title: Twitch and M-wave potentiation induced by intermittent maximal voluntary quadriceps contractions: differences between direct quadriceps and femoral nerve stimulation.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  M-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.
  
  
  RESULTS
  Potentiation 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.
  
  
  CONCLUSIONS
  In 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.
authors.affiliation: Department of Electrical and Electronic Engineering, Universidad Pública de Navarra DIEE, Campus de Arrosadía s/n, 31006, Pamplona, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Rodriguez-Falces
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Maffiuletti
authors.forename: Nicolas
authors.initials: N
authors.lastname: Place
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001703:Biophysics; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005221:Fatigue; D005260:Female; D005267:Femoral Nerve / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D052097:Quadriceps Muscle / Q000294:innervation* / Q000502:physiology*; D018709:Statistics, Nonparametric
keywords: M-wave potentiation; direct quadriceps stimulation; femoral nerve stimulation; neuromuscular electrical stimulation; twitch potentiation