Spinal neuronal mechanisms explaining the modulation of soleus H-reflexes during sustained passive rotation of the hip joint.
OBJECTIVE
The aim of this study was to investigate the mechanism of modulation of soleus H-reflexes during sustained passive rotation of the hip joint.


METHODS
Healthy men participated as subjects in this study. In the supine position, soleus maximum H-reflexes were recorded during rotation of the hip joint. To examine the roles of muscle spindles, we recorded H-reflexes while applying vibration to muscles around the hip joint. Furthermore, to assess the modulation of pre- and postsynaptic inputs to soleus motoneurons, H-reflexes were conditioned by common peroneal nerve stimulation or transcranial magnetic stimulation (TMS).


RESULTS
The ratio of the maximum H-reflex to the maximum M-response was significantly reduced in externally rotated positions of the hip joint compared to neutral position. In these positions, presynaptic inhibition, assessed by D1 inhibition, was significantly increased. H-reflexes were reduced during vibration, irrespective of muscles involved and hip position. Facilitation of H-reflex induced by conditioning-TMS showed insignificant differences across all hip positions.


CONCLUSIONS
These findings suggest that Ia afferents induced by rotation of the hip joint presumably inhibit soleus H-reflexes presynaptically.


CONCLUSIONS
Based on the results, therapists could efficiently modulate the spasticity of the lower legs of hemiplegic patients during rotation of the hip joint.
Narita
Tomohiro
T
Division of Human Sciences, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashi-Hiroshima, 739-8521, Japan.
Liang
Nan
N
Morishita
Takuya
T
Ninomiya
Masato
M
Morisaki
Kazushi
K
Kasai
Tatsuya
T
Funase
Kozo
K
D000328:Adult; D006181:H-Reflex / Q000502:physiology*; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010543:Peroneal Nerve / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*; D016683:Supine Position / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D014732:Vibration; D055815:Young Adult