The intervention group will develop an activity with self-monitoring called Cardiovascular Biofeedback or Cardiac Frequency Variability (CFV). This intervention will be measured by the Software Emwave Pro Plus during 4 weeks, which send out a sign captured by a non-invasive sensor such as an ear lobe fixed photoplethysmograph. This photoplethysmograph verifies blood flow alterations through an optical method. Cardiac frequency oscillations may be estimated both by the quantity of blood infrared lights absorbed or reflected, and by variations in blood volume and pressure. Captured physiological signs will be recorded during ten minutes by the Software Emwave Pro Plus®, which is adapted to biofeedback training.

The placebo group will develop an activity without self monitoring. In order to keep blindness between the groups the activities will be processed by an electronic device - the on line app Jigsaw Puzzles. This app consists of a puzzle with different levels of difficulties, and is played in a tablet.

Each participant will be performing in the study during four weeks, with two encounters each week (total: four weeks). While the participant will be performing its activity he/she will be monitored by the researchers through CFV (Cardiac Frequency Variability) - with no visualization of the computer monitor.

The control group will answer the research protocol in two moments (D1 and D8), to evaluate

This intervention will be measured by the Software Emwave Pro Plus during 4 weeks, which send out a sign captured by a non-invasive sensor such as an ear lobe fixed photoplethysmograph.

Stress evaluation will be measured by the 23 items Work Stress Scale (WST), likert scale with each item corresponding to a stressor and the reaction the subject has to it. Scores vary from 23 to 111 points, with good reliability (COM µ = 0,91). Results were obtained by the items media sum, considering occupational stress as low (values between 1 and 2), moderate (2,01 to 2,99), or high (3 to 5).