The machines were set under verification of their functionality with a voltmeter every three months and any moment in case they had been exposed to water. This was carried out by an engineer who did not have contact with patients and who did not participate in their clinical evaluation or follow up. The participants could not feel if the machine was working and neither could they mention in which group they were. The machines of placebo were identical to the machines in actual operation in both phases of the study. The only difference was that the hybrid circuits crucial for the generation of the electromagnetic field had been removed. As the subjects could not feel the change, there was no possibility that the subjects had knowledge about which of the machines provided therapy and which ones did not. At any moment the researchers were blinded to distinguish which of the devices was active and which one was not. The patients carried the devices continuously, except when there was the risk of contaminating them with water, as when bathing.