title: M-wave, H- and V-reflex recruitment curves during maximal voluntary contraction.
abstract: OBJECTIVE
  To investigate whether the H reflex-M wave recruitment curves obtained during maximal voluntary contraction (MVC) differ from rest and to determine the stimulation intensities allowing to record stable reflex responses.
  
  
  METHODS
  Full recruitment curves (precision, 2 mA) were obtained from the soleus muscle in 14 volunteers at rest and during plantar flexion MVCs.
  
  
  RESULTS
  Maximal M-wave reached significantly larger amplitude during MVC (+2.2 [0.4; 3.9] mV) for a higher stimulation intensity (+7.9 [-0.4; 16] mA). Similarly, maximal H-reflex reached significantly larger amplitude during MVC than at rest (+3.2 [0.9; 5.5] mV) for a much higher stimulation intensity (+17.7 [9.7; 25.7] mA). V-wave amplitude plateaued only when M-wave during MVC plateaued, that is, at higher intensity than M-wave at rest. V-wave was correlated to the maximal H-reflex during MVC (r = 0.79, P < 0.05).
  
  
  CONCLUSIONS
  Electrically evoked potentials showed a specific recruitment curve during MVC with higher maximal values attained for higher stimulation intensities. Thus, recording reflex responses during MVC based on intensities determined at rest or as a percentage of M-wave may yield inaccurate results. V-wave presented a plateau for stimulation intensity of 1.5 times the onset of the resting M-wave plateau. Evoked potentials obtained during actual contractions should be normalized to M-waves obtained during contractions of the same force level.
authors.affiliation: Research and Education Centre, ASPETAR, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar. sebastien.racinais@aspetar.com
authors.forename: Sebastien
authors.initials: S
authors.lastname: Racinais
authors.forename: Nicola A
authors.initials: NA
authors.lastname: Maffiuletti
authors.forename: Olivier
authors.initials: O
authors.lastname: Girard
mesh_terms: D000328:Adult; D004558:Electric Stimulation / Q000295:instrumentation / Q000379:methods; D004576:Electromyography / Q000295:instrumentation / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011999:Recruitment, Neurophysiological / Q000502:physiology*; D012018:Reflex / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology; D019415:Torque; D014836:Volition / Q000502:physiology*; D055815:Young Adult