To verify that the baseline conditions were adequate for the start of the collection, the volunteer remained 15 minutes at rest in supine position . They were measured and recorded : blood pressure by auscultation , using a mercury sphygmomanometer and a stethoscope ; and heart rate at rest by a heart rate monitor , with all measures carried out by the same researcher . Then the volunteer remained in the same position and was initiated to collect data with the registration of iR -R by Polar heart rate monitor model RS800CX (Polar Electro Co.Ltda . Kempele , Finland ) for 15 min. During the registration time, the participants maintained spontaneous respiration , were told not to talk , not sleep and avoid sudden movements . Subsequently , the recorded iR - R were transferred via an interface to a computer compatible for Polar softwere , the data being further processed into .txt format.