• Javier Rodriguez-Falces, Nicola A Maffiuletti, and Nicolas Place.
• Department of Electrical and Electronic Engineering, Universidad Pública de Navarra DIEE, Campus de Arrosadía s/n, 31006, Pamplona, Spain.
• Muscle Nerve. 2013 Dec 1; 48 (6): 920-9.

IntroductionThe aim of this study was to investigate differences in twitch and M-wave potentiation in the quadriceps femoris when electrical stimulation is applied over the quadriceps muscle belly versus the femoral nerve trunk.MethodsM-waves and mechanical twitches were evoked using direct quadriceps muscle and femoral nerve stimulation between 48 successive isometric maximal voluntary contractions (MVC) from 10 young, healthy subjects. Potentiation was investigated by analyzing the changes in M-wave amplitude recorded from the vastus medialis (VM) and vastus lateralis (VL) muscles and in quadriceps peak twitch force.ResultsPotentiation of twitch, VM M-wave, and VL M-wave were greater for femoral nerve than for direct quadriceps stimulation (P < 0.05). Despite a 50% decrease in MVC force, the amplitude of the M-waves increased significantly during exercise.ConclusionsIn addition to enhanced electrogenic Na(+) -K(+) pumping, other factors (such as synchronization in activation of muscle fibers and muscle architectural properties) may significantly influence the magnitude of M-wave enlargement.Copyright © 2013 Wiley Periodicals, Inc.

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