Utility of Field Tests for Predicting Cardiorespiratory Fitness and Prescribing Exercise Intensity in Cardiac Rehabilitation Programs: A Randomized Crossover Trial

The aims of this study are the following: To examine whether field tests predict cardiorespiratory fitness in people with coronary heart disease (CHD) and to determine if heart rate (HR) agreement between the first ventilatory threshold (VT₁) and field tests is sufficient for prescribing exercise intensity. Participants randomly completed field tests and a cardiopulmonary exercise test (CPET). Linear regression models were developed to predict VT₁. Agreement between predicted and measured peak oxygen consumption (V̇O_2peak) as well as field test terminal HR and HR at VT₁ (VT_1HR) was assessed using Pearson correlations, Bland-Altman analyses, mean absolute percentage error (MAPE), Lin's concordance correlation coefficient (CCC), and standard error of estimate (SEE). Agreement between predicted and measured V̇O_2peak was modest (Pearson's r = 0.27-0.77; Lin's CCC = 0.132-0.735; MAPE = 16.1-30.1%; SEE = 4.7-6.8 mL·kg^-1·min^-1). Agreement between field test terminal HR and VT_1HR was moderate (Pearson's r = 0.50-0.67; Lin's CCC = 0.36-0.68; MAPE = 8.9-13.7%; SEE = 11.9-18.7 bpm; Bland-Altman 95%LOA = -3.5 to 13.7 bpm). Field tests demonstrated variable accuracy for predicting V̇O_2peak, with none meeting predefined agreement criteria. Regression models indicate field tests can estimate VT_1; however, levels of HR agreement indicate CPET is necessary for prescribing exercise intensity.