Comprehensive Physiology Wiley Online Library
For Librarians For Authors Editors About

Airway, Lung, and Respiratory Muscle Function During Exercise

Jerome A. Dempsey, Lewis Adams, Dorothy M. Ainsworth, Ralph F. Fregosi, Charles G. Gallagher, Abe Guz, Bruce D. Johnson, Scott K. Powers

10.1002/cphy.cp120111

Source: Supplement 29: Handbook of Physiology, Exercise: Regulation and Integration of Multiple Systems

Originally published: 1996

Published online: January 2011

Full Article on Wiley Online Library



Abstract

The sections in this article are:

1 Regulation of the Upper Airway During Exercise
1.1 Anatomy and Physiology of the Upper Airway
1.2 Contractile Properties and Endurance of Upper Airway Muscles
1.3 Changes in Upper Airway Flow Resistance During Exercise
1.4 Upper Airway Muscle Activities during Exercise
1.5 Oronasal Distribution of Respiratory Airflow
2 Effects of Exercise on Passive Respiratory Mechanics
2.1 Elastic Properties
2.2 Total Lung Capacity
2.3 Expiratory Flow Rates, Vital Capacity, and Residual Volume
3 Breathing Pattern During Exercise
3.1 Mechanical Breathing Pattern
3.2 Methods of Assessment of Respiratory Muscle Contraction
3.3 Pattern of Respiratory Muscle Contraction
3.4 Influence of Sensory Feedback on Breathing Pattern
3.5 Influence of Respiratory Mechanics on Breathing Pattern
3.6 Influence of Duration of Exercise on Breathing Pattern
3.7 Influence of Mode of Exercise on Breathing Pattern
3.8 Breathing Pattern during Recovery from Exercise
3.9 Physiological Implications of Exercise Breathing Pattern
4 Importance of Respiratory Load in Regulation of Exercise Hyperpnea
4.1 Helium‐Oxygen Unloading
4.2 Unloading with Pressure Assist
4.3 Conclusion
5 Locomotor‐Respiration Interdependence
5.1 Entrainment—the Most Obvious Locomotor‐Respiratory Interaction
5.2 How Does Entrainment Effect Ventilation?
5.3 Is there Stronger Evidence to Support a Significant Biomechanical Effect of Locomotion on Respiration in Dogs?
5.4 Are Biomechanical Effects Important in Entrainment in Humans?
5.5 Locomotory: Respiratory Interactions, Independent of Entrainment
5.6 Conclusion
6 Respiratory Muscle Perfusion and Energetics
6.1 Oxygen Cost of Hyperpnea
6.2 Respiratory Muscle Blood Flow
7 Exercise‐Induced Respiratory Muscle Fatigue
7.1 Respiratory System Design
8 Assessment of Diaphragm Fatigue in Animal Models
8.1 Glycogen Depletion
8.2 Fiber Type Recruitment
9 Definition of Fatigue
9.1 Task Failure vs. Objective Assessment of Fatigue
9.2 Contractile Changes with Fatigue
10 Predicting Respiratory Muscle Fatigue During Exercise
10.1 Application of Resting Tests to Respiratory Muscle Function During Exercise
11 Assessment of Respiratory Muscle Fatigue in Humans
11.1 Volitional Tests
11.2 Volitional Tests Applied to Exercise
11.3 Nonvolitional Tests
11.4 Bilateral Phrenic Nerve Stimulation (BPNS)
12 Characteristics of Diaphragm Fatigue
12.1 High‐ vs. Low‐Frequency Fatigue
12.2 Sites and Mechanisms of Respiratory Muscle Fatigue
12.3 Central Fatigue in Humans
12.4 Neurotransmission Fatigue
13 Bilateral Phrenic Nerve Stimulation Applied to Exercise
13.1 Short‐Term Exercise
13.2 Endurance Exercise
13.3 Factors Contributing to the Decline in Twitch Pdi Following Exercise
13.4 Role of Diaphragmatic Force Output in Fatigue
14 Consequences of Exercise‐Induced Diaphragmatic Fatigue
14.1 Fatigue vs. Task Failure
14.2 Does Training of Respiratory Muscles Affect Exercise Performance?
14.3 Altered Respiratory Muscle Recruitment with Fatigue
15 Physical Training Effects on Respiratory Muscles
15.1 Respiratory Muscle Morphology and Contractile Properties
15.2 Whole‐Body Training: Effects on Rodent Respiratory Muscles
15.3 Whole‐Body Exercise: Effects on Human Respiratory Muscle Performance
15.4 Specific Respiratory Muscle Training
16 Respiratory Sensation During Exertion
16.1 Mechanisms of Respiratory Sensations during Exercise
16.2 Methods of Assessing Respiratory Sensations
16.3 Respiratory Movements
16.4 An Urge to Breathe
16.5 A Sense of Respiratory Effort
16.6 Respiratory Sensation as a Respiratory Controller during Exercise
16.7 Respiratory Sensation as a Limiting Factor during Exercise
16.8 Conclusions
17 Summary—Pulmonary System Limitations and Their Effects on Exercise Performance
17.1 Absence of Pulmonary System Limitations in the Normally Fit
18 Contrasting Adaptabilities: Demand vs. Capacity
18.1 Alveolar Capillary Diffusion Surface of the Lung
18.2 Ventilatory Limitations/Constraints
18.3 Inadequate Alveolar Ventilation and V.O2max Limitations
18.4 Endurance Exercise Performance
19 Special Circumstances Favoring Pulmonary Limitations to Exercise Performance in Health
19.1 Hypoxia of High Altitudes
19.2 Aging Effects on Pulmonary Limitations
Figure 1. Figure 1.

a, Sagittal section of the human head and neck, showing the upper airways and some of the associated musculature. NC, nasal constrictor muscles; DN, dilator naris muscle; HP, hard palate; GG, genioglossus muscle; GH, geniohyoid muscle; H, hyoid bone; SH, sternohyoid muscle; SP, soft palate; EG, epiglottis. b, Section through the posterior pharynx showing some of the musculature acting on the soft palate and pharyngeal wall. TVP, tensor veli palatini muscle; LVP, levator veli palatini muscle; SC, superior pharyngeal constrictor muscles; SP, soft palate, c, Superior view of the larynx, showing the major laryngeal adductor and abductor muscles. TA, thyroarytenoid muscle; PCA, posterior cricoarytenoid muscle; TC, AC, and CC, thyroid, arytenoid and cricoid cartilages, respectively. See test for explanation of anatomy and muscular actions.

Parts b and c adapted from Bartlett 41 and Warwick and Williams 420, respectively
Figure 2. Figure 2.

Top, Nasal airway pressure–flow relationships obtained during voluntary hyperpnea in a healthy subject. The tests were performed before (control) and after (exercise) exhausting cycle ergometer exercise. Note that the curves are nonlinear, showing the marked flow dependence of upper airway resistance. Also note that prior exercise shifts the pressure–flow curve to the right, indicating that exercise hyperpnea decreases resistance. Bottom, Log transformation of the data shown in the top panel, demonstrating the technique for determining the flow rate at the transition (tr) from laminar to turbulent flow. See text for detailed explanation of figure.

From Olson et al. 301
Figure 3. Figure 3.

Influence of exercise intensity on the integrated EMG activity of the nasal dilator muscles (AN EMG), mean inspiratory flow (VT/T1) and inspired pulmonary ventilation (V1). Values for both nasal and total VT/T1 and V1 are given, as indicated on the insets. Note that the plateau in both of these variables at exercise intensities exceeding 60% of the peak power coincides with the plateau in the AN EMG. * Significantly different than resting control value (P < 0.05); + significantly different than nasal V1 (P < 0.05).

From R. F. Fregosi and R. L. Lansing, unpublished observations
Figure 4. Figure 4.

Recordings showing changes in flow through the nose and mouth, and integrated EMG activity of the nasal dilator muscles (“alae nasi”) when a representative subject voluntarily changes the breathing route from nasal to oral during cycling exercise. Note that during nose breathing EMG activity is much higher, and the onset of the EMG burst precedes the onset of flow (vertical dashed lines). Also note that when the flow route changes from nasal to oral in midexpiration (A), the EMG amplitude is diminished but EMG onset no longer precedes the onset of flow. In contrast, when flow route changes at the end of expiration (B), EMG amplitude is diminished but onset time does not change. Thus, when the upper airway was configured for oral flow well before the next inspiration (A), the nervous system no longer had to activate the alae nasi musculature early and intensely in order to protect the nasal airway from collapse. In contrast, when the switch from nasal to oral flow was made at the very end of expiration (B), the system was still configured for a nasal breath, and the EMG burst preceded the onset of flow. However, the system soon sensed the absence of nasal flow and made appropriate adjustments during the breath, resulting in a reduced EMG amplitude. Taken together, these data suggest that (1) the configuration of the entire upper airway, presumably determined by a feedforward mechanism, is more important than local reflex mechanisms in determining the onset of upper airway muscle activities, and (2) local reflex mechanisms can alter burst amplitude during a breath (see text)

From Wheatley, Amis, and Engel 426
Figure 5. Figure 5.

Comparison of breathing pattern in normal humans during maximal incremental exercise and endurance exercise. The initial increase in minute ventilation is due to increases in both tidal volume and respiratory frequency. However, tidal volume stops increasing at high levels of ventilation and further increases in ventilation are due to increasing respiratory frequency alone. Tidal volume is less and respiratory frequency greater during endurance exercise at high levels of ventilation

Data obtained from Syabbalo et al. 397.] See text for details
Figure 6. Figure 6.

Young adult average tidal flow–volume and pressure–volume loops and minute ventilation (E) for eight athletes during rest and progressive exercise, which averaged 42%, 61%, 83%, 95%, and 100% of maximal oxygen uptake. Tidal flow–volume curves are shown plotted within preexercise (solid line) and postexercise (dashed line) maximum flow–volume curves. Tidal pressure–volume curves are shown also with constraints for effective pressure generation on expiration (Pmaxe) and the capacity for pressure generation on inspiration (Pcapi). Widths of Pmaxe and Pcapi at a given lung volume indicate 95% confidence intervals. The loops at a minute ventilation of 117 liter · min−1 represent the typical response to maximum short‐term exercise in an untrained young adult subject (maximum o2 40–50 ml · kg−1 · min−1). The E of 169 liters/min was the average response to maximum exercise in the trained subject (maximum o2 = 70–80 ml · kg−1 · min−1)

From Johnson, Saupe and Dempsey 208
Figure 7. Figure 7.

Time course of flow; lung volume; respiratory muscle pressure (Pmus); dynamic capacity of inspiratory muscles to generate pressure (Pcapi); and ratio of inspiratory Pmus to Pcapi before exercise, during light exercise, and during moderately heavy exercise. Data are the average from three subjects during cycle exercise. PIIA is postinspiratory muscle activity. Numbers in the bottom row are mean and peak Pmusl/PcapI. See text for details.

From B. Krishnan, T. Zintel, and C. G. Gallagher, unpublished data
Figure 8. Figure 8.

Equine costal diaphragmatic EMG (raw and moving time‐averaged); gastric, esophageal, and transdiaphragmatic pressure (PG, PE, and Pdi); and accelerometer tracing indicating left forelimb impact (arrows) during walking and during galloping (11 ms). Note that the foot plant activity does not occur during a consistent phase of the respiratory cycle when the horse is walking, whereas phase‐linking is apparent during the gallop.

From Ainsworth et al. (9
Figure 9. Figure 9.

Canine breathing patterns are highly variable, as shown in this figure for one dog trotting on the treadmill while unencumbered by a breathing mask. The two types of patterns—high‐frequency type A (left panel), a pure high frequency oscillation in the esophageal pressure; and mixed‐frequency type B (right panel), a slower inherent breathing pattern with superimposed high‐frequency oscillations in the esophageal pressure—are apparent. Esophageal pressure (Pe), crural (CR), costal (CS), transverse abdominal (TA) EMG, and foot plant left hindlimb (FP) are shown. In type A and type B, decrements in esophageal pressure (and airflow) are always associated with electrical activation of the costal and crural diaphragm. In type B, oscillations in the esophageal pressure during expiration occur at intervals related to foot plant and hence TA activation.

From Ainsworth et al. 12
Figure 10. Figure 10.

Inspiratory flow (VI); electrical activity of the parasternal (PS, rib cage inspiratory), crural (CR), and costal (CS) diaphragm, and transverse abdominal (TA) muscles and sonomicrometry tracing of the costal diaphragm (SONO CS) in one dog at rest and during trotting. Note that either at rest or during exercise, phasic electrical activity of both inspiratory and expiratory muscles is evident and that phasic shortening of the costal diaphragm (downward displacement of SONO tracing) occurs only during electrical activation. This breathing pattern is representative of high‐frequency breathing with fb = 115 breaths · min−1

From Ainsworth et al. 12
Figure 11. Figure 11.

Inspiratory flow (VI) or tidal volume and gastric pressure (PG) traces from a human (left panel) and a dog (right panel). In the dog, note that at the onset of exercise, mean gastric pressure increases due to tonic increases in abdominal muscle activity.

From Ainsworth et al. 11.] In the human, gastric pressure increases during the transition from the walk to the jog. (From Henke et al. 183.] (Please note, in the dog an increased gastric pressure moves upward in the figure; whereas in the human the PG scales are reversed and increased PG moves down
Figure 12. Figure 12.

Oxygen cost of exercise hyperpnea. Right panel shows the effects of increasing ventilation on the per unit oxygen cost of breathing (mean values ±95% confidence interval). Left panel shows the effects of increasing ventilation on the total oxygen cost of breathing expressed as a percentage of the total body O2 (O2TOT) during moderate, heavy, and maximum progressive exercise. [Individual subject values (N = 9).] Values for the O2 cost of breathing were obtained in resting subjects from the measured increases in O2 that accompanied steady‐state mimicking of the pressure–volume loop, ∫ Pdi, ∫ Pg, fb, VT, and EELV obtained during various exercise intensities.

From Aaron et al. 1,2
Figure 13. Figure 13.

Example of bilateral phrenic nerve stimulation (BPNS) performed before and after exercise at 1 and 10 Hz. Both esophageal (Pe) and gastric (Pg) pressure fell following exercise, causing the reduction in the Pdi waveform amplitude. At 1 Hz stimulation, a prolongation in relaxation rate of the Pdi waveform was also observed. No changes were observed in the amplitude of the M‐waves from either the left or right hemidiaphragm.

From Johnson et al. 204
Figure 14. Figure 14.

Comparison of diaphragmatic fatigue produced by exercise vs. that produced by mimicking various levels of diaphragmatic force at rest. Plotted is the diaphragmatic force index (time integral for Pdi multiplied times breathing frequency) achieved during exercise in the studies by Johnson et al. 204 (circles), Babcock et al. 33 (triangles), and Mador et al. 257 (squares) vs. the percentage fall in Pdi amplitude with supramaximal stimulation. This is shown relative to the force produced during resting hyperpnea vs. the fall in the Pdi waveform amplitude after this voluntary maneuver. Note that after performing the resting hyperpnea for the same time period as achieved during exercise (95% ), significant fatigue does not occur until a time integral of 600 cm H2 O s · min−1, whereas during exercise significant fatigue occurs at much lower levels of diaphragmatic work.
Figure 15. Figure 15.

Influence of fatigue on the dynamic capacity for pressure generation by the diaphragm. Note during heavy exercise (95% of ) that the peak diaphragmatic pressure produced during exercise (closed circles) approaches 70% of the dynamic capacity for producing transdiaphragmatic pressures (open circles). When a 20%–25% reduction in the maximal force‐generating capacity of the diaphragm is considered, peak Pdi produced during exercise approaches 90%–95% of this capacity (open circles).
Figure 16. Figure 16.

The fiber cross‐sectional area (μm2) to capillary number in three human respiratory muscles compared to a mixed fiber locomotor muscle.

Data are from Mizuno 286.] a, different (P < 0.05) from all other muscle; **, different (P < 0.05) from internal and external intercostals; *, different (P < 0.05) from internal intercostals
Figure 17. Figure 17.

Influence of exercise intensity and duration on the increase in citrate synthase (CS) activity in the costal diaphragm of rats following a 10‐week endurance running training program. Nine groups of animals trained at each of three exercise intensities (low = ∼55% VO2max; medium = ∼65% VO2max; high = 75%) and each of three exercise durations (30, 60, and 90 min · day−1).

Data are from Powers et al. 327
Figure 18. Figure 18.

Influence of exercise intensity and duration on the increase in citrate synthase (CS) activity in the crural diaphragm and parasternal intercostal muscles of rats following a 10‐week endurance running training program. Nine groups of animals trained at each of three exercise intensities (low = ∼55% VO2max; medium = ∼65% VO2max; high = 75%) and each of three exercise durations (30, 60, 90 min · day−1).

Data are from Powers et al. 327
Figure 19. Figure 19.

A schematic representation of known (solid lines) and putative (broken lines) neural pathways showing possible interactions between areas of respiratory control and respiratory‐related sensations during respiratory stimulation (e.g., exercise). The figure is intended to provide an “anatomical” basis to which the reader can refer, with respect to some of the research findings and ideas discussed in this review.
Figure 20. Figure 20.

Time course of end‐tidal PCO2 (PETCO2) and subjective ratings of air hunger (urge to breathe) in four subjects (RB, BL, DY, and SL) during complete neuromuscular paralysis. Subjects underwent fixed mechanical ventilation and made ratings (via a tourniqueted arm) as inspired CO2 concentration was surreptitiously increased; ratings were made using a seven‐point scale ranging from zero through slight (SLT) and moderate (MOD) to extreme (EXTR) with intermediate rating options. Nonparametric correlation coefficients (r) were calculated between ratings and the level of PETCO2 two min earlier (to allow for “equilibration” of medullary PCO2.

From Banzett et al. 38
Figure 21. Figure 21.

Relationship of alveolar ventilation (A) to arterial PCO2 () at various levels of maximum exercise (CO2) according to the alveolar air equation. Values shown for total minute ventilation (E) assume a VD/VT of 0.20 at maximum exercise. Note that to achieve a given level of hyperventilation at maximum exercise (e.g., a = 30 mm Hg), the ventilatory requirements are markedly different for the sedentary subject (CO2 = 3 liter · min−1, E ∼ 120 liter · min−1) vs. that achieved in the highly fit (CO2 = 6 liter · min−1; E > 190 liter · min−1). The shaded areas show the wide range of alveolar hyperventilation achieved at maximum exercise among healthy subjects across the fitness continuum with substantial overlap but a tendency for less hyperventilation at the higher maximum CO2 in the highly fit.


Figure 1.

a, Sagittal section of the human head and neck, showing the upper airways and some of the associated musculature. NC, nasal constrictor muscles; DN, dilator naris muscle; HP, hard palate; GG, genioglossus muscle; GH, geniohyoid muscle; H, hyoid bone; SH, sternohyoid muscle; SP, soft palate; EG, epiglottis. b, Section through the posterior pharynx showing some of the musculature acting on the soft palate and pharyngeal wall. TVP, tensor veli palatini muscle; LVP, levator veli palatini muscle; SC, superior pharyngeal constrictor muscles; SP, soft palate, c, Superior view of the larynx, showing the major laryngeal adductor and abductor muscles. TA, thyroarytenoid muscle; PCA, posterior cricoarytenoid muscle; TC, AC, and CC, thyroid, arytenoid and cricoid cartilages, respectively. See test for explanation of anatomy and muscular actions.

Parts b and c adapted from Bartlett 41 and Warwick and Williams 420, respectively


Figure 2.

Top, Nasal airway pressure–flow relationships obtained during voluntary hyperpnea in a healthy subject. The tests were performed before (control) and after (exercise) exhausting cycle ergometer exercise. Note that the curves are nonlinear, showing the marked flow dependence of upper airway resistance. Also note that prior exercise shifts the pressure–flow curve to the right, indicating that exercise hyperpnea decreases resistance. Bottom, Log transformation of the data shown in the top panel, demonstrating the technique for determining the flow rate at the transition (tr) from laminar to turbulent flow. See text for detailed explanation of figure.

From Olson et al. 301


Figure 3.

Influence of exercise intensity on the integrated EMG activity of the nasal dilator muscles (AN EMG), mean inspiratory flow (VT/T1) and inspired pulmonary ventilation (V1). Values for both nasal and total VT/T1 and V1 are given, as indicated on the insets. Note that the plateau in both of these variables at exercise intensities exceeding 60% of the peak power coincides with the plateau in the AN EMG. * Significantly different than resting control value (P < 0.05); + significantly different than nasal V1 (P < 0.05).

From R. F. Fregosi and R. L. Lansing, unpublished observations


Figure 4.

Recordings showing changes in flow through the nose and mouth, and integrated EMG activity of the nasal dilator muscles (“alae nasi”) when a representative subject voluntarily changes the breathing route from nasal to oral during cycling exercise. Note that during nose breathing EMG activity is much higher, and the onset of the EMG burst precedes the onset of flow (vertical dashed lines). Also note that when the flow route changes from nasal to oral in midexpiration (A), the EMG amplitude is diminished but EMG onset no longer precedes the onset of flow. In contrast, when flow route changes at the end of expiration (B), EMG amplitude is diminished but onset time does not change. Thus, when the upper airway was configured for oral flow well before the next inspiration (A), the nervous system no longer had to activate the alae nasi musculature early and intensely in order to protect the nasal airway from collapse. In contrast, when the switch from nasal to oral flow was made at the very end of expiration (B), the system was still configured for a nasal breath, and the EMG burst preceded the onset of flow. However, the system soon sensed the absence of nasal flow and made appropriate adjustments during the breath, resulting in a reduced EMG amplitude. Taken together, these data suggest that (1) the configuration of the entire upper airway, presumably determined by a feedforward mechanism, is more important than local reflex mechanisms in determining the onset of upper airway muscle activities, and (2) local reflex mechanisms can alter burst amplitude during a breath (see text)

From Wheatley, Amis, and Engel 426


Figure 5.

Comparison of breathing pattern in normal humans during maximal incremental exercise and endurance exercise. The initial increase in minute ventilation is due to increases in both tidal volume and respiratory frequency. However, tidal volume stops increasing at high levels of ventilation and further increases in ventilation are due to increasing respiratory frequency alone. Tidal volume is less and respiratory frequency greater during endurance exercise at high levels of ventilation

Data obtained from Syabbalo et al. 397.] See text for details


Figure 6.

Young adult average tidal flow–volume and pressure–volume loops and minute ventilation (E) for eight athletes during rest and progressive exercise, which averaged 42%, 61%, 83%, 95%, and 100% of maximal oxygen uptake. Tidal flow–volume curves are shown plotted within preexercise (solid line) and postexercise (dashed line) maximum flow–volume curves. Tidal pressure–volume curves are shown also with constraints for effective pressure generation on expiration (Pmaxe) and the capacity for pressure generation on inspiration (Pcapi). Widths of Pmaxe and Pcapi at a given lung volume indicate 95% confidence intervals. The loops at a minute ventilation of 117 liter · min−1 represent the typical response to maximum short‐term exercise in an untrained young adult subject (maximum o2 40–50 ml · kg−1 · min−1). The E of 169 liters/min was the average response to maximum exercise in the trained subject (maximum o2 = 70–80 ml · kg−1 · min−1)

From Johnson, Saupe and Dempsey 208


Figure 7.

Time course of flow; lung volume; respiratory muscle pressure (Pmus); dynamic capacity of inspiratory muscles to generate pressure (Pcapi); and ratio of inspiratory Pmus to Pcapi before exercise, during light exercise, and during moderately heavy exercise. Data are the average from three subjects during cycle exercise. PIIA is postinspiratory muscle activity. Numbers in the bottom row are mean and peak Pmusl/PcapI. See text for details.

From B. Krishnan, T. Zintel, and C. G. Gallagher, unpublished data


Figure 8.

Equine costal diaphragmatic EMG (raw and moving time‐averaged); gastric, esophageal, and transdiaphragmatic pressure (PG, PE, and Pdi); and accelerometer tracing indicating left forelimb impact (arrows) during walking and during galloping (11 ms). Note that the foot plant activity does not occur during a consistent phase of the respiratory cycle when the horse is walking, whereas phase‐linking is apparent during the gallop.

From Ainsworth et al. (9


Figure 9.

Canine breathing patterns are highly variable, as shown in this figure for one dog trotting on the treadmill while unencumbered by a breathing mask. The two types of patterns—high‐frequency type A (left panel), a pure high frequency oscillation in the esophageal pressure; and mixed‐frequency type B (right panel), a slower inherent breathing pattern with superimposed high‐frequency oscillations in the esophageal pressure—are apparent. Esophageal pressure (Pe), crural (CR), costal (CS), transverse abdominal (TA) EMG, and foot plant left hindlimb (FP) are shown. In type A and type B, decrements in esophageal pressure (and airflow) are always associated with electrical activation of the costal and crural diaphragm. In type B, oscillations in the esophageal pressure during expiration occur at intervals related to foot plant and hence TA activation.

From Ainsworth et al. 12


Figure 10.

Inspiratory flow (VI); electrical activity of the parasternal (PS, rib cage inspiratory), crural (CR), and costal (CS) diaphragm, and transverse abdominal (TA) muscles and sonomicrometry tracing of the costal diaphragm (SONO CS) in one dog at rest and during trotting. Note that either at rest or during exercise, phasic electrical activity of both inspiratory and expiratory muscles is evident and that phasic shortening of the costal diaphragm (downward displacement of SONO tracing) occurs only during electrical activation. This breathing pattern is representative of high‐frequency breathing with fb = 115 breaths · min−1

From Ainsworth et al. 12


Figure 11.

Inspiratory flow (VI) or tidal volume and gastric pressure (PG) traces from a human (left panel) and a dog (right panel). In the dog, note that at the onset of exercise, mean gastric pressure increases due to tonic increases in abdominal muscle activity.

From Ainsworth et al. 11.] In the human, gastric pressure increases during the transition from the walk to the jog. (From Henke et al. 183.] (Please note, in the dog an increased gastric pressure moves upward in the figure; whereas in the human the PG scales are reversed and increased PG moves down


Figure 12.

Oxygen cost of exercise hyperpnea. Right panel shows the effects of increasing ventilation on the per unit oxygen cost of breathing (mean values ±95% confidence interval). Left panel shows the effects of increasing ventilation on the total oxygen cost of breathing expressed as a percentage of the total body O2 (O2TOT) during moderate, heavy, and maximum progressive exercise. [Individual subject values (N = 9).] Values for the O2 cost of breathing were obtained in resting subjects from the measured increases in O2 that accompanied steady‐state mimicking of the pressure–volume loop, ∫ Pdi, ∫ Pg, fb, VT, and EELV obtained during various exercise intensities.

From Aaron et al. 1,2


Figure 13.

Example of bilateral phrenic nerve stimulation (BPNS) performed before and after exercise at 1 and 10 Hz. Both esophageal (Pe) and gastric (Pg) pressure fell following exercise, causing the reduction in the Pdi waveform amplitude. At 1 Hz stimulation, a prolongation in relaxation rate of the Pdi waveform was also observed. No changes were observed in the amplitude of the M‐waves from either the left or right hemidiaphragm.

From Johnson et al. 204


Figure 14.

Comparison of diaphragmatic fatigue produced by exercise vs. that produced by mimicking various levels of diaphragmatic force at rest. Plotted is the diaphragmatic force index (time integral for Pdi multiplied times breathing frequency) achieved during exercise in the studies by Johnson et al. 204 (circles), Babcock et al. 33 (triangles), and Mador et al. 257 (squares) vs. the percentage fall in Pdi amplitude with supramaximal stimulation. This is shown relative to the force produced during resting hyperpnea vs. the fall in the Pdi waveform amplitude after this voluntary maneuver. Note that after performing the resting hyperpnea for the same time period as achieved during exercise (95% ), significant fatigue does not occur until a time integral of 600 cm H2 O s · min−1, whereas during exercise significant fatigue occurs at much lower levels of diaphragmatic work.



Figure 15.

Influence of fatigue on the dynamic capacity for pressure generation by the diaphragm. Note during heavy exercise (95% of ) that the peak diaphragmatic pressure produced during exercise (closed circles) approaches 70% of the dynamic capacity for producing transdiaphragmatic pressures (open circles). When a 20%–25% reduction in the maximal force‐generating capacity of the diaphragm is considered, peak Pdi produced during exercise approaches 90%–95% of this capacity (open circles).



Figure 16.

The fiber cross‐sectional area (μm2) to capillary number in three human respiratory muscles compared to a mixed fiber locomotor muscle.

Data are from Mizuno 286.] a, different (P < 0.05) from all other muscle; **, different (P < 0.05) from internal and external intercostals; *, different (P < 0.05) from internal intercostals


Figure 17.

Influence of exercise intensity and duration on the increase in citrate synthase (CS) activity in the costal diaphragm of rats following a 10‐week endurance running training program. Nine groups of animals trained at each of three exercise intensities (low = ∼55% VO2max; medium = ∼65% VO2max; high = 75%) and each of three exercise durations (30, 60, and 90 min · day−1).

Data are from Powers et al. 327


Figure 18.

Influence of exercise intensity and duration on the increase in citrate synthase (CS) activity in the crural diaphragm and parasternal intercostal muscles of rats following a 10‐week endurance running training program. Nine groups of animals trained at each of three exercise intensities (low = ∼55% VO2max; medium = ∼65% VO2max; high = 75%) and each of three exercise durations (30, 60, 90 min · day−1).

Data are from Powers et al. 327


Figure 19.

A schematic representation of known (solid lines) and putative (broken lines) neural pathways showing possible interactions between areas of respiratory control and respiratory‐related sensations during respiratory stimulation (e.g., exercise). The figure is intended to provide an “anatomical” basis to which the reader can refer, with respect to some of the research findings and ideas discussed in this review.



Figure 20.

Time course of end‐tidal PCO2 (PETCO2) and subjective ratings of air hunger (urge to breathe) in four subjects (RB, BL, DY, and SL) during complete neuromuscular paralysis. Subjects underwent fixed mechanical ventilation and made ratings (via a tourniqueted arm) as inspired CO2 concentration was surreptitiously increased; ratings were made using a seven‐point scale ranging from zero through slight (SLT) and moderate (MOD) to extreme (EXTR) with intermediate rating options. Nonparametric correlation coefficients (r) were calculated between ratings and the level of PETCO2 two min earlier (to allow for “equilibration” of medullary PCO2.

From Banzett et al. 38


Figure 21.

Relationship of alveolar ventilation (A) to arterial PCO2 () at various levels of maximum exercise (CO2) according to the alveolar air equation. Values shown for total minute ventilation (E) assume a VD/VT of 0.20 at maximum exercise. Note that to achieve a given level of hyperventilation at maximum exercise (e.g., a = 30 mm Hg), the ventilatory requirements are markedly different for the sedentary subject (CO2 = 3 liter · min−1, E ∼ 120 liter · min−1) vs. that achieved in the highly fit (CO2 = 6 liter · min−1; E > 190 liter · min−1). The shaded areas show the wide range of alveolar hyperventilation achieved at maximum exercise among healthy subjects across the fitness continuum with substantial overlap but a tendency for less hyperventilation at the higher maximum CO2 in the highly fit.

References
 1. Aaron, E. A., K. G. Henke, D. F. Pegelow, and J. A. Dempsey. Effects of mechanical unloading of the respiratory system on exercise and respiratory muscle endurance. Med. Sci. Sports Exerc. 17: 290, 1985.
 2. Aaron, E. A., B. D. Johnson, C. K. Seow, and J. A. Dempsey. Oxygen cost of exercise hyperpnea: measurement. J. Appl. Physiol. 72: 1810–1817, 1992.
 3. Aaron, E.A., K. C. Seow, B. D. Johnson, and J. A. Dempsey. Oxygen cost of exercise hyperpnea: implications for performance. J. Appl. Physiol. 72: 1818–1825, 1992.
 4. Adams, L., N. Chronos, R. Lane, and A. Guz. The measurement of breathlessness induced in normal subjects: validity of two scaling techniques. Clin. Sci. 69: 7–16, 1985.
 5. Adams, L., N. Chronos, R. Lane, and A. Guz. The measurement of breathlessness induced in normal subjects: individual differences. Clin. Sci. 70: 131–140, 1986.
 6. Adams, L., G. Fink, B. Wuyam, K. Murphy, J. Watson, J. A. Innes, I. Kobayashi, D. R. Corfield, R. S. J. Frackowiak, T. Jones, and A. Guz. Use of positron emission tomography to study motor cortical control of breathing during and following exercise in man. Proceedings of the Sixth International Symposium on Modelling and Control of Ventilation, London, 1995 (in press).
 7. Adams, L., and A. Guz. Dyspnea on exertion. In: Exercise: Pulmonary Physiology and Pathophysiology, edited by B. J. Whipp and K. Wasserman. New York: Marcel Dekker. Inc., 1991, p. 449–494.
 8. Adams, L., R. Lane, S. A. Shea, A. Cockcroft, and A. Guz. Breathlessness during different forms of ventilatory stimulation: a study of mechanisms in normal subjects and respiratory patients. Clin. Sci. 69: 663–672, 1985.
 9. Ainsworth, D. M., S. W. Eicker, N. G. Ducharme, and R. P. Hackett. Exercise‐induced activation of the equine diaphragm. Proc. Vet. Resp. Symp. 13: A19, 1994.
 10. Ainsworth, D. M., C. A. Smith, S. W. Eicker, K. S. Henderson, and J. A. Dempsey. The effects of chemical versus locomotory stimuli on respiratory muscle activity in the awake dog. Respir. Physiol. 78: 163–176, 1989.
 11. Ainsworth, D. M., C. A. Smith, S. W. Eicker, K. S. Henderson, and J. A. Dempsey. The effects of locomotion on respiratory muscle activity in the awake dog. Respir. Physiol. 78: 145–162, 1989.
 12. Ainsworth, D. M., C. A. Smith, K. S. Henderson, and J. A. Dempsey. High frequency breathing in exercising dogs requires respiratory muscle activity. Proceedings of the Sixth International Symposium on Modelling and Control of Ventilation, London, 1995 (in press).
 13. Ainsworth, D. M., C. A. Smith, B. D. Johnson, S. W. Eicker, K. S. Henderson, and J. A. Dempsey. Vagal contributions to respiratory muscle activity during eupnea in the awake dog. J. Appl. Physiol. 72: 1355–1361, 1992.
 14. Ainsworth, D. M., C. A. Smith, B. D. Johnson, S. W. Eicker, K. S. Henderson, and J. A. Dempsey. Vagal modulation of respiratory muscle activity in awake dogs during exercise and hypercapnia. J. Appl. Physiol. 72: 1362–1367, 1992.
 15. Aldrich, T., and J. Karpel. Inspiratory muscle resistive training in respiratory failure. Am. Rev. Respir. Dis. 131: 461–462, 1985.
 16. Altose, M. D., N. S. Cherniack, and A. P. Fishman. Respiratory sensations and dyspnea. J. Appl. Physiol. 58: 1051–1054, 1985.
 17. Ameredes, B. T., W. F. Brechue, G. M. Andrew, and W. N. Stainsby. Force‐velocity shifts with repetitive isometric and isotonic contractions of canine gastrocnemius in situ. J. Appl. Physiol. 73: 2105–2111, 1992.
 18. Ameredes, B. T., B. D. Johnson, and G. C. Sieck. Depression of diaphragm maximal velocity of unloaded shortening after repetitive isovelocity contractions. Am. J. Respir. Crit. Care Med. 149: A797, 1994.
 19. Anholm, J. D., R. L. Johnson, and M. Ramanthon. Changes in cardiac output during sustained maximal ventilation in humans. J. Appl. Physiol. 63: 181–187, 1987.
 20. Anholm, J. D., J. Stray‐Gundersen, M. Ramanathan, and R. L. Johnson, Jr.. Sustained maximal ventilation after endurance exercise in athletes. J. Appl. Physiol. 67: 1759–1763, 1989.
 21. Ariano, M., R. Armstrong, and V. Edgerton. Hindlimb muscle fiber populations of five mammals. J. Histochem. Cytochem. 21: 51–55, 1973.
 22. Armstrong, R. B. Mechanisms of exercise‐induced delayed onset muscular soreness: a brief review. Med. Sci. Sports Exerc. 16: 529–538, 1984.
 23. Armour, J., R. M. Donnelly, and P. T. Bye. The large lungs of elite swimmers: an increased alveolar number. Eur. Resp. J. 6: 237–247, 1993.
 24. Art, T., D. Desmecht, H. Amory, and P. Lekeux. Synchronization of locomotion and respiration in trotting ponies. J. Exp. Biol. 155: 245–259, 1991.
 25. Asmussen, E. Muscular exercise, In: Handbook of Physiology, Respiration, edited by W. O. Fenn and H. Rahn. Washington, DC: Am. Physiol. Soc., 1964, p. 939–978.
 26. Astrand, P. O., and K. Rodhal. Physical training. In: Textbook of Work Physiology, New York: McGraw‐Hill, 1985, p. 412–485.
 27. Attenburrow, D. P. Time relationship between the respiratory cycle and limb cycle in the horse. Equine Vet. J. 14: 69–72, 1982.
 28. Aubier, M., G. Farkas, A. D. Troyer, R. Mozes, and C. Roussos. Detection of diaphragmatic fatigue in man by phrenic stimulation. J. Appl. Physiol. Respir. Environ. Exerc. Physiol. 50: 538–544, 1981.
 29. Aubier, M., D. Murciano, Y. Lecocguic, N. Vires, and R. Pariente. Bilateral phrenic stimulation: a simple technique to assess diaphragmatic fatigue in humans. J. Appl. Physiol. 58: 58–64, 1985.
 30. Babb, T. G., and J. R. Rodarte. Lung volumes during low‐intensity steady‐state cycling. J. Appl. Physiol. 70: 934–937, 1991.
 31. Babcock, M. A., B. D. Johnson, D. F. Pegelow, O. E. Suman, D. Griffin, and J. A. Dempsey. Hypoxic effects on exercise‐induced diaphragmatic fatigue in normal healthy humans. J. Appl. Physiol. 78: 82–92, 1995.
 32. Babcock, M. A., D. F. Pegelow, and J. A. Dempsey. Aerobic fitness effects on exercise‐induced diaphragmatic fatigue. Am. J. Respir. Crit. Care Med. 149: A799, 1994.
 33. Babcock, M. A., D. F. Pegelow, S. R. McClaran, O. E. Suman, and J. A. Dempsey. Contribution of diaphragmatic force output to exercise‐induced diaphragm fatigue. J. Appl. Physiol. 78: 1710–1719, 1995.
 34. Bai, T. R., B. J. Rabinovitch, and R. L. Pardy. Near maximal voluntary hyperpnoea and ventilatory muscle function. J. Appl. Physiol. 57: 1742–1748, 1984.
 35. Banner, N. R., M. H. Lloyd, R. D. Hamilton, J. A. Innes, A. Guz, and M. H. Yacoub. Cardiopulmonary response to dynamic exercise after heart and combined heart‐lung transplantation. Br. Heart J. 61: 215–223, 1989.
 36. Bannister, R. G., and D. J. C. Cunningham. The effects on the respiration and performance during exercise of adding oxygen to the inspired air. J. Physiol. (Lond.) 125: 118–137, 1954.
 37. Banzett, R. B., R. W. Lansing, and R. Brown. High level quadriplegics perceive lung volume change. J. Appl. Physiol. 62: 567–573, 1987.
 38. Banzett, R. B., R. W. Lansing, R. Brown, G. P. Topulos, D. Yager, S. M. Steele, B. Londono, S. H. Loring, M. B. Reid, L. Adams, and C. S. Nations. “Air hunger” from increased PCO2 persists after complete neuromuscular block in humans. Respir. Physiol. 81: 1–17, 1990.
 39. Banzett, R. B., R. W. Lansing, M. B. Reid, L. Adams, and R. Brown. “Air hunger” arising from increased PCO2 in mechanically ventilated quadriplegics. Respir. Physiol 76: 53–68, 1989.
 40. Banzett, R. B., J. Mead, M. B. Reid, and G. P. Topulos. Locomotion in men has no appreciable mechanical effect on breathing. J. Appl. Physiol. 72: 1922–1926, 1991.
 41. Bartlett, D. J. Upper airway motor systems. In: Handbook of Physiology, The Respiratory System, Control of Breathing, edited by N. S. Cherniack and J. G. Widdicombe. Bethesda, MD: Am. Physiol. Soc., 1986, p. 223–245.
 42. Basmajian, J. V., and C. R. Dutta. Electromyography of the pharyngeal constrictors and levator palati in man. Anat. Rec. 139: 561–563, 1961.
 43. Bayev, K. V., V. K. Beresovskii, T. G. Kebkalo, and L. A. Savoskina. Afferent and efferent connections of brainstem locomotor regions: study by means of horseradishperoxidase transport technique. Neuroscience 26: 871–891, 1988.
 44. Bayly, W. M., D. R. Hodgson, D. A. Schulz, J. A. Dempsey, and P. D. Gollnick. Exercise‐induced hypercapnia in the horse. J. Appl. Physiol. 67: 1958–1966, 1989.
 45. Bazzy, A. R., L. M. Pang, S. R. Akabas, and G. G. Haddad. O2 metabolism of the sheep diaphragm during flow resistive loaded breathing. J. Appl. Physiol. 66: 2305–2311, 1989.
 46. Bechbache, R. R., and J. Duffin. The entrainment of breathing frequency by exercise rhythm. J. Physiol. (Lond.) 272: 553–561, 1977.
 47. Bellemare, F., and B. Bigland‐Ritchie. Central components of diaphragmatic fatigue assessed by phrenic nerve stimulation. J. Appl. Physiol. 62: 1307–1316, 1987.
 48. Bellemare, F., and N. Garzaniti. Failure of neuromuscular propagation during human maximal voluntary contraction. J. Appl. Physiol. 64: 1084–1093, 1988.
 49. Bellemare, F., and A. Grassino. Effect of pressure and timing of contraction on human diaphragm fatigue. J. Appl. Physiol. Respir. Environ. Exerc. Physiol. 53: 1190–1195, 1982.
 50. Bellemare, F., and A. Grassino. Evaluation of human diaphragm fatigue. J. Appl. Physiol. 53: 1196–1206, 1982.
 51. Belman, M., and G. Gaesser. Ventilatory muscle training in the elderly. J. Appl. Physiol. 64: 899–905, 1988.
 52. Belman, M., S. Thomas, and M. Lewis. Resistive breathing training in patients with chronic obstructive pulmonary disease. Chest 90: 663–670, 1986.
 53. Bergstrom, J., L. Hermansen, E. Hultman, and B. Saltin. Diet, muscle glycogen and physical performance. Acta Physiol. Scand. 71: 140–150, 1967.
 54. Bernasconi, P., and J. Kohl. Analysis of co‐ordination between breathing and exercise rhythms in man. J. Physiol. (Lond.) 471: 693–706, 1993.
 55. Bigland‐Ritchie, B. Muscle fatigue and the influence of changing neural drive. Clin. Chest Med. 5: 21–34, 1984.
 56. Blackie, S. P., M. S. Fairbarn, N. G. McElvaney, P. G. Wilcox, N. J. Morrison, and R. L. Pardy. Normal values and ranges for ventilation and breathing pattern at maximal exercise. Chest 100: 136–142, 1991.
 57. Boutellier, U., R. Buchel, A. Kundert, and C. Spengler. The respiratory system as an exercise limiting factor in normal trained subjects. Eur. J. Appl. Physiol. 65: 347–353, 1992.
 58. Boutellier, U., and P. Piwko. The respiratory system as an exercise limiting factor in normal sedentary subjects. Eur. J. Appl. Physiol. 64: 145–152, 1992.
 59. Bradley, M. E., and D. E. Leith. Ventilatory muscle training and the oxygen cost of sustained hyperpnea. J. Appl. Physiol. 45: 885–892, 1978.
 60. Bramble, D. M. Respiratory patterns and control during unrestrained human running. In: Modelling and Control of Breathing, edited by B. J. Whipp and D. M. Wiberg. New York: Elsevier Biomedical, 1983, p. 213–220.
 61. Bramble, D. M. Axial‐appendicular dynamics and the integration of breathing and gait in mammals. Am. Zool. 29: 171–186, 1989.
 62. Bramble, D. M., and D. R. Carrier. Running and breathing in mammals. Science 219: 251–256, 1983.
 63. Bramble, D. M., and F. A. Jenkins. Mammalian locomotor‐respiratory integration: implication for diaphragmatic and pulmonary design. Science 262: 235–240, 1993.
 64. Brice, A. G., and H. G. Welch. Metabolic and cardiorespiratory responses to He‐O2 breathing during exercise. J. Appl. Physiol. 54: 387–392, 1983.
 65. Bridger, G. P., and D. F. Proctor. Maximum nasal inspiratory flow and nasal resistance. Ann. Otol. 79: 481–488, 1970.
 66. Brody, A. W., R. R. Stoughton, T. L. Connoly, J. J. Shehan, J. J. Navin, and E. E. Kobald. Experimental value of the Reynolds critical flow in the human airway. J. Lab. Clin. Med. 67: 43–57, 1966.
 67. Brooke, M., and K. Kaiser. Three myosin adenosine triphosphatase systems: the nature of their pH lability and sulfhydryl dependence. J. Histochem. Cytochem. 18: 670–672, 1970.
 68. Buchtal, F., and A. K. Faaborg. Electromyography of laryngeal and respiratory muscles. Ann. Otol. Rhinol. Laryngol. 73: 118–123, 1964.
 69. Burdon, J. G. W., E. F. Juniper, K. J. Killian, F. E. Hargreave, and E. J. M. Campbell. The perception of breathlessness in asthma. Am. Rev. Respir. Dis. 126: 825–828, 1982.
 70. Bye, P. T. P., S. A. Esau, K. R. Walley, P. T. Macklem, and R. L. Pardy. Ventilatory muscles during exercise in air and oxygen in normal men. J. Appl. Physiol. Respir. Environ. Exerc. Physiol. 56: 464–471, 1984.
 71. Caillaud, C., F. Anselme, J. Mercier, and C. Prefaut. Pulmonary gas exchange and breathing pattern during and after exercise in highly trained athletes. Eur. J. Appl. Physiol. 67: 431–437, 1993.
 72. Caretti, D. M., P. C. Szlyk, and I. V Sils. Effects of exercise modality on patterns of ventilation and respiratory timing. Respir. Physiol. 90: 201–211, 1992.
 73. Carlo, W. A., R. J. Martin, E. F. Abboud, E. N. Bruce, and K. P. Strohl. Effects of sleep state and hypercapnia on alae nasi and diaphragm EMG in preterm infants. J. Appl. Physiol. 54: 1590–1596, 1983.
 74. Catchside, P. G., and G. C. Scroop. Lactate kinetics in resting and exercising forearms during moderate‐intensity supine leg exercise. J. Appl. Physiol. 74: 435–443, 1993.
 75. Cha, E. J., D. Sedlock, and S. M. Yamashiro. Changes in lung volume and breathing pattern during exercise and CO2 inhalation in humans. J. Appl. Physiol. 62: 1544–1550, 1987.
 76. Chen, Z., F. L. Eldridge, and P. G. Wagner. Respiratory‐associated rhythmic firing of midbrain neurones in cats: relation to level of respiratory drive. J. Physiol. (Lond.) 437: 305–325, 1991.
 77. Chen, Z., F. L. Eldridge, and P. G. Wagner. Respiratory‐associated thalamic activity is related to level of respiratory drive. Respir. Physiol. 90: 99–113, 1992.
 78. Cherniack, N. S., and M. D. Altose. Mechanisms of dyspnea. Clin. Chest Med. 8: 207–214, 1987.
 79. Cherniack, N. S., Y. Oku, G. M. Saidel, E. N. Bruce, and M. D. Altose. Optimization of breathing through perceptual mechanisms. In: Control of Breathing and Dyspnea, edited by T. T. Takishima and N. S. Cherniack. Oxford: Pergamon Press, 1991, p. 337–345.
 80. Chonan, T., M. B. Mulholland, M. D. Altose, and N. S. Cherniack. Effects of changes in level and pattern of breathing on the sensation of dyspnea. J. Appl. Physiol. 69: 1290–1295, 1990.
 81. Chronos, N., L. Adams, and A. Guz. Effect of hyperoxia and hypoxia on exercise‐induced breathlessness in normal subjects. Clin. Sci. 74: 531–537, 1988.
 82. Clanton, T., G. Dixon, and J. Drake. Inspiratory muscle conditioning using a threshold loading device. Chest 87: 62–66, 1985.
 83. Clanton, T. L., G. F. Dixon, J. Drake, and J. E. Gadek. Effects of swim training on lung volumes and inspiratory muscle conditioning. J. Appl. Physiol. 62: 39–46, 1987.
 84. Clark, J. M., F. C. Hagerman, and R. Gelfand. Breathing patterns during submaximal and maximal exercise in elite oarsmen. J. Appl. Physiol. 55: 440–446, 1983.
 85. Clark, J. M., R. E. Sinclair, and J. B. Lennox. Chemical and non‐chemical components of ventilation during hypercapnic exercise in man. J. Appl. Physiol. 48: 1065–1076, 1980.
 86. Clifford, P. S., J. T. Litzow, J. H. von Colditz, and R. L. Coon. Effect of chronic pulmonary denervation on ventilatory responses to exercise. J. Appl. Physiol. 61: 603–610, 1986.
 87. Close, R. Dynamic properties of mammalian muscles. Physiol. Rev. 52: 129–197, 1972.
 88. Coast, J. R., P. S. Clifford, T. W. Henrich, J. Stray‐Gunderson, and R. L. Johnson. Maximal inspiratory pressure following maximal exercise in trained and untrained subjects. Med. Sci. Sports Exerc. 22: 811–815, 1990.
 89. Cole, P. Nasal airflow resistance. In: Respiratory Function of the Upper Airway, edited by O. P. Mathew and G. S. Ambrogio. New York: Marcel Dekker, Inc., 1988, p. 391–414.
 90. Cole, P., R. Forsyth, and J. S. Haight. Respiratory resistance of the oral airway. Am. Rev. Respir. Dis. 22: 363–365, 1982.
 91. Cole, P., R. Forsyth, and J. S. Haight. Effects of cold air and exercise on nasal patency. Ann. Otol. Rhinol. Laryngol. 92: 196–198, 1983.
 92. Connel, D., and R. F. Fregosi. Influence of nasal airflow and resistance on nasal dilator muscle activities during exercise. J. Appl. Physiol. 74: 2529–2536, 1993.
 93. Connel, D., R. Lansing, and R. F. Fregosi. Influence of exercise intensity and nasal flow resistance on activities of human nasal dilator muscles. FASEB J. 5: A1476, 1991.
 94. Crapo, R. O. The aging lung. In: Pulmonary Disease in the Elderly Patient, edited by D. A. Mahler. New York: Marcel Dekker, Inc., 1993, p. 1–25.
 95. Crossfilt, M., and J. Widdicombe. Physical characteristics of the chest and lungs and the work of breathing in different mammalian species. J. Physiol. (Lond.) 158: 1–14, 1961.
 96. Cunningham, D. A., P. B. Goade, and J. B. Critz. Cardiorespiratory response to exercise on a rowing and bicycle ergometer. Med. Sci. Sports 7: 37–43, 1975.
 97. Dallimore, N. S., and R. Eccles. Changes in human nasal resistance associated with exercise, hyperventilation and rebreathing. Acta Otolaryngol. 84: 416–421, 1977.
 98. Daubenspeck, J. A. Mechanical factors in breathing pattern regulation in humans. Ann. Biomed. Eng. 9: 409–424, 1981.
 99. Davies, A. M., and R. Eccles. The effects of nasal airflow on the electromyographic activity of nasal muscles in the anaesthetized cat. J. Physiol. (Lond.) 358: 102P, 1984.
 100. Dehann, A., M. A. N. Lodder, and A. J. Sergeant. Age related effects of fatigue and recovery from fatigue in rat medial gastrocnemius muscle. Q. J. Exp. Physiol. 74: 715–726, 1989.
 101. Demediuk, B. H., H. Manning, J. Lilly, V. Fencl, S. E. Weinberger, J. W. Weiss, and R. M. Schwartzstein. Dissociation between dyspnea and respiratory effort. Am. Rev. Respir. Dis. 146: 1222–1225, 1992.
 102. Dempsey, J. A. Is the lung built for exercise? Med. Sci. Sports Med. 18: 143–155, 1986.
 103. Dempsey, J. A., E. Aaron, and B. J. Martin. Pulmonary function and prolonged exercise. In: Perspectives in Exercise. Science and Sports Medicine, edited by D. R. Lamb and R. Murray. Indianapolis: Benchman Press, 1988, p. 75–124.
 104. Dempsey, J. A., P. G. Hanson, and K. S. Henderson. Exercise‐induced arterial hypoxaemia in healthy human subjects at sea level. J. Physiol. (Lond.) 355: 161–175, 1984.
 105. Dempsey, J. A., and B. D. Johnson. Demand vs capacity in the healthy pulmonary system. Schweiz. Z. Sportmed. Jahrgang 40: 55–64, 1992.
 106. Dempsey, J. A., B. D. Johnson, and K. W. Saupe. Adaptations and limitations in the pulmonary system during exercise. Chest 97: 81S–87S, 1990.
 107. Dempsey, J. A., S. Powers, and N. Gledhill. Cardiovascular and pulmonary adaptations to physical activity: discussion. In: Exercise, Fitness and Health, edited by C. Bouchard, et al. Champaign, IL: Human Kinetics, 1994, p. 205–216.
 108. DeTroyer, A., M. Sampson, S. Sigrist, and P. Macklem. The diaphragm: two muscles. Science 213: 237–238, 1981.
 109. DeTroyer, A., M. Sampson, S. Sigrist, and P. Macklem. Action of the costal and crural parts of the diaphragm during breathing. J. Appl. Physiol. 53: 30–39, 1982.
 110. Dick, T. E., F. J. Kong, and A. J. Berger. Correlation of recruitment order with axonal conduction velocity for supraspinally driven motor units. J. Neurophysiol. 57: 245–259, 1987.
 111. Dick, T. E., F. J. Kong, and A. J. Berger. Recruitment order of diaphragmatic motor units obeys Hennemans's size principle. In: Respiratory Muscles and Their Neuromotor Control, edited by G. C. Sieck, S. G. Gandevia, and W. E. Cameron. New York: Alan R. Liss, 1987, p. 249–261.
 112. DiMarco, A. F., D. A. Wolfson, S. B. Gottfried, and M. D. Altose. Sensation of inspired volume in normal subjects and quadriplegic patients. J. Appl. Physiol. 53: 1481–1486, 1982.
 113. Dodd, S. L., S. K. Powers, D. Thompson, G. Landry, and J. Lawler. Exercise performance following intense short‐term ventilatory work. Int. J. Sports Med. 10: 48–52, 1989.
 114. Duchateau, J., and K. Hainaut. Electrical and mechanical failures during sustained and intermittent contractions in humans. J. Appl. Physiol. 58: 942–947, 1985.
 115. Eccles, R. The central rhythm of the nasal cycle. Acta Otolaryngol. 86: 464–468, 1978.
 116. Edman, K. A. P., and A. R. Mattiazzi. Effects of fatigue and altered pH on isometric force and velocity of shortening at zero load in frog muscle fibers. J. Muscle Res. Cell Motil. 2: 321–334, 1981.
 117. Edwards, R. H. T. Human muscle function and fatigue. Human Muscle Fatigue: Physiological Mechanisms, edited by R. Porter and J. Whelan. London: Pitman, 1981, p. 1–18.
 118. Edwards, R. H. T. Biochemical basis of fatigue in exercise performance: catastrophic theory of muscular fatigue. In: Biochemistry of Exercise, edited by H. Knuttgen, J. Vogel, and J. Poortmans. Champaign, IL: Human Kinetics, 1983, p. 3–28.
 119. El‐Manshawi, A., K. J. Killian, E. Summers, and N. L. Jones. Breathlessness during exercise with and without resistive loading. J. Appl. Physiol. 61: 896–905, 1986.
 120. England, S. J., and D. Bartlett, Jr.. Changes in respiratory movements of the human vocal cords during hyperpnea. J. Appl. Physiol. 52: 780–785, 1982.
 121. England, S. J., D. Bartlett, Jr., and S. L. Knuth. Comparison of human vocal cord movements during isocapnic hypoxia and hypercapnia. J. Appl. Physiol. 53: 81–86, 1982.
 122. Enoka, R. M., and D. G. Stuart. Neurobiology of muscle fatigue. J. Appl. Physiol. 72: 1631–1648, 1992.
 123. Erickson, B. K., J. Seavon, K. Kubo, A. Hiraga, M. Kai, Y. Yamaya, and P. D. Wagner. Mechanisms of reduction in alveolar‐arterial PO2 difference by helium breathing in the exercising horse. J. Appl. Physiol. 76: 2794–2801, 1994.
 124. Esau, S. A., P. T. Bye, and R. L. Pardy. Changes in rate of relaxation of sniffs with diaphragmatic fatigue in humans. J. Appl. Physiol. 55: 731–735, 1983.
 125. Evans, D. L., E. B. Silverman, D. R. Hodgson, M. D. Eaton, and R. J. Rose. Gait and respiration in standard‐bred horses when pacing and galloping. Res. Vet. Sci. 37: 233–239, 1994.
 126. Faaborg‐Andersen, K. L. Electromyographic investigation of intrinsic laryngeal muscles in humans. Acta Physiol. Scand. 41: 1–149, 1957.
 127. Fairbarn, M. S., K. C. Courts, R. L. Pardy, and D. C. McKenzie. Improved respiratory muscle endurance of highly trained cyclists and the effects on maximal exercise performance. Int. J. Sports Med. 12: 66–70, 1991.
 128. Fenn, W. O., and H. Rahn. Handbook of Physiology. Respiration. Washington, DC: Am. Physiol. Soc., 1964.
 129. Ferris, B. G., J. Mead, and L. H. Opie. Partitioning of respiratory flow resistance in man. J. Appl. Physiol. 19: 653–658, 1964.
 130. Fink, B. R. The Human Larynx. New York: Raven Press, 1975.
 131. Fitts, R. H. Cellular mechanisms of muscle fatigue. Physiol. Rev. 74: 49–94, 1994.
 132. Fitzgerald, R. S., M. X. Hauer, G. G. Bierkamper, and H. Raff. Responses of in vitro rat diaphragm to changes in acid base environment. J. Appl. Physiol. 57: 1202–1210, 1984.
 133. Flynn, C., H. V. Forster, L. G. Pan, and G. E. Bisgard. Role of hilar nerve afferents in hyperpnea of exercise. J. Appl. Physiol. 59: 798–806, 1985.
 134. Forster, H. V., B. K. Erickson, T. F. Lowry, L. G. Pan, M. J. Korducki, and A. L. Forster. Effect of helium‐induced ventilatory unloading on breathing and diaphragm EMG in awake ponies. J. Appl. Physiol. 77: 452–462, 1994.
 135. Forsyth, R. D., P. Cole, and R. J. Shephard. Exercise and nasal patency. J. Appl. Physiol. 55: 860–865, 1983.
 136. Fowler, W. S. Breaking point of breath‐holding. J. Appl. Physiol. 6: 539–545, 1954.
 137. Fox, J., H. Kreisman, A. Colacone, and N. Wolkove. Respiratory volume perception through the nose and mouth determined noninvasively. J. Appl. Physiol. 61: 436–439, 1986.
 138. Freedman, S., R. Lane, and A. Guz. Breathlessness and respiratory mechanics during reflex or voluntary hyperventilation in patients with chronic airflow limitation. Clin. Sci. 73: 311–318, 1987.
 139. Fregosi, R. F., and J. A. Dempsey. Effects of exercise in normoxia and acute hypoxia on respiratory muscle metabolites. J. Appl. Physiol. 60: 1274–1283, 1986.
 140. Frevert, C. S., C. S. Nations, H. J. Seeherman, S. H. Loring, and R. B. Banzett. Airflow associated with stride in the horse. Physiologist 33: A83, 1990.
 141. Fuller, D., J. Sullivan, E. Essif, K. Personius, and R. F. Fregosi. Measurement of the EMG‐force relationship during voluntary and exercise‐induced contractions in a human upper airway muscle. J. Appl. Physiol. 79: 270–278, 1995.
 142. Gallagher, C. G. Exercise and chronic obstructive pulmonary disease. Med. Clin. North Am. 74: 619–641, 1990.
 143. Gallagher, C. G., E. Brown, and M. Younes. Breathing pattern during maximal exercise and during submaximal exercise with hypercapnia. J. Appl. Physiol. 63: 238–244, 1987.
 144. Gallagher, C. G., W. Huda, M. Rigby, D. Greenberg, and M. Younes. Lack of radiographic evidence of interstitial pulmonary edema after maximal exercise in normal subjects. Am. Rev. Respir. Dis. 137: 474–476, 1988.
 145. Gallagher, C. G., and M. Younes. Breathing pattern during and after maximal exercise in patients with chronic obstructive disease, interstitial lung disease, and cardiac disease, and in normal subjects. Am. Rev. Respir. Dis. 133: 581–586, 1986.
 146. Gallagher, C. G., and M. Younes. Effect of pressure assist on ventilation and respiratory mechanics in heavy exercise. J. Appl. Physiol. 66: 1824–1837, 1989.
 147. Gandevia, S. C. Neural mechanisms underlying the sensation of breathlessness: kinesthetic parallels between respiratory and limb muscles. Aust. N. Z. J. Med. 18: 83–91, 1988.
 148. Gandevia, S. L., K. J. Killian, and E. J. M. Campbell. The effect of respiratory muscle fatigue on respiratory sensations. Clin. Sci. 60: 463–466, 1981.
 149. Gandevia, S. C., K. J. Killian, D. K. Mckenzie, M. Crawford, G. M. Allen, R. B. Gorman, and J. P. Hales. Respiratory sensation, cardiovascular control, kinaesthesia and transcranial stimulation during complete paralysis in humans. J. Physiol. (Lond.) 470: 85–108, 1993.
 150. Gandevia, S. C., and D. K. McKenzie. Activation of the human diaphragm during maximal static efforts. J. Physiol. (Lond.) 367: 45–56, 1985.
 151. Garlando, F., J. Kohl, E. A. Koller, and P. Pietsch. Effect of coupling the breathing and cycling rhythms on oxygen uptake during bicycle ergometry. Eur. J. Appl. Physiol. 54: 497–501, 1985.
 152. Giesbrecht, G. G., F. Ali, and M. Younes. Short‐term effect of tidal pleural pressure swings on pulmonary blood flow during rest and exercise. J. Appl. Physiol. 71: 465–473, 1991.
 153. Gilbert, R., and J. J. Auchincloss. Mechanics of breathing in normal subjects during brief, severe exercise. J. Lab. Clin. Med. 73: 439–450, 1969.
 154. Gillespie, D. J., and R. E. Hyatt. Respiratory mechanics in the unanesthetized dog. J. Appl. Physiol. 36: 98–102, 1974.
 155. Gillespie, J. R., G. L. Landgren, and D. E. Leith. 1: 2 ratio of breathing to stride frequencies in a galloping horse breathing 6% CO2. Equine Exerc. Physiol. 3: 66–70, 1991.
 156. Goldman, M., G. Grimby, and J. Mead. Mechanical work of breathing derived from rib cage and abdominal V‐P partitioning. J. Appl. Physiol. 41: 752–764, 1976.
 157. Gollnick, P., M. Riedy, J. Quintinskie, and L. Bertocci. Difference in metabolic potential of skeletal muscle fibres and their significance for metabolic control. J. Exp. Biol. 115: 191–199, 1985.
 158. Gorski, J., Z. Namiot, and J. Giedrojc. Effect of exercise on metabolism of glycogen and triglycerides in the respiratory muscles. Pflugers Arch. 377: 251–254, 1978.
 159. Gosselin, L. E., M. Betlach, A. C. Vailas, and D. P. Thomas. Training induced alterations in young and senescent rat diaphragm muscle. J. Appl. Physiol. 72: 1506–1511, 1992.
 160. Gowda, K., T. Zintel, C. McParland, R. Orchard, and C. G. Gallagher. Diagnostic value of maximal exercise tidal volume. Chest 98: 1351–1354, 1990.
 161. Granath, A., E. Horie, and H. Linderholm. Compliance and resistance of the lungs in the sitting and supine positions at rest and during work. Scand. J. Clin. Lab. Invest. 11: 226–234, 1959.
 162. Green, H. J., M. E. Ball‐Burnett, M. A. Morrissey, J. Kile, and G. C. Abraham. Glycogen utilization in rat respiratory muscles during intense running. Can. J. Physiol. Pharmacol. 66: 917–923, 1988.
 163. Green, H., M. Plyley, D. Smith, and J. Kile. Extreme endurance training and fiber type adaptation in rat diaphragm. J. Appl. Physiol. 66: 1914–1920, 1986.
 164. Grillner, S., J. Nilsson, and A. Thorstensson. Intraabdominal pressure changes during natural movements in man. Acta. Physiol. Scand. 103: 275–283, 1978.
 165. Grimby, G., M. Goldman, and J. Mead. Respiratory muscle action inferred from rib cage and abdominal V‐P partitioning. J. Appl. Physiol. 41: 739–751, 1976.
 166. Grimby, G., B. Saltin, and L. Wilhemson. Pulmonary flow volume and pressure volume relationship during submaximal and maximal exercise in young well‐trained men. Bull. Physiopathol. Respir. 7: 57–168, 1971.
 167. Grinton, S., S. Powers, J. Lawler, D. Criswell, S. Dodd, and W. Edwards. Endurance training‐induced increases in expiratory muscle oxidative capacity. Med. Sci. Sports Exerc. 24: 551–555, 1992.
 168. Gross, D., A. Grassino, W. R. D. Ross, and P. T. Macklem. Electromyogram pattern of diaphragmatic fatigue. J. Appl. Physiol. Respir. Environ. Exerc. Physiol. 46: 1–7, 1979.
 169. Gutting, S. M., H. V. Forster, T. F. Lowry, A. G. Brice, and L. G. Pan. Respiratory muscle recruitment in awake ponies during exercise and CO2 inhalation. Respir. Physiol. 86: 315–332, 1991.
 170. Hagberg, J. M., J. E. Yerg, and D. R. Seals. Pulmonary function in young and older athletes and untrained men. Appl. Physiol. 65: 101–105, 1988.
 171. Haight, J., and P. Cole. Site and function of the nasal valve. Laryngoscope 93: 49–55, 1983.
 172. Hairston, L. E., and E. K. Sauerland. Electromyography of the human palate: discharge patterns of the levator and tensor veli palatini. Electromyogr. Clin. Neurophysiol. 21: 287–297, 1981.
 173. Hamilton, L. H. Nasal airway resistance: its measurement and regulation. Physiologist 22: 43–49, 1979.
 174. Hamilton, A., G. Obminski, E. Summers, M. L. Jones, and K. J. Killian. Endurance capacity and symptom limitation during extreme exertion. Am. J. Respir. Crit. Care Med. 149: A776, 1994.
 175. Hamm, T., P. Nemeth, L. Solanki, D. Gordon, R. Reinking, and D. Stuart. Association between biochemical and physiological properties in single motor units. Muscle Nerve 11: 245–254, 1988.
 176. Hanel, B., and N. Secher. Maximal oxygen uptake and work capacity after inspiratory muscle training: a controlled study. J. Sports Sci. 9: 43–52, 1991.
 177. Hanson, P. A., A. Claremont, J. A. Dempsey, and W. G. Reddan. Determinants and consequences of ventilatory responses to competitive endurance running. J. Appl. Physiol. 52: 615–623, 1982.
 178. Harms, C. A., and J. M. Stager. How peripheral chemosensitivity and inadequate hyperventilation contribute to exercise‐induced hypoxemia. J. Appl. Physiol. 79: 575–580, 1995.
 179. Harty, H. R., and L. Adams. Dose dependency of perceived breathlessness on hypoventilation during exercise in normal subjects. J. Appl. Physiol. 77: 2666–2674, 1994.
 180. Harty, H. R., C. J. Mummery, L. Adams, R. B. Banzatt, I. G. Wright, N. R. Banner, M. H. Yacoub, and A. Guz. Ventilatory release of the urge to breathe sensation in humans: are pulmonary receptors important? J. Physiol. (Lond.) 490: 805–815, 1996.
 181. Haxhiu, M. A., E. van Lunteren, J. Mitra, and N. S. Cherniack. Responses to chemical stimulation of upper airway muscles and diaphragm in awake cats. J. Appl. Physiol. 56: 397–403, 1984.
 182. Hellstrand, E. Morphological and histochemical properties of tongue muscles in cats. Acta Physiol. Scand. 110: 187–198, 1980.
 183. Henke, K. G., M. Sharratt, D. Pegelow, and J. A. Dempsey. Regulation of end‐expiratory lung volume during exercise. J. Appl. Physiol. 64: 135–146, 1988.
 184. Henneman, E., and L. M. Mendell. Functional organization of motoneuron pool and its inputs. In: Handbook of Physiology, The Nervous System, Motor Control, edited by V. B. Brooks. Bethesda, MD: Am. Physiol. Soc., 1981, p. 423–507.
 185. Hershenson, M. B., Y. Kikuchi, and S. H. Loring. Relative strengths of the chest wall muscles. J. Appl. Physiol. 65: 852–862, 1988.
 186. Hey, E. N., B. B. Lloyd, D. Cunningham, M. Jukes, and D. Bolton. Effects of various respiratory stimuli on the depth and frequency of breathing in man. Respir. Physiol. 1: 193–205, 1966.
 187. Hill, N. S., C. Jacoby, and H. W. Farber. Effect of an endurance triathalon on pulmonary function. Med. Sci. Sports Exerc. 23: 1260–1264, 1991.
 188. Holloszy, J., and E. Coyle. Adaptations of skeletal muscle to endurance exercise and their metabolic consequences. J. Appl. Physiol. 56: 831–838, 1984.
 189. Hornicke, H., R. Meixner, and U. Pollman. Respiration in exercising horses. In: Equine Exercise Physiology, edited by D. H. Snow, S. G. M. Persson, and R. J. Rose. Cambridge: Granta Editions, 1983, p. 7–16.
 190. Hu, A., F. H. Comtois, and A. E. Grassino. Optimal diaphragmatic blood perfusion. J. Appl. Physiol. 72: 149–157, 1992.
 191. Hubmayr, R. D., W. J. Litchy, P. C. Gay, and S. B. Nelson. Transdiaphragmatic twitch pressure: effects of lung volume and chest wall shape. Am. Rev. Respir. Dis. 139: 647–652, 1989.
 192. Hudgel, D. W., K. R. Chapman, C. Faulks, and C. Hendricks. Changes in inspiratory muscle electrical activity and upper airway resistance during periodic breathing induced by hypoxia during sleep. Am. Rev. Respir. Dis. 135: 899–906, 1987.
 193. Hussain, S. N. A., and R. L. Pardy. Inspiratory muscle function with restrictive chest wall loading during exercise in normal humans. J. Appl. Physiol. 58: 2027–2032, 1985.
 194. Hussain, S. N. A., R. L. Pardy, and J. A. Dempsey. Mechanical impedance as determinant of inspiratory neural drive during exercise in humans. J. Appl. Physiol. 59: 365–375, 1985.
 195. Hyland, R. H., N. L. Jones, A. C. P. Powles, S. C. M. Lenkie, R. G. Vanderlinden, and S. W. Epstein. Primary alveolar hypoventilation treated with nocturnal electrophrenic respiration. Am. Rev. Respir. Dis. 117: 165–172, 1978.
 196. Ianuzzo, C. D., E. Noble, N. Hamilton, and B. Dabrowski. Effects of streptozotocin diabetes, insulin treatment, and training on the diaphragm. J. Appl. Physiol. 52: 1471–1475, 1982.
 197. Ianuzzo, C. D., M. J. Spalding, and H. Williams. Exercise‐induced glycogen utilization by the respiratory muscles. J. Appl. Physiol. 62: 1405–1409, 1987.
 198. Issa, F. G., P. Edwards, E. Szeto, D. Lauff, and C. Sullivan. Genioglossus and breathing responses to airway occlusion: effect of sleep and route of occlusion. J. Appl. Physiol. 64: 543–549, 1988.
 199. Issa, F. G., and C. E. Sullivan. Upper airway closing pressures in obstructive sleep apnea. J. Appl. Physiol. 57: 520–527, 1984.
 200. Jammes, Y., B. Buchler, S. Delpierre, A. Rasidakis, C. Grimaud, and C. Roussos. Phrenic afferents and their role in inspiratory control. J. Appl. Physiol. 60: 854–860, 1986.
 201. Jasinskas, C. L., B. A. Wilson, and J. Hoare. Entrainment of breathing rate to movement frequency during work at two intensities. Respir. Physiol. 42: 199–209, 1980.
 202. Jensen, J. I., S. Lyager, and O. F. Pedersen. The relationship between maximal ventilation, breathing pattern and mechanical limitation of ventilation. J. Physiol. (Lond.) 309: 521–532, 1980.
 203. Johnson, B. D., M. L. Austrup, and G. C. Sieck. Diaphragm contractile properties in transgenic mice overexpressing CuZn‐superoxide dismutase. Am. J. Respir. Crit. Care Med. 149: A322, 1994.
 204. Johnson, B. D., M. A. Babcock, O. E. Suman, J. A. Dempsey. Exercise‐induced diaphragmatic fatigue in healthy humans. J. Physiol. (Lond.) 460: 385–405, 1993.
 205. Johnson, B. D., M. S. Badr, and J. A. Dempsey. Impact of the aging pulmonary system on the response to exercise. Clin. Chest Med. 15: 229–246, 1994.
 206. Johnson, B. D., W. G. Reddan, D. F. Pegelow, K. C. Seow, and J. A. Dempsey. Flow limitation and regulation of function residual capacity during exercise in a physically active aging population. Am. Rev. Respir. Dis. 143: 960–967, 1991.
 207. Johnson, B. D., W. G. Reddan, K. G. Seow, and J. A. Dempsey. Mechanical constraints on exercise hyperpnea in a fit aging population. Am. Rev. Respir. Dis. 143: 968–977, 1991.
 208. Johnson, B. D., K. W. Saupe, and J. A. Dempsey. Mechanical constraints on exercise hyperpnea in endurance athletes. J. Appl. Physiol. 73: 874–886, 1992.
 209. Johnson, B. D., P. D. Scanlon, and K. C. Beck. Regulation of ventilatory capacity during exercise in asthmatics. J. Appl. Physiol. (in press).
 210. Johnson, B. D., and G. C. Sieck. Activation‐induced reduction of SDH activity in diaphragm muscle fibers. J. Appl. Physiol. 75: 2689–2695, 1993.
 211. Johnson, B. D., and G. C. Sieck. Differential susceptibility of diaphragm muscle fibers to neuromuscular transmission failure. J. Appl. Physiol. 75: 341–348, 1993.
 212. Jones James, H. Circulatory function during exercise: Integration of convection and diffusion. Adv. Vet. Sci. Comp. Med. 38A: 217–251, 1994.
 213. Jones, N. L. Determinants of breathing patterns. In: Exercise: Pulmonary Physiology and Pathophysiology, edited by B. J. Whipp and K. Wasserman. New York: Marcel Dekker, Inc., 1991, p. 99–119.
 214. Jones, N. L., K. J. Killian, and D. G. Stubbing. The thorax during exercise. In: The Thorax, edited by C. Roussos and P. Macklem. New York: Marcel Dekker, Inc., 1985, p. 627–661.
 215. Kagawa, J., and H. D. Kerr. Effects of brief graded exercise on specific airway conductance in normal subjects. J. Appl. Physiol. 28: 138–144, 1970.
 216. Karlsson, J., and B. Saltin. Diet, muscle glycogen and endurance performance. J. Appl. Physiol. 31: 203–206, 1971.
 217. Katz‐Salamon, M., C. Von Euler, and O. Franzen. Perception of mechanical factors in breathing. In: Physical Work and Effort, edited by G. Borg. Oxford: Pergamon Press, 1976, p. 101–113.
 218. Kaufman, M. P., K. J. Rybicki, and J. H. Mitchell. Hind‐limb muscular contraction reflexly decreases total pulmonary resistance in dogs. J. Appl. Physiol. 59: 1521–1526, 1985.
 219. Killian, K. J. Limitation of exercise by dyspnea. Can. J. Sport Sci. 12: 53S–60S, 1987.
 220. Killian, K. J., D. D. Bucens, and E. J. M. Campbell. Effect of breathing patterns on the perceived magnitude of added loads to breathing. J. Appl. Physiol. 52: 578–584, 1982.
 221. Killian, K. J., and E. J. Campbell. Mechanisms of dyspnea. In: Dyspnea, edited by D. A. Mahler. New York: Futura Publishing Co., 1990, p. 55–73.
 222. Killian, K. J., S. C. Gandevia, E. Summers, and E. J. M. Campbell. Effect of increased lung volume on perception of breathlessness, effort and tension. J. Appl. Physiol. 57: 686–691, 1984.
 223. Killian, K. J., P. Leblanc, D. H. Martin, E. Summers, N. L. Jones, and E. J. M. Campbell. Exercise capacity and ventilatory, circulatory, and symptom limitation in patients with chronic airflow limitation. Am. Rev. Respir. Dis. 146: 935–940, 1992.
 224. Klas, J. V., and J. A. Dempsey. Voluntary vs reflex regulation of maximal exercise flow: volume loop. Am. Rev. Respir. Dis. 139: 150–156, 1989.
 225. Klausen, K., N. H. Secher, J. P. Clausen, O. Harding, and J. Trap‐Jensen. Central and regional circulatory adaptations to one‐leg training. J. Appl. Physiol. Respir. Environ. Exerc. Physiol. 52: 976–983, 1982.
 226. Kohl, J., E. A. Roller, and M. Jager. Relation between pedalling and breathing rhythm. Eur. J. Appl. Physiol. 47: 223–237, 1981.
 227. Krishnan, B., T. Zintel, C. McParland, and C. G. Gallagher. The evolution of respiratory motor output in constant load heavy exercise. FASEB J. 5: A1480, 1991.
 228. Krishnan, B., T. Zintel, C. McParland, and C. G. Gallagher. Lack of importance of respiratory muscle load in ventilatory regulation during heavy exercise. J. Physiol. (Lond.) 1995 (in press).
 229. Kuei, J. H., R. Shadmehr, and G. C. Sieck. Relative contribution of neurotransmission failure to diaphragm fatigue. J. Appl. Physiol. 68: 174–180, 1990.
 230. Kugelberg, E. Histochemical composition, contraction speed, and fatigability of rat soleus motor units. J. Neurol. Sci. 20: 177–198, 1973.
 231. Kuna, S. T., R. A. Day, G. Insalaco, and R. D. D. Villeponteaux. Posterior cricoarytenoid activity in normal adults during involuntary and voluntary hyperventilation. J. Appl. Physiol. 70: 1377–1385, 1991.
 232. Kurtz, D., J. Krieger, and J. C. Stierle. EMG activity of cricothyroid and chin muscles during wakefulness and sleeping in the sleep apnea syndrome. Electroencephalogr. Clin. Neurophysiol. 45: 777–784, 1978.
 233. Lafortuna, C. L., A. E. Minetti, and P. Mognoni. Inspiratory flow pattern in humans. J. Appl. Physiol. Respir. Environ. Exerc. Physiol. 57: 1111–1119, 1984.
 234. Lafortuna, C. L., and F. Saibene. Mechanics of breathing in horses at rest and during exercise. J. Exp. Biol. 155: 245–259, 1991.
 235. Landgren, G. L., J. R. Gillespie, and D. E. Leith. No ventilatory response in thoroughbreds galloping at 14 m·s 1. In: Equine Exercise Physiology, edited by S. G. Persoon, A. Lindholm, and L. B. Jeffcott. Davis, CA: ICEEP, 1991, p. 59–65.
 236. Lane, R., and L. Adams. Metabolic acidosis and breathlessness during exercise and hypercapnia in man. J. Physiol. (Lond.) 461: 47–61, 1993.
 237. Lane, R., L. Adams, and A. Guz. Is low‐level respiratory resistive loading during exercise perceived as breathlessness? Clin. Sci. 73: 627–634, 1987.
 238. Lane, R., L. Adams, and A. Guz. The effects of hypoxia and hypercapnia on perceived breathlessness during exercise in humans. J. Physiol. (Lond.) 428: 579–593, 1990.
 239. Lane, R., A. Cockcroft, L. Adams, and A. Guz. Arterial oxygen saturation and breathlessness in patients with chronic obstructive airways disease. Clin. Sci. 72: 693–698, 1987.
 240. Lane, R., A. Cockcroft, and A. Guz. Voluntary isocapnic hyperventilation and breathlessness during exercise in normal subjects. Clin. Sci. 73: 519–523, 1987.
 241. Lawler, J., S. K. Powers, and D. Thompson. Linear relationships between V.O2max and V.O2max decrement during exposure to acute hypoxia. J. Appl. Physiol. 64: 1486–1492, 1988.
 242. Leblanc, P., D. M. Bowie, E. Summers, N. L. Jones, and K. J. Killian. Breathlessness and exercise in patients with cardiorespiratory disease. Am. Rev. Respir. Dis. 133: 21–25, 1986.
 243. Leblanc, P., E. Summers, M. D. Inman, N. L. Jones, E. Campbell, and K. J. Killian. Inspiratory muscles during exercise: a problem of supply and demand. J. Appl. Physiol. 64: 2482–2489, 1988.
 244. Leevers, A. M., and J. D. Road. Abdominal muscle activation by expiratory threshold loading in awake dogs. Respir. Physiol. 93: 289–303, 1993.
 245. Leiter, J. C., S. L. Knuth, and D. B. Bartlett, Jr.. Dependence of pharyngeal resistance on genioglossal EMG activity, nasal resistance and flow. J. Appl. Physiol. 73: 584–590, 1992.
 246. Leith, D., and M. Bradley. Ventilatory muscle strength and endurance training. J. Appl. Physiol. 41: 508–516, 1976.
 247. Levine, S., M. Gillen, P. Weiser, G. Feiss, M. Goldman, and D. Henson. Inspiratory pressure generation: comparison of subjects with COPD and age‐matched normals. J. Appl. Physiol. 65: 888–899, 1988.
 248. Levine, S., and D. Henson. Low‐frequency diaphragmatic fatigue in spontaneously breathing humans. J. Appl. Physiol. 64: 672–680, 1988.
 249. Lindinger, M. I., G. J. F. Heigenhauser, R. S. McKelvie, and N. L. Jones. Role of nonworking muscle on blood metabolites and ions with intense intermittent exercise. Am. J. Physiol. 258 (Regulatory Integrative Comp. Physiol. 27): R148–R149, 1990.
 250. Lindstedt, S. L., J. F. Hokanson, D. J. Wells, S. D. Swain, H. Hoppeler, and V. Navarra. Running energetics in the prong horn antelope. Nature 353: 748–750, 1991.
 251. Lindstedt, S. L., R. G. Thomas, and D. E. Leith. Does peak inspiratory flow contribute to setting V.O2max? Respir. Physiol. 95: 109–118, 1994.
 252. Loke, J. D. M., and J. A. Virgulto. Respiratory muscle fatigue after marathon running. J. Appl. Physiol. 52: 821–824, 1982.
 253. Loring, S. H., J. Mead, and T. B. Waggener. Determinants of breathing frequency during walking. Respir. Physiol. 82: 177–188, 1990.
 254. Louhevaara, V., A. Sovijarvi, J. Ilmarinen, and P. Teraslinna. Differences in cardiorespiratory responses during and after arm crank and cycle exercise. Acta Physiol. Scand. 138: 133–143, 1990.
 255. MacDonald, M. E., R. L. Kirby, S. T. Nugent, and D. A. MacLeod. Locomotor‐respiratory coupling during wheelchair propulsion. J. Appl. Physiol. 72: 1375–1379, 1992.
 256. Mador, M. J., and F. A. Acevedo. Effect of respiratory muscle fatigue on breathing pattern during incremental exercise. Am. Rev. Respir. Dis. 143: 462–468, 1991.
 257. Mador, M. J., U. J. Magalang, A. Rodis, and T. J. Kufel. Diaphragmatic fatigue after exercise in healthy human subjects. Am. Rev. Respir. Dis. 148: 1571–1575, 1993.
 258. Mahler, D. A., and J. Loke. Lung function after marathon running at warm and cold ambient temperatures. Am. Rev. Respir. Dis. 124: 154–157, 1981.
 259. Mahler, D. A., C. R. Shuhart, E. Brew, and T. A. Stukel. Ventilatory responses and entrainment of breathing during rowing. Med. Sci. Sports Exerc. 23: 186–192, 1991.
 260. Mann, D. G., C. S. Sasaki, H. Fukuda, M. Suzuki, and J. R. Hernandez. Dilator naris muscle. Ann. Otol. 86: 362–370, 1977.
 261. Manning, H. L., S. A. Shea, R. M. Schwartzstein, R. W. Lansing, R. Brown, and R. B. Banzett. Reduced tidal volume increases “air hunger” at fixed PCO2 in ventilated quadriplegics. Respir. Physiol. 90: 19–30, 1992.
 262. Manohar, M. Blood flow to the respiratory and limb muscles and to abdominal organs during maximal exertion in ponies. J. Physiol. (Lond.) 377: 25–35, 1986.
 263. Manohar, M. Vasodilator reserve in respiratory muscles during maximal exertion in ponies. J. Appl. Physiol. 60: 1571–1577, 1986.
 264. Manohar, M. Costal vs. crural diaphragmatic blood flow during submaximal and near‐maximal exercise in ponies. J. Appl. Physiol. 65: 1514–1519, 1988.
 265. Manohar, M., and A. S. Hassan. The diaphragm does not produce ammonia or lactate during high density short‐term exercise. Am. J. Physiol. 259 (Heart Circ. Physiol. 28): H1185–H1189, 1990.
 266. Manohar, M., and A. S. Hassan. Diaphragmatic energetics during prolonged exhaustive exercise. Am. Rev. Respir. Dis. 144: 415–418, 1991.
 267. Marciniuk, D., D. McKim, R. Sanii, and M. Younes. Role of central respiratory muscle fatigue in endurance exercise in normal subjects. J. Appl. Physiol. 76: 236–241, 1994.
 268. Marciniuk, D. D., G. Sridhar, R. E. Clemens, T. A. Zintel, and C. G. Gallagher. Lung volumes and expiratory flow limitation during exercise in interstitial lung disease. J. Appl. Physiol. 77: 963–973, 1994.
 269. Maron, M. B., L. H. Hamilton, and M. G. Maksud. Alterations in pulmonary function consequent to competitive marathon running. Med. Sci. Sports Exerc. 11: 244–249, 1979.
 270. Martin, B., M. Heintzelman, and H. Chen. Exercise performance after ventilatory work. J. Appl. Physiol. 52: 1581–1585, 1982.
 271. Mathew, O. P., Y. K. Abu‐Osba, and B. T. Thach. Influence of upper airway pressure changes on genioglossus muscle respiratory activity. J. Appl. Physiol. 52: 438–444, 1982.
 272. McBride, B., and W. A. Whitelaw. A physiological stimulus to upper airway receptors in humans. J. Appl. Physiol. 51: 1189–1197, 1981.
 273. McClaran, S. R., M. Babcock, D. Pegelow, W. Reddan, and J. Dempsey. Longitudinal effects of aging on lung function at rest and exercise in the healthy active fit elderly adult. J. Appl. Physiol. 78: 1957–1968, 1995.
 274. McCool, F. D., D. R. McCann, D. E. Leith, and F. G. Hoppin, Jr. Pressure–flow effects on endurance of inspiratory muscles. J. Appl. Physiol. 60: 299–303, 1986.
 275. McCool, F. D., G. T. Tzelepis, D. E. Leith, and F. G. Hoppin, Jr.. Oxygen cost of breathing during fatiguing inspiratory resistive loads. J. Appl. Physiol. 66: 2045–2055, 1989.
 276. McDermott, J. C., G. C. Elder, and A. Bonen. Adrenal hormones enhance glycogenolysis in nonexercising muscle during exercise. J. Appl. Physiol. 63: 1275–1283, 1987.
 277. McParland, C., B. Krishnan, J. Lobo, and C. G. Gallagher. Effect of physical training on breathing pattern during progressive exercise. Respir. Physiol. 90: 311–323, 1992.
 278. McParland, C., J. Mink, and C. G. Gallagher. Respiratory adaptations to dead space loading during maximal incremental exercise. J. Appl. Physiol. 70: 55–62, 1991.
 279. Mead, J. Control of respiratory frequency. J. Appl. Physiol. 15: 325–336, 1960.
 280. Mead, J., and E. Agostoni. Dynamics of breathing. In: Handbook of Physiology, Respiration, edited by W. O. Fenn and H. Rahn. Washington, DC: Am. Physiol. Soc., 1964, p. 411–427.
 281. Messner, T. Everest: Expedition to the Ultimate. London: Kaye and Ward, 1979.
 282. Metzger, J., and R. Fitts. Contractile and biochemical properties of diaphragm: effects of exercise and fatigue. J. Appl. Physiol. 60: 1752–1758, 1986.
 283. Mezzanotte, W. S., D. J. Tangel, and D. P. White. Mechanisms of control of alae nasi muscle activity. J. Appl. Physiol. 72: 925–933, 1992.
 284. Miles, D. S., A. D. Enoch, and S. C. Grevey. Interpretation of changes in DLCO and pulmonary function after running five miles. Respir. Physiol. 66: 135–145, 1986.
 285. Mitchinson, A. G., and J. M. Yoffey. Respiratory displacement of the larynx, hyoid bone and tongue. J. Anat. 81: 118–121, 1947.
 286. Mizuno, M. Human respiratory muscles: fibre morphology and capillary supply. Eur. Respir. J. 4: 587–601, 1991.
 287. Mizuno, M., and N. H. Secher. Histochemical characteristics of human expiratory and inspiratory intercostal muscles. J. Appl. Physiol. 67: 592–598, 1989.
 288. Moore, R. L., and P. D. Gollnick. Response of ventilatory muscles of the rat to endurance training. Pflugers Arch. 392: 268–271, 1982.
 289. Morgan, D., W. Kohrt, B. Bates, and J. Skinner. Effects of respiratory muscle endurance training on ventilatory and endurance performance of moderately trained cyclists. Int. J. Sports Med. 8: 88–93, 1987.
 290. Moxham, J., R. H. T. Edwards, M. Aubier, A. Detroyer, G. Farkas, P. T. Macklem, and C. Roussos. Changes in EMG power spectrum (high to low) with force fatigue in humans. J. Appl. Physiol. 53: 1094–1099, 1982.
 291. Muza, S. R., M. T. Silverman, G. C. Gilmore, H. K. Hellerstein, and S. G. Kelsen. Comparison of scales used to quantitate the sense of effort to breathe in patients with chronic obstructive pulmonary disease. Am. Rev. Respir. Dis. 141: 909–913, 1990.
 292. National Heart, Lung and Blood Institute. Workshop Summary. Respiratory Muscle Fatigue: Report of the Respiratory Muscle Fatigue Workshop Group. Am. Rev. Respir. Dis. 142: 474–480, 1990.
 293. Nava, S., E. Zanotti, C. Rampulla, and A. Rossi. Respiratory muscle fatigue does not limit exercise performance during moderate endurance run. J. Sports Med. Phys. Fitness 32: 39–44, 1992.
 294. Niinimaa, V., P. Cole, S. Mintz, and R. J. Shephard. The switching point from nasal to oro‐nasal breathing. Respir. Physiol. 42: 61–71, 1980.
 295. Niinimaa, V., P. Cole, S. Mintz, and R. J. Shephard. Oronasal distribution of respiratory airflow. Respir. Physiol. 43: 69–75, 1981.
 296. Ohki, M., M. Hasegawa, N. Kurita, and I. Watanabe. Effects of exercise on nasal resistance and nasal blood flow. Acta Otolaryngol. 104: 328–333, 1987.
 297. Okabe, S., T. Chonan, W. Hida, M. Satoh, Y. Kikuchi, and T. Takishima. Role of chemical drive in recruiting upper airway and inspiratory intercostal muscles in patients with obstructive sleep apnea. Am. Rev. Respir. Dis. 147: 190–195, 1993.
 298. O'Kroy, J., and J. Coast. Effects of flow and resistive training on respiratory muscle strength and endurance. Respiration 60: 279–283, 1993.
 299. O'Kroy, J., R. A. Loy, and J. R. Coast. Pulmonary function changes following exercise. Med. Sci. Sports Exerc. 24: 1359–1364, 1992.
 300. Olafsson, S., and R. E. Hyatt. Ventilatory mechanics and expiratory flow limitation during exercise in normal subjects. J. Clin. Invest. 48: 564–573, 1969.
 301. Olson, L. G., J. M. Fouke, P. L. Hoekje, and K. P. Strohl. A biomechanical view of upper airway function. In: Regulation of Breathing, edited by O. P. M. Ambrogio. New York: Marcel Dekker, 1988, p. 359–389.
 302. Olson, L. G., and K. P. Strohl. The response of the nasal airway to exercise. Am. Rev. Respir. Dis. 135: 356–359, 1987.
 303. Onal, E., M. Lopata, and T. D. O'Connor. Diaphragmatic and genioglossal electromyogram responses to CO2 rebreathing in humans. J. Appl. Physiol. 50: 1052–1055, 1981.
 304. Onal, E., M. Lopata, and T. D. O'Connor. Diaphragmatic and genioglossal electromyogram responses to isocapnic hypoxia in humans. Am. Rev. Respir. Dis. 124: 215–217, 1981.
 305. O'Neill, P. A., R. D. Stark, S. C. Allen, and T. B. Stretton. The relationship between breathlessness and ventilation during steady state exercise. Clin. Respir. Physiol. 22: 247–250, 1986.
 306. Opie, L. H., A. C. Smith, and J. M. K. Spalding. Conscious appreciation of the effects produced by independent changes of ventilation volume and end‐tidal PCO2 in paralysed patients. J. Physiol. (Lond.) 149: 494–499, 1959.
 307. Otis, A. B. The work of breathing. In: Handbook of Physiology, Respiration, edited by W. O. Fenn and H. Rahn. Washington, DC: Am. Physiol. Soc., 1964, p. 463–476.
 308. Otis, A. B., W. A. Fenn, and H. Rahn. Mechanics of breathing in man. J. Appl. Physiol. 2: 592–607, 1950.
 309. Pagala, M. K. D., T. Namba, and D. Grob. Failure of neuromuscular transmission and contractility during muscle fatigue. Muscle Nerve 7: 454–464, 1984.
 310. Painter, R., and D. Cunningham. Analyses of human respiratory flow patterns. Respir. Physiol. 87: 293–307, 1992.
 311. Pardy, R. L., and P. T. P. Bye. Diaphragmatic fatigue in normoxia and hyperoxia. J. Appl. Physiol. 58: 738–742, 1985.
 312. Pardy, R., W. D. Reid, and M. Belman. Respiratory muscle training. In: Clinics in Chest Medicine: Respiratory Muscles: Function in Health and Disease, edited by M. Belman. Philadelphia: W. B. Saunders Company, 1988, p. 287–296.
 313. Paterson, D. J., G. A. Wood, R. N. Marshall, A. R. Morton, and A. Harrison. Entrainment of respiratory frequency to exercise rhythm during hypoxia. J. Appl. Physiol. 62: 1767–1771, 1987.
 314. Paterson, D. J., G. A. Wood, A. R. Morton, and J. D. Henstridge. The entrainment of ventilation frequency to exercise rhythm. Eur. J. Appl. Physiol. Occup. Physiol. 55: 530–537, 1986.
 315. Paton, J. Y., S. Swaminathan, C. W. Sargent, A. Hawksworth, and T. G. Keens. Ventilatory response to exercise in children with congenital central hypoventilation syndrome. Am. Rev. Respir. Dis. 147: 1185–1191, 1993.
 316. Pearce, D. H., and H. J. Milhorn. Dynamic and steady‐state respiratory responses to bicycle exercise. J. Appl. Physiol. 41: 959–967, 1977.
 317. Pelletier, N., and D. E. Leith. Ventilation and CO2 exchange in exercising horses: effect of inspired O2 fraction. J. Appl. Physiol. 78: 654–662, 1995.
 318. Pelligrino, R., V. Brussasco, J. R. Rodarte, and T. G. Babb. Expiratory flow limitation and regulation of end‐expiratory lung volume during exercise. J. Appl. Physiol. 74: 2552–2558, 1993.
 319. Permutt, S., and R. A. Wise. Mechanical interaction of respiration and circulation. In: Handbook of Physiology, The Respiratory System, Mechanics of Breathing, edited by P. T. Macklem and J. Mead. Bethesda, MD: Am. Physiol. Soc., 1986, p. 647–656.
 320. Person, R. S. Rhythmic activity of a group of human motoneurons during voluntary contraction of a muscle. Electroencephalogr. Clin. Neurophysiol. 36: 585–595, 1974.
 321. Pertuze, J., A. Watson, and N. B. Pride. Maximum airflow through the nose. J. Appl. Physiol. 70: 1369–1376, 1991.
 322. Pette, D., and R. Staron. Cellular and molecular diversities of mammalian skeletal muscle fibers. Rev. Physiol. Biochem. Pharmacol. 116: 2–76, 1990.
 323. Polacheck, J., R. Strong, J. Arens, C. Davies, I. Metcalf, and M. Younes. Phasic vagal influence on inspiratory motor output in anesthesized human subjects. J. Appl. Physiol. Respir. Environ. Exerc. Physiol. 49: 609–619, 1980.
 324. Poon, C. S. Ventilatory control in hypercapnia and exercise: optimization hypothesis. J. Appl. Physiol. 62: 2447–2459, 1987.
 325. Poon, C. S., S. A. Ward, and B. J. Whipp. Influence of inspiratory assistance on ventilatory control during moderate exercise. J. Appl. Physiol. 62: 551–560, 1987.
 326. Powers, S., D. Criswell, J. Lawler, L. Ji, D. Martin, R. Herb, and G. Dudley. Influence of exercise and fiber type on antioxidant enzyme activity in rat skeletal muscle. Am. J. Physiol. 266 (Regulatory Integrative Comp. Physiol. 35): R375–R380, 1994.
 327. Powers, S., D. Criswell, J. Lawler, D. Martin, L. Ji, R. Herb, and G. Dudley. Regional training‐induced alterations in diaphragmatic oxidative and antioxidant enzymes. Respir. Physiol. 95: 227–237, 1994.
 328. Powers, S., D. Criswell, F. K. Lieu, S. Dodd, and H. Silverman. Diaphragmatic fiber type specific adaptation. Respir. Physiol. 89: 195–207, 1992.
 329. Powers, S. K., D. Criswell, F. Lieu, S. Dodd, and H. Silverman. Exercise‐induced cellular alterations in the diaphragm. Am. J. Physiol. 263 (Regulatory Integrative Comp. Physiol. 32): R1093–R1096, 1992.
 330. Powers, S., S. Grinton, J. Lawler, D. Criswell, and S. Dodd. High intensity exercise training‐induced metabolic alterations in respiratory muscles. Respir. Physiol. 89: 169–177, 1992.
 331. Powers, S., J. Lawler, D. Criswell, S. Dodd, S. Grinton, G. Bagby, and H. Silverman. Endurance training‐induced cellular adaptations in respiratory muscles. J. Appl. Physiol. 68: 2114–2118, 1990.
 332. Powers, S., J. Lawler, D. Criswell, K. L. Fu, and D. Martin. Aging and respiratory muscle metabolic plasticity: effects of endurance training. J. Appl. Physiol. 72: 1068–1073, 1992.
 333. Powers, S., J. Lawler, D. Criswell, H. Silverman, V. F. H. S. Grinton, and D. Harkins. Regional metabolic differences in the rat diaphragm. J. Appl. Physiol. 69: 648–650, 1990.
 334. Powers, S. K., J. Lawler, J. A. Dempsey, S. Dodd, and G. Landry. Effects of incomplete pulmonary gas exchange on VO2 max. J. Appl. Physiol. 66: 2491–2495, 1989.
 335. Prabhu, B., T. Zintel, D. Marciniuk, R. Clemens, and C. G. Gallagher. Lack of effect of pedalling frequency on breathing pattern during bicycle ergometry. Am. Rev. Respir. Dis. 145: A582, 1992.
 336. Prefaut, C., F. Anselme, C. Caillaud, and J. Masse‐Biron. Exercise‐induced hypoxemia in older athletes. J. Appl. Physiol. 76: 120–126, 1994.
 337. Proctor, D. F. The upper respiratory tract. In: Pulmonary Diseases and Disorders, edited by A. P. Fishman. New York: McGraw‐Hill, 1979, p. 3–17.
 338. Proctor, D. F. Form and function of the upper airways and larynx. In: Handbook of Physiology, The Respiratory System, Mechanics of Breathing, edited by P. T. Macklem and J. Mead. Bethesda, MD: Am. Physiol. Soc., 1986, p. 63–73.
 339. Redline, S., S. B. Gottfried, and M. D. Altose. Effect of changes in inspiratory muscle strength on the sensation of respiratory force. J. Appl. Physiol. 70: 240–245, 1991.
 340. Redline, S., and K. P. Strohl. Influence of upper airway sensory receptors on respiratory muscle activation in humans. J. Appl. Physiol. 63: 368–374, 1987.
 341. Reid, M. B., K. E. Haack, K. M. Franchek, P. A. Valberg, L. Kobzik, and M. S. West. Reactive oxygen in skeletal muscle. I. Intracellular oxidant kinetics and fatigue in vitro. J. Appl. Physiol. 73: 1797–1804, 1992.
 342. Reiser, P., R. Moss, G. Giulian, and M. Greaser. Shortening velocity in single fibers from adult rabbit soleus muscle is correlated with myosin heavy chain composition. J. Biol. Chem. 260: 9077–9080, 1985.
 343. Remmers, J. E., J. G. Brooks, and S. M. Tenney. Effect of controlled ventilation on the tolerable limit of hypercapnia. Respir. Physiol. 4: 78–90, 1968.
 344. Richerson, H. B., and P. M. Seebohm. Nasal airway response to exercise. J. Allergy 41: 269–284, 1968.
 345. Road, J., R. Vahi, P. Del Rio, and A. Grassino. In vivo contractile properties of fatigued diaphragm. J. Appl. Physiol. 63: 471–478, 1987.
 346. Roberts, D., and D. J. Smith. Biochemical aspects of peripheral muscle fatigue, a review. Sports Med. 7: 125–138, 1989.
 347. Robertson, E., and J. Kjeldgaard. Improvement in ventilatory muscle function with running. J. Appl. Physiol. 52: 1400–1406, 1982.
 348. Rodenstein, D. O., and D. C. Stanescu. Soft palate and oronasal breathing in humans. J. Appl. Physiol. 57: 651–657, 1984.
 349. Roussos, C. Ventilatory muscle fatigue governs breathing frequency. Bull. Eur. Physiopathol. Respir. 20: 445–451, 1984.
 350. Roussos, C. Respiratory muscle fatigue and ventilatory failure. Chest 97: 89S–96S, 1990.
 351. Roussos, C., M. Fixley, D. Gross, and P. T. Macklem. Fatigue of inspiratory muscles and their synergistic behaviour. J. Appl. Physiol. 46: 897–904, 1979.
 352. Roussos, C. S., and P. T. Macklem. Diaphragmatic fatigue in man. J. Appl. Physiol. 43: 189–197, 1977.
 353. Rubinstein, I., N. Zamel, A. S. Rebuck, V. Hoffstein, A. D. D'Urzo, and A. S. Slutsky. Dichotomous airway response to exercise in asthmatic patients. Am. Rev. Respir. Dis. 138: 1164–1168, 1988.
 354. Saibene, F., P. Mognoni, C. L. Lafortuna, and R. Mostardi. Oronasal breathing during exercise. Pflugers Arch. 378: 65–69, 1978.
 355. St John, W. M., and D. Zhou. Differing control of neural activities during various portions of expiration in the cat. J. Physiol. (Lond.) 418: 189–204, 1989.
 356. St John, W. M., D. Zhou, and R. F. Fregosi. Expiratory neural activities in gasping. J. Appl. Physiol. 66: 223–231, 1989.
 357. Salman, D. S., D. F. Proctor, D. L. Swift, and S. A. Evering. Nasal resistance: description of a method and effect of temperature and humidity changes. Ann. Otol. 80: 736–743, 1971.
 358. Salomone, R. J., and E. van Lunteren. Effects of hypoxia and hypercapnia on geniohyoid contractility and endurance. J. Appl. Physiol. 71: 709–715, 1991.
 359. Saltin, B., and J. Karlsson. Muscle glycogen utilization during work of different intensities. In: Advances in Experimental Medicine and Biology. Muscle Metabolism During Exercise, edited by B. Pernow and B. Saltin. New York: Plenum Press, 1971, p. 289–299.
 360. Saltin, B., and L. Rowell. Functional adaptations to physical activity and inactivity. Federation Proc. 39: 1506–1513, 1980.
 361. Sauerland, E. K., and R. M. Harper. The human tongue during sleep: electromyographic activity of the genioglossus muscle. Exp. Neurol. 51: 160–170, 1976.
 362. Scardella, A. T., N. Krawciw, J. T. Petrozzino, M. A. Co, T. V. Santiago, and N. H. Edelman. Strength and endurance characteristics of the normal human genioglossus. Am. Rev. Respir. Dis. 148: 179–184, 1993.
 363. Schoene, R. B., S. Lahiri, P. H. Hackett, R. M. Peters, Jr., J. S. Milledge, C. J. Pizzo, F. H. Sarnquist, S. J. Boyer, D. J. Graber, K. H. Maret, and J. B. West. Relationship of hypoxic ventilatory response to exercise performance on Mount Everest. J. Appl. Physiol. 56: 1478–1483, 1984.
 364. Schwartzstein, R. M., H. L. Manning, J. W. Weiss, and S. E. Weinberger. Dyspnea: a sensory experience. Lung 168: 185–199, 1990.
 365. Sciurba, F. C., G. R. Owens, M. H. Sanders, P. G. Bartley, R. L. Hadesty, I. L. Paradis, and J. P. Costantino. Evidence of an altered pattern of breathing during exercise in recipients of heart‐lung transplants. N. Engl. J. Med. 319: 1186–1192, 1988.
 366. Secher, N. H., J. P. Clausen, K. Klausen, I. Noer, and J. Trap‐Jensen. Central and regional circulatory effects of adding arm exercise to leg exercise. Acta Physiol. Scand. 100: 288–297, 1977.
 367. Sekizawa, S., and H. Tsubone. Nasal receptors responding to noxious chemical irritants. Respir. Physiol. 96: 37–48, 1994.
 368. Sharratt, M. T., K. G. Henke, E. A. Aaron, D. F. Pegelow, and J. A. Dempsey. Exercise‐induced changes in functional residual capacity. Respir. Physiol. 70: 313–326, 1987.
 369. Shea, S. A., L. P. Andres, D. C. Shannon, and R. B. Banzett. Ventilatory response to exercise in humans lacking ventilatory chemosensitivity. J. Physiol. (Land.) 468: 623–640, 1993.
 370. Shea, S. A., R. B. Banzett, and R. W. Lansing. Respiratory sensations and their role in the control of breathing. In: Regulation of Breathing, edited by J. A. Dempsey and A. I. Pack. New York: Marcel Dekker, Inc., 1994, p. 923–957.
 371. Shephard, R. J. The oxygen cost of breathing during vigorous exercise. Q. J. Exp. Physiol. 51: 336–350, 1966.
 372. Shephard, R. J. The maximum sustained voluntary ventilation in exercise. Clin. Sci. 32: 167–176, 1967.
 373. Shephard, R. J. Effects of training upon respiratory function. Med. Sport 33: 9–17, 1980.
 374. Shindoh, C., A. DiMarco, A. Thomas, P. Manubay, and G. Supinski. Effect of N‐acetylcysteine on diaphragm fatigue. J. Appl. Physiol. 68: 2107–2113, 1990.
 375. Sieck, G. C. Diaphragm muscle: structural and functional organization. Clin. Chest Med. 9: 195–210, 1988.
 376. Sieck, G. C., and M. Fournier. Changes in diaphragm motor unit EMG during fatigue. J. Appl. Physiol. 68: 1917–1926, 1990.
 377. Sieck, G. C., and M. Fournier. Diaphragm motor unit recruitment during ventilatory and nonventilatory behaviors. J. Appl. Physiol. 66: 2539–2545, 1989.
 378. Sieck, G. C., M. Lewis, and C. Blanco. Effects of undernutrition on diaphragm fiber size, SDH activity and fatigue resistance. J. Appl. Physiol. 66: 2196–2205, 1989.
 379. Smith, C. A., D. M. Ainsworth, K. S. Henderson, and J. A. Dempsey. Differential responses of expiratory muscle to chemical stimuli in awake dogs. J. Appl. Physiol. 66: 384–391, 1989.
 380. Smith, C. A., D. M. Ainsworth, K. S. Henderson, and J. A. Dempsey. Differential timing of respiratory muscles in response to chemical stimuli in awake dogs. J. Appl. Physiol. 66: 392–399, 1989.
 381. Stark, R. D., S. A. Gambles, and J. A. Lewis. Methods to assess breathlessness in healthy subjects: a critical evaluation and application to analyze the acute effects of diazepam and promethazine on breathlessness induced by exercise or by exposure to raised levels of carbon dioxide. Clin. Sci. 61: 429–439, 1981.
 382. Stauber, W. T. Eccentric action of muscles: physiology, injury, and adaptation. In: Exercise and Sport Sciences Reviews, edited by K. B. Pandolf. Baltimore, MD: Williams & Wilkins, 1989, p. 157–185.
 383. Steinacker, J. M., M. Both, and B. J. Whipp. Pulmonary mechanics and entrainment of respiration and stroke rate during rowing. Int. J. Sports Med. 14: S15–S19, 1993.
 384. Stevens, S. S. Sensation and measurement. In: Psychophysics. Introduction to its Perceptual, Neural and Social Prospects, edited by G. Stevens. New York: John Wiley & Sons, 1975, p. 37–62.
 385. Strohl, K. P. Respiratory activation of the facial nerve and alar muscles in anaesthetized dogs. J. Physiol. (Lond.) 363: 351–362, 1985.
 386. Strohl, K. P., J. Hensley, M. Hallett, N. A. Saunders, and R. H. Ingram. Activation of upper airway muscles before onset of inspiration in normal humans. J. Appl. Physiol. 49: 638–642, 1980.
 387. Strohl, K. P., C. F. O'Cain, and A. S. Slutsky. Alae nasi activation and nasal resistance in healthy subjects. J. Appl. Physiol. 52: 1432–1437, 1982.
 388. Stubbing, D. G., K. J. Killian, and E. J. M. Campbell. The quantification of respiratory sensations by normal subjects. Respir. Physiol. 44: 251–260, 1981.
 389. Stubbing, D. G., L. D. Pengelly, J. Morse, and N. L. Jones. Pulmonary mechanics during exercise in normal males. J. Appl. Physiol. 49: 506–510, 1980.
 390. Stulbarg, M. S., and L. Adams. Manifestations of respiratory disease: dyspnea. In: Textbook of Respiratory Medicine, Vol. 1, Part 2, edited by J. F. Murray and J. A. Nadel. Philadelphia: W. B. Saunders Company, 1994, p. 511–528.
 391. Sugiura, T., A. Morimoto, and N. Murakami. Effects of endurance training on myosin heavy‐chain isoforms and enzyme activity in the rat diaphragm. Pflugers Arch. 421: 77–81, 1992.
 392. Sugiura, T., A. Morimoto, Y. Sakata, T. Watanabe, and N. Murakami. Myosin heavy chain isoform changes in rat diaphragm are induced by endurance training. Jpn. J. Physiol. 40: 759–763, 1990.
 393. Sugiura, T., S. Morita, A. Morimoto, and N. Murakami. Regional differences in myosin heavy chain isoforms and enzyme activities of the rat diaphragm. J. Appl. Physiol. 73: 506–509, 1992.
 394. Suratt, P. M., R. McTier, and S. C. Wilhoit. Alae nasi electromyographic activity and timing in obstructive sleep apnea. J. Appl. Physiol. 58: 1252–1256, 1985.
 395. Swinburn, C. R., J. M. Wakefield, and P. W. Jones. Relationship between ventilation and breathlessness during exercise in chronic obstructive airways disease is not altered by prevention of hypoxemia. Clin. Sci. 67: 515–519, 1984.
 396. Syabbalo, N. C., A. Bundgaard, and J. G. Widdicombe. Effects of exercise on nasal airflow resistance in healthy subjects and in patients with asthma and rhinitis. Bull. Eur. Pbysiopathol. Respir. 21: 507–513, 1985.
 397. Syabbalo, N. C., B. Krishnan, T. Zintel, and C. G. Gallagher. Differential ventilatory control during constant work rate and incremental exercise. Respir. Physiol. 97: 175–187, 1994.
 398. Syabbalo, N., T. Zintel, R. Watts, and C. G. Gallagher. Carotid chemoreceptors and respiratory adaptations to dead space loading during incremental exercise. J. Appl. Physiol. 75: 1378–1384, 1993.
 399. Szal, S. E., and R. B. Schoene. Ventilatory response to rowing and cycling in elite oarswomen. J. Appl. Physiol. 67: 264–269, 1989.
 400. Tamaki, N. Effect of endurance training on muscle fiber composition and capillary supply in rat diaphragm. Eur. J. Appl. Physiol. 56: 127–131, 1987.
 401. Taylor, C. R., R. H. Karns, E. W. Weibe, and H. Hoppeler. Adaptive variation in the mammalian respiratory system in relation to energetic demand. Respir. Physiol. 69: 1–28, 1987.
 402. Tenney, S. M., and J. C. Leiter. The control of breathing: an uninhibited survey from the perspective of comparative physiology. In: Regulation of Breathing, edited by J. A. Dempsey and A. I. Pack. New York: Marcel Dekker, Inc., 1994, p. 3–39.
 403. Tenney, S. M., and R. E. Reese. The ability to sustain great breathing efforts. Respir. Physiol. 5: 187–201, 1968.
 404. Thoden, J. S., J. A. Dempsey, W. G. Reddan, M. L. Birnbaum, H. V. Forster, R. F. Grover, and J. Rankin. Ventilatory work during steady‐state response to exercise. Federation Proc. 28: 1316–1321, 1969.
 405. Tsubone, H. Nasal flow receptors of the rat. Respir. Physiol. 75: 51–64, 1989.
 406. Tsubone, H. Nasal “pressure” receptors. Jpn. J. Vet. Sci. 52: 225–232, 1990.
 407. Uribe, J., C. Stump, C. Tipton, and R. Fregosi. Influence of exercise training on the oxidative capacity of rat abdominal muscles. Respir. Physiol. 88: 171–180, 1992.
 408. Van de Graaff, W. B. Thoracic influence on upper airway patency. J. Appl. Physiol. 65: 2124–2131, 1988.
 409. Van Lunteren, E., and P. Manubay. Contractile properties of feline genioglossus, sternohyoid and sternothyroid muscles. J. Appl. Physiol. 72: 1010–1015, 1992.
 410. Van Lunteren, E., and R. J. Martin. Pharyngeal dilator muscle contractile and endurance properties in neonatal piglets. Respir. Physiol. 92: 65–75, 1993.
 411. Van Lunteren, E., R. J. Salomone, P. Munaby, G. S. Supinski, and T. E. Dick. Contractile and endurance properties of geniohyoid and diaphragm muscles. J. Appl. Physiol. 69: 1992–1997, 1992.
 412. Van Lunteren, E., and K. P. Strohl. The muscles of the upper airway. In: Clinics of Chest Medicine, edited by J. Widdicombe. Philadelphia: W. B. Saunders Company, 1986, p. 171–188.
 413. Van Lunteren, E., W. B. Van de Graaff, D. M. Parker, J. Mitra, M. A. Haxhiu, K. P. Strohl, and N. S. Cherniack. Nasal and laryngeal reflex responses to negative upper airway pressure. J. Appl. Physiol. 56: 746–752, 1984.
 414. Ward, M. E., S. A. Magder, and S. N. Hussain. Oxygen delivery‐independent effect of blood flow on diaphragm fatigue. Am. Rev. Respir. Dis. 145: 1058–1063, 1992.
 415. Ward, S. A., and B. J. Whipp. Effects of peripheral and central chemoreceptor activation on the isopneic rating of breathing in exercise in humans. J. Physiol. (Lond.) 411: 27–43, 1989.
 416. Ward, S. A., B. J. Whipp, and C. S. Poon. Density‐dependent airflow and ventilatory control during exercise. Respir. Physiol. 49: 267–277, 1982.
 417. Ware, J. H., D. W. Dockery, T. A. Louis, X. Xu, B. K. Ferris, and F. E. Speizer. Longitudinal cross‐sectional estimates of pulmonary function decline in never‐stroking adults. Am. J. Epidemiol. 132: 685–700, 1990.
 418. Warren, G. L., K. J. Cureton, and P. B. Sparling. Does lung function limit performance in a 24‐hour ultramarathon? Respir. Physiol. 78: 253–264, 1989.
 419. Warren, J. B., S. J. Jennings, and T. J. H. Clark. Effect of adrenergic and vagal blockade on the normal human airway response to exercise. Clin. Sci. 66: 79–85, 1984.
 420. Warwick, R., and P. L. Williams. Gray's Anatomy. Philadelphia: W. B. Saunders Company, 1973, p. 1245–1248.
 421. Wasserman, K., B. J. Whipp, and R. Casaburi. Respiratory control during exercise. In: Handbook of Physiology, The Respiratory System, Mechanics of Breathing, edited by P. T. Macklem and J. Mead. Bethesda, MD: Am. Physiol. Soc., 1986, p. 595–620.
 422. Watson, T. W. J., and W. A. Whitelaw. Voluntary hyperventilation changes recruitment order of parasternal intercostal motor units. J. Appl. Physiol. 62: 187–193, 1987.
 423. Webber, C. L., and K. Pleschka. Structural and functional characteristics of individual phrenic motoneurons. Pflugers Arch. 364: 113–121, 1976.
 424. Weibel, E. R., L. B. Marques, M. Constantinopol, F. Doffey, P. Gehr, and C. R. Taylor. The pulmonary gas exchanger. Respir. Physiol. 69: 81–100, 1987.
 425. West, D. W., C. G. Ellis, and E. J. M. Campbell. Ability of man to detect increases in his breathing. J. Appl. Physiol. 39: 372–376, 1975.
 426. Wheatley, J. R., T. C. Amis, and L. A. Engel. Influence of airflow temperature and pressure on alae nasi electrical activity. J. Appl. Physiol. 71: 2283–2291, 1991.
 427. Wheatley, J. R., T. C. Amis, and L. A. Engel. Nasal and oral airway pressure–flow relationships. J. Appl. Physiol. 71: 2317–2324, 1991.
 428. Wheatley, J. R., T. C. Amis, and L. A. Engel. Oronasal partitioning of ventilation during exercise. J. Appl. Physiol. 71: 546–551, 1991.
 429. Wheatley, J. R., T. C. Amis, and L. A. Engel. Relationship between alae nasi activation and breathing route during exercise in humans. J. Appl. Physiol. 71: 118–124, 1991.
 430. Wheatley, J. R., A. Brancatisano, and L. A. Engel. Cricothyroid muscle responses to increased chemical drive in awake normal humans. J. Appl. Physiol. 70: 2233–2241, 1991.
 431. Wheatley, J. R., D. J. Tangel, W. S. Mezzanotte, and D. P. White. Influence of sleep on response to negative airway pressure of tensor palatini muscle and retropalatal airway. J. Appl. Physiol. 75: 2117–2124, 1993.
 432. Whipp, B. J., and R. L. Pardy. Breathing during exercise. In: Handbook of Physiology, The Respiratory System, Mechanics of Breathing, edited by P. T. Macklem and J. Mead. Bethesda, MD: Am. Physiol. Soc., 1986, p. 605–630.
 433. Widdicombe, J. G. Respiratory reflexes in man and other mammalian species. Clin. Sci. 21: 163–170, 1961.
 434. Wilhoit, S. C., and P. M. Suratt. Effect of nasal obstruction on upper airway muscle activation in normal subjects. Chest 92: 1053–1055, 1987.
 435. Wilson, D. G., and H. G. Welch. Effects of varying concentrations of N2/O2 and He/O2 on exercise tolerance in man. Med. Sci. Sports Exerc. 12: 380–384, 1980.
 436. Wilson, R. C., and P. W. Jones. A comparison of the visual analogue scale and modified Borg scale for the measurement of dyspnoea during exercise. Clin. Sci. 76: 277–282, 1989.
 437. Winning, A. J., R. D. Hamilton, and A. Guz. Ventilation and breathlessness on maximal exercise in patients with interstitial lung disease after local anaesthetic aerosol inhalation. Clin. Sci. 74: 275–281, 1988.
 438. Winning, A. J., R. D. Hamilton, S. A. Shea, C. Knott, and A. Guz. The effect of airway anaesthesia on the control of breathing and the sensation of breathlessness in man. Clin. Sci. 68: 215–225, 1985.
 439. Wolkove, N., M. D. Altose, S. G. Kelsen, P. G. Kondapalli, and N. S. Cherniack. Perception of changes in breathing in normal human subjects. J. Appl. Physiol. 50: 78–83, 1981.
 440. Yamashiro, S. M., and F. S. Grodins. Respiratory cycle optimization in exercise. J. Appl. Physiol. 62: 337–345, 1973.
 441. Yan, S., I. Lichros, S. Zakynthinos, and P. T. Macklem. Effect of diaphragmatic fatigue on control of respiratory muscles and ventilation during CO2 rebreathing. J. Appl. Physiol. 75 (3): 1364–1370, 1993.
 442. Yonge, R. P., and E. S. Petersen. Entrainment of breathing in rhythmic exercise. In: Modelling and Control of Breathing, edited by B. J. Whipp and D. M. Wilberg. New York: Elsevier Biomedical, 1983, p. 197–204.
 443. Younes, M. Determinants of thoracic excursions. In: Exercise—Pulmonary Physiology and Pathophysiology, edited by B. J. Whipp and K. Wasserman. New York: Marcel Dekker, Inc., 1991, p. 1–66.
 444. Younes, M., D. Bilan, D. Jung, and H. Kroker. An apparatus for altering the mechanical load of the respiratory system. J. Appl. Physiol. 62: 2491–2499, 1987.
 445. Younes, M., and J. Burks. Breathing pattern during and after exercise of different intensities. J. Appl. Physiol. 59: 898–908, 1985.
 446. Younes, M., and G. Kivinen. Respiratory mechanics and breathing pattern during and following maximal exercise. J. Appl. Physiol. 57: 1773–1782, 1984.
 447. Young, I. S., R. M. Alexander, A. J. Woakes, P. J. Butler, and L. Anderson. The synchronization of ventilation and locomotion in horses (Equus caballus). J. Exp. Biol. 166: 19–31, 1992.
 448. Zechman, F. W., and R. L. Wiley. Afferent inputs to breathing: Respiratory sensation. In: Handbook of Physiology, The Respiratory System, Control of Breathing, edited by N. S. Cherniack and J. G. Widdicombe. Bethesda, MD: Am. Physiol. Soc., 1986, p. 449–474.

Contact Editor

Submit a note to the editor about this article by filling in the form below.

* Required Field

Article Title: Airway, Lung, and Respiratory Muscle Function During Exercise
 

How to Cite

Jerome A. Dempsey, Lewis Adams, Dorothy M. Ainsworth, Ralph F. Fregosi, Charles G. Gallagher, Abe Guz, Bruce D. Johnson, Scott K. Powers. Airway, Lung, and Respiratory Muscle Function During Exercise. Compr Physiol 2011, Supplement 29: Handbook of Physiology, Exercise: Regulation and Integration of Multiple Systems: 448-514. First published in print 1996. doi: 10.1002/cphy.cp120111