title: Repeated high-intensity exercise modulates Ca(2+) sensitivity of human skeletal muscle fibers.
abstract: The effects of short-term high-intensity exercise on single fiber contractile function in humans are unknown. Therefore, the purposes of this study were: (a) to access the acute effects of repeated high-intensity exercise on human single muscle fiber contractile function; and (b) to examine whether contractile function was affected by alterations in the redox balance. Eleven elite cross-country skiers performed four maximal bouts of 1300 m treadmill skiing with 45 min recovery. Contractile function of chemically skinned single fibers from triceps brachii was examined before the first and following the fourth sprint with respect to Ca(2+) sensitivity and maximal Ca(2+) -activated force. To investigate the oxidative effects of exercise on single fiber contractile function, a subset of fibers was incubated with dithiothreitol (DTT) before analysis. Ca(2+) sensitivity was enhanced by exercise in both MHC I (17%, P < 0.05) and MHC II (15%, P < 0.05) fibers. This potentiation was not present after incubation of fibers with DTT. Specific force of both MHC I and MHC II fibers was unaffected by exercise. In conclusion, repeated high-intensity exercise increased Ca(2+) sensitivity in both MHC I and MHC II fibers. This effect was not observed in a reducing environment indicative of an exercise-induced oxidation of the human contractile apparatus.
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster, University of Southern Denmark, Odense, Denmark.
authors.forename: K D
authors.initials: KD
authors.lastname: Gejl
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster, University of Southern Denmark, Odense, Denmark.
authors.forename: L G
authors.initials: LG
authors.lastname: Hvid
authors.affiliation: Department of Health Sciences, Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, Sweden.
authors.forename: S J
authors.initials: SJ
authors.lastname: Willis
authors.affiliation: Department of Health Sciences, Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Andersson
authors.affiliation: Department of Health Sciences, Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, Sweden.|Swedish Olympic Committee, Stockholm, Sweden.
authors.forename: H-C
authors.initials: HC
authors.lastname: Holmberg
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster, University of Southern Denmark, Odense, Denmark.
authors.forename: R
authors.initials: R
authors.lastname: Jensen
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster, University of Southern Denmark, Odense, Denmark.
authors.forename: U
authors.initials: U
authors.lastname: Frandsen
authors.affiliation: Department of Infectious Diseases and CMRC, The Centre of Inflammation and Metabolism, Rigshospitalet, Copenhagen, Denmark.|Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Hansen
authors.affiliation: Department of Infectious Diseases and CMRC, The Centre of Inflammation and Metabolism, Rigshospitalet, Copenhagen, Denmark.|Department of Clinical Biochemistry, Rigshospitalet, Copenhagen, Denmark.
authors.forename: P
authors.initials: P
authors.lastname: Plomgaard
authors.affiliation: Department of Sports Science and Clinical Biomechanics, SDU Muscle Research Cluster, University of Southern Denmark, Odense, Denmark.|Department of Health Sciences, Swedish Winter Sports Research Centre, Mid Sweden University, Östersund, Sweden.
authors.forename: N
authors.initials: N
authors.lastname: Ørtenblad
mesh_terms: D000328:Adult; D000975:Antioxidants / Q000378:metabolism; D001132:Arm; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D004229:Dithiothreitol / Q000494:pharmacology; D015444:Exercise / Q000502:physiology*; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000502:physiology*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology*; D052097:Quadriceps Muscle / Q000166:cytology; D011897:Random Allocation; D012865:Skiing / Q000502:physiology*; D055815:Young Adult
chemical_list: D000975:Antioxidants; D005978:Glutathione; D002118:Calcium; D004229:Dithiothreitol; D019803:Glutathione Disulfide
keywords: Sprint skiing; fatigue; muscle fiber; specific force