Abstract: Background: The ventilatory equivalent for CO2 (VE ⁄ VCO2) is the simplest way to predict the ventilatory efficiency. Objectives: This study aimed to investigate the impact of treadmill and cycle ergometer exercise tests on ventilatory outcomes in healthy adolescents. Methods: In this clinical trial with cross-over design, 52 adolescents aged 11-16 years old (Age (year) 13.8 ± 0.17, Height (cm) 157.4 ±0.95, Weight (Kg) 51.73 ± 1.24 -Mean± S.E), went through treadmill and cycle ergometer exercise tests with a 6-day wash-out in July-August 2019, Tehran, Iran. Through a RAMP protocol, participants were asked to perform the maximal treadmill or cycle ergometer exercise and continue the test until exhaustion. Gas exchange and heart rate (HR) were obtained breath by breath during the test. Time, HR, VE/VCO2, minute ventilation) VE (, end-tidal CO2 (PetCO2), and dead space to tidal volume Ratios (VD/VT) were transferred to the computer and recorded. All data were reported at two time points: 1) Anaerobic Threshold V-Slop Method (AT), 2) PEAK. Independent t-test was performed to compare the two types of exercise, using SPSS 16, and p˂0.05 was considered significant. Results: The results showed that the type of exercise for Time and VE / VCO2 there is a significant difference in two points, but for HR (p=0.004), VE (p=0.0001), PetCO2 (p=0.008), and VD/VT (p=0.004) significant difference only in AT point. Conclusions: Several physiological mechanisms occurring during the development stage could affect individuals’ respiratory parameters; however, in general, the type of exercise test affects VE / VCO2 .
