• Javier Rodriguez-Falces, Nicola A Maffiuletti, and Nicolas Place.
• Department of Electrical and Electronical Engineering, Universidad Pública de Navarra DIEE, Campus de Arrosadía s/n 31006, Pamplona, Spain.
• Muscle Nerve. 2013 Nov 1; 48 (5): 752-61.

IntroductionIn this study we investigated differences in the spatial recruitment of motor units (MUs) in the quadriceps when electrical stimulation is applied over the quadriceps belly versus the femoral nerve.MethodsM-waves and mechanical twitches were evoked using over-the-quadriceps and femoral nerve stimulation of gradually increasing intensity from 22 young, healthy subjects. Spatial recruitment was investigated using recruitment curves of M-waves recorded from the vastus medialis (VM) and vastus lateralis (VL) and of twitches recorded from the quadriceps.ResultsAt maximal stimulation intensity (Imax), no differences were found between nerve and over-the-quadriceps stimulation. At submaximal intensities, VL M-wave amplitude was higher for over-the-quadriceps stimulation at 40% Imax, and peak twitch force was greater for nerve stimulation at 60% and 80% Imax.ConclusionsFor the VM, MU spatial recruitment during nerve and over-the-quadriceps stimulation of increasing intensity occurred in a similar manner, whereas significant differences were observed for the VL.Copyright © 2013 Wiley Periodicals, Inc.

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