Ventilation and entrainment of breathing during cycling and running in triathletes

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 (up arrow GRADE) and while running at increasing speed and constant grade (up arrow 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, Delta(V) over dot(E)/(V) over dotO(2) between nonentrained and entrained breaths was measured at each load. Results: Mean E was higher in CE (57.2 +/- 21.9%) than in up arrow GRADE (46.9 +/- 18.7%) and up arrow SPEED (41.4 +/- 17.2%). E decreased at high loads in CE and up arrow SPEED but not in up arrow GRADE. In the group of subjects, E correlated with the degree of fitness (evaluated as (V) over dot(2Tvent)/(V) over dotO(2peak%)) only during up arrow GRADE. By multiple 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. (V) over dot(E)/(V) over dotO(2) was lower in entrained than nonentrained breaths at each load in CE and up arrow 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 up arrow GRADE protocols.