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.