title: Acute postural modulation of the soleus H-reflex after Achilles tendon vibration.
abstract: Alteration of Soleus (SOL) H-reflex has been reported after prolonged vibratory exposure and it was hypothesized that presynaptic inhibition, known to depress the H-reflex during vibration, largely contributed to the H-reflex changes. To confirm this hypothesis, the purpose of the present study was to quantify the SOL H-reflex changes between sitting and standing positions (postural modulation) with or without the after-effects of 1h of Achilles tendon vibration. Indeed, postural modulation of the SOL H-reflex has been reported to inform on the level of presynaptic inhibition exerted on Ia afferents. SOL H-reflex and M waves were measured in healthy voluntary subjects in both sitting and standing positions before and after 1h of Achilles vibration (frequency: 50 Hz) applied in sitting position (vibration group, n=11) or before and after 1h of sitting position only (control group, n=6). SOL H(max)/M(max) ratios were calculated. Furthermore, in order to quantify presynaptic inhibition induced by prolonged vibration, an index of SOL H-reflex postural modulation was calculated as the standing H(max)/M(max) ratio relative to the sitting one. After 1h of Achilles tendon vibration, a significant decrease in the SOL H(max)/M(max) ratio was observed both in sitting and standing positions (p<0.05). However, the decrease was more pronounced in the standing position, leading to a significant decrease of the index of SOL H-reflex postural modulation. Those results suggest that presynaptic inhibition could have largely contributed to the H-reflex decrease observed after one bout of vibration.
authors: Université de Technologie, Compiègne CNRS UMR 7338, Biomécanique et Bioingénierie, F-60205 Compiègne Cedex, France.
authors: Thomas
authors: T
authors: Lapole
authors: Francis
authors: F
authors: Canon
authors: Chantal
authors: C
authors: Pérot
mesh_terms: D000125:Achilles Tendon / Q000502:physiology*; D000328:Adult; D004576:Electromyography; D006181:H-Reflex; D006801:Humans; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture; D014732:Vibration