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.