What is the central question of this study? Is the attenuation of the respiratory muscle metaboreflex preserved after detraining? What is the main finding and its importance? Inspiratory muscle training increased respiratory muscle strength and attenuated the respiratory muscle metaboreflex as evident by lower heart rate and blood pressure. After 5weeks of no inspiratory muscle training (detraining), respiratory muscle strength was still elevated and the metaboreflex was still attenuated. The benefits of inspiratory muscle training persist after cessation of training, and attenuation of the respiratory metaboreflex follows changes in respiratory muscle strength. Respiratory muscle training (RMT) improves respiratory muscle (RM) strength and attenuates the RM metaboreflex. However, the time course of muscle function loss after the absence of training or 'detraining' is less known and some evidence suggest the respiratory muscles atrophy faster than other muscles. We sought to determine the RM metaboreflex in response to 5weeks of RMT and 5weeks of detraining. An experimental group (2F, 6M; 26±4years) completed 5weeks of RMT and tibialis anterior (TA) training (each 5days/week at 50% of maximal inspiratory pressure (MIP) and 50% maximal isometric force, respectively) followed by 5weeks of no training (detraining) while a control group (1F, 7M; 24±1years) underwent no intervention. Prior to training (PRE), post-training (POST) and post-detraining (DETR), all participants underwent a loaded breathing task (LBT) to failure (60% MIP) while heart rate and mean arterial blood pressure (MAP) were measured. Five weeks of training increased RM (18±9%, P<0.001) and TA (+34±19%, P<0.001) strength and both remained elevated after 5weeks of detraining (MIP-POST vs. MIP-DETR: 154±31 vs. 153±28cmH2O, respectively, P=0.853; TA-POST vs. TA-DETR: 86±19 vs. 85±16N, respectively, P=0.982). However, the rise in MAP during LBT was attenuated POST (-11±17%, P=0.003) and DETR (-9±9%, P=0.007) during the iso-time LBT. The control group had no change in MIP (P=0.33), TA strength (P=0.385), or iso-time MAP (P=0.867) during LBT across all time points. In conclusion, RM and TA have similar temporal strength gains and the attenuation of the respiratory muscle metaboreflex remains after 5weeks of detraining.
Read full abstract