Validity of a perceptually-regulated step test protocol for assessing cardiorespiratory fitness in healthy adults.

PURPOSE: To determine whether maximal oxygen uptake (VO2max) could be predicted accurately and reliably from a 2-step, perceptually-regulated exercise test (PRET) in healthy adults.

METHODS: Sixteen participants (31.7 ± 11.3 years, 3 females) completed three PRETs (separated by 24-72 h) and one maximal, perceptually-regulated, graded exercise test (PRETmax) on a motorized treadmill. Oxygen uptake (VO2) and heart rate (HR) were recorded during each test. VO2 values for RPE range 9-15 were extrapolated to RPE 20 and age-predicted maximal HR (HRmax) using individual linear regression analysis to predict VO2max values compared to measured VO2max.

RESULTS: VO2 and HR values were consistent between each of four RPE levels of the PRET. ICC values ranged between 0.76 and 0.85. Predicted VO2max from both methods were lower than measured VO2max (p < 0.01). Limits of agreement (LoA) for measured (41.4 ± 5.3 ml kg(-1) min(-1)) versus predicted VO2max from each of the three PRETs using RPE20 were -1.2 ± 15.6, -1.0 ± 7.2 and -2.1 ± 5.5 and for HRmax were -1.8 ± 4.2; -2.6 ± 4.2 and -2.4 ± 4.4 ml kg(-1) min(-1) for PRET 1, 2 and 3, respectively.

CONCLUSIONS: The step PRET elicited significant and reliable increases in VO2 across the four RPE levels, but under-estimated treadmill VO2max. However, there was better agreement between measured and predicted VO2max when extrapolated to HRmax. As evidence indicates the underestimation of VO2max is explained by the difference in the mode of exercise, the step PRET provides a simple and convenient test of cardiorespiratory fitness.