It is known that nociceptive afferences in visceral pain and visceral disorders increase sensitization in subjects suffering from fibromyalgia. These patients use to present visceral comorbidities. Those comorbidities include that of peridiaphragmatic organs, which are supplied by the phrenic nerve among other innervations. It is known that peridiaphragmatic organs trigger referred pain in the neck area, via the phrenic nerves. So, the phrenic nociceptive afferences can be contributing to enhance the state of sensitization in fibromyalgia. This study aims to analyze the ability of phrenic nerve infiltration to diminish sensitization in subjects suffering fibromyalgia, by means of a randomized controlled trial.