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