Suzuki S, Suzuki J, Okubo T
First Department of Internal Medicine, Yokohama City University School of Medicine, Japan.
J Appl Physiol (1985). 1991 Jun;70(6):2632-9. doi: 10.1152/jappl.1991.70.6.2632.
We examined expiratory muscle fatigue during expiratory resistive loading in 11 normal subjects. Subjects breathed against expiratory resistances at their own breathing frequency and tidal volume until exhaustion or for 60 min. Respiratory muscle strength was assessed from both the maximum static expiratory and inspiratory mouth pressures (PEmax and PImax). At the lowest resistance, PEmax and PImax measured after completion of the expiratory loaded breathing were not different from control values. With higher resistance, both PEmax and PImax were decreased (P less than 0.05), and the decrease lasted for greater than or equal to 60 min. The electromyogram high-to-low frequency power ratio for the rectus abdominis muscle decreased progressively during loading (P less than 0.01), but the integrated EMG activity did not change during recovery. Transdiaphragmatic pressure during loading was increased 3.6-fold compared with control (P less than 0.05). These findings suggest that expiratory resistive loaded breathing induces muscle fatigue in both expiratory and inspiratory muscles. Fatigue of the expiratory muscles can be attributed directly to the high work load and that of the inspiratory muscles may be related to increased work due to shortened inspiratory time.
我们对11名正常受试者在呼气阻力负荷期间的呼气肌疲劳进行了研究。受试者以自己的呼吸频率和潮气量对抗呼气阻力呼吸，直至疲劳或持续60分钟。通过最大静态呼气和吸气口腔压力（PEmax和PImax）评估呼吸肌力量。在最低阻力时，呼气负荷呼吸完成后测得的PEmax和PImax与对照值无差异。随着阻力增加，PEmax和PImax均降低（P<0.05），且降低持续≥60分钟。腹直肌肌电图高频与低频功率比在负荷期间逐渐降低（P<0.01），但在恢复期间肌电图积分活动未改变。负荷期间的跨膈压与对照相比增加了3.6倍（P<0.05）。这些发现表明，呼气阻力负荷呼吸可导致呼气肌和吸气肌疲劳。呼气肌疲劳可直接归因于高工作负荷，而吸气肌疲劳可能与吸气时间缩短导致的工作增加有关。
