The effects of long-term bed rest on H-reflex and motor evoked potential in the human soleus muscle during standing.
H-reflex and motor evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) in soleus muscle of five normal subjects were investigated before and after 20 days 6 degree head-down bed rest (BR). Soleus H-reflex during standing following bed rest decreased in all five subjects. The size of the maximum H-reflex (Hmax), expressed as a percentage of the maximum M-response (Mmax), decreased from 63.3+/-23.3% before BR to 26.7+/-12.5% after BR. However, there were no significant differences between MEPs before and after bed rest. Moreover, MEP/Hmax after bed rest was larger than before bed rest in all subjects. These results indicate a strong inhibition of H-reflex and no adaptation of MEP in soleus muscle during standing following bed rest.
Yamanaka
K
K
Motor Dysfunction Division, Research Institute, National Rehabilitation Center for the Disabled, Saitama, Japan. yamanaka@rehab.go.jp
Yamamoto
S
S
Nakazawa
K
K
Yano
H
H
Suzuki
Y
Y
Fukunaga
T
T
D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D015225:Magnetoencephalography; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture / Q000502:physiology*