Relationship of Respiratory Effort Sensation to Expiratory Muscle Fatigue during Expiratory Threshold Loading

Suzuki, Shunsuke; Suzuki, Junnichi; Ishii, Toshiharu; Akahori, Tadashi; Ōkubo, Takao

doi:10.1164/ajrccm/145.2_pt_1.461

Cited by 44 publications

(24 citation statements)

References 5 publications

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“…It is, therefore, not clear what purpose the recruitment of abdominal muscles could serve during exercise in COPD patients. If abdominal muscle recruitment does not assist inspiratory muscle function then, logically, it should be detrimental, both because of energetic considerations and because it might give rise to dyspnoea [24]. In the present study, the magnitude of abdominal muscle recruitment was variable between subjects; this observation is of interest if one accepts the view that abdominal muscle use represents a vestigial reflex which cannot be suppressed [20].…”

Section: Significance Of the Findingsmentioning

confidence: 67%

Respiratory muscle activity in patients with COPD walking to exhaustion with and without pressure support

Kyroussis¹,

Polkey²,

Hamnegärd³

et al. 2000

Eur Respir J

115

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The function of the diaphragm and other respiratory muscles during exercise in chronic obstructive pulmonary disease (COPD) remains controversial and few data exist regarding respiratory muscle pressure generation in this situation.The inspiratory pressure/time products of the oesophageal and transdiaphragmatic pressure, and the expiratory gastric pressure/time product during exhaustive treadmill walking in 12 patients with severe COPD are reported. The effect of noninvasive positive pressure ventilation during treadmill exercise was also examined in a subgroup of patients (n=6).During free walking, the inspiratory pressure/time products rose early in the walk and then remained level until the patients were forced to stop because of intolerable dyspnoea. In contrast, the expiratory gastric pressure/time product increased progressively throughout the walk. When patients walked the same distance assisted by noninvasive positive pressure ventilation, a substantial reduction was observed in the inspiratory and expiratory pressure/time products throughout the walk. When patients walked with positive pressure ventilation for as long as they could, the pressure/time products observed at exercise cessation were lower than those observed during exercise cessation after free walking.It is concluded that, in severe chronic obstructive pulmonary disease, inspiratory muscle pressure generation does not increase to meet the demands imposed by exhaustive exercise, whereas expiratory muscle pressure generation rises progressively. Inspiratory pressure support was shown to substantially unload all components of the respiratory muscle pump. Eur Respir J 2000; 15: 649±655.

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Section: Significance Of the Findingsmentioning

confidence: 67%

Respiratory muscle activity in patients with COPD walking to exhaustion with and without pressure support

Kyroussis¹,

Polkey²,

Hamnegärd³

et al. 2000

Eur Respir J

115

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“…Subjects had to expire through this device achieving a target pressure corresponding to at least 50% of their individual PE max similar to previous studies (Derchak et al 2002;Haverkamp et al 2001;Suzuki et al 1992). The target expiratory pressure was displayed to the subjects on a mercury column and had to be maintained as a square wave.…”

Section: Resistive Breathingmentioning

confidence: 94%

Expiratory muscle fatigue impairs exercise performance

et al. 2007

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High-intensity, exhaustive exercise may lead to inspiratory as well as expiratory muscle fatigue (EMF). Induction of inspiratory muscle fatigue (IMF) before exercise has been shown to impair subsequent exercise performance. The purpose of the present study was to determine whether induction of EMF also aVects subsequent exercise performance. Twelve healthy young men performed Wve 12-min running tests on a 400-m track on separate days: a preliminary trial, two trials after induction of EMF, and two trials without prior muscle fatigue. Tests with and without prior EMF were performed in an alternate order, randomly starting with either type. EMF was deWned as a ¸20% drop in maximal expiratory mouth pressure achieved during expiratory resistive breathing against 50% maximal expiratory mouth pressure. The average distance covered in 12 min was signiWcantly smaller during exercise with prior EMF compared to control exercise (2872 § 256 vs. 2957 § 325 m; P = 0.002). Running speed was consistently lower (0.13 m s ¡1 ) throughout the entire 12 min of exercise with prior EMF. A signiWcant correlation was observed between the level of EMF (decrement in maximal expiratory mouth pressure after resistive breathing) and the reduction in running distance (r 2 = 0.528, P = 0.007). Perceived respiratory exertion was higher during the Wrst 800 m and heart rate was lower throughout the entire test of running with prior EMF compared to control exercise (5.3 § 1.6 vs. 4.5 § 1.7 points, P = 0.002; 173 § 10 vs. 178 § 7 beats min ¡1 , P = 0.005). We conclude that EMF impairs exercise performance as previously reported for IMF.

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“…The progressive recruitment of accessory respiratory muscles would be expected to increase sensory input to the central nervous system and, therefore, increase the intensity of dyspnea. Respiratory muscle fatigue per se may increase the intensity of dyspnea (31,125,126,138), but this effect appears to be specific to the accessory respiratory muscles because diaphragm fatigue does not increase neural respiratory drive assessed by diaphragm electromyogram (66), and specific loading of the diaphragm does not increase the sensation of inspiratory effort (18,138). Factors independent of fatigue can also modify dyspnea and potentially influence exercise tolerance.…”

Section: Mechanisms By Which Respiratory Muscle Fatigue Could Affect mentioning

confidence: 99%

Exercise-induced respiratory muscle fatigue: implications for performance

Romer

Polkey²

2008

Journal of Applied Physiology

256

212

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Romer LM, Polkey MI. Exercise-induced respiratory muscle fatigue: implications for performance. J Appl Physiol 104: 879 -888, 2008. First published December 20, 2007 doi:10.1152/japplphysiol.01157.2007.-It is commonly held that the respiratory system has ample capacity relative to the demand for maximal O 2 and CO2 transport in healthy humans exercising near sea level. However, this situation may not apply during heavy-intensity, sustained exercise where exercise may encroach on the capacity of the respiratory system. Nerve stimulation techniques have provided objective evidence that the diaphragm and abdominal muscles are susceptible to fatigue with heavy, sustained exercise. The fatigue appears to be due to elevated levels of respiratory muscle work combined with an increased competition for blood flow with limb locomotor muscles. When respiratory muscles are prefatigued using voluntary respiratory maneuvers, time to exhaustion during subsequent exercise is decreased. Partially unloading the respiratory muscles during heavy exercise using low-density gas mixtures or mechanical ventilation can prevent exercise-induced diaphragm fatigue and increase exercise time to exhaustion. Collectively, these findings suggest that respiratory muscle fatigue may be involved in limiting exercise tolerance or that other factors, including alterations in the sensation of dyspnea or mechanical load, may be important. The major consequence of respiratory muscle fatigue is an increased sympathetic vasoconstrictor outflow to working skeletal muscle through a respiratory muscle metaboreflex, thereby reducing limb blood flow and increasing the severity of exerciseinduced locomotor muscle fatigue. An increase in limb locomotor muscle fatigue may play a pivotal role in determining exercise tolerance through a direct effect on muscle force output and a feedback effect on effort perception, causing reduced motor output to the working limb muscles. respiratory muscles; exercise; diaphragm; abdominals; magnetic stimulation; metaboreflex THE PURPOSE OF THIS MINIREVIEW is to address the question of whether the respiratory demands of exercise contribute significantly toward exercise limitation, either directly through limitations of the respiratory muscle pump or indirectly through effects on limb blood flow and locomotor muscle fatigue. We describe the mechanical and metabolic costs of meeting the ventilatory requirements of exercise. We then ask whether the respiratory muscles fatigue with exercise, what factors contribute to any such fatigue, and what the implications of these factors are for exercise tolerance. Finally, we deal with the potential mechanisms by which respiratory muscle fatigue could compromise exercise tolerance and whether it is possible to overcome this potential respiratory limitation. Our review focuses on the healthy young adult exercising near sea level. However, we also consider special circumstances that determine the balance between metabolic demand and respiratory system capacity in the highly trained endurance ...

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Relationship of Respiratory Effort Sensation to Expiratory Muscle Fatigue during Expiratory Threshold Loading

Cited by 44 publications

References 5 publications

Respiratory muscle activity in patients with COPD walking to exhaustion with and without pressure support

Respiratory muscle activity in patients with COPD walking to exhaustion with and without pressure support

Expiratory muscle fatigue impairs exercise performance

Exercise-induced respiratory muscle fatigue: implications for performance

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