NCHS Data Brief ■ No. 153 ■ May 2014

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for Health Statistics

Physical fitness has been defined as “a set of attributes that people have 

or achieve that relates to the ability to perform physical activity” (1). 

Cardiorespiratory fitness is one component of physical fitness and is defined 

as the “ability of the circulatory and respiratory systems to supply fuel during 

sustained physical activity and to eliminate fatigue products after supplying 

fuel” (1). Cardiorespiratory fitness is most often measured by maximal oxygen 

uptake (VO2

max), which is the maximum capacity of the body to transport 

and use oxygen during physical activity (2). This report presents the most 

recent national data on the percentage of youth who had adequate levels of 

cardiorespiratory fitness. Adequate levels of cardiorespiratory fitness are based 

on standards that are age- and sex-specific and established based on how fit 

children need to be for good health. 

Keywords: exercise testing • National Health and Nutrition Examination 

Survey • National Youth Fitness Survey

One-half of boys and about one-third of girls aged

12–15 years had adequate levels of cardiorespiratory fitness. 

Key findings

Data from the National 

Health and Nutrition 

Examination Survey 

(NHANES), 1999–2004 

and the NHANES National 

Youth Fitness Survey, 

2012

• In 2012, about 42% of

U.S. youth aged 12–15 years

had adequate levels of 

cardiorespiratory fitness. 

• The percentage of youth 

who had adequate levels of 

cardiorespiratory fitness did 

not differ by race and Hispanic 

origin, or by family income-topoverty ratio.

• The percentage of youth 

who had adequate levels 

of cardiorespiratory fitness 

decreased as weight status 

increased.

• The percentage of youth 

aged 12–15 who had adequate 

levels of cardiorespiratory 

fitness decreased from 52.4% 

in 1999–2000 to 42.2% in 

2012. 

Cardiorespiratory Fitness Levels Among U.S.

Youth Aged 12–15 Years: United States, 1999–2004 and 2012

Jaime Gahche, M.P.H.; Tala Fakhouri, Ph.D., M.P.H.; Dianna D. Carroll, Ph.D.; Vicki L. Burt, Sc.M., R.N.; 

Chia-Yih Wang, Ph.D.; and Janet E. Fulton, Ph.D.

Figure 1. Percentage of youth aged 12–15 who had adequate levels of cardiorespiratory fitness, 

by sex and age group: United States, 2012

42.2 43.6 40.6

1

50.2 1

51.2 1

49.1

33.8 35.7 31.8

0

20

40

60

80

100

Total (12–15 years) 12–13 years 14–15 years

Percent

Confidence interval Total Boys Girls

1

Significantly different from girls in the same age category, p < 0.05.

NOTE: Access data table for Figure 1 at: http://www.cdc.gov/nchs/data/databriefs/db153_table.pdf#1.

SOURCE: CDC/NCHS, NHANES National Youth Fitness Survey, 2012.
NCHS Data Brief ■ No. 153 ■ May 2014

■  2  ■

• Overall, 42.2% of youth aged 12–15 years had adequate levels of cardiorespiratory fitness in 

2012 (Figure 1). 

• A higher percentage of boys (50.2%) aged 12–15 had adequate levels of cardiorespiratory 

fitness compared with girls of the same age (33.8%). 

• A similar pattern between age groups was observed for youth aged 12–13 and 14–15. 

For both age groups, a higher percentage of boys than girls had adequate levels of 

cardiorespiratory fitness. 

• There was no significant difference between the younger and older age groups, for girls or 

boys, in the percentage of those who had adequate levels of cardiorespiratory fitness. 

The percentage of youth aged 12–15 who had adequate levels of 

cardiorespiratory fitness did not differ by race and Hispanic origin or family 

income-to-poverty ratio. 

• There was no difference in the percentage who had adequate levels of cardiorespiratory 

fitness among non-Hispanic white, non-Hispanic black, and Hispanic youth (Figure 2).

• There was no statistically significant difference in the percentage of youth who had adequate 

levels of cardiorespiratory fitness among youth in families with incomes less than 130% 

of the federal poverty guidelines (43.5%), 130%–349% of the federal poverty guidelines 

(39.6%), or 350% or more of the federal poverty guidelines (43.6%). 

43.6

39.6

43.5

42.7

37.6

44.2

0 20 40 60 80 100

350% or more

130%–349%

Less than 130%

Hispanic

Non-Hispanic black

Non-Hispanic white

Percent

Race and other

 Hispanic origin

Family income-to-

 poverty ratio 

Confidence interval

Figure 2. Percentage of youth aged 12–15 who had adequate levels of cardiorespiratory fitness, by race and Hispanic

origin and family income-to-poverty ratio: United States, 2012

NOTE: Access data table for Figure 2 at: http://www.cdc.gov/nchs/data/databriefs/db153_table.pdf#2.

SOURCE: CDC/NCHS, NHANES National Youth Fitness Survey, 2012.
NCHS Data Brief ■ No. 153 ■ May 2014

■  3  ■

A higher percentage of normal weight youth had adequate levels of 

cardiorespiratory fitness compared with overweight or obese youth.

• Among all youth aged 12–15, a higher percentage of normal weight youth (54.1%) had 

adequate levels of cardiorespiratory fitness compared with overweight (29.9%) or obese 

(20.0%) youth (Figure 3).

20.0

29.9

2

54.1

0 20 40 60 80 100

Obese

Overweight

Normal weight1

Percent

Figure 3. Percentage of youth aged 12–15 who had adequate levels of cardiorespiratory fitness, by weight status: 

United States, 2012

1

Normal weight category also includes underweight category.

2

Significant linear trend by weight status, p < 0.05.

NOTE: Access data table for Figure 3 at: http://www.cdc.gov/nchs/data/databriefs/db153_table.pdf#3.

SOURCE: CDC/NCHS, NHANES National Youth Fitness Survey, 2012.

Confidence interval
NCHS Data Brief ■ No. 153 ■ May 2014

■  4  ■

The percentage of youth aged 12–15 who had adequate levels of 

cardiorespiratory fitness decreased from 52.4% in 1999–2000 to 42.2% in 

2012. 

• Overall, 52.4% of youth in 1999–2000, 51.1% in 2001–2002, 47.6% in 2003–2004, and 

42.2% in 2012 had adequate levels of cardiorespiratory fitness (Figure 4). 

• A higher percentage of boys than girls had adequate levels of cardiorespiratory fitness for all 

periods. 

• The percentage of boys who had adequate cardiorespiratory fitness levels decreased 

significantly from 64.8% in 1999–2000 to 50.2% in 2012. The percentage of girls decreased 

from 40.5% in 1999–2000 to 33.8% in 2012, however, this was not significant.

0

20

40

60

80

100

Girls2

Boys1,2

Total

1

NHANES NNYFS 2012

2003–2004

NHANES

2001–2002

NHANES

1999–2000

Percent

Figure 4. Percentage of youth aged 12–15 who had adequate levels of cardiorespiratory fitness, by sex and survey

period: United States, 1999–2004 and 2012

1

Significant linear trend.

2

Statistically significant difference for boys compared with girls for all time periods, p < 0.05.

NOTES: NHANES is National Health and Nutrition Examination Survey. NNYFS is NHANES National Youth Fitness Survey. Access data table for Figure 4 at: 

http://www.cdc.gov/nchs/data/databriefs/db153_table.pdf#4.

SOURCES: CDC/NCHS, National Health and Nutrition Examination Survey, 1999–2000, 2001–2002, 2003–2004 and NHANES National Youth Fitness Survey, 

2012.

52.4 51.1

47.6

42.2

64.8 63.1

59.2

50.2

40.5 40.4

35.4

33.8
NCHS Data Brief ■ No. 153 ■ May 2014

■  5  ■

Summary

This report presents the percentage of U.S. youth aged 12–15 who had adequate levels of 

cardiorespiratory fitness, by sex, age group, race and Hispanic origin, family income-to-poverty 

ratio, weight status, and across time. The findings indicate that one-half of boys and one-third 

of girls aged 12–15 had adequate levels of cardiorespiratory fitness. No significant differences 

were found in the percentage of youth having adequate levels of cardiorespiratory fitness by race 

and Hispanic origin, or by family income-to-poverty ratio. Compared with normal weight youth, 

a smaller percentage of overweight and obese youth had adequate levels of cardiorespiratory 

fitness. About one in five adolescents aged 12–19 in the United States is obese (3). 

The percentage of youth who had adequate levels of cardiorespiratory fitness was compared 

across four survey periods: NHANES 1999–2000, 2001–2002, 2003–2004, and NNYFS 2012. 

The findings indicate the percentage of youth with adequate cardiorespiratory fitness decreased 

from 52.4% in 1999–2000 to 42.2% in 2012. 

Definitions

Adequate Cardiorespiratory Fitness: Refers to the “Healthy Fitness Zone” threshold established 

and developed by the Cooper Institute’s fitness assessment, FITNESSGRAM, a youth physical 

fitness testing program that has been used by schools and school districts nationally. The 

“Healthy Fitness Zone” threshold is age- and sex-specific. It was established by comparing youth 

cardiorespiratory fitness levels with measures of health in a nationally representative sample 

(NHANES 1999–2002) aged 12–18 (4). 

Family income-to-poverty ratio (FIPR): Calculated by dividing family income by a poverty 

measure specific for family size. The U.S. Department of Health and Human Services’ poverty 

guidelines were used as the poverty measure to calculate FIPR (5). FIPR accounts for inflation. 

Income eligibility for participation in the Supplemental Nutrition Assistance Program (SNAP) is 

130% of the FIPR (< 130% FIPR) (6). Larger FIPRs indicate greater income.

Weight status: Categories were based on the Centers for Disease Control and Prevention’s (CDC) 

sex-specific 2000 body mass index (BMI)-for-age growth charts for the United States (7). The 

three categories were underweight or normal weight (a BMI-for-age less than the 85th percentile), 

overweight (a BMI-for-age ranging from the 85th to less than the 95th percentile), and obese (a 

BMI-for-age greater than or equal to the 95th percentile).

Data sources and methods

NHANES 1999–2000, 2001–2002, and 2003–2004 and NNYFS 2012 were used for the analyses 

presented in this report, and all data are publicly available on the NHANES website. Both 

NHANES and NNYFS are conducted by CDC’s National Center for Health Statistics (NCHS) to 

monitor the health and nutritional status of the U.S. population. Both of these population-based 

surveys use a complex, stratified, multistage probability cluster sampling design. NHANES 

data collection is based on a nationally representative sample covering all ages of the civilian 

noninstitutionalized United States (8). NNYFS was a 1-year survey conducted in 2012 to obtain 

data on the physical activity and fitness levels of children and adolescents aged 3–15 years in 

the United States (9). This survey was conducted in conjunction with the 2012 NHANES and 
NCHS Data Brief ■ No. 153 ■ May 2014

■  6  ■

the survey design was based on the design for NHANES, with the NNYFS sample selected from 

an independent sample of dwelling units within the segments selected for NHANES. In both 

NHANES and NNYFS, participants received an interview at their homes and then a physical 

fitness examination in a specially equipped mobile examination center. 

Cardiorespiratory fitness was measured using a submaximal treadmill test. This test was 

conducted using the same protocol for all survey periods (10,11). Participants were assigned to 

one of five treadmill test protocols varying in grade and speed based on sex, age, BMI, and level 

of self-reported physical activity. The goal of each protocol was to elicit a heart rate that was 

approximately 75% of the age-predicted maximal heart rate. Heart rates after each of the two 

exercise stages were then used in an equation to estimate VO2

max. The percentage of youth who 

had adequate levels of cardiorespiratory fitness was then determined based on the thresholds set 

by The Cooper Institute (12). 

Self-reported race and Hispanic origin groups as defined in NHANES and used in the analysis 

were non-Hispanic white, non-Hispanic black, Hispanic, and ‘‘other.’’ Following NCHS 

recommendations, the ‘‘other’’ racial or ethnic group was included in the estimates for the total 

sample, but was not presented separately as a group. 

All analyses used the examination sample weights, which account for unequal probabilities of 

selection, person-level nonresponse, and a poststratification adjustment to the estimated U.S. 

population. Taylor series linearization was used to calculate standard errors. Confidence limits of 

95% were constructed using the Wald method. Differences between groups were assessed using 

a univariate t statistic at the p < 0.05 significance level with the appropriate degrees of freedom. 

To test for linear trends, the null hypothesis of a nonlinear trend was examined using orthogonal 

polynomials. Statistical analyses were conducted using SAS version 9.3 (SAS Institute, Inc., 

Cary, N.C.) and SUDAAN version 11.0 (RTI International, Research Triangle Park, N.C.). 

About the authors

Jaime Gahche, Tala Fakhouri, Vicki L. Burt, and Chia-Yih Wang are with CDC’s National Center 

for Health Statistics, Division of Health and Nutrition Examination Surveys. Dianna D. Carroll 

is with CDC’s National Center on Birth Defects and Developmental Disabilities, and Janet E. 

Fulton is with CDC’s National Center for Chronic Disease Prevention and Health Promotion.

References

1. Caspersen CJ, Powell KE, Christenson GM. Physical activity, exercise, and physical fitness: 

Definitions and distinctions for health-related research. Public Health Rep 100(2):126–31. 1985.

2. Gordon RS, Franklin KL, Baker JS, Davies B. Determination of aerobic work and power on 

a rope-braked cycle ergometer by direct measurement. Appl Physiol Nutr Metab 31(4):392–7. 

2006.

3. Ogden CL, Carroll MD, Kit BK, Flegal KM. Prevalence of childhood and adult obesity in the 

United States, 2011–2012. JAMA 311(8):806–14. 2014.
NCHS Data Brief ■ No. 153 ■ May 2014

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4. Welk GJ, Laurson KR, Eisenmann JC, Cureton KJ. Development of youth aerobic-capacity 

standards using receiver operating characteristic curves. Am J Prev Med 41(4 Suppl 2):S111–6. 

2011.

5. U.S. Department of Health and Human Services. Poverty guidelines, research, and 

measurement. Available from: http://aspe.hhs.gov/POVERTY/index.cfm [Accessed March 25, 

2014].

6. U.S. Department of Agriculture. Supplemental Nutrition Assistance Program (SNAP): 

Eligibility. Available from: http://www.fns.usda.gov/snap/eligibility [Accessed March 28, 2014].

7. Ogden CL, Flegal KM. Changes in terminology for childhood overweight and obesity. 

National health statistics reports; no 25. Hyattsville, MD: National Center for Health Statistics. 

2010.

8. Zipf G, Chiappa M, Porter KS, et al. National Health and Nutrition Examination Survey: Plan 

and operations, 1999–2010. National Center for Health Statistics. Vital Health Stat 1(56). 2013.

9. Centers for Disease Control and Prevention. National Health and Nutrition Examination 

Survey National Youth Fitness Survey (NNYFS), 2012. Hyattsville, MD: National Center for 

Health Statistics. 2013. Available from: http://www.cdc.gov/nchs/data/nnyfs/NNYFS_Plan_Ops.

pdf [Accessed November 5, 2013].

10. Centers for Disease Control and Prevention. National Youth Fitness Survey (NYFS) 

Treadmill Examination Manual. Hyattsville, MD: National Center for Health Statistics. 2013. 

Available from: http://www.cdc.gov/nchs/data/nnyfs/Treadmill.pdf [Accessed November 5, 

2013].

11. Centers for Disease Control and Prevention. Cardiovascular Fitness Procedures Manual. 

Hyattsville, MD: National Center for Health Statistics. 2004. Available from: http://www.cdc.gov/

nchs/data/nhanes/nhanes_03_04/cv_99-04.pdf [Accessed November 5, 2013].

12. Meredith MD, Welk GJ. Fitnessgram & Activitygram Test Administration Manual, Updated 

4th Edition. Dallas, TX: The Cooper Institute. 2010.
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Suggested citation

Gahche J, Fakhouri T, Carroll DD, et al. 

Cardiorespiratory fitness levels among U.S. 

youth aged 12–15 years: United States, 

1999–2004 and 2012. NCHS data brief, no 

153. Hyattsville, MD: National Center for 

Health Statistics. 2014.

Copyright information

All material appearing in this report is in 

the public domain and may be reproduced 

or copied without permission; citation as to 

source, however, is appreciated.

National Center for Health 

Statistics

Charles J. Rothwell, M.S., M.B.A., Director

Jennifer H. Madans, Ph.D., Associate 

Director for Science

Division of Health and Nutrition

 Examination Surveys

Kathryn S. Porter, M.D., M.S., Director