Inspiratory muscle training abolishes the blood lactate increase associated with volitional hyperpnoea superimposed on exercise and accelerates lactate and oxygen uptake kinetics at the onset of exercise

We examined the effects of inspiratory muscle training (IMT) upon volitional hyperpnoea-mediated increases in blood lactate ([lac−]B) during cycling at maximal lactate steady state (MLSS) power, and blood lactate and oxygen uptake kinetics at the onset of exercise. Twenty males formed either an IMT (n = 10) or control group (n = 10). Prior to and following a 6-week intervention, two 30 min trials were performed at MLSS (207 ± 28 W), determined using repeated 30 min constant power trials. The first was a reference trial, whereas during the second trial, from 20 to 28 min, participants mimicked the breathing pattern commensurate with 90% of the maximal incremental exercise test minute ventilation (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}_{\text{E}} $$\end{document}). Prior to the intervention, the MLSS [lac−]B was 3.7 ± 1.8 and 3.9 ± 1.6 mmol L−1 in the IMT and control groups, respectively. During volitional hyperpnoea, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{V}_{\text{E}} $$\end{document} increased from 79.9 ± 9.5 and 76.3 ± 15.4 L min−1 at 20 min to 137.8 ± 15.2 and 135.0 ± 19.7 L min−1 in IMT and control groups, respectively; [lac−]B concurrently increased by 1.0 ± 0.6 (+27%) and 0.9 ± 0.7 mmol L−1 (+25%), respectively (P < 0.05). Following the intervention, maximal inspiratory mouth pressure increased 19% in the IMT group only (P < 0.01). Following IMT only, the increase in [lac−]B during volitional hyperpnoea was abolished (P < 0.05). In addition, the blood lactate (−28%) and phase II oxygen uptake (−31%) kinetics time constants at the onset of exercise and the MLSS [lac−]B (−15%) were reduced (P < 0.05). We attribute these changes to an IMT-mediated increase in the oxidative and/or lactate transport capacity of the inspiratory muscles.