Repeatability and reproducibility of changes in thoracoabdominal compartmental volumes and breathing pattern during...

To determine how repeatable thoracoabdominal compartmental contributions to tidal volume (V_T) are across different intensities of exercise, and to examine if the pattern of breathing for a given minute ventilation (V̇_E) is reproducible between constant-load and ramp exercise tests.

Ten healthy adults (age: 27 ± 6 yr, peak oxygen uptake: 42 ± 5 mL min^-1 kg^-1) completed a 25 W·min^-1 ramp cycling test to exhaustion and two repetitions of a step cycling test on separate days. V_T, breathing rate (BR), and V̇_E were assessed using a bi-directional turbine, and thoracic and abdominal contributions to V_T were measured using respiratory inductance plethysmography. Repeatability (step vs. step) and reproducibility (step vs. ramp) of responses were assessed using the intra-class correlation coefficient (ICC).

The relative compartment contributions to V_T during step exercise were highly repeatable for low (ICC = 0.87, p = 0.003), moderate (ICC = 0.89, p = 0.002) and heavy (ICC = 0.93, p = 0.001) exercise. Inter-individual differences in response to higher intensity exercise were observed, as two participants had significant relationships between V_T and their percent compartmental contributions to V_T, but five others did not. No differences were identified between ramp and step exercise tests for V_T (main effect: p = 0.61) or BR (main effect: p = 0.77) at matched V̇_E for each intensity, and the pattern of breathing was reproducible for each intensity.

These findings suggest the way young healthy adults breathe for a given V̇_E is repeatable day-to-day and reproducible between different exercise protocols.