Variability of ventilation during exercise is greater in adolescents than in adults

Adolescence involves rapid physiological changes that may affect ventilatory control. This study used Poincaré and approximate entropy (ApEn) analyses to assess ventilatory variability and randomness during steady-state exercise in adolescents and adults. Twelve adolescents (10-14 years) and 10 adults (25-35 years) completed 20 min of submaximal cycling at 1.0 W·kg^-1. The final 15 min were analyzed using Poincaré and ApEn. Continuous variables were expressed as median (interquartile range) and compared by the Mann-Whitney U-test (α = 0.05). Adolescents showed greater breathing frequency (BF) standard deviation (SD) 1 4.7 (3.7-5.4) vs. 2.6 (2.5-3.3) 1·min^-1 (p < 0.01), BF SD2 4.9 (4.2-6.8) vs. 3.6 (3.5-4.3) 1 min^-1 (p = <0.05) and minute ventilation (V̇_E) relative to body weight SD1 0.02 (0.02-0.03) vs. 0.01 (0.01-0.02) L·min^-1·kg (p = <0.01). ApEn was also higher in adolescents for V̇_E 1.23 (1.20-1.32) vs. 1.01 (0.93-1.25) (p = <0.05), BF 1.26 (1.24-1.33) vs. 1.17 (1.01-1.18) (p < 0.01) and tidal volume 1.33 (1.26-1.37) vs. 1.23 (1.14-1.27) (p < 0.05). This study suggests that adolescents showed greater ventilatory variability and randomness compared to adults, likely reflecting developmental plasticity and immature ventilatory control.