Jonathan Wagner, Max Niemeyer, Denis InfangerID, Timo Hinrichs,Clement Guerra, Christopher Klenk,
Karsten Ko¨nigsteinID, Christian Cajochen, Arno Schmidt-Trucksa, Raphael KnaierID

https://doi.org/10.1371/journal.pone.0245306

Objective
This study compared the robustness of a V_ O2-plateau definition and a verification-phase
protocol to day-to-day and diurnal variations in determining the true V_ O2max. Further, the
additional value of a verification-phase was investigated.
Methods
Eighteen adults performed six cardiorespiratory fitness tests at six different times of the day
(diurnal variation) as well as a seventh test at the same time the sixth test took place (dayto-
day variation). A verification-phase was performed immediately after each test, with a
stepwise increase in intensity to 50%, 70%, and 105% of the peak power output.
Results
Participants mean V_ O2peak was 56 ± 8 mL/kg/min. Gwet’s AC1 values (95% confidence
intervals) for the day-to-day and diurnal variations were 0.64 (0.22, 1.00) and 0.71 (0.42,
0.99) for V_ O2-plateau and for the verification-phase 0.69 (0.31, 1.00) and 0.07 (−0.38, 0.52),
respectively. In 66% of the tests, performing the verification-phase added no value, while, in
32% and 2%, it added uncertain value and certain value, respectively, in the determination
of V_ O2max.
Conclusion
Compared to V_ O2-plateau the verification-phase shows lower reliability, increases costs
and only adds certain value in 2% of cases.