Effect of expiratory muscle fatigue on exercise tolerance and locomotor muscle fatigue in healthy humans

High-intensity exercise (≥90% of maximal O2 uptake) sustained to the limit of tolerance elicits expiratory muscle fatigue (EMF). We asked whether prior EMF affects subsequent exercise tolerance. Eight male subjects (means ± SD; maximal O2 uptake = 53.5 ± 5.2 ml·kg−1·min−1) cycled at 90% of peak power output to the limit of tolerance with (EMF-EX) and without (CON-EX) prior induction of EMF and for a time equal to that achieved in EMF-EX but without prior induction of EMF (ISO-EX). To induce EMF, subjects breathed against an expiratory flow resistor until task failure (15 breaths/min, 0.7 expiratory duty cycle, 40% of maximal expiratory gastric pressure). Fatigue of abdominal and quadriceps muscles was assessed by measuring the reduction relative to prior baseline values in magnetically evoked gastric twitch pressure (Pgatw) and quadriceps twitch force (Qtw), respectively. The reduction in Pgatw was not different after resistive breathing vs. after CON-EX (−27 ± 5 vs. −26 ± 6%; P = 0.127). Exercise time was reduced by 33 ± 10% in EMF-EX vs. CON-EX (6.85 ± 2.88 vs. 9.90 ± 2.94 min; P < 0.001). Exercise-induced abdominal and quadriceps muscle fatigue was greater after EMF-EX than after ISO-EX (−28 ± 9 vs. −12 ± 5% for Pgatw, P = 0.001; −28 ± 7 vs. −14 ± 6% for Qtw, P = 0.015). Perceptual ratings of dyspnea and leg discomfort (Borg CR10) were higher at 1 and 3 min and at end exercise during EMF-EX vs. during ISO-EX ( P < 0.05). Percent changes in limb fatigue and leg discomfort (EMF-EX vs. ISO-EX) correlated significantly with the change in exercise time. We propose that EMF impaired subsequent exercise tolerance primarily through an increased severity of limb locomotor muscle fatigue and a heightened perception of leg discomfort.

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Faculty Opinions recommendation of Effect of expiratory muscle fatigue on exercise tolerance and locomotor muscle fatigue in healthy humans.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1123188.580321 ◽

2008 ◽

Author(s):

Craig Harms

Keyword(s):

Muscle Fatigue ◽

Exercise Tolerance ◽

Expiratory Muscle ◽

Healthy Humans

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Expiratory muscle fatigue does not regulate operating lung volumes during high-intensity exercise in healthy humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.00066.2013 ◽

2013 ◽

Vol 114 (11) ◽

pp. 1569-1576 ◽

Cited By ~ 9

Author(s):

Bryan J. Taylor ◽

Stephen C. How ◽

Lee M. Romer

Keyword(s):

Muscle Fatigue ◽

High Intensity ◽

Expiratory Flow Limitation ◽

Lung Volumes ◽

Expiratory Muscle ◽

Healthy Humans ◽

Resistive Breathing ◽

Expiratory Muscles ◽

Expiratory Flow ◽

Pressure Changes

To determine whether expiratory muscle fatigue (EMF) is involved in regulating operating lung volumes during exercise, nine recreationally active subjects cycled at 90% of peak work rate to the limit of tolerance with prior induction of EMF (EMF-ex) and for a time equal to that achieved in EMF-ex without prior induction of EMF (ISO-ex). EMF was assessed by measuring changes in magnetically evoked gastric twitch pressure. Changes in end-expiratory and end-inspiratory lung volume (EELV and EILV) and the degree of expiratory flow limitation (EFL) were quantified using maximal expiratory flow-volume curves and inspiratory capacity maneuvers. Resistive breathing reduced gastric twitch pressure (−24 ± 14%, P = 0.004). During EMF-ex, EELV decreased from rest to the 3rd min of exercise [39 ± 8 vs. 27 ± 7% of forced vital capacity (FVC), P = 0.001] before increasing toward baseline (34 ± 8% of FVC end exercise, P = 0.073 vs. rest). EILV increased from rest to the 3rd min of exercise (54 ± 8 vs. 84 ± 9% of FVC, P = 0.006) and remained elevated to end exercise (88 ± 9% of FVC). Neither EELV ( P = 0.18) nor EILV ( P = 0.26) was different at any time point during EMF-ex vs. ISO-ex. Four subjects became expiratory flow limited during the final minute of EMF-ex and ISO-ex; the degree of EFL was not different between trials (37 ± 18 vs. 35 ± 16% of tidal volume, P = 0.38). At end exercise in both trials, EELV was greater in subjects without vs. subjects with EFL. These findings suggest that 1) contractile fatigue of the expiratory muscles in healthy humans does not regulate operating lung volumes during high-intensity sustained cycle exercise; and 2) factors other than “frank” EFL cause the terminal increase in EELV.

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Exercise-induced Expiratory Muscle Fatigue in Healthy Humans

Medicine & Science in Sports & Exercise ◽

10.1249/00005768-200605001-02488 ◽

2006 ◽

Vol 38 (Supplement) ◽

pp. S381-S382

Author(s):

Bryan J. Taylor ◽

Stephen C. How ◽

Lee M. Romer ◽

Alison McConnell

Keyword(s):

Muscle Fatigue ◽

Expiratory Muscle ◽

Healthy Humans ◽

Exercise Induced

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Effect of exercise-induced arterial hypoxemia on quadriceps muscle fatigue in healthy humans

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00332.2005 ◽

2006 ◽

Vol 290 (2) ◽

pp. R365-R375 ◽

Cited By ~ 83

Author(s):

Lee M. Romer ◽

Hans C. Haverkamp ◽

Andrew T. Lovering ◽

David F. Pegelow ◽

Jerome A. Dempsey

Keyword(s):

Muscle Fatigue ◽

Femoral Nerve ◽

Quadriceps Muscle ◽

Cycle Ergometer ◽

Arterial Hypoxemia ◽

Healthy Humans ◽

Peripheral Mechanism ◽

Evoked Force ◽

Exercise Induced ◽

Intensity Of Exercise

The effect of exercise-induced arterial hypoxemia (EIAH) on quadriceps muscle fatigue was assessed in 11 male endurance-trained subjects [peak O2 uptake (V̇o2 peak) = 56.4 ± 2.8 ml·kg−1·min−1; mean ± SE]. Subjects exercised on a cycle ergometer at ≥90% V̇o2 peak to exhaustion (13.2 ± 0.8 min), during which time arterial O2 saturation (SaO2) fell from 97.7 ± 0.1% at rest to 91.9 ± 0.9% (range 84–94%) at end exercise, primarily because of changes in blood pH (7.183 ± 0.017) and body temperature (38.9 ± 0.2°C). On a separate occasion, subjects repeated the exercise, for the same duration and at the same power output as before, but breathed gas mixtures [inspired O2 fraction (FiO2) = 0.25–0.31] that prevented EIAH (SaO2 = 97–99%). Quadriceps muscle fatigue was assessed via supramaximal paired magnetic stimuli of the femoral nerve (1–100 Hz). Immediately after exercise at FiO2 0.21, the mean force response across 1–100 Hz decreased 33 ± 5% compared with only 15 ± 5% when EIAH was prevented ( P < 0.05). In a subgroup of four less fit subjects, who showed minimal EIAH at FiO2 0.21 (SaO2 = 95.3 ± 0.7%), the decrease in evoked force was exacerbated by 35% ( P < 0.05) in response to further desaturation induced via FiO2 0.17 (SaO2 = 87.8 ± 0.5%) for the same duration and intensity of exercise. We conclude that the arterial O2 desaturation that occurs in fit subjects during high-intensity exercise in normoxia (−6 ± 1% ΔSaO2 from rest) contributes significantly toward quadriceps muscle fatigue via a peripheral mechanism.

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Exercise-induced quadriceps muscle fatigue in men and women: effects of arterial oxygen content and respiratory muscle work

The Journal of Physiology ◽

10.1113/jp274068 ◽

2017 ◽

Vol 595 (15) ◽

pp. 5227-5244 ◽

Cited By ~ 19

Author(s):

Paolo B. Dominelli ◽

Yannick Molgat-Seon ◽

Donald E. G. Griesdale ◽

Carli M. Peters ◽

Jean-Sébastien Blouin ◽

...

Keyword(s):

Muscle Fatigue ◽

Oxygen Content ◽

Respiratory Muscle ◽

Quadriceps Muscle ◽

Arterial Oxygen ◽

Men And Women ◽

Arterial Oxygen Content ◽

Muscle Work ◽

Exercise Induced

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Pulmonary Function Subsequent to Expiratory Muscle Fatigue in Healthy Humans

International Journal of Sports Medicine ◽

10.1055/s-2001-17612 ◽

2001 ◽

Vol 22 (7) ◽

pp. 498-503 ◽

Cited By ~ 9

Author(s):

H. C. Haverkamp ◽

M. Metelits ◽

J. Hartnett ◽

K. Olsson ◽

J. R. Coast

Keyword(s):

Pulmonary Function ◽

Muscle Fatigue ◽

Expiratory Muscle ◽

Healthy Humans

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Antianginal Effect of Isosorbide Dinitrate Spray in Patients with Exercise-Induced Stable Angina

Journal of International Medical Research ◽

10.1177/030006058601400603 ◽

1986 ◽

Vol 14 (6) ◽

pp. 303-305

Author(s):

Matti Äärynen ◽

Kari Soininen

Keyword(s):

Heart Disease ◽

Isosorbide Dinitrate ◽

Stable Angina ◽

Exercise Tolerance ◽

Active Drug ◽

Double Blind ◽

Exercise Time ◽

Antianginal Effect ◽

Exercise Induced ◽

Randomized Crossover Study

Ten patients with stable exercise-induced angina took part in this study. Isosorbide dinitrate and placebo sprays were administered in a double-blind, randomized crossover study. The dose of isosorbide dinitrate given was two squirts (=2–5 mg) 2 min before testing. When taken before exercise it significantly improved (p≤0.014) exercise tolerance. Significant (p≤0.0005) ischaemic changes in the electrocardiogram also occurred. These effects occurred later than with placebo. Exercise time was prolonged with the active drug. The results of this study show that isosorbide dinitrate spray improves the exercise tolerance of patients with ischaemic heart disease.

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Exercise-induced respiratory muscle fatigue: implications for performance

Journal of Applied Physiology ◽

10.1152/japplphysiol.01157.2007 ◽

2008 ◽

Vol 104 (3) ◽

pp. 879-888 ◽

Cited By ~ 134

Author(s):

Lee M. Romer ◽

Michael I. Polkey

Keyword(s):

Blood Flow ◽

Muscle Fatigue ◽

Respiratory System ◽

Exercise Tolerance ◽

Respiratory Muscle ◽

Respiratory Muscles ◽

Time To Exhaustion ◽

Respiratory Muscle Fatigue ◽

Objective Evidence ◽

Exercise Induced

It is commonly held that the respiratory system has ample capacity relative to the demand for maximal O2and CO2transport in healthy humans exercising near sea level. However, this situation may not apply during heavy-intensity, sustained exercise where exercise may encroach on the capacity of the respiratory system. Nerve stimulation techniques have provided objective evidence that the diaphragm and abdominal muscles are susceptible to fatigue with heavy, sustained exercise. The fatigue appears to be due to elevated levels of respiratory muscle work combined with an increased competition for blood flow with limb locomotor muscles. When respiratory muscles are prefatigued using voluntary respiratory maneuvers, time to exhaustion during subsequent exercise is decreased. Partially unloading the respiratory muscles during heavy exercise using low-density gas mixtures or mechanical ventilation can prevent exercise-induced diaphragm fatigue and increase exercise time to exhaustion. Collectively, these findings suggest that respiratory muscle fatigue may be involved in limiting exercise tolerance or that other factors, including alterations in the sensation of dyspnea or mechanical load, may be important. The major consequence of respiratory muscle fatigue is an increased sympathetic vasoconstrictor outflow to working skeletal muscle through a respiratory muscle metaboreflex, thereby reducing limb blood flow and increasing the severity of exercise-induced locomotor muscle fatigue. An increase in limb locomotor muscle fatigue may play a pivotal role in determining exercise tolerance through a direct effect on muscle force output and a feedback effect on effort perception, causing reduced motor output to the working limb muscles.

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Exercise-induced abdominal muscle fatigue in healthy humans

Journal of Applied Physiology ◽

10.1152/japplphysiol.01389.2005 ◽

2006 ◽

Vol 100 (5) ◽

pp. 1554-1562 ◽

Cited By ~ 46

Author(s):

Bryan J. Taylor ◽

Stephen C. How ◽

Lee M. Romer

Keyword(s):

Peak Oxygen Uptake ◽

Abdominal Muscle ◽

Rectus Abdominis ◽

Voluntary Activation ◽

Abdominal Muscles ◽

Electromyographic Activity ◽

Membrane Excitability ◽

Healthy Humans ◽

Gastric Pressure ◽

Exercise Induced

The abdominal muscles have been shown to fatigue in response to voluntary isocapnic hyperpnea using direct nerve stimulation techniques. We investigated whether the abdominal muscles fatigue in response to dynamic lower limb exercise using such techniques. Eleven male subjects [peak oxygen uptake (V̇o2 peak) = 50.0 ± 1.9 (SE) ml·kg−1·min−1] cycled at >90% V̇o2 peak to exhaustion (14.2 ± 4.2 min). Abdominal muscle function was assessed before and up to 30 min after exercise by measuring the changes in gastric pressure (Pga) after the nerve roots supplying the abdominal muscles were magnetically stimulated at 1–25 Hz. Immediately after exercise there was a decrease in Pga at all stimulation frequencies (mean −25 ± 4%; P < 0.001) that persisted up to 30 min postexercise (−12 ± 4%; P = 0.001). These reductions were unlikely due to changes in membrane excitability because amplitude, duration, and area of the rectus abdominis M wave were unaffected. Declines in the Pga response to maximal voluntary expiratory efforts occurred after exercise (158 ± 13 before vs. 145 ± 10 cmH2O after exercise; P = 0.005). Voluntary activation, assessed using twitch interpolation, did not change (67 ± 6 before vs. 64 ± 2% after exercise; P = 0.20), and electromyographic activity of the rectus abdominis and external oblique increased during these volitional maneuvers. These data provide new evidence that the abdominal muscles fatigue after sustained, high-intensity exercise and that the fatigue is primarily due to peripheral mechanisms.

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