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Sarcoplasmic reticulum function and muscle contractile character following fatiguing exercise in humans
Author(s) -
Hill Christopher A.,
Thompson Martin W.,
Ruell Patricia A.,
Thom Jeanette M.,
White Michael J.
Publication year - 2001
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 - 10.1111/j.1469-7793.2001.0871h.x
Subject(s) - isometric exercise , calcium , endoplasmic reticulum , medicine , endocrinology , chemistry , muscle contraction , stimulation , skeletal muscle , muscle fatigue , electromyography , biochemistry , physical medicine and rehabilitation
1 This study examined the alterations in calcium release, calcium uptake and calcium ATPase activity of skeletal muscle sarcoplasmic reticulum in response to a bout of intense dynamic knee extensor exercise, and the relationship between these changes and alterations in muscle contractile characteristics in the human quadriceps. 2 In biopsy samples taken from the vastus lateralis, sarcoplasmic reticulum calcium release and calcium uptake were significantly depressed ( P < 0.01 and 0.05, respectively) immediately following the exercise with no alteration in the sarcoplasmic reticulum Ca 2+ ‐ATPase activity. 3 A 33 % reduction in the maximum voluntary isometric torque was found following the exercise, with reduced torques from electrically evoked isometric contractions at low frequencies of stimulation (10 and 20 Hz) but not at higher frequencies (50 and 100 Hz). 4 The depressed calcium release was correlated ( P < 0.05) with a decreased ratio of torques generated at 20:50 Hz, indicating an involvement in low frequency fatigue; however, no correlations between the muscle relaxation times or rates of change of torque and calcium uptake were observed.