Introduction: Shoulder pain is a common condition and can have great impact on daily living. Examination and treatment of sensitive areas in the muscles is an important part of the treatment of various shoulder disorders today. Palpation and pain provocation is used to diagnose and to distinguish between different reasons to symptoms in the area. It is well understood that soreness in infraspinatus for long period of time can cause symptoms as tension in the shoulder muscles. But it is unknown if it is due to changed muscle tone or due to other reasons. Method: Muscle tone was measured before and after mechanical stimulation of a trigger point in the infraspinatus to clarify any change. Also an analyze for a correlation between muscle pain and the spread of pain were made. Results: The results are based on data from 40 subjects. All subjects achieved local pain during stimulation of the trigger point in infraspinatus. On the stimulated side, there were found a significant difference in muscle tone in both infraspinatus, deltoid and brachioradialis measured from baseline to post-stimulation. None significant correlations were found between PPT, VAS, pain area and changes in muscle tone. Conclusion: As a result of the mechanical stimulation it has been demonstrated a significantly increased muscle tone measured by the parameter natural oscillationfrequency in all three muscles (P <0.05). On this basis, it is concluded that measurement of muscle tone can be used as a clinical study of muscle pain in order to clarify pain patterns.