Influence of Inspiratory Muscle Training of Various Intensities on the Physical Performance of Long-Distance Runners

The aim of this study was to assess the efficacy of inspiratory muscle training (IMT) at different intensities on the pulmonary function and physiological adaptations of long-distance runners undergoing sports training. This study involved 25 long-distance runners. The subjects were randomly divided into three groups depending on the type of IMT applied: POWERbreathe device (group 1), Threshold IMT device (group 2), and a control group. The following lung variables were evaluated: vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in one second (FEV₁) and peak expiratory flow (PEF). Respiratory muscle strength was assessed by maximum inspiratory pressure (PImax) and maximum expiratory pressure (PE_max). Spiroergometric measures included: heart rate (HR), oxygen uptake (VO_2max), carbon dioxide production (VCO_2max), maximum ventilation (VE) and respiratory exchange rate (RER), which were measured breath by breath using a gas analyser (VYNTUS CPX). Group 1, which used the POWERbreathe device, showed significant increases in all assessed physiological and physical performance variables. In group 2, which used the Threshold device, only VO_2max, VE and tRER ventilation were significantly increased to a similar level as that observed in group 1. In the control group, we only observed a significant reduction in saturation. The use of IMT with a higher intensity resulted in significant improvements in all tested variables of lung ventilation and respiratory muscle strength. Also, after training, lactate accumulation was significantly decreased. Physiological characteristics (VO_2max/kg) and muscle respiratory strength variables were significantly improved in the group that used the POWERbreathe device after 8 weeks of training.