Relationship between respiratory muscle strength and exercise tolerance

[Purpose] This study was performed to clarify the relationship between respiratory muscle strength and exercise tolerance. [Subjects and Methods] Nine healthy adult male subjects (mean age 20.9 ± 0.3 years) were instructed to perform a ramp load exercise using a cycle ergometer. As measures of inspiratory muscle strength, maximal expiratory mouth pressure (PEmax) and maximal inspiratory mouth pressure (PImax) were measured before exercise and immediately, 15 minutes and 30 minutes after exercise. As measures of respiratory response, minute ventilation, respiratory frequency, tidal volume and oxygen uptake were measured using an exhaled gas analyzer. Heart rate was calculated from R-R intervals on an electrocardiogram as a measure of heart rate response. [Results] The results revealed significant correlations between PEmax and maximal exercise load, PImax and maximal exercise load, PEmax and peak VO₂ and PImax and peak VO₂. PEmax measured immediately after exercise was lower than that measured immediately before exercise. [Conclusion] These findings suggest a correlation between respiratory muscle strength, especially expiratory muscle strength, and exercise performance.