulse peaking than
the bicycle and implies that the peaking phenomenon may be
related to circulatory efficiency in adapting to different
modes of exercise. Level of fitness was not an important
factor in determining an individual's tendency for sub
maximal oxygen-pulse peaking based upon the extremes of
104
fitness in this study. These results may not be general
ized to the total population due to the homogeneous sample
studied.
The comparison between exercise modalities indicates
that higher maximal values can be obtained for men in
oxygen uptake and oxygen pulse on the treadmill, while
higher ventilatory equivalent and R were found on the
bicycle. The differences reported between test devices in
this study are consistent with the results of previous
investigators.
Prediction of maximal oxygen consumption from submaxi
mal steady-state data on the bicycle ergometer was relia
ble within +10 percent based upon the finding that the
standard error of estimation of the prediction equations
was less than 10 percent of the maximal observed values.
Submaximal oxygen pulse was a better predictor of oxygen
consumption at all steady-state levels than either sub
maximal oxygen consumption or submaximal heart rate. Body
surface area and heart rate were the most important varia
bles included for the prediction of maximal oxygen con
sumption using multiple regression analysis.
Conclusions
The findings suggest that under the experimental
conditions of this investigation:
1. The observation reported by Balke (1954) that a
peak in oxygen pulse coincides in time with the respiratory
105
exchange ratio exceeding unity and at a heart rate achiev
ing approximately 180 beats per minute cannot be supported
by the present findings in young, healthy, fit subjects.
Of course, from these results one should not exclude the
possibility that oxygen-pulse peaking does occur earlier
during exercise progression in older, less-fit, and/or
possibly unhealthy individuals.
2. The time-course study of oxygen pulse during
increasing work intensity provides a good indication of
cardiorespiratory fitness. Those individuals with a high
oxygen pulse for any given level of exercise will,
.
in
most cases, attain a higher maximal oxygen consumption
regardless of exercise modality.
3. Multiple regression analysis appears to be a more
accurate way of predicting maximal oxygen consumption than
prediction from any one variable. However, the errors of
prediction are such that if precision is required in
assessing cardiovascular function, it would be desirable
to make direct measurements.
Recommendations
Examination of the oxygen-pulse time course was found
to be a useful noninvasive tool in the investigation of
cardiorespiratory adjustment to stress. However, the
interpretation of the results was limited due to the lack
of specific information about physiologic changes in blood
106
gasses and cardiac function at high exercise intensity.
Several important research questions as to an individual's
adaptation to exercise are suggested as a result of the
findings of this investigation.
In the research area, further investigation is needed
to:
1. Relate changes in peripheral blood flow distribu
tion and a-v oxygen difference during high intensity exer
cise to oxygen-pulse progression.
2. Evaluate the changes in cardiac output and stroke
volume at the time oxygen pulse declines during exercise.
3. Examine the effect of age upon the oxygen-pulse
time course.
4. Investigate the effect that a physical condition
ing program may have on the oxygen-pulse time course in
those who exhibit submaximal oxygen-pulse peaking.
5. Examine the effect of inadequate respiratory
responsiveness to metabolic acidosis on heart rate accele
ration and/or circulatory efficiency.
6. Examine the effect that perceived exertion may
have on the acceleration of heart rate during high inten
sity exercise.
7. Examine the effect of heat stress on the oxygen
pulse time course.
107
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114
R BERT ALLEN WI WELL
1945 Born in Lo Angele , California
1964 Graduated fr m Long Beach Polytechnic High chool,
Long Bea h, alifornia
1967-70 Profcs ional Ba eball Pitcher, Atlanta Brave Baseball
Club, Atlan a, Georgia
1968 B.A., niversity of California, Los Ang Ics
1970 M.S., UnivLrsity of California, Los Angeles
1971 75 Graduate Student, University of outhcrn alifornia,
Los Angele
1974-75 Teaching Assist nt Univcr it of South rn California
1975- Assistant Profes or of Phy iology, Departm ·n t of
Gerontology, Univen,ity of Southern alifornia

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Asset Metadata

Creator Wiswell, Robert Allen (author)

Core Title An investigation of oxygen-pulse time course as a measure of cardiorespiratory adaptation to exercise

School College of Letters, Arts and Sciences

Degree Doctor of Philosophy

Degree Program Physical Education

Degree Conferral Date 1975-07

Publication Date 07/28/1975

Defense Date 07/28/1975

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest

Format theses (aat)

Language English

Contributor Electronically uploaded by the author (provenance)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-oUC25331

Unique identifier UC25331

Identifier Ph.D. P.Ed. '76 W818 (call number),etd-WiswellRob-1975.pdf (filename)

Legacy Identifier etd-WiswellRob-1975

Document Type Dissertation

Format theses (aat)

Rights Wiswell, Robert Allen

Internet Media Type application/pdf

Type texts

Source 20230120-usctheses-microfilm-box5 (batch), University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

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Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA

Repository Email cisadmin@lib.usc.edu