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A Proposed Experimental Model of Myofascial Trigger Points in Human Muscle after Slow Eccentric Exercise

Background The purpose of this study was to develop an experimental model of myofascial trigger points to investigate their pathophysiology. Methods Fifteen healthy volunteers who gave informed consent underwent repetitive eccentric exercise of the third finger of one hand (0.1Hz repetitions, three sets at five minute intervals) until exhaustion. Physical examination, pressure pain threshold, and electrical pain threshold of the skin, fascia and muscle were measured immediately afterwards and for seven days. Needle electromyogram (EMG) was also recorded in a subgroup of participants. Results Pressure pain thresholds decreased to a minimum on the second day after the exercise, then gradually returned to baseline values by the seventh day. On the second day, a ropy band was palpated in the exercised forearm muscle and the electrical pain threshold of the fascia at the palpable band was the lowest among the measured loci and tissues. Needle EMG activity accompanied with dull pain sensation was recorded only when the electrode was located on or near the fascia of the palpable band on the second day of exercise. Conclusion These results suggest that eccentric exercise may yield a useful model for the investigation of the myofascial trigger points and/or acupuncture points. The sensitised nociceptors at the fascia of the palpable band might be a possible candidate for the localised tender region.