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The Capital Region of Denmark - a part of Copenhagen University Hospital
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Repeated high-intensity exercise modulates Ca(2+) sensitivity of human skeletal muscle fibers

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  • K D Gejl
  • L G Hvid
  • S J Willis
  • E Andersson
  • H-C Holmberg
  • R Jensen
  • U Frandsen
  • J Hansen
  • P Plomgaard
  • N Ørtenblad
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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.

Original languageEnglish
JournalScandinavian Journal of Medicine and Science in Sports
Volume26
Pages (from-to)488-97
ISSN0905-7188
DOIs
StatePublished - 2016

ID: 45864123