Exercise-Induced bronchoconstriction (EIB) is related to increased ventilation (VE) during exercise and describes the transient airway narrowing following exercise. A reliable diagnosis is essential for optimal treatm...Exercise-Induced bronchoconstriction (EIB) is related to increased ventilation (VE) during exercise and describes the transient airway narrowing following exercise. A reliable diagnosis is essential for optimal treatment. The impact of a repeated exercise challenge test (ECT) in a clinical setting is not well established and conducting a repeated ECT with the possibility to adjust the exercise intensity on an individual basis may give more information. The aim of the study was to evaluate the test-retest reliability of an ECT for EIB and its association with exercise intensity. Methods: After examination by a pulmonologist, 20 referred subjects with symptoms strong indications of Exercise-Induced bronchoconstriction performed two consecutive exercise challenge tests on a treadmill. The exercise intensity of the repeated test was adjusted. Forced expiratory volume in 1 second (FEV1) was measured before and 1, 3, 6, 10, and 15 minutes after exercise. EIB was defined as a reduction of ≥ 10% in FEV1. Ventilation and heart rate were measured during exercise. Results: Five subjects tested positive in both tests, and ten subjects tested negative in both tests. Three subjects tested positive in the first test only, while two subjects tested positive in the second test only. The exercise intensity was not significantly different between the two tests for any of the subjects. Conclusion: There were 25% divergences in the diagnostic results of two consecutive exercise challenge tests. The difference in the test results was not explained by a difference in the exercise intensity.展开更多
The peculiar attributes of muscles that are stretched when active have been noted for nearly a century.Understandably,the focus of muscle physiology has been primarily on shortening and isometric contractions,as eloqu...The peculiar attributes of muscles that are stretched when active have been noted for nearly a century.Understandably,the focus of muscle physiology has been primarily on shortening and isometric contractions,as eloquently revealed by A.V.Hill and subsequently by his students.When the sliding filament theory was introduced by A.F.Huxley and H.E.Huxley,it was a relatively simple task to link Hill's mechanical observations to the actions of the cross bridges during these shortening and isometric contractions.In contrast,lengthening or eccentric contractions have remained somewhat enigmatic.Dismissed as necessarily causing muscle damage,eccentric contractions have been much more difficult to fit into the cross-bridge theory.The relatively recent discovery of the giant elastic sarcomeric filament titin has thrust a previously missing element into any discussion of muscle function,in particular during active stretch.Indeed,the unexpected contribution of giant elastic proteins to muscle contractile function is highlighted by recent discoveries that twitchin-actin interactions are responsible for the"catch"property of invertebrate muscle.In this review,we examine several current theories that have been proposed to account for the properties of muscle during eccentric contraction.We ask how well each of these explains existing data and how an elastic filament can be incorporated into the sliding filament model.Finally,we review the increasing body of evidence for the benefits of including eccentric contractions into a program of muscle rehabilitation and strengthening.展开更多
文摘Exercise-Induced bronchoconstriction (EIB) is related to increased ventilation (VE) during exercise and describes the transient airway narrowing following exercise. A reliable diagnosis is essential for optimal treatment. The impact of a repeated exercise challenge test (ECT) in a clinical setting is not well established and conducting a repeated ECT with the possibility to adjust the exercise intensity on an individual basis may give more information. The aim of the study was to evaluate the test-retest reliability of an ECT for EIB and its association with exercise intensity. Methods: After examination by a pulmonologist, 20 referred subjects with symptoms strong indications of Exercise-Induced bronchoconstriction performed two consecutive exercise challenge tests on a treadmill. The exercise intensity of the repeated test was adjusted. Forced expiratory volume in 1 second (FEV1) was measured before and 1, 3, 6, 10, and 15 minutes after exercise. EIB was defined as a reduction of ≥ 10% in FEV1. Ventilation and heart rate were measured during exercise. Results: Five subjects tested positive in both tests, and ten subjects tested negative in both tests. Three subjects tested positive in the first test only, while two subjects tested positive in the second test only. The exercise intensity was not significantly different between the two tests for any of the subjects. Conclusion: There were 25% divergences in the diagnostic results of two consecutive exercise challenge tests. The difference in the test results was not explained by a difference in the exercise intensity.
基金supported by Kiisa Nishikawa: the National Science Foundation (IOS-0732949, IOS-1025806, and IOS1456868 IIP-1237878 and IIP-1521231)the W.M. Keck Foundation+5 种基金the Technology Research Initiative Fund of Northern Arizona UniversityPaul LaStayo:National Institutes of Health (ROIAG031255R21CA114523R21AG18701(with Stan Lindstedt))the Foundation for Physical Therapythe University of Utah Research Foundation
文摘The peculiar attributes of muscles that are stretched when active have been noted for nearly a century.Understandably,the focus of muscle physiology has been primarily on shortening and isometric contractions,as eloquently revealed by A.V.Hill and subsequently by his students.When the sliding filament theory was introduced by A.F.Huxley and H.E.Huxley,it was a relatively simple task to link Hill's mechanical observations to the actions of the cross bridges during these shortening and isometric contractions.In contrast,lengthening or eccentric contractions have remained somewhat enigmatic.Dismissed as necessarily causing muscle damage,eccentric contractions have been much more difficult to fit into the cross-bridge theory.The relatively recent discovery of the giant elastic sarcomeric filament titin has thrust a previously missing element into any discussion of muscle function,in particular during active stretch.Indeed,the unexpected contribution of giant elastic proteins to muscle contractile function is highlighted by recent discoveries that twitchin-actin interactions are responsible for the"catch"property of invertebrate muscle.In this review,we examine several current theories that have been proposed to account for the properties of muscle during eccentric contraction.We ask how well each of these explains existing data and how an elastic filament can be incorporated into the sliding filament model.Finally,we review the increasing body of evidence for the benefits of including eccentric contractions into a program of muscle rehabilitation and strengthening.
