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Effect of stretching on the elastic characteristics and the contractile component of frog striated muscle
Author(s) -
Cavagna Giovanni A.,
Citterio G.
Publication year - 1974
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.1974.sp010552
Subject(s) - isometric exercise , contraction (grammar) , isotonic , sartorius muscle , chemistry , muscle contraction , anatomy , biophysics , medicine , biology
1. The force—velocity relationship and the stress—strain curve of the so‐called series elastic component (s.e.c.) of frog sartorius, semitendinosus and gastrocnemius have been determined during shortening against a given force (isotonic quick‐release) and at high speed (controlled release): ( a ) from a state of isometric contraction and ( b ) after stretching of the contracted muscle. In both cases the muscle was released from the same length: this was usually slightly greater than the muscle's resting length. 2. The muscle released immediately after being stretched is able to shorten against a constant force, P , equal to or even greater than the isometric force, P 0 , at the same length. When the force P applied to the muscle is reduced below P 0 the velocity of shortening is greater after stretching, and the force—velocity curve is therefore shifted along the velocity axis: the shift is maximal when P is near to P 0 and it decreases rapidly with decreasing P . 3. The extent of shortening of the s.e.c. required to make the force fall from P 0 to zero is 50–100% greater when the muscle is released immediately after stretching than when it is released from a state of isometric contraction. This difference is found by using either the controlled release method or the isotonic quick‐release method. 4. If a time interval is left between the end of stretching and the onset of shortening of the contracted muscle (controlled release method), the length change of the s.e.c., for a given fall of the force, is reduced and approaches that taking place when the muscle is released from a state of isometric contraction. 5. Curare does not affect the results described above, indicating that these do not depend on modification of the neuromuscular transmission. 6. It is concluded that stretching a contracted muscle modifies temporarily: ( a ) its elastic characteristics, as shown by the greater amount of mechanical energy released for a given fall of the force at the muscle's extremities, and ( b ) its contractile machinery, as it is suggested by the change of the force—velocity relationship.