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Striated muscle fatigue is caused by e‐c coupling and metabolic alterations
Author(s) -
Santos Bianca Maria Alves,
Chang Ruchan,
Garcia Karla Paola,
GonzalezSerratos Hugo
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.961.11
Subject(s) - stimulation , coupling (piping) , chemistry , muscle fatigue , medicine , biophysics , materials science , physical medicine and rehabilitation , biology , electromyography , metallurgy
The mechanism of fatigue is not well understood. There are two propositions: a failure of e‐c(e‐c) as the tubular action potential (TAP); and an increase of ATP by products. We propose that both mechanisms may take place during fatigue development. First e‐c like the TAP and then metabolic alterations. Metabolic alterations may take place later after prolonged repetitive stimulation. To distinguish between these possibilities we used two paradigms, in one we stimulated the muscles at high frequencies continuously, in the other we stimulated them repetitively at high frequency with rest periods for the TAP to recover. When muscles were stimulated continuously with 60 Hz stimulations with out resting periods, the force dropped by 75% within a few seconds. The tension drop time course followed a liner function varying from10 sec at 60 Hz to 45 sec at 20 Hz of stimulation. With 60 Hz the recovery time was within 2 sec and was dependent on the frequency of stimulation. When muscles were stimulated repetitively with resting periods between stimulations (60 Hz 2 sec stimulations every 3 sec, 1 sec resting period) the force dropped by 75% in approximately 480 sec. The recovery time was then around 50 sec. We concluded that the two types of fatigue (metabolic and e‐c coupling) take place. The earlier drop in tensions may be due to failures of TAPs and the later be due to metabolic alterations.