Volume 55, Issue 1 pp. 35-45
Clinical Research

New insights into the potentiation of the first and second phases of the M-wave after voluntary contractions in the quadriceps muscle

Javier Rodriguez-Falces PhD

Corresponding Author

Javier Rodriguez-Falces PhD

Department of Electrical and Electronical Engineering, Universidad Pública de Navarra D.I.E.E., Campus de Arrosadía s/n, 31006 Pamplona, Spain

Correspondence to: J. Rodriguez-Falces; e-mail: [email protected]Search for more papers by this author
Nicolas Place PhD

Nicolas Place PhD

Institute of Sport Sciences and Department of Physiology, University of Lausanne, Lausanne, Switzerland

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First published: 12 May 2016
Citations: 17

ABSTRACT

Introduction: We investigated the mechanisms underlying the potentiation of the first and second phases of the compound action potential (M-wave) after conditioning contractions. Methods: M-waves were evoked in the knee extensors before and after isometric maximal voluntary contractions (MVCs) of 1 s, 3 s, 6 s, 10 s, 30 s, and 60 s. The amplitude, duration, and area of the M-wave first and second phases were measured during the 10-min period after each contraction. Results: The magnitude of the M-wave first phase was enlarged only after MVCs of 30 s and 60 s, whereas the second phase increased after all MVCs, regardless of their duration. The enlargement of the first phase remained for longer than 2 min, whereas the potentiation of the second phase lasted only 20 s. Conclusions: Potentiation of the first phase is the result of fatigue-induced membrane changes, whereas enlargement of the second phase is probably related to shortening of muscle fascicles. Muscle Nerve 55: 35–45, 2017

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