Ventilation and entrainment of breathing during cycling and running in triathletes

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.

Eight triathletes performed three incremental tests until exhaustion: while cycling (CE), while running at increasing grade and constant speed (increasing GRADE) and while running at increasing speed and constant grade (increasing 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, deltaVE/VO2 between nonentrained and entrained breaths was measured at each load.

Mean E was higher in CE (57.2+/-21.9%) than in increasing GRADE (46.9+/-18.7%) and increasing SPEED (41.4+/-17.2%). E decreased at high loads in CE and increasing SPEED but not in increasing GRADE. In the group of subjects, E correlated with the degree of fitness (evaluated as VO2Tvent/VO2peak%) only during increasing 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 increasing GRADE experiments, but the difference was small.

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 increasing GRADE protocols.