Peak power output measurement
RPE, hypoxia
HYPOXIA
In the second visit to the laboratory, a maximal incremental test was performed under hypoxia using a cycle ergometer (Cyclus 2, RBM Elektronik-automation GmbH, Leipzig, Germany) by each participant to determine the peak power output (PPO). To do so, each participant first was exposed to hypoxia for 30 min in a resting position and then performed an incremental cycling test until voluntary exhaustion. Before starting the test, the position of the saddle was adjusted for each participant and this position was recorded to be used in the subsequent sessions. The test started at 50 W for 2 min with the pedal cadence of 60 rpm and then, the power output increased by 50 W each 3 min (with the same cadence, 60 rpm) until the volitional exhaustion. Verbal encouragement was applied to avoid test withdrawal before reaching the real point of failure. Participants reported their RPE on a 0–100 Borg scale during the last 10 s of each 3-min phase and at the time of exhaustion. Meeting two of the following criteria during the incremental test was deemed as the point of real exhaustion: (1) HR ≥ 90% of age-predicted maximal HR (220-age), (2) inability to maintain the pedal cadence of 60 rpm for more than 5 s despite verbal encouragement, (3) RPE ≥ 90. The PPO was calculated according to the following formula: 