UTILITY OF A NON-EXERCISE METHOD
OF ESTIMATING AEROBIC CAPACITY
University of Northern Iowa
Aerobic capacity is the ability to exercise at
relatively high intensities for extended
periods of time.
Many exercise physiologists believe aerobic
capacity is the best indicator of overall
physical fitness in a person (Blair, 1995).
Maximal oxygen uptake (VO2max) is a direct
measure of aerobic capacity
Heart rate is an indication of the amount of work
the heart must do to meet the demands of the
body during work and exercise (Wilmore & Costill,
It is well known that heart rate and oxygen
consumption increase linearly with exercise
intensity and that they are linearly related to
each other (ACSM, 2000).
Physically trained individuals have a lower
resting heart rates as compared to sedentary
individuals (Dixon, Kamath, McCartney, & Fallen, 1992).
Maximum heart rate is defined as the highest
heart rate value attainable during an all-out
effort to the point of exhaustion (Wilmore & Costill,
Maximum heart rate is largely associated
with one’s age, steadily decreasing about one
beat per year beginning in early adolescence.
It can be estimated by subtracting one’s age
(in years) from 220.
Heart Rate Variability
HRV is defined as the beat-to-beat
alterations in heart rate and is based on the
changes in R-R intervals from one beat to the
Heart Rate Variability
Some authors conclude that HRV increases
due to training (Dixon and colleagues, 1992).
Age is another factor that affects heart rate
variability (HRV). With increasing age, HRV
decreases. (Molgaard, Sorensen, & Bjerregaard, 1991).
This suggests the important role of long-term
exercise and its effect in mitigating the loss of
HRV in active people.
Measuring Aerobic Capacity
Field test protocols include:
step tests, bicycle ergometer tests, distance run
tests, walking tests, and shuttle run tests.
Distance run tests have been the test of
choice for estimating aerobic capacity among
children in a school setting.
moderately high reliability and validity, ranging
from approximately .60 to .90 (Safrit, 1990)
The PACER Test
“Progressive Aerobic Cardiovascular
The PACER is the recommended assessment
for aerobic capacity in the FITNESSGRAM
test battery and has become quite popular in
recent years, particular in school settings
(Meredith & Welk, 2005).
The PACER Test
The controlled nature of the workload (pace)
serves to largely eliminate the problem with
pacing that is a limitation of distance run
The resultant score on the PACER is the total
number of laps completed. The longer a
person continues, the higher the rate of
estimated oxygen uptake.
The PACER Test
Reliability of the PACER among youth has
consistently been reported as moderate or
high, with reliability coefficients ranging from
r = .64 to r = .96
(Legar, et al., 1982; Van Mechelen, Hlobil & Kemper, 1986; Liu, Plowman, &
Looney, 1992; Mahar et al., 1997; Plowman & Liu, 1999; Beets & Pitetti,
The Pacer Test
Validity of the PACER for predicting aerobic
capacity in children and adolescents ranges
from approximately r = .55 to r = .90,
depending upon the gender and age of the
(Leger et al., 1988; Van Mechelen, Hlobil & Kemper, 1986; Boreham,
Paliczka, & Nichols, 1990; Liu, Plowman, & Looney, 1992; Mahar et al.,
1997; Mahar, Crotts, McCammon, & Rowe, 2002; McIver, Pfeiffer,
Mahar, & Pate, 2004; Mahar, Welk, Rowe, Crotts, & McIver, 2006;
Cureton & Plowman, 2006)
According to Erdmann and colleagues
(1999), non-exercise prediction of VO2max
would be useful as a nontraditional method in
estimating aerobic capacity in youth.
Such a prediction test could be used as a
screening tool, particularly suited for those
individuals with inconsistent pacing efforts
during exercise field testing.
Studies have shown that N-EX equations for
predicting aerobic capacity are relatively
accurate for an adult population
R values ranging from .73 to .93
(Jackson et al., 1990; Heil et. al, 1995; George et. al, 1997; Matthews et. al,
1999; Bradshaw et al., 2005; Jurca et al., 2005)
Jackson and colleagues (1990) found that the
accuracy of prediction is substantially lower
among highly fit subjects
Polar Fitness Test
The Polar F11 HRM measures 255 heart beats in a 3-5
minute time period during which the subject relaxes
in a supine position (Polar Electro Oy, 2006).
A 4-point scale, adapted from the 7-point NASA/JSC
scale developed by Jackson et al. (1990), is used to
assess physical activity level.
About half the variance of one’s OwnIndex score
(i.e., VO2max) is explained by the combination of
heart rate variability, resting heart rate, and physical
activity assessment. The other half is explained by
the demographic variables of gender, age, height,
Polar Fitness Test
The general consensus is that the Polar
Fitness Test is a valid and reliable measure of
maximal aerobic power in adult men and
women. (Validity, R=.97) (Polar Electro Oy, 2006)
There appears to be sparse research on the
use of the Polar Fitness Test and its
associated HRMs with children.
The present study was designed to test the
utility of the Polar Fitness Test as a measure
of aerobic capacity in an adolescent
population by comparing estimates of VO2max
by the Polar F11 HRM with VO2max predicted
using the PACER test.
Participants in this study consisted 33 of high
school students (18 males and 15 females)
Age ranged from 14 to 18 years
All were students of Grundy Center High
school in Grundy Center, Iowa [USA] during
The PACER was administered in accordance
with recommended test procedures (Meredith &
All students are required to take the test
during the first part of the academic
Testing took place inside the school
gymnasium on a 20-meter shuttle run course.
During the PACER testing, the students were
encouraged by their teachers to put forth
maximum effort for as long as possible.
Students were instructed to aim for their
heart rate to be as close to their predicted
maximum heart rate (220 - participant’s age).
While performing the PACER test, all
students wore heart rate monitors.
Polar Test Protocol
The Polar Fitness Test was administered to
participating students within a few weeks of
completing the PACER test.
All participating students were fitted with a
Polar F11 HRM in order to calculate their
OwnIndex score, the equivalent to VO2max.
The following variables were pre-loaded by the
investigator into each student’s HRM: age,
height, weight, sex, and activity level.
Activity level was based on self-reported activity
assessment using the 4-level scale prescribed for
use with Polar heart rate monitors (Polar Electro Oy,
The activity levels were as follows:
1 – low (does not participate regularly in
recreational sport or heavy physical activity);
2 – middle (participates regularly in recreation
3 – high (participates regularly, at least 3 times a
week, in heavy physical activity);
4 – top (participates regularly in heavy physical
exercise at least 5 times a week).
Polar Test Protocol
Participants sat quietly for approximately 2
minutes in order to obtain their resting heart
To obtain the measures for heart rate and heart
rate variability, participants were instructed to:
limit body movement, refrain from talking, and lie
(sit) quietly for approximately 5 minutes.
During this time the Polar F11 HRM obtained
measures on 255 heart beats (Polar Electro Oy, 2006).
Scores (laps completed) obtained during the
PACER test were converted to maximal
oxygen consumption (VO2max) (Welk, 2008).
Means and standard deviations were
calculated for all measured variables.
An independent groups t-test was used to
determine if there was a significant difference
between males and females on the variables
The relationship between VO2max scores
estimated using the PACER test and VO2max
scores derived from the Polar Fitness Test was
determined using the Pearson product-
A dependent groups (paired) t-test was used to
test for significant differences in mean VO2max
estimated from the two tests.
Effect size was calculated to estimate the
magnitude of the difference.
Participants were classified as to whether they
met the age and gender specific Healthy Fitness
Zone standards using VO2max estimates obtained
from each test.
Classification equivalency between the two methods
was calculated using the Kappa statistic.
A Bland-Altman analysis and plot was used to
assess the level of agreement between the
PACER and the Polar Fitness Test (Bland &
The Bland-Altman technique is a graphical
All statistical analyses were performed using
the Statistical Package for the Social
Sciences, version 11.0 (SPSS Inc., Chicago, IL).
The significance level was set at = .05 for all
The Pearson product-moment correlation
between PACER predicted VO2max and
VO2max predicted from the Polar Fitness
Test using the Polar F11 HRM was r = 0.62 (p <
20 30 40 50 60
POLAR Fitness Test Predicted VO2max
Scatter plot of relationship between PACER predicted VO2max and Polar Fitness Test
Results of a paired t-test indicated a
significant difference between PACER
predicted VO2max and Polar Fitness Test
(t = 4.61, df = 32, p < .05).
Effect size was estimated by calculating
Cohen’s d for repeated measures which
resulted in a value of 1.61
a large effect according to Cohen (1988).
The mean difference score ( SD) between
PACER predicted VO2max and Polar Fitness Test
predicted VO2max for the total sample was 6.69
with the Polar Fitness Test yielding a lower VO2max for
24 of the 33 research participants.
The Polar Fitness Test predicted higher VO2max
values for six participants, while three
participants had virtually the same estimated
VO2max values using the two tests.
Bland-Altman plot and 95% confidence limits
which illustrate the degree of agreement
between the two methods of estimating
Coefficient kappa was used to determine the
criterion-referenced equivalence between the
PACER and the Polar Fitness Test using the Polar
The resultant kappa value of 0.16 was not
statistically significant (p > .05) and constitutes
“slight agreement.” (Landis and Koch, 1977)
This indicates that the adolescents in the present
study were classified differently by the two tests.
This study was designed to investigate the utility of a non-
exercise procedure for predicting aerobic capacity in
adolescent boys and girls.
Specifically, the study examined the equivalency of the
Polar Fitness Test (i.e., Polar F11 HRM) and the PACER in
predicting VO2max among a sample of high school students.
The results suggest that the Polar Fitness Test and the
PACER do not provide similar information about the
aerobic capacity among the study sample.
The environmental conditions in a typical school setting
may not be conducive to the proper administration of the
Polar Fitness Test.
Lack of a laboratory-based criterion measure makes
it impossible to judge whether the Polar Fitness Test
or the PACER is the more valid test of aerobic
The inability to precisely follow the standardized
directions for the Polar Fitness Test may have
compromised the accuracy of the predicted aerobic
The study sample was very homogeneous in nature
and included only one ethnic/racial minority student.
the results of the current suggest that the Polar
Fitness Test and the PACER do not provide similar
information about the aerobic capacity among
The results indicate that, compared to the
PACER, the Polar Fitness Test consistently
underestimates the aerobic capacity of adolescent
boys and girls.
The practical side of the study indicates that the
environmental conditions and lack of control in a
typical school setting may not be conducive to the
proper administration of the Polar Fitness Test.
Suggestions for Future
Validation of Polar Test with children and adolescents
Control internal validity, with a measurement of the Polar
Test in “laboratory- like” settings.
Administer the Polar Test at the same time of day for all
Have each participant during the Polar Test in a lying
Use true resting heart rate values for participants taken
over a 24 hour period with a HRM.