Reliability and validity of the steep ramp test to assess cardiorespiratory fitness in apparently healthy adults

Purpose
To investigate the test-retest reliability and validity of the steep ramp test (SRT), a short and practical maximal exercise test on a cycle ergometer, for assessing CRF in apparently healthy adults aged 25–85 years.

Methods
To determine test-retest reliability, the reliability group performed the SRT twice within 2–14 days. The intraclass correlation coefficient (ICC) for the attained work rate at peak exercise (WRpeak) at the SRT was calculated and agreement was evaluated using Bland-Altman plots. The smallest detectable change (SDC) was calculated. To determine criterion and construct validity of the SRT, the validity group performed both the SRT and cardiopulmonary exercise testing (CPET) on a single day. Correlation analyses were used to assess the relationship between SRT WRpeak and oxygen uptake (V̇O2) at peak exercise (V̇O2peak), V̇O2 at the first ventilatory threshold (V̇O2VT1), and the oxygen uptake efficiency slope (OUES) achieved during CPET.

Results
In the reliability group (n = 66, 35 males), the ICC for SRT WRpeak was 0.992. Limits of agreement ranged from − 18.6 W (-5.4%) to 24.1 W (6.5%). The SDC was 15 W, 0.2 W/kg, or 4.2%. In the validity group (n = 61, 33 males), CPET V̇O2peak, V̇O2VT1, and OUES showed Pearson’s correlation coefficients with SRT WRpeak of 0.936, 0.806, and 0.891, respectively. The following equation predicts V̇O2peak (mL/min) from SRT performance: -280.784 + (8.680 × SRT WRpeak (in W)) (adjusted R2 = 0.874, SEE = 318.476).

Conclusion
This study demonstrated excellent test-retest reliability, very high criterion validity, and high construct validity of the SRT for assessing CRF in apparently healthy adults.