title: Contractile fatigue, muscle morphometry, and blood lactate in chronic obstructive pulmonary disease.
abstract: We hypothesized that patients with chronic obstructive pulmonary disease developing contractile fatigue of the quadriceps during cycle exercise may have characteristic metabolic and muscle features that could increase their susceptibility to fatigue, thus differentiating them from those who do not develop fatigue. We examined, in 32 patients, the fiber-type proportion, enzymatic activities, and capillary density in the vastus lateralis and the arterial blood lactate level during constant work-rate cycling exercise. Contractile fatigue was defined as a postexercise fall in quadriceps twitch force greater than 15% of resting values. Twenty-two patients developed contractile fatigue after exercise. No significant differences were found between fatiguers and non-fatiguers for the endurance time, fiber-type proportion, and oxidative enzyme activities. The lactate dehydrogenase activity was significantly higher (p < 0.05) and muscle capillarization significantly reduced in fatiguers (p < 0.05). Compared with non-fatiguers, the arterial lactate level during exercise was significantly higher in fatiguers (p < 0.001). A significant relationship was found between the fall in quadriceps twitch force and lactate dehydrogenase activity, capillary/fiber ratio, and blood lactate level. We conclude that changes in muscle enzymatic profile and capillarization with a greater reliance on glycolytic metabolism during exercise are associated with contractile fatigue in patients with chronic obstructive pulmonary disease.
authors.affiliation: Centre de Recherche, Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, Québec, Canada.
authors.forename: Didier
authors.initials: D
authors.lastname: Saey
authors.forename: Annie
authors.initials: A
authors.lastname: Michaud
authors.forename: Annabelle
authors.initials: A
authors.lastname: Couillard
authors.forename: Claude H
authors.initials: CH
authors.lastname: Côté
authors.forename: M Jeffery
authors.initials: MJ
authors.lastname: Mador
authors.forename: Pierre
authors.initials: P
authors.lastname: LeBlanc
authors.forename: Jean
authors.initials: J
authors.lastname: Jobin
authors.forename: François
authors.initials: F
authors.lastname: Maltais
mesh_terms: D000368:Aged; D002196:Capillaries / Q000473:pathology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D015444:Exercise; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000473:pathology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D011859:Radiography; D012146:Rest; D013848:Thigh
chemical_list: D019344:Lactic Acid; D007770:L-Lactate Dehydrogenase; D002950:Citrate (si)-Synthase