Purpose: It has long been suggested that inspiratory muscle activity may impact blood lactate levels ([Lac−]B) during the recovery from dynamic exercise. In this study, we tested the hypothesis that inspiratory muscle activation during recovery from intense exercise would contribute to La− clearance, thus leading to reduced [Lac−]B.
Methods: Twelve healthy men underwent two maximal, incremental exercise tests on different days. During a 20-min inactive recovery period, they breathed freely or against a fixed inspiratory resistance of 15 cm H2O. During recovery, pulmonary gas exchange was continuously monitored, and serial samples of arterialized venous blood were obtained for [Lac−]B, pH, PCO2, and HCO3−.
Results: Subjects presented similar ventilatory and gas-exchange responses at peak exercise during both experimental conditions. [Lac−]B during recovery was reduced with inspiratory resistance (7.7 ± 1 vs 10.4 ± 1, 7.8 ± 2 vs 10.3 ± 2, and 7.3 ± 1 vs 9.7 ± 2 mM at 5, 7, and 9 min of recovery, respectively; P < 0.05), but no differences were found for blood acid-base status. Inspiratory resistance was associated with increased metabolic demand (V˙O2 and V˙CO2) but improved ventilatory efficiency, with lower V˙E/[V˙CO2] and increased alveolar ventilation.
Conclusion: These data are consistent with the notion that inspiratory muscles may be net consumers of lactate during recovery from intense exercise.
1Exercise Pathophysiology Research Laboratory, 2Biomedical Engineering, and 3Cardiology Divisions, Hospital de Clinicas de Porto Alegre, Porto Alegre, BRAZIL; 4Department of Medicine, Faculty of Medicine, Federal University of Rio Grande Sul, Porto Alegre, BRAZIL; and 5Pulmonary Function and Clinical Exercise Physiology Unit, Respiratory Division, Federal University of Sao Paulo, Sao Paulo, BRAZIL
Address for correspondence: Jorge P. Ribeiro, M.D., Sc.D., Associate Professor and Chief on Noninvasive Cardiology, Hospital de Cli`nicas de Porto Alegre, Rua Ramiro Barcelos 2350, 90035-007, Porto Alegre, RS, Brazil; E-mail: firstname.lastname@example.org.
Submitted for publication March 2007.
Accepted for publication August 2007.