Adams, Lewis

Abstract The sections in this article are: Regulation of the Upper Airway During Exercise Anatomy and Physiology of the Upper Airway Contractile Properties and Endurance of Upper Airway Muscles Changes in Upper Airway Flow Resistance During Exercise Upper Airway Muscle Activities during Exercise Oronasal Distribution of Respiratory Airflow Effects of Exercise on Passive Respiratory Mechanics Elastic Properties Total Lung Capacity Expiratory Flow Rates, Vital Capacity, and Residual Volume Breathing Pattern During Exercise Mechanical Breathing Pattern Methods of Assessment of Respiratory Muscle Contraction Pattern of Respiratory Muscle Contraction Influence of Sensory Feedback on Breathing Pattern Influence of Respiratory Mechanics on Breathing Pattern Influence of Duration of Exercise on Breathing Pattern Influence of Mode of Exercise on Breathing Pattern Breathing Pattern during Recovery from Exercise Physiological Implications of Exercise Breathing Pattern Importance of Respiratory Load in Regulation of Exercise Hyperpnea Helium‐Oxygen Unloading Unloading with Pressure Assist Conclusion Locomotor‐Respiration Interdependence Entrainment—the Most Obvious Locomotor‐Respiratory Interaction How Does Entrainment Effect Ventilation? Is there Stronger Evidence to Support a Significant Biomechanical Effect of Locomotion on Respiration in Dogs? Are Biomechanical Effects Important in Entrainment in Humans? Locomotory: Respiratory Interactions, Independent of Entrainment Conclusion Respiratory Muscle Perfusion and Energetics Oxygen Cost of Hyperpnea Respiratory Muscle Blood Flow Exercise‐Induced Respiratory Muscle Fatigue Respiratory System Design Assessment of Diaphragm Fatigue in Animal Models Glycogen Depletion Fiber Type Recruitment Definition of Fatigue Task Failure vs. Objective Assessment of Fatigue Contractile Changes with Fatigue Predicting Respiratory Muscle Fatigue During Exercise Application of Resting Tests to Respiratory Muscle Function During Exercise Assessment of Respiratory Muscle Fatigue in Humans Volitional Tests Volitional Tests Applied to Exercise Nonvolitional Tests Bilateral Phrenic Nerve Stimulation ( BPNS ) Characteristics of Diaphragm Fatigue High‐ vs. Low‐Frequency Fatigue Sites and Mechanisms of Respiratory Muscle Fatigue Central Fatigue in Humans Neurotransmission Fatigue Bilateral Phrenic Nerve Stimulation Applied to Exercise Short‐Term Exercise Endurance Exercise Factors Contributing to the Decline in Twitch Pdi Following Exercise Role of Diaphragmatic Force Output in Fatigue Consequences of Exercise‐Induced Diaphragmatic Fatigue Fatigue vs. Task Failure Does Training of Respiratory Muscles Affect Exercise Performance? Altered Respiratory Muscle Recruitment with Fatigue Physical Training Effects on Respiratory Muscles Respiratory Muscle Morphology and Contractile Properties Whole‐Body Training: Effects on Rodent Respiratory Muscles Whole‐Body Exercise: Effects on Human Respiratory Muscle Performance Specific Respiratory Muscle Training Respiratory Sensation During Exertion Mechanisms of Respiratory Sensations during Exercise Methods of Assessing Respiratory Sensations Respiratory Movements An Urge to Breathe A Sense of Respiratory Effort Respiratory Sensation as a Respiratory Controller during Exercise Respiratory Sensation as a Limiting Factor during Exercise Conclusions Summary—Pulmonary System Limitations and Their Effects on Exercise Performance Absence of Pulmonary System Limitations in the Normally Fit Contrasting Adaptabilities: Demand vs. Capacity Alveolar Capillary Diffusion Surface of the Lung Ventilatory Limitations/Constraints Inadequate Alveolar Ventilation and Limitations Endurance Exercise Performance Special Circumstances Favoring Pulmonary Limitations to Exercise Performance in Health Hypoxia of High Altitudes Aging Effects on Pulmonary Limitations

Chest wall strapping has been used to assess mechanisms of dyspnea with restrictive lung disease. This study examined the hypothesis that dyspnea with restriction depends principally on the degree of reflex ventilatory stimulation. We compared dyspnea at the same (iso)ventilation when added dead space provided a component of the ventilatory stimulus during exercise. Eleven healthy men undertook a randomized controlled crossover trial that compared four constant work exercise conditions: 1) control (CTRL): unrestricted breathing at 90% gas exchange threshold (GET); 2) CTRL+dead space (DS): unrestricted breathing with 0.6-l dead space, at isoventilation to CTRL due to reduced exercise intensity; 3) CWS: chest wall strapping at 90% GET; and 4) CWS+DS: chest strapping with 0.6-l dead space, at isoventilation to CWS with reduced exercise intensity. Chest strapping reduced forced vital capacity by 30.4 ± 2.2% (mean ± SE). Dyspnea at isoventilation was unchanged with CTRL+DS compared with CTRL (1.93 ± 0.49 and 2.17 ± 0.43, 0–10 numeric rating scale, respectively; P = 0.244). Dyspnea was lower with CWS+DS compared with CWS (3.40 ± 0.52 and 4.51 ± 0.53, respectively; P = 0.003). Perceived leg fatigue was reduced with CTRL+DS compared with CTRL (2.36 ± 0.48 and 2.86 ± 0.59, respectively; P = 0.049) and lower with CWS+DS compared with CWS (1.86 ± 0.30 and 4.00 ± 0.79, respectively; P = 0.006). With unrestricted breathing, dead space did not change dyspnea at isoventilation, suggesting that dyspnea does not depend on the mode of reflex ventilatory stimulation in healthy individuals. With chest strapping, dead space presented a less potent stimulus to dyspnea, raising the possibility that leg muscle work contributes to dyspnea perception independent of the ventilatory stimulus. NEW & NOTEWORTHY Chest wall strapping was applied to healthy humans to simulate restrictive lung disease. With chest wall strapping, dyspnea was reduced when dead space substituted for part of a constant exercise stimulus to ventilation. Dyspnea associated with chest wall strapping depended on the contribution of leg muscle work to ventilatory stimulation. Chest wall strapping might not be a clinically relevant model to determine whether an alternative reflex ventilatory stimulus mimics the intensity of exertional dyspnea.