The relative contribution to the plantar-flexor torque of the soleus motor units activated by the H reflex and M response in humans.
This study proposes a method of quantifying the relative contribution to the plantar-flexor torque of soleus H and M responses evoked by tibial nerve stimulation. For ten subjects, the amplitude of the twitch produced by the H wave was plotted against the corresponding potential, for stimuli producing H without M (i.e. in the ascending portion of the H-recruitment curve). It was then assumed that the contribution of H to twitches produced by M plus H was similar for similar H waves on the curve-descending portion. Hence, the contribution of M was estimated, for the range of M waves including those accompanying H(max). The estimated mechanical contributions of H and M wave increase linearly with their potentials, the slope of the relationship being greater for H than M. The interpretation of this finding is discussed. A simple formula for assessing the contribution of the H wave to the twitch torque is given.
Maffiuletti
N A
NA
Groupe Analyse du Mouvement, UFR STAPS, Université de Bourgogne, BP 27877 - 21078 Cedex, Dijon, France. nicola.maffiuletti@u-bourgogne.fr
Martin
A
A
Van Hoecke
J
J
Schieppati
M
M
D000200:Action Potentials / Q000502:physiology; D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology*; D019415:Torque