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Muscle glycogen stores and fatigue
Author(s) -
Ørtenblad Niels,
Westerblad Håkan,
Nielsen Joachim
Publication year - 2013
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2013.251629
Subject(s) - glycogen , myofibril , skeletal muscle , muscle contraction , sarcomere , glycolysis , sarcoplasm , medicine , chemistry , contractility , endoplasmic reticulum , endocrinology , myocyte , biology , biochemistry , enzyme
Studies performed at the beginning of the last century revealed the importance of carbohydrate as a fuel during exercise, and the importance of muscle glycogen on performance has subsequently been confirmed in numerous studies. However, the link between glycogen depletion and impaired muscle function during fatigue is not well understood and a direct cause‐and‐effect relationship between glycogen and muscle function remains to be established. The use of electron microscopy has revealed that glycogen is not homogeneously distributed in skeletal muscle fibres, but rather localized in distinct pools. Furthermore, each glycogen granule has its own metabolic machinery with glycolytic enzymes and regulating proteins. One pool of such glycogenolytic complexes is localized within the myofibrils in close contact with key proteins involved in the excitation–contraction coupling and Ca 2+ release from the sarcoplasmic reticulum (SR). We and others have provided experimental evidence in favour of a direct role of decreased glycogen, localized within the myofibrils, for the reduction in SR Ca 2+ release during fatigue. This is consistent with compartmentalized energy turnover and distinctly localized glycogen pools being of key importance for SR Ca 2+ release and thereby affecting muscle contractility and fatigability.