Respiratory Muscle Work Compromises Leg Blood Flow During Maximal Exercise

“This study hypothesized that during exercise at maximal O2 consumption (VO2max), high demand for respiratory muscle blood flow would elicit locomotor muscle vasoconstriction and compromise limb blood flow.”


“Work of breathing normally incurred during maximal exercise causes vasoconstriction in locomotor muscles and compromises locomotor muscle perfusion and VO2.”

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Exercise-Induced Diaphragmatic Fatigue In Healthy Humans

“In part of this study, twelve healthy subjects (33 +/- 3 years) with a variety of fitness levels exercised at 95 and 85% VO2, max to exhaustion.


“Significant diaphragmatic fatigue is caused by the ventilatory requirements imposed by heavy endurance exercise in healthy persons with a variety of fitness levels. The magnitude of the fatigue and the likelihood of its occurrence increases as the relative intensity of the exercise exceeds 85% of VO2, max.”

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Aerobic Fitness Effects On Exercise-Induced Low-Frequency Diaphragm Fatigue

“Bilateral phrenic nerve stimulation was used to compare the amount of exercise-induced diaphragm fatigue between two groups of healthy subjects, a high-fit group and a fit group.”


“The high-fit subjects showed diaphragm fatigue as a result of heavy endurance exercise but were also partially protected from excessive fatigue, despite high ventilatory requirements, because their hyperventilatory response to endurance exercise was reduced, their diaphragm was utilized less in providing the total ventilatory response, and possibly their diaphragm aerobic capacity was greater.”

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