Figure 1
Representative tracings of the sniff pressure curve and its derivative (dP/dt), surface electromyography of sternocleidomastoid (SCM), scalene (ESC), parasternal (PARA) and rectus abdominis (RA) muscles, and shortening velocity index of the global (ΔVCW/dt) and ribcage (ΔVRCp/dt) inspiratory muscles obtained in one subject before (Pre) and after (Post1, Post2 … Post10 – recovery) the fatigue protocol. Grey and black traces of the surface electromyography signal represent raw and root mean squared data, respectively. The calculation of the time constant of the relaxation curve (τ) is shown by drawing a tangent line at the initial rate of decay. Median frequency (MDF) and high/low frequency power (H/L) are also expressed. SNIP: sniff nasal inspiratory pressure; CT: contraction time; ½RT: half-time of relaxation curve; MRPD: maximum rate of pressure development; MRR: maximum relaxation rate; µV: microvolts; cmH2O: centimeters of water; L·s: liter per second. *MRPD and MRR are represented in the figure without normalization by peak pressure.
