Aerobic Fitness Percentiles for
U.S. Adolescents
Joey C. Eisenmann, PhD, Kelly R. Laurson, PhD, Gregory J. Welk, PhD
Background: Although aerobic fıtness has been well studied, establishing developmental patterns
from previous studies has some limitations including selection bias and the statistical modeling of
growth-related data.
Purpose: The purpose of this study was to develop age-, gender-, and race-specifıc smoothed
percentiles for aerobic fıtness using the LMS (L⫽skewness, M⫽median, and S⫽coeffıcient of
variation) statistical procedure in a large, multiethnic, nationally representative sample of U.S.
adolescents aged 12–18 years.
Methods: Data from the National Health and Nutrition Examination Survey (NHANES [1999 –
2000 and 2001–2002]) were combined. In all, 2997 subjects (1478 boys and 1519 girls) completed a
treadmill exercise test from which maximal oxygen consumption (VO2max) was estimated from
heart rate response. Percentile curves were determined by using the LMS procedure, which fıts
smooth percentile curves to reference data.
Results: Separate LMS curves were initially prepared for each gender and race; however, since the
overall distribution of the data was not different for whites, blacks, and Hispanics, the participants
were combined, and separate centile curves were prepared for boys and girls. Specifıc percentile
values were created from the LMS curves, and the age- and gender-specifıc values for LMS are
provided for calculation of individual z-scores (SD scores). In general, there is a slight increase in
estimated VO2max of boys aged 12–15 years and then it remains stable. In girls, there is slight
decrease in estimated VO2max across ages 12–18 years. Boys have higher values than girls at every
age-specifıc percentile.
Conclusions: This study presents age- and gender-specifıc percentiles for U.S. youth aged 12–18
years based on NHANES (1999 –2002), and adds to the recent application of the LMS statistical
procedure for the construction of growth percentiles for a variety of outcomes. Comparisons are
made to current FITNESSGRAM® thresholds.
(Am J Prev Med 2011;41(4S2):S106 –S110) © 2011 American Journal of Preventive Medicine
Introduction
T
here has been considerable interest in the healthrelated physical fıtness of contemporary children
and adolescents.1,2 Besides body composition,
and more specifıcally body fatness or its clinical
outcome— obesity—aerobic (or cardiorespiratory) fıtness also receives considerable attention as a healthFrom the Departments of Kinesiology and Pediatrics and Human Development (Eisenmann), Michigan State University, East Lansing; The Healthy
Weight Center at Helen DeVos Children’s Hospital (Eisenmann), Grand
Rapids, Michigan; the School of Kinesiology and Recreation, Illinois State
University (Laurson), Normal, Illinois; and the Department of Kinesiology,
Iowa State University (Welk), Ames, Iowa
Address correspondence to: Joey C. Eisenmann, PhD, 27P IM Circle,
Department of Kinesiology, Michigan State University, East Lansing MI
48824. E-mail: jce@msu.edu.
0749-3797/$17.00
doi: 10.1016/j.amepre.2011.07.005
S106 Am J Prev Med 2011;41(4S2):S106 –S110
related fıtness trait. A main reason why aerobic fıtness
receives attention is the link between aerobic fıtness and
chronic disease in adults.3,4 In children and adolescents,
aerobic fıtness is associated with cardiovascular disease
risk factors5,6 and other health outcomes.2 Recent reports
have indicated that approximately one third of U.S. adolescents possess inadequate levels of aerobic fıtness.7,8
The development of clinical thresholds or recommended
levels of health outcomes in youth generally takes on two
approaches. The fırst is to understand the general developmental pattern in the trait of interest (i.e., age- and genderassociated variation). The second is to determine a specifıc
level that adversely affects risk of health or disease outcome.
The developmental pattern of aerobic fıtness has been well
studied, including the classic cross-sectional investigations
of Robinson9 and Astrand,10 and longitudinal studies (e.g.,
Saskatchewan Growth and Development Study11), and has
© 2011 American Journal of Preventive Medicine • Published by Elsevier Inc.
Eisenmann et al / Am J Prev Med 2011;41(4S2):S106 –S110
12–14
been extensively reviewed.
However, establishing developmental patterns from these data has some limitations,
including selection bias and the statistical modeling of
growth-related data. Recently, the LMS (L⫽skewness,
M⫽median, and S⫽coeffıcient of variation) statistical procedure has become widely used to construct growth percentiles for a variety of outcomes (e.g., height, waist circumference, blood pressure).15–20 In this paper, the LMS procedure
is extended and some of the previous limitations are addressed regarding our understanding of the age- and gender-specifıc variation in aerobic fıtness by creating age-,
gender-, and race-specifıc smoothed percentiles for aerobic
fıtness using the LMS procedure based on a large, nationally
representative data set (National Health and Nutrition Examination Survey, NHANES [1999 –2002]).
Methods
Design and Study Subjects
The National Health and Nutrition Examination Survey is a program of studies conducted by the National Center for Health Statistics, CDC (NCHS/CDC) designed to assess the health and nutritional status of citizens of the U.S. through interviews and direct
physical examinations. Unweighted sample sizes for each 2-year
wave of NHANES has a sample of approximately 2000 school-aged
children and adolescents aged 8 –18 years. However, for this paper,
data of the children aged 12–18 years were combined from the
cross-sectional waves of NHANES (1999 –2000 and 2001–2002)
because aerobic fıtness data are available only for subjects aged
12–18 years (approximately 3300 students). Since this is a nationally representative sample that includes white, black, Hispanic,
Asian, and other ethnic/race groups, the results are generalizable to
U.S. children and adolescents.
All measurements were taken by trained health technicians in
the Mobile Examination Center. Furthermore, quality control
checks were included throughout the data collection procedure.
The training, examination protocol, and quality control procedures are outlined in the NHANES procedures manuals available at
www.cdc.gov/nchs/data/nhanes. Since the data used herein are
publicly available and de-identifıed, approval from an IRB was not
necessary. The entire NHANES protocol was reviewed and approved by the NCHS IRB.
Assessment of Aerobic Fitness
Aerobic fıtness was considered as the estimated maximal oxygen
consumption (VO2max). The aerobic fıtness test was performed by
trained health technicians who were monitored twice per year and
participated in annual retraining for quality control purposes.
Since a maximal exercise test was not feasible in a large sample, the
protocol used a submaximal exercise test. Based on gender, age,
BMI, and self-reported level of physical activity, the non-exercise
VO2max was estimated and used for participant assignment to one
of eight treadmill test protocols.
The goal of each protocol was to elicit a heart rate that was
approximately 75% of the age-predicted maximum (220 – age) by
the end of the test; however, adolescents were allowed to reach 90%
of age-predicted maximum. Each protocol included a 2-minute
October 2011
S107
warm-up, two 3-minute exercise stages, and a 2-minute cool-down
period. Heart rate was monitored continuously using an automated monitor with four electrodes connected to the thorax and
abdomen of the participant and was recorded at the end of warmup, each exercise stage, and each minute of recovery. At the end of
warm-up and each exercise stage, participants were asked to rate
their perceived exertion using the Borg scale. VO2max was estimated by extrapolation of heart rate from the two 3-minute exercise stages to the age-specifıc maximal heart rate (see Appendix G
in the Cardiovascular Fitness Procedures Manual for details of the
equation; www.cdc.gov/nchs/data/nhanes). As adolescents with a
true VO2max greater than 75 mL/kg/min are uncommon, maximal
oxygen consumption values greater than this were set equal to 75
mL/kg/min (1.3% of subjects, n⫽39).
Data Analysis
Descriptive statistics for boys and girls were calculated using SAS v
9.1. Age-, gender-, and race-specifıc percentiles were calculated for
white, black, and Hispanic adolescents. Construction of the centile
curves was performed using the LMS ChartMaker Pro Version 2.3
software program (The Institute of Child Health), which fıts
smooth centile curves to reference data using the LMS method.15
The LMS method essentially summarizes the changing distributions by three curves representing the median (M), coeffıcient of
variation (S), and skewness (L), the latter expressed as a Box-Cox
power transformation. The M curve was fıtted fırst, followed by S
and then L. The three curves are fıtted as cubic splines by nonlinear
regression, and the extent of smoothing required is expressed in
terms of smoothing parameters or equivalent df. Criteria used to
judge the fıt of the curves included equivalent df indices and Q Test
curves (values between –2 and ⫹2).
Results
Descriptive characteristics of the sample by gender are
shown in Table 1. The analytic sample consisted of 1478
boys and 1519 girls, of whom 24.7% were white, 28.2%
black, 43.1% Hispanic, and 4.0% other (values are unweighted percentages).
Separate LMS curves were initially prepared for
each gender and race (fıgures to be included on the
FITNESSGRAM® website). However, since the overall
distribution of the data was not different for whites,
Table 1. Physical characteristics of the sample, aged
12–19 years, NHANES (1999 –2002)
Boys (n⫽1478)
Girls (n⫽1519)
Age (years)
15.6 (0.1)
15.5 (0.1)
Height (cm)
170.1 (0.5)
161.3 (0.2)
Body mass (kg)
66.4 (0.7)
60.2 (0.5)
BMI
22.7 (0.2)
23.0 (0.2)
Estimated VO2max
(mL/kg/min)
46.6 (0.5)
39.0 (0.3)
Note: Values are M (SE).
NHANES, National Health and Nutrition Examination Survey; VO2max,
maximal oxygen consumption
S108
Eisenmann et al / Am J Prev Med 2011;41(4S2):S106 –S110
Figure 1. Estimated VO2max in U.S. boys aged 12–18
years
P, percentile; VO2max, maximal oxygen consumption
blacks, and Hispanics, the participants were combined by
race, and separate centile curves were prepared for boys
(Figure 1) and girls (Figure 2). The specifıc percentile
values created from the LMS curves are provided in Table
2 for girls and boys. In general, there is a slight increase in
estimated VO2max in boys aged 12–15 years (42 to 46
mL/kg/min) and then it remains stable. In girls, there is
slight decrease in estimated VO2max across ages 12–18
years (39 to 37 mL/kg/min). Boys have higher values than
girls at every age-specifıc percentile.
The LMS procedure generates age- and genderspecifıc values (Table 3). These values depict the nature
of the age-related distributions for boys and girls and
can be used to calculate z-scores (SD scores) (z-score
or SD score ⫽ [(Measurement/M)L–1]/(L ⫻ S).
that VO2max decreases during adolescence. Although the
median values show a slight decrease, one may argue that
without knowing the SE of the estimate for the prediction
equation, the VO2max values may be fairly stable.
In recent years, the physical fıtness of youth has been a
concern.1,2 Much of this concern is based on the pediatric
obesity epidemic. It is important to note that body fatness
is one component of health-related physical fıtness.21
Prior to the pediatric obesity epidemic beginning in the
mid-1980s, several studies in pediatric exercise science
focused on VO2max of children. In 1985, Krahenbuhl et
al.12 summarized the available data on directly measured
aerobic fıtness and constructed scatterplots (VO2max by
age) of the available data with a regression line that has
often been cited as the “reference” value for boys and
girls. However, many of the studies included in this review were based on convenient samples, and this perhaps
resulted in higher “typical” values (e.g., 52 mL/kg/min in
boys). In addition, Washington et al.22 published normative data for VO2max from a sample of 151 (70 girls and
81 boys) aged 7–13 years that became widely disseminated for clinical exercise testing.23 The percentiles presented herein are based on NHANES, which employs
random representative sampling involving several race
groups. Thus, this sampling scheme represents a major
strength of the current paper.
On the other hand, a limitation to the current report is
that VO2max was estimated from a submaximal test
rather than being directly measured via indirect calorimetry during a maximal test. Unfortunately, the validity of
this submaximal treadmill test to predict VO2max in
Discussion
This study presents age- and gender-specifıc percentiles
for U.S. youth aged 12–18 years, and adds to the recent
application of the LMS statistical procedure for the construction of growth percentiles for a variety of outcomes
(e.g., height, waist circumference, blood pressure).15–20
These reference values can be used as normative data and
also for baseline values for subsequent surveillance of the
aerobic fıtness level of U.S. adolescents.
The age- and gender-related developmental patterns of
aerobic fıtness have been well studied in nonrepresentative
samples.12–14 Aside from the specifıc values, the growth
curves for boys are similar to previous research on developmental changes in aerobic fıtness. In general, VO2max remains relatively stable in boys. In girls, it is generally thought
Figure 2. Estimated VO2max in U.S. girls aged 12–18
years
P, percentile; VO2max, maximal oxygen consumption
www.ajpmonline.org
Eisenmann et al / Am J Prev Med 2011;41(4S2):S106 –S110
S109
Table 2. Smoothed LMS curves for various percentiles of estimated VO2max (mL/kg/
min) in the 1999 –2002 NHANES
170 beats/minute (PWC
170) is a submaximal test
based on heart rate. In
2nd
5th
10th
15th
25th
50th
75th
90th
95th
this regard, PWC 170 revealed high correlation
BOYS
with VO2max, r ⫽0.84 in
Age (years)
24 boys and 24 girls
12
30.0
32.0
33.9
35.2
37.5
42.3
48.1
54.6
59.2
(mean age ⫽ 15.5⫾0.6
13
30.7
32.7
34.7
36.1
38.4
43.4
49.4
56.0
60.6
years).24 Another limitation is the cross-sectional
14
31.3
33.4
35.5
37.0
39.4
44.5
50.7
57.4
62.0
design. To fully under15
32.0
34.2
36.4
37.9
40.4
45.7
52.0
58.8
63.4
stand the development of
16
32.3
34.6
36.8
38.4
40.9
46.3
52.6
59.4
64.1
VO2max during adoles17
32.2
34.6
36.8
38.4
41.0
46.4
52.8
59.5
64.1
cence, longitudinal studies are required so that
18
32.1
34.5
36.8
38.4
41.0
46.5
52.8
59.5
64.1
the individual trajectories
GIRLS
of VO2max can be examAge (years)
ined by taking into consideration the timing and
12
28.4
30.0
31.6
32.8
34.7
39.0
44.3
50.5
55.1
tempo of growth and
13
27.9
29.6
31.2
32.4
34.4
38.6
43.8
49.7
53.9
maturation.
14
27.4
29.1
30.8
32.1
34.1
38.3
43.4
48.9
52.8
This is not the fırst re15
27.0
28.8
30.5
31.8
33.8
38.0
43.0
48.4
52.1
port to present percentiles for VO2max using
16
26.7
28.5
30.3
31.5
33.5
37.8
42.9
48.3
52.0
these data. Pate and col17
26.7
28.4
30.1
31.4
33.4
37.7
42.9
48.8
52.9
leagues7 calculated un18
26.4
28.1
29.8
31.0
33.0
37.4
42.9
49.2
53.8
smoothed deciles. The
percentiles resulting from
Note: Age indicates whole age group (e.g., 8.0 – 8.99 years).
the LMS procedure were
LMS, L⫽skewness, M⫽median, and S⫽coefficient of variation; NHANES, National Health and Nutrition
Examination Survey; VO2max, maximal oxygen consumption
comparable to the deciles
of estimated VO2max valadolescents aged 12–18 years is not available. The estimaues recently reported by Pate et al. However, they comtion of VO2max is based on the well-established concept
bined age groups (e.g., 12 and 13 years) and did not present
of the linear association between heart rate and VO2 used
LMS coeffıcients for the calculation of an individual SD score.
The calculation of an individual SD score or z-score may prove
in several submaximal exercise tests. Similarly, a test
important to research and clinic evaluation.
such as the physical working capacity at a heart rate of
Table 3. Age-specific LMS values for boys and girls aged 12–18 years
Boys
Age
(years)
Girls
L
M
S
L
M
S
12
–0.60
42.3
0.185
–0.95
39.0
0.180
13
–0.54
43.4
0.186
–0.74
38.6
0.180
14
–0.48
44.5
0.186
–0.54
38.3
0.180
15
–0.42
45.7
0.186
–0.42
38.0
0.180
16
–0.36
46.3
0.186
–0.42
37.8
0.182
17
–0.30
46.4
0.187
–0.59
37.7
0.187
18
–0.24
46.5
0.188
–0.75
37.4
0.194
LMS, L⫽skewness, M⫽median, and S⫽coefficient of variation
October 2011
The importance of aerobic fıtness in clinical and
health screenings is noteworthy, given its relationship with cardiovascular
disease risk factors in
youth and other health
outcomes2 and the tracking of VO2max from adolescence into adulthood,25
where it is known to influence morbidity and mortality.3,4 Despite the increased recognition of
aerobic fıtness as a risk
factor for adverse chronic
medical conditions,26 there
S110
Eisenmann et al / Am J Prev Med 2011;41(4S2):S106 –S110
remains little consensus on a universally accepted classifıcation system for childhood and adolescence. Currently, thresholds from FITNESSGRAM,27 a comprehensive youth fıtness assessment program that provides
criterion-referenced standards for health-related physical
fıtness, are widely used in the U.S. Using the previous
FITNESSGRAM healthy fıtness zone thresholds, about
33% of U.S. adolescents have a “low fıtness” level.7,8 Data
are not available to determine prevalence of low fıtness
using the new samples.
This brief report presents the age- and gender-specifıc
percentiles for aerobic fıtness of a nationally representative sample of U.S. boys and girls aged 12–18 years. This
information provides useful reference data to facilitate
future epidemiology research on aerobic fıtness in youth.
Publication of this article was supported by The Cooper Institute through a philanthropic gift from Lyda Hill.
No fınancial disclosures were reported by the authors of this
paper.
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