Inhibitory effect of needle penetration on vibration-induced finger flexion reflex in humans.
BACKGROUND
Vibration-induced finger flexion reflex (VFR) in the upper extremity is inhibited by needle insertion acupuncture to the large intestine 4 (LI4) at the hand. This claim has a limitation because the inhibitory effect is deduced only from reduction in the maximum finger flexion (FF) force during the tonic flexion reflex by vibratory stimulation after acupuncture.


METHODS
The study was a crossover design with two conditions-acupuncture and control-to which 16 healthy volunteers were subjected. VFR in the upper extremity was induced by applying vibratory stimulation on the volar side of the middle fingertip of the right hand, before and after acupuncture at the right LI4 in 16 healthy volunteers. We measured the area under the curve (AUC) of finger flexion force and surface electromyogram (EMG) in the flexor muscles, in addition to the maximum FF force during vibratory stimulation. We compared AUC, surface EMG and maximum FF force in the acupuncture condition with those in the control condition. We also estimated the correlation between AUC, surface EMG and maximum FF force.


RESULTS
AUC, surface EMG and maximum FF force were significantly reduced (p <0.01) after acupuncture compared with those of the control group. A strong correlation was observed in maximum FF force versus AUC (r=0.98, p <0.01) and surface EMG (r=0.77, p <0.01).


CONCLUSIONS
Acupuncture at ipsilateral LI4 inhibited tonic activities in the finger flexor muscles during VFR, which suggests that afferent input with needle penetration has inhibitory effect on the motor neuronal activities in the reflex circuits of VFR.
Takakura
Nobuari
N
Department of Acupuncture and Moxibustion, Faculty of Health Sciences, Tokyo Ariake University of Medical and Health Sciences, Koto-ku, Tokyo 135-0063, Japan. takakura@t-ariake.ac.jp
Yajima
Hiroyoshi
H
Takayama
Miho
M
Kawase
Akiko
A
Homma
Ikuo
I
D015669:Acupuncture Points; D000328:Adult; D019540:Area Under Curve; D018592:Cross-Over Studies; D004576:Electromyography; D005260:Female; D005385:Fingers / Q000294:innervation* / Q000502:physiology; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation*; D012016:Reference Values; D012018:Reflex / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology; D014732:Vibration; D055815:Young Adult
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