Key Concepts about the Cardiovascular Fitness Data Files

The main outcome of this component is the estimated maximal oxygen uptake (VO2max). Based on sex- and age-specific criteria, the estimated VO2max also is categorized and reported as a low, moderate, or high level of cardiovascular fitness. Detailed descriptions of the protocol are provided in the NHANES Cardiovascular Fitness Procedures Manual.1

The cardiovascular fitness component was implemented in the NHANES MEC from 1999 to 2006 (half sample in 2005-2006) for eligible study participants aged 12-49. When possible, it is strongly recommended that data users merge the cardiovascular fitness data collected in multiple cycles of NHANES from 1999 to 2006 to ensure an adequate sample size for analysis. Information on how to merge and append data from separate cycles will be covered in Course 2, Module 3: Merge & Append Datasets.

To ensure the safety and validity of the treadmill test used to measure cardiovascular fitness, a series of exclusion criteria were developed to exclude participants with conditions that might endanger them during the testing or affect the estimation of the VO2max from the exam. Key points regarding exclusions, early test terminations, and protocol modifications for the cardiovascular fitness examination can be found in the Additional Resources section of this tutorial. A complete list of exclusion criteria and categorical classification variables are provided in Appendix A of the Cardiovascular Fitness Documentation, Codebook, and Frequencies.1  The examination status for each participant is indicated by the variable CVDEXSTS.  Participants with valid treadmill fitness data are indicated by a code of “1”. Participants who did not have a VO2max estimated either did not participate in the treadmill test or the data obtained during the treadmill test were insufficient for calculating VO2max. 

The data are provided in a single file, found on the Examination page for each NHANES 2-year cycle.

Cardiovascular Fitness

File Name: CVX
Data Contained in the Data File:

  • CVX exam status
  • Comment code for the exam status
  • Reasons for exclusion
  • Self-reported participant physical activity level
  • Predicted VO2max based on sex, age, body mass index, and self-reported physical activity level
  • Assigned treadmill exercise protocol
  • Actual protocol used in stages 1 and 2
  • Estimated VO2max, predicted based on submaximal treadmill test
  • Cardiovascular fitness level, categorized as low, moderate, or high based on available reference standards 2-5


  1. NHANES Cardiovascular Fitness Procedures Manual
  2. American College of Sports Medicine. (1995). ACSM’s Guidelines for Exercise Testing and Prescription, 6th edition. Philadelphia, PA: Lippincott Williams and Wilkins Company.
  3. Blair, S.N., Kohl, H.W. 3rd, Paffenbarger, R.S. Jr., et al. (1989). Physical Fitness and All-Cause Mortality. A Prospective Study of Healthy Men and Women. JAMA, 262(17), 2395-401.
  4. Cureton, K.J. and Warren, G.L. (1990). Criterion-Referenced Standards for Youth Health-Related Fitness Tests: A Tutorial. Research Quarterly for Exercise and Sport, 61(1), 7-19.
  5. Cureton, K.J. and Plowman, S.A. (1999). Aerobic Capacity Assessments. In Welk G.J., Morrow, J.R. Jr., and Falls H.B. (Ed.) Fitnessgram Reference Guide (pp. 66-86). Dallas, TX: Cooper Institute.


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