Reliability of peak O2 uptake and O2 uptake kinetics in step exercise tests in healthy subjects

•This study proposes an alternative stress test to evaluate VO2 on-kinetics, i.e., step tests. This extends our possibilities to a more cost-effective methodology in this field.•VO2 on-kinetics evaluation on step tests are reliable in healthy subjects.•New studies in selected patients groups would be necessary to establish this method in clinical settings.•Adjustments in step height, exercise intensities and individualized approach will be necessary to expand its application.

To date little is known about the reliability of peak oxygen consumption (V˙O2PEAK) in incremental metronome paced step tests (IST) and the reliability of on-kinetics V˙O2 has never been studied. We aimed to study the reliability of both tests. Eleven healthy subjects performed two ISTs until exhaustion. On two different days two duplicate 4 min constant metronome paced step tests (CST) were performed. V˙O2PEAK, mean response time (MRT) and phase II time constant (τ) were tested for reproducibility using the paired t-tests, in addition to the limits of agreement (LOA) and within subject coefficient of variation (COV). With a 95% LOA of 0.38 to 0.26 L min−1, −8.7 to 9.1 s and −9.9 to 10.5 s they exhibit a COV of 3%, 4.5% and 6.9% for V˙O2PEAK, MRT and τ respectively. ST are sufficiently reliable for maximal and submaximal aerobic power assessments in healthy subjects and new studies of oxygen uptake kinetics in selected patient groups are warranted.