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

Adolescents demonstrated greater short-term breathing frequency variability than adults during submaximal exercise.

• Breathing frequency SD1 was 4.7 (3.7–5.4) vs. 2.6 (2.5–3.3) 1·min-1 in adolescents vs. adults (p < 0.01)
• Breathing frequency SD2 was 4.9 (4.2–6.8) vs. 3.6 (3.5–4.3) 1·min-1 in adolescents vs. adults (p < 0.05)
• SD1 and SD2 are Poincaré plot measures reflecting short-term and long-term variability, respectively
• 12 adolescents (10–14 years) and 10 adults (25–35 years) were compared

Adolescents showed greater minute ventilation variability relative to body weight than adults.

• V̇E relative to body weight SD1 was 0.02 (0.02–0.03) vs. 0.01 (0.01–0.02) L·min-1·kg in adolescents vs. adults (p < 0.01)
• This was assessed using Poincaré analysis during the final 15 minutes of a 20-minute submaximal cycling bout at 1.0 W·kg-1
• Continuous variables were expressed as median (interquartile range) and compared by the Mann-Whitney U-test (α = 0.05)

Approximate entropy of ventilatory variables was higher in adolescents than adults, indicating greater randomness in breathing patterns.

• ApEn for V̇E was 1.23 (1.20–1.32) vs. 1.01 (0.93–1.25) in adolescents vs. adults (p < 0.05)
• ApEn for breathing frequency was 1.26 (1.24–1.33) vs. 1.17 (1.01–1.18) in adolescents vs. adults (p < 0.01)
• ApEn for tidal volume was 1.33 (1.26–1.37) vs. 1.23 (1.14–1.27) in adolescents vs. adults (p < 0.05)
• Higher ApEn values indicate greater irregularity and randomness in the time series

The study protocol involved submaximal steady-state cycling with ventilatory analysis performed over the final 15 minutes.

• Participants completed 20 minutes of submaximal cycling at 1.0 W·kg-1
• The final 15 minutes of exercise were analyzed using Poincaré and approximate entropy (ApEn) analyses
• Sample included 12 adolescents aged 10–14 years and 10 adults aged 25–35 years
• Both Poincaré plot descriptors (SD1, SD2) and ApEn were used to assess ventilatory variability and randomness

Greater ventilatory variability in adolescents is interpreted as reflecting developmental plasticity and immature ventilatory control.

• The authors state findings "likely reflect developmental plasticity and immature ventilatory control"
• Adolescence involves rapid physiological changes that may affect ventilatory control
• Both measures of variability (Poincaré SD1/SD2) and randomness (ApEn) were consistently higher in adolescents across multiple ventilatory parameters