Respiratory sensation in normal subjects: The relationship between inspiratory motor drive and perception during resistive loading and pressure threshold loading

This study had two primary purposes, the first was to determine the effect of inspiratory muscle strength training (IMST) on load detection (LD), magnitude estimation (ME) and respiratory related evoked potentials (RREP). The second purpose was to compare cross modality matching, using handgrip, with a numerical scale, Borg scale, for expressing breathing difficulty during ventilatory loading. Two types of ventilatory load were used: resistive load (DeltaR) and pressure threshold load (APT). Two experiments were performed.;Twenty-three subjects completed the experiments. The subjects were trained at 75% MIP, 6 breaths a set, 4 sets a day for a total of 4 weeks. The results showed that high intensity-low repetition pressure threshold IMST significantly increased maximum inspiratory pressure (MEP), accompanied with decreased P 0.1. The MEP increased from 97.8 +/- 3.81 cmH2O to 132.2 +/- 4.5 cmH2O, while P0.1 decreased from 1.53 +/- 0.14 cmH2O to 1.19 +/- 0.11 cmH2O. The IMST did not affect LD of DeltaR but decreased LD of DeltaPT. The slope of log Pm-log HG did not change. The subjects generated less Pm/MIP but reported the similar handgrip response. The early latency components of the RREP: P1, Nf, P1a and N1, were not affected by IMST.;Handgrip and Borg scale ME were compared in the second experiment. The identical protocols were followed. The result showed that the subjects reported significantly lower Borg scale values but similar handgrip values. It is believed that subjects have the tendency to change their points of reference with the handgrip, which gives the Borg scale better repeatability.;In summary, IMST can significantly improve muscle strength and decrease inspiratory drive, which results in decreased load perception. Decreased perception can be reflected in decreased detection of loads and a decreased ME of loads if the Borg scale is used. Both handgrip and Borg scale successfully represented how subjects sensed load levels within a single session. When comparing between sessions, cross modality matching with the handgrip failed to register consistent values because the subjects tended to change their points of reference from one session to the next. The Borg scale, in contrast, showed good repeatability.