title: Diaphragmatic fatigue is counterbalanced during exhaustive long-term exercise.
abstract: Based on externally paced (repetitive) short-term trials exercise-induced diaphragmatic fatigue has been shown to manifest after rather than during exercise. The current study aimed at investigating diaphragmatic contractility and diaphragmatic fatigue during self-paced long-term exhaustive exercise at maximally tolerated loading by the use of supramaximal twitch transdiaphragmatic pressure (TwPdi). Seven trained subjects (VO(2max) 63.3+/-13.9 ml kg(-1) min(-1)) performed self-paced long-term exhaustive exercise at maximally tolerated loading (45 min+endspurt, initial workload 85% VO(2max)) followed by recovery (9 min). TwPdi (every 45 s) and ergospirometric data (continuously) were assessed throughout the protocol. Diaphragmatic contractility tended to initially increase during the exercise protocol with a slight decline and final increase during endspurt. Diaphragmatic fatigue manifested only after exercise termination (TwPdi rest 2.6+/-0.8 kPa; TwPdi exercise start/mid/end 2.9+/-0.7 kPa vs. 2.6+/-0.8 kPa vs. 2.4+/-0.6 kPa; TwPdi endspurt/recovery 2.7+/-0.8 kPa vs. 1.9+/-0.6 kPa). In conclusion, diaphragmatic contractility tends to decrease but manifestation of diaphragmatic fatigue is counterbalanced during self-paced long-term exhaustive exercise at maximally tolerated loading.
authors.affiliation: Department of Pneumology, University Hospital Freiburg, Freiburg, Germany. hans-joachim.kabitz@uniklinik-freiburg.de
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Kabitz
authors.forename: David
authors.initials: D
authors.lastname: Walker
authors.forename: Anja
authors.initials: A
authors.lastname: Schwoerer
authors.forename: Stephan
authors.initials: S
authors.lastname: Walterspacher
authors.forename: Florian
authors.initials: F
authors.lastname: Sonntag
authors.forename: Daniel
authors.initials: D
authors.lastname: Schlager
authors.forename: Kai
authors.initials: K
authors.lastname: Roecker
authors.forename: Wolfram
authors.initials: W
authors.lastname: Windisch
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology; D003964:Diaphragm / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006321:Heart / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008168:Lung / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D010807:Physical Endurance / Q000502:physiology; D012129:Respiratory Function Tests; D013147:Spirometry; D055815:Young Adult