Medicine and science in sports and exercise
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Med Sci Sports Exerc · Oct 1993
Inspiratory muscle performance relative to the ventilatory threshold in healthy subjects.
Inspiratory muscle performance, ventilation, and gas exchange were studied during exercise in healthy subjects to look for typical changes of pattern of contraction at the ventilatory threshold (VT). The steepening of the slope of carbon dioxide output (VCO2) vs oxygen uptake (VO2) at the VT was accompanied by a nonlinear increase of the mean rate of esophageal pressure development (Pes/TI) vs the esophageal pressure time index (PTIes) reflecting both the relative force (Pbreath/Pesmax) and duration (TI/TTOT) required for inspiration. ⋯ Inspiratory muscle performance during exercise should link the increased metabolic rate to ventilatory output. We conclude that 1) there exists an inspiratory muscle threshold that is well correlated to commonly used gas exchange thresholds, and 2) the efficiency of ventilation and gas exchange during exercise could be linked to pressure and timing of inspiratory muscle contraction.