Peak Circulatory Power during Maximal Cardiopulmonary Exercise Testing: Reference Standards from the FRIEND Registry

Med Sci Sports Exerc. 2022 Jun 30. doi: 10.1249/MSS.0000000000002985. Online ahead of print.


Purpose: Normative standards for key cardiopulmonary exercise test variables, including peak circulatory power (CircP), are needed to guide the interpretation of clinical exercise responses in individuals with and without disease.

Objective: To establish age- and sex-specific reference standards for peak CircP derived from a healthy cohort from the Fitness Registry and the Importance of Exercise: A National Database (FRIEND).

Methods: Cardiopulmonary exercise test (CPX) data from apparently healthy males and females from eight FRIEND United States exercise laboratories were considered. Inclusion criteria included ages 20-79 years and a maximal, symptom-limited exercise test performed on a treadmill or cycle ergometer. CircP was calculated as the product of peak oxygen consumption and peak systolic blood pressure. Reference values were determined on both treadmill and cycle ergometer for males and females per age decade. A stepwise linear regression to predict CircP was derived from two-thirds of the sample while the remaining one-third was used as a validation cohort.

Results: A total of 6736 CPX tests (47% treadmill, 53% female) were included in the analysis. Overall, CircP was higher in males, higher on tests conducted on a treadmill, and decreased with age. Sex, exercise mode, age, and body mass index were the most significant contributors to CircP (multiple R = .75, R2 = .57, RMSE = 1,200 mmHg·mlO2·kg-1·min-1, P < 0.001). Using the generated prediction equation, the average percent-predicted CircP for the validation cohort was 101.3 ± 28.1%.

Conclusions: These results establish reference standards for CircP, a potentially important prognostic indicator of cardiovascular health. Future research exploring the role of percentiles and percent-predicted values for CircP are necessary as they may provide additional prognostic insight.