Dry Needling Reverses Vibration-induced Changes in Spinal Motoneuronal Pool:Is there any Basis for its Action on Muscle Tone?

Acupuncture or dry needling, in clinical practice have been used successfully in the treatment of pain associated with muscle tone alterations. However a possible direct effect on muscle tone has never been clearly separated from its analgesic action. The H-reflex is a recognised neurophysiological index of the excitability of spinal motor neuron pool. This reflex is highly inhibited by the application of a vibration stimulus of 100 Hz. The aim of the study was to evaluate in a group of normal subjects and in absence of pain if acupuncture stimulation was capable of acting at the segmental level, modifying the 100 Hz vibratory inhibition of the H-reflex. H-reflex amplitude significantly varied in relation to the application of vibratory stimulus and acupuncture stimuli. Before vibration (H-Basal) the average amplitude was 292 ± 59.3 I¼V. During vibration (H-Vib) the amplitude reduced to 118 ± 73.6 I¼V (H-Bas vs. H-Vib p<0.05). Insertion of the needle (H-Vib+needle) produced a statistically significant increase in amplitude of the H-reflex to 218.8 ± 95 I¼V (H-Vib vs. H-Vib+Ago p<0.05). Through the use of neurophysiological techniques on man e.g. H-reflex, the existence of a direct effect of acupuncture on the excitability of the spinal motor neurons has been demonstrated suggesting an action of acupuncture on muscle tone separate from its well-known analgesic effect.