Fig. (3) Progression of twitch transdiaphragmatic pressures (TwPdi) for the two consecutive exercise protocols and recovery phase during spontaneous breathing (left panel) and during non-invasive ventilation (right panel). Data are presented as mean. T-bars represent 95% confi-dence interval of the mean. I-V represent consecutive measurements. HEET = heavy-intensity exercise testing; NIV = non-invasive ventila-tion; SB = spontaneous breathing.