Step two

On the second day in the laboratory, volunteers performed the CPET on a cycle ergometer (Quinton Corival® 400, Seattle, USA) with a ramp-type protocol to assess the CF. The power increment was calculated using the formula described by Wasserman, considering height, age, and sex [14]. The test consisted of: (1) five minutes at rest, (2) three minutes unloaded warm-up, (3) 9.6±1.4 minutes ramp protocol (with 20.7±7.1 watts per minute increment), and (4) six minutes unloaded cycling for active recovery. All volunteers were encouraged to keep a constant cycling of 60 to 65 rpm and were stimulated to continue the CPET until volitional fatigue. The oxygen uptake and minute ventilation were measured breath-by-breath by a metabolic system (Vmax29c, Sensor Medics, Yorba Linda, CA, USA) calibrated before each experiment, according to the manufacturer’s manual. Moreover, heart rate (HR) was calculated during the exercise based on a single lead ECG system (BioAmp FE132, ADInstruments, Australia).

The interruption criteria were according to previous work [16], and just one volunteer had the CPET interrupted due to the unexpected (excessively high) increase in arterial pressure. One volunteer was also excluded from this study due to oxygen desaturation on resting immediately before the CPET.