Aerobic exercise training preceded by respiratory muscle endurance training: a synergistic action enhances the hypoxic aerobic capacity

Excerpt

We would like to thank Esposito and Ferretti (2010) for their constructive comments on our recent work (Keramidas et al. 2010a) regarding the effect of respiratory muscle endurance training (RMT) on normoxic and hypoxic exercise performance. In their letter, they suggest that the marked increase of the hypoxic aerobic capacity that we observed (Keramidas et al. 2010a) could be ascribed, in part, to the decreased circulatory (R _Q) and peripheral (R _p) resistance (di Prampero and Ferretti 1990) induced by the aerobic exercise training that followed RMT (Esposito and Ferretti 2010). This is a reasonable hypothesis and, in fact, is supported by the findings in our recent study (Keramidas et al. 2010b), in which we investigated the effect of a 30-min voluntary isocapnic hyperpnoea task on cerebral, respiratory and leg muscle oxygenation, measured by NIRS during a subsequent constant-power cycle ergometer test. In particular, we observed that when short-term respiratory work preceded the endurance exercise test, the regional blood volume, as reflected by the total hemoglobin (Δ[tHb]) (Van Beekvelt et al. 2001), in the vastus lateralis and serratus anterior muscle, markedly diminished compared to the control constant-power test. These responses seem to reflect the inability of the circulatory system to meet the increasing energy demands of both locomotor and respiratory muscles (Vogiatzis et al. 2009), and most likely explains the higher perception of dyspnoea and leg effort that the participants experienced during our RMT protocol (Keramidas et al. 2010a). Hence, we assume that the hypoxic microenvironment in the working muscles as a consequence of the two combined (synergetic) training stimuli (RMT and aerobic exercise) is much greater than that induced by each stimulus individually, thus potentially enhancing the central (Ekblom et al. 1968) and peripheral (Costes et al. 2001) training responses of the subjects in our study (Keramidas et al. 2010a). …