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The influence of muscle length on the development of fatigue in toad sartorius
Author(s) -
Aljure Emilio F.,
Borrero Luis M.
Publication year - 1968
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.1968.sp008651
Subject(s) - isometric exercise , myofilament , toad , sarcomere , mathematics , muscle fatigue , contraction (grammar) , crossbridge , anatomy , isotonic , muscle contraction , tension (geology) , chemistry , physics , electromyography , medicine , thermodynamics , physical medicine and rehabilitation , compression (physics) , myocyte
1. Fatigue curves were obtained on muscles contracting at length ( L ) different from the optimal ( L o ), and performing isometric tetani of fixed duration at regular intervals. Every sixth tetanus occurred at L o , the remainder took place at L . The parameters of the fatigue curve were compared with those of controls contracting always at L o . Fatigability was measured as the coefficient of exponential decrease of tension with time. 2. Fatigability varied linearly with length in shortened and lengthened muscles, but the slopes of the relations were significantly different for the two groups. 3. The tension values from single experimental muscles fell on two independent curves, one for those obtained at L o , another for data at L . The same muscle showed, therefore, two different fatigue processes which followed independent temporal evolutions. 4. Points 2 and 3 of this Summary imply that fatigue is a process dependent on the actual setting of the myofilaments during contraction and not distributed uniformly within the sarcomere. 5. It is proposed that fatigue results from local changes taking place at discrete reactive points in the myofilament. The experimental results are discussed in terms of this hypothesis and of the sliding model of contraction.