Key Concepts about Identifying Cardiovascular Fitness Variables and File Locations

NHANES data files are organized into four categories:

  • Demographics files contain survey design variables, such as sample weights, strata, and primary sampling units, as well as demographic characteristics, such as sex, age, and race.
  • Examination files contain information collected through interviews in the mobile exam center and physical exams (including anthropometric and physical activity data, dental exams, and 24-hour dietary recall interviews).
  • Laboratory files contain results from analyses of blood, urine, hair, tuberculin skin test, air, and household dust and water specimens.
  • Questionnaire files contain data collected through household and Mobile Examination Center (MEC) interviews.

Cardiovascular fitness variables are included in the CVX data file, which is stored in the Examination section for each 2-year cycle of the continuous NHANES. 

The CVX file includes the estimated maximal oxygen uptake for study participants, extrapolated from results of the submaximal treadmill test. The file also includes variables to describe whether participants successfully completed the test, their cardiovascular fitness level, and their assigned treadmill exercise protocol.

Sample of Cardiovascular Fitness Variables
Variable Name Description
SEQN Respondent sequence number
CVDEXSTS & CVDEXCMT CV fitness exam status and comment code
CVDEXCL1 – CVDEXCL6 Exclusion criteria
CVQ220A – CVQ220M Categorical stopping criteria status
CVDEXLEN Length of CV fitness exam
CVDPMHR Predicted maximal heart rate (per min)
CVXPARC Physical activity readiness code
CVDVOMAX Predicted VO2max (ml/kg/min)
CVAPROT Assigned exercise protocol
CVDPROT Exercise protocol  used in stage 1 and 2
CVDESVO2 Predicted cardiovascular fitness (based on age, body mass index, and self reported active level)
CVDFITLV Estimated cardiovascular fitness level