Purpose: To assess whether entrainment of breathing (E) during exercise: 1) differed according to the test protocol in well-trained triathletes, and 2) improved ventilatory efficiency during exercise.
Methods: Eight triathletes performed three incremental tests until exhaustion: while cycling (CE), while running at increasing grade and constant speed (↑ GRADE) and while running at increasing speed and constant grade (↑ SPEED), respectively. E was evaluated as the percentage of breaths occurring at respiratory rates (F) corresponding to integer ratios of the exercise cycle rate. To assess whether E improved ventilatory efficiency,Δ˙VE/˙VO2 between nonentrained and entrained breaths was measured at each load.
Results: Mean E was higher in CE (57.2 ± 21.9%) than in ↑ GRADE (46.9± 18.7%) and ↑ SPEED (41.4 ± 17.2%). E decreased at high loads in Ce and ↑ SPEED but not in ↑ GRADE. In the group of subjects, E correlated with the degree of fitness (evaluated as˙VO2Tvent/˙VO2peak%) only during ↑ GRADE. By multiple regression analysis on all data, minute ventilation correlated with CO2 production but not with the exercise cycle rate; however, either F or tidal volume correlated significantly with both these variables.˙VE/˙VO2 was lower in entrained than nonentrained breaths at each load in CE and ↑ GRADE experiments, but the difference was small.
Conclusions: In spite of some differences among protocols, triathletes showed significant E during incremental exercise tests. Spontaneous E appeared to slightly improve ventilatory efficiency during CE and ↑ GRADE protocols.