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Activation of fast‐twitch fibers assessed with twitch potentiation
Author(s) -
Sasaki Kazushige,
Tomioka Yukie,
Ishii Naokata
Publication year - 2012
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.23290
Subject(s) - long term potentiation , contraction (grammar) , muscle contraction , stimulation , chemistry , tibial nerve , medicine , anatomy , receptor
: The augmentation of twitch response following brief muscle activation, called twitch potentiation, has been shown to be much more pronounced in fast‐twitch than in slow‐twitch fibers. We thus explored the possibility of twitch potentiation as a noninvasive measure of fast‐twitch fiber activation, by studying its dependence on the intensity of preceding contraction. Methods : Twitch contraction of plantar flexor muscles was evoked with supramaximal stimulation of the posterior tibial nerve, before and immediately after 6‐s voluntary contractions at intensities of 10–100% of maximal voluntary contraction (MVC). Results : Except for low‐intensity contractions (< 30%MVC), voluntary contraction induced twitch potentiation, the magnitude of which increased with increasing contraction intensity ( P < 0.001). The shortened contractile process was associated with the potentiation. Conclusions : These results are consistent with the concept of “hierarchical order of fiber activation”, suggesting that the magnitude of twitch potentiation reflects the activation of fast‐twitch fibers during a brief contraction. Muscle Nerve 46: 218–227, 2012