The test was considered maximal if it met a minimum of two of the following criteria: a plateau in heart rate (HR) or HR within 10% of maximal predicted HR; a plateau in VO2 or an increase of no more than 150 ml·min−1; a respiratory exchange ratio value greater than 1.15. HR was monitored continuously during exercise by a HR monitor (Polar FS1, Polar Electro Inc. Lake Success, NY).