Acupuncture has been recognized as an useful treatment for muscle pain, muscle fatigue and muscle hypertonus in sports medicine. This study developed an experimental model to investigate the effect of acupuncture on muscular disorders.
Twenty-seven rabbits, anesthetized with pentobarbital (i. v.) were used. The anterior tibial muscle was exposed, and the distal end of the tendon was cut then attached to the push-pull gauge and tension during the isometric contraction induced by electrical stimulation of the muscle was recorded.
The tension was measured immediately before and 15, 30, 45 and 60min after the electrical stimulation. The frequencies of 1, 10, 20, 30, and 50Hz were used as the conditioning stimulation (1ms in duration, 60s).
Tension was decreased after the conditioning electrical stimulation of muscle. High frequency of stimuli tended to induce a marked decrease in tension.
Acupuncture stimulation (leaving the needle in place for 10min) reduced the decrement of the evoked tension by 30Hz tetanic stimulus significantly (p<0.05), and enhanced the recovery. Occlusion of the blood vessel supplying the muscle potentiated the decrement of evoked tension, and acupuncture stimulation still reduced the initial decrement of the evoked tension, suggesting that acupuncture acted on the blood flow in the muscle. After transection of the nerve innervating the muscle, acupuncture stimulation still demonstreted the same effect.
These results suggest that the acupuncture stimulation induces vasodilatation by axon reflex and the subsequent increase in blood flow to the muscle induces the recovery of reduced tension by tetanic contraction.