Key Concepts about Cardiovascular Fitness Data Collection Methods

Cardiovascular Fitness Data Collection

Submaximal treadmill testing was used to estimate cardiovascular fitness levels during the NHANES survey cycles of 1999 to 2006 for participants aged 12 to 49 years. Each participant was assigned to one of eight treadmill test protocols of increasing exercise workload, based on a predicted maximal oxygen uptake (VO₂ max). 

The goal of each protocol was to elicit a heart rate that was approximately 75 percent of the age-predicted maximum heart rate (PMHR) by the end of the test [PMHR = (220 - (age at interview)]. If the heart rate at the end of the warm-up period was below 50% or above 60% of an individual’s PMHR, the initial protocol was modified to provide a more appropriate exercise workload to elicit the target heart rate. Specific details are provided in Appendix J of the Cardiovascular Fitness Procedures Manual.¹

The primary outcome measure of the submaximal treadmill test, estimated VO₂ max, is a linear function of heart rate and oxygen consumption during exercise. Due to the nature of extrapolating cardiovascular fitness from a submaximal test, some VO₂ max estimates may appear physiologically implausible. This subject, and guidance on how extreme values should be handled in an analysis, will be addressed in Course 2 of the tutorial.

Exclusions, early test terminations, and protocol modifications can affect data interpretation. Once you develop your research question, you should review these to evaluate whether or not they have the potential to affect your analyses. For additional information, visit the Additional Resources section of this tutorial.