Analysis of Respiratory Muscle Fatigue Caused by Breath-loading at 50% Maximum Expiratory Mouth Pressure

Abstract

[Purpose] To clarify the characteristics of respiratory muscle fatigue in breath-loading at 50% maximum expiratory mouth pressure. [Subjects] Eleven healthy males. [Methods] We measured the maximum inspiratory and expiratory mouth pressures, (PImax) and PEmax, during breath-loading and rest, and used electromyography (EMG) frequency analysis to verify the state of the trapezius, sternocleidomastoid, pectoralis major, abdominal rectus, and internal and external oblique muscles. [Results] PImax and PEmax decreased over time and recovered after rest. The median frequency decreased in the rectus abdominis and internal and external oblique muscles at PImax, and in the trapezius, rectus abdominis, and internal and external oblique muscles at PEmax. During the rest period of 30 min, recovery was observed in the external oblique muscle at PImax, and in the abdominal rectus and external oblique muscles at PEmax. [Conclusion] Our results suggest that respiratory muscle fatigue caused by expiratory resistance loading causes decreases in PImax and PEmax.